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Essay Samples on Universe

Unraveling the cosmos: about the origin of the universe.

The question of how the universe came into existence has intrigued humanity for centuries. This essay delves into the fascinating journey of understanding the origin of the universe, from ancient creation myths to modern cosmological theories. As scientists and philosophers grapple with this profound question,...

• Space Exploration

From Geocentric to Heliocentric: The Evolution of Astronomical Thought

Aristotle Aristotle once said, “You will never do anything in this world without courage. It is the greatest quality of the mind next to honor.” Aristotle is one of the most well-known, influential scientists and Philosophers of his time. He made significant impact in many...

History of Telescopes and the Revolutionary Launch of the Hubble Space Telescope

Up until a few 400 years ago, the only thing mankind knew about the universe was from many many passed down stories and observations seen with the human eye. Italian astronomer Galileo Galilei decided to apply his knowledge and build his own telescope in 1610;...

• Hubble Telescope

Analysis of the Probabilities of Earth Extinction Scenarios

No matter how unique Earth is, the planet has a lifespan will only have a few billions of years to support life. So what will humans do once Earth becomes expired? Where can we go? And how long can we beat extinction? There are several...

Science Behind the Birth and Death of the Stars

When we look up at the night sky, we are entranced by the millions of bright dots scattered across the airspace. Some of these dots are planets, and others are galaxies. Most, however, are stars. Stars came into existence around 400 million years after the...

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Analysis of Hannah Arendt's Essay The Conquest of Space and the Stature of Man

Hannah Arendt questions whether man’s stature has improved or declined in the pursuit of space technology and exploration of the universe. “The Conquest of Space and the Stature of Man”, is an essay written by Arendt which adresses this very complex question and it gives...

• Hannah Arendt

Pesticides and Their Effects to the Earth's Atmosphere

In our everyday lives many farmers are using pesticides to protect their fields from pests and insects. Their use is not only restricted to agricultural fields, but they are also employed in homes in the form of sprays, poisons and powders for controlling cockroaches, mosquitoes,...

Planets' Atmosphere Analysis and Atmosphere’s Protection

Introduction The name atmosphere name means vapour (atmos) and sphere (sphaira) coming from the Greek language. The atmosphere is a layer which consists out of other layers of gasses surrounding a planet, the atmosphere is held in place by the gravity of a planet. On...

Black Holes: When Something Is Nothing

Abstract The present text will explore the properties and characteristics of black holes in our universe, formulated through studies and evidences concluded by researchers. This research will likewise investigate topics of Primordial Black Holes and the existence of a Super Massive Black Hole within a...

Black Holes: Bizarre Cosmological Objects

Abstract In this report, I am going to discuss about the fundamentals of black holes and their relevance to modern research scenario. We have a lot of informations about black holes but there are still several questions to be answered regarding black hole physics. Keywords:...

Black Holes - The Most Bizarre Objects Within The Universe

The occasion horizon of a dark hole is connected to the object's elude velocity — the speed that one would have to be surpassed to elude the dark hole's gravitational drag. The closer somebody came to a black hole, the more noteworthy the speed they...

Black Holes One of the Biggest Mysteries in the Universe

The universe is a wide and complex place with billions of planets and stars, as well as countless theories and unanswered questions. Scientist may know most of what is going on in space. One of the few things, that until this day scientists cannot explain,...

The Magnificent Universe: The Beauty of an Eclipse I Witnessed

Everything began when i have lost the bet with jack. I thought it was my last day in the city. And had to pack my bags. Until i remembered that he has a favor to fulfil. So i called jack to remind him. I was...

• Solar Eclipse

Stars as the Wonders of the Universe

Think about your normal daily life and how the sun impacts it. Now think about what it can do and how it was made. These stars are made of giant balls of gas and can live for millions, or even billions of years. Stars are...

Hubble Space Telescope: Creation, Usage and Prospects

Launched in April 24th, 1990, the motivation behind the Hubble Space Telescope is to assemble light from inestimable articles so researchers can all the more likely comprehend the universe around us. In light of the fact that the telescope went over numerous troubles, for example,...

The Story of How Hubble Telescope Came to Be

The modern telescope can gaze far into the night sky, giving scientist a picture of what lies beyond Earth. But there's a major problem with these telescopes. Their limited by the earthly atmosphere. Substances like greenhouse gasses and light pollution due to nearby cities or...

Spitzer Space Telescope and a New Way to See the Universe

Observing the universe by using infrared goggles, that’s is basically what Spitzer does. Spitzer’s infrared sensors detect heat from objects that optical telescope and our eyes can’t see. Which the newest technology, this have given us the opportunity to look right through dense clouds of...

International Effort in Investigating and Exploring Mars

Curiosity is an innate urge in human nature. When explorers discovered the new world, thousands flocked to explore it out of curiosity. We are on the cusp of great exploration, the planets in our solar system have started to be explored, starting with Mars. Mars...

Exploring the Technicalities of Time Travel in Interstellar Travel

Interstellar travel is the idea of travel from one star system or planetary system to another through means of either crewed or unscrewed spacecrafts. Such a feat would be exceptionally difficult. For example, interplanetary travel within our own solar system is generally under 30 AU...

• Time Travel

Comprehension of Time as Relative and a Construct

Time is characterized as a deliberate or quantifiable period, a continuum that need spatial measurements. This wide definition does not have the straightforward clarification that people are looking for. There are numerous researchers, rationalists, and masterminds who have attempted to invest energy into comprehension terms....

Humanity's Understanding of Time Through Science

Approximately 13.7 billion years ago at a single point in space, our universe exploded into existence and has since expanded into the universe we recognise today, bringing with it forces, matter and energy. Our planet Earth formed 9.1 billion years later, with human life emerging...

The Role of God in Coyne's A Catholic Scientist Looks at Evolution

A Catholic Scientist Looks at Evolution In this article, A Catholic Scientist Looks at Evolution, by George Coyne, two main points are discussed. The first being that the Intelligent Design (ID) Movement showcases a God as a designer God, which actually belittles God despite evoking...

• Catholic Church

Assessing the Pilgrim's Guides in Dante's The Divine Comedy

The Guardians of the Universe Dante’s great epic poem is widely considered the preeminent work of Italian literature and is seen as one of the very greatest works of world literature, largely because Dante has deftly incorporated some of the most astonishing intricate and alarming...

Overview Of Star Citizen – An Upcoming Multiplayer Space Trading And Combat Game

The anticipation keeps gathering up steam as gamers patiently await the release of Star Citizen, the multiplayer, space trading and combat game which might just usurp its predecessors when it eventually drops. In 2011, Chris Roberts and his crew at Cloud Imperium Games commenced work...

• Video Games

Our Life In The Scope Of A Galaxy

Every person that has ever lived in the history of existence, whether they lived under a principal of tyranny or love, conquered nations or built them, lives for a brief moment on a rock in an indifferent Galaxy. The unescapable reality of the sheer size...

The Issue Of The Benefits Of Space Exploration

Space exploration is an interesting topic because it has led to many discoveries and technological breakthroughs. Even with this in mind, the relevancy of space exploration is questioned because of some negative effects of space exploration. Lots of governments and people do not see the...

• Advantages of Technology

The Beginning Of Universe And Its Expansion

Try to think of nothing in its purest form. That thought, let alone the sentence that summoned it should perfectly exemplify a paradox. You see, the idea of nothing is simply a theory. That is why our story begins nearly 14 billion years ago, and...

Best topics on Universe

1. Unraveling the Cosmos: About the Origin of the Universe

2. From Geocentric to Heliocentric: The Evolution of Astronomical Thought

3. History of Telescopes and the Revolutionary Launch of the Hubble Space Telescope

4. Analysis of the Probabilities of Earth Extinction Scenarios

5. Science Behind the Birth and Death of the Stars

6. Analysis of Hannah Arendt’s Essay The Conquest of Space and the Stature of Man

7. Pesticides and Their Effects to the Earth’s Atmosphere

8. Planets’ Atmosphere Analysis and Atmosphere’s Protection

9. Black Holes: When Something Is Nothing

10. Black Holes: Bizarre Cosmological Objects

11. Black Holes – The Most Bizarre Objects Within The Universe

12. Black Holes One of the Biggest Mysteries in the Universe

13. The Magnificent Universe: The Beauty of an Eclipse I Witnessed

14. Stars as the Wonders of the Universe

15. Hubble Space Telescope: Creation, Usage and Prospects

• Archaeology
• Quantum Mechanics
• Language Diversity
• Alan Turing

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The Cosmic Perspective

By Neil deGrasse Tyson

Natural History Magazine

The 100 th essay in the “Universe” series.

Embracing cosmic realities can give us a more enlightened view of human life.

Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered… but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above [their] low contracted prejudices. James Ferguson, Astronomy Explained Upon Sir Isaac Newton’s Principles, And Made Easy To Those Who Have Not Studied Mathematics (1757)

Long before anyone knew that the universe had a beginning, before we knew that the nearest large galaxy lies two and a half million light years from Earth, before we knew how stars work or whether atoms exist, James Ferguson’s enthusiastic introduction to his favorite science rang true. Yet his words, apart from their eighteenth-century flourish, could have been written yesterday.

But who gets to think that way? Who gets to celebrate this cosmic view of life? Not the migrant farmworker. Not the sweatshop worker. Certainly not the homeless person rummaging through the trash for food. You need the luxury of time not spent on mere survival. You need to live in a nation whose government values the search to understand humanity’s place in the universe. You need a society in which intellectual pursuit can take you to the frontiers of discovery, and in which news of your discoveries can be routinely disseminated. By those measures, most citizens of industrialized nations do quite well.

Yet the cosmic view comes with a hidden cost. When I travel thousands of miles to spend a few moments in the fast-moving shadow of the Moon during a total solar eclipse, sometimes I lose sight of Earth.

When I pause and reflect on our expanding universe, with its galaxies hurtling away from one another, embedded within the ever-stretching, four-dimensional fabric of space and time, sometimes I forget that uncounted people walk this Earth without food or shelter, and that children are disproportionately represented among them.

When I pore over the data that establish the mysterious presence of dark matter and dark energy throughout the universe, sometimes I forget that every day—every twenty-four-hour rotation of Earth—people kill and get killed in the name of someone else’s conception of God, and that some people who do not kill in the name of God kill in the name of their nation’s needs or wants.

When I track the orbits of asteroids, comets, and planets, each one a pirouetting dancer in a cosmic ballet choreographed by the forces of gravity, sometimes I forget that too many people act in wanton disregard for the delicate interplay of Earth’s atmosphere, oceans, and land, with consequences that our children and our children’s children will witness and pay for with their health and well-being.

And sometimes I forget that powerful people rarely do all they can to help those who cannot help themselves.

I occasionally forget those things because, however big the world is—in our hearts, our minds, and our outsize atlases—the universe is even bigger. A depressing thought to some, but a liberating thought to me.

Consider an adult who tends to the traumas of a child: a broken toy, a scraped knee, a schoolyard bully. Adults know that kids have no clue what constitutes a genuine problem, because inexperience greatly limits their childhood perspective.

As grown-ups, dare we admit to ourselves that we, too, have a collective immaturity of view? Dare we admit that our thoughts and behaviors spring from a belief that the world revolves around us? Apparently not. And the evidence abounds. Part the curtains of society’s racial, ethnic, religious, national, and cultural conflicts, and you find the human ego turning the knobs and pulling the levers.

Now imagine a world in which everyone, but especially people with power and influence, holds an expanded view of our place in the cosmos. With that perspective, our problems would shrink—or never arise at all—and we could celebrate our earthly differences while shunning the behavior of our predecessors who slaughtered each other because of them.

Back in February 2000, the newly rebuilt Hayden Planetarium featured a space show called Passport to the Universe , which took visitors on a virtual zoom from New York City to the edge of the cosmos. En route the audience saw Earth, then the solar system, then the 100 billion stars of the Milky Way galaxy shrink to barely visible dots on the planetarium dome.

Within a month of opening day, I received a letter from an Ivy League professor of psychology whose expertise was things that make people feel insignificant. I never knew one could specialize in such a field. The guy wanted to administer a before-and-after questionnaire to visitors, assessing the depth of their depression after viewing the show. Passport to the Universe, he wrote, elicited the most dramatic feelings of smallness he had ever experienced.

How could that be? Every time I see the space show (and others we’ve produced), I feel alive and spirited and connected. I also feel large, knowing that the goings-on within the three-pound human brain are what enabled us to figure out our place in the universe.

Allow me to suggest that it’s the professor, not I, who has misread nature. His ego was too big to begin with, inflated by delusions of significance and fed by cultural assumptions that human beings are more important than everything else in the universe.

In all fairness to the fellow, powerful forces in society leave most of us susceptible. As was I … until the day I learned in biology class that more bacteria live and work in one centimeter of my colon than the number of people who have ever existed in the world. That kind of information makes you think twice about who—or what—is actually in charge.

From that day on, I began to think of people not as the masters of space and time but as participants in a great cosmic chain of being, with a direct genetic link across species both living and extinct, extending back nearly 4 billion years to the earliest single-celled organisms on Earth.

know what you’re thinking: we’re smarter than bacteria.

No doubt about it, we’re smarter than every other living creature that ever walked, crawled, or slithered on Earth. But how smart is that? We cook our food. We compose poetry and music. We do art and science. We’re good at math. Even if you’re bad at math, you’re probably much better at it than the smartest chimpanzee, whose genetic identity varies in only trifling ways from ours. Try as they might, primatologists will never get a chimpanzee to learn the multiplication table or do long division.

If small genetic differences between us and our fellow apes account for our vast difference in intelligence, maybe that difference in intelligence is not so vast after all.

Imagine a life-form whose brainpower is to ours as ours is to a chimpanzee’s. To such a species our highest mental achievements would be trivial. Their toddlers, instead of learning their ABCs on Sesame Street, would learn multivariable calculus on Boolean Boulevard. Our most complex theorems, our deepest philosophies, the cherished works of our most creative artists, would be projects their schoolkids bring home for Mom and Dad to display on the refrigerator door. These creatures would study Stephen Hawking (who occupies the same endowed professorship once held by Newton at the University of Cambridge) because he’s slightly more clever than other humans, owing to his ability to do theoretical astrophysics and other rudimentary calculations in his head.

If a huge genetic gap separated us from our closest relative in the animal kingdom, we could justifiably celebrate our brilliance. We might be entitled to walk around thinking we’re distant and distinct from our fellow creatures. But no such gap exists. Instead, we are one with the rest of nature, fitting neither above nor below, but within.

Need more ego softeners? Simple comparisons of quantity, size, and scale do the job well.

Take water. It’s simple, common, and vital. There are more molecules of water in an eight-ounce cup of the stuff than there are cups of water in all the world’s oceans. Every cup that passes through a single person and eventually rejoins the world’s water supply holds enough molecules to mix 1,500 of them into every other cup of water in the world. No way around it: some of the water you just drank passed through the kidneys of Socrates, Genghis Khan, and Joan of Arc.

How about air? Also vital. A single breathful draws in more air molecules than there are breathfuls of air in Earth’s entire atmosphere. That means some of the air you just breathed passed through the lungs of Napoleon, Beethoven, Lincoln, and Billy the Kid.

Time to get cosmic. There are more stars in the universe than grains of sand on any beach, more stars than seconds have passed since Earth formed, more stars than words and sounds ever uttered by all the humans who ever lived.

Want a sweeping view of the past? Our unfolding cosmic perspective takes you there. Light takes time to reach Earth’s observatories from the depths of space, and so you see objects and phenomena not as they are but as they once were. That means the universe acts like a giant time machine: the farther away you look, the further back in time you see—back almost to the beginning of time itself. Within that horizon of reckoning, cosmic evolution unfolds continuously, in full view.

Want to know what we’re made of? Again, the cosmic perspective offers a bigger answer than you might expect. The chemical elements of the universe are forged in the fires of high-mass stars that end their lives in stupendous explosions, enriching their host galaxies with the chemical arsenal of life as we know it. The result? The four most common chemically active elements in the universe—hydrogen, oxygen, carbon, and nitrogen—are the four most common elements of life on Earth. We are not simply in the universe. The universe is in us.

Yes, we are stardust. But we may not be of this Earth. Several separate lines of research, when considered together, have forced investigators to reassess who we think we are and where we think we came from.

First, computer simulations show that when a large asteroid strikes a planet, the surrounding areas can recoil from the impact energy, catapulting rocks into space. From there, they can travel to—and land on—other planetary surfaces. Second, microorganisms can be hardy. Some survive the extremes of temperature, pressure, and radiation inherent in space travel. If the rocky flotsam from an impact hails from a planet with life, microscopic fauna could have stowed away in the rocks’ nooks and crannies. Third, recent evidence suggests that shortly after the formation of our solar system, Mars was wet, and perhaps fertile, even before Earth was.

Those findings mean it’s conceivable that life began on Mars and later seeded life on Earth, a process known as panspermia. So all earthlings might—just might—be descendants of Martians.

Again and again across the centuries, cosmic discoveries have demoted our self-image. Earth was once assumed to be astronomically unique, until astronomers learned that Earth is just another planet orbiting the Sun. Then we presumed the Sun was unique, until we learned that the countless stars of the night sky are suns themselves. Then we presumed our galaxy, the Milky Way, was the entire known universe, until we established that the countless fuzzy things in the sky are other galaxies, dotting the landscape of our known universe.

Today, how easy it is to presume that one universe is all there is. Yet emerging theories of modern cosmology, as well as the continually reaffirmed improbability that anything is unique, require that we remain open to the latest assault on our plea for distinctiveness: multiple universes, otherwise known as the  multiverse , in which ours is just one of countless bubbles bursting forth from the fabric of the cosmos.

The cosmic perspective flows from fundamental knowledge. But it’s more than just what you know. It’s also about having the wisdom and insight to apply that knowledge to assessing our place in the universe. And its attributes are clear:

• The cosmic perspective comes from the frontiers of science, yet it’s not solely the province of the scientist. The cosmic perspective belongs to everyone.
• The cosmic perspective is humble.
• The cosmic perspective is spiritual—even redemptive—but not religious.
• The cosmic perspective enables us to grasp, in the same thought, the large and the small.
• The cosmic perspective opens our minds to extraordinary ideas but does not leave them so open that our brains spill out, making us susceptible to believing anything we’re told.
• The cosmic perspective opens our eyes to the universe, not as a benevolent cradle designed to nurture life but as a cold, lonely, hazardous place.
• The cosmic perspective shows Earth to be a mote, but a precious mote and, for the moment, the only home we have.
• The cosmic perspective finds beauty in the images of planets, moons, stars, and nebulae but also celebrates the laws of physics that shape them.
• The cosmic perspective enables us to see beyond our circumstances, allowing us to transcend the primal search for food, shelter, and sex.
• The cosmic perspective reminds us that in space, where there is no air, a flag will not wave—an indication that perhaps flag waving and space exploration do not mix.
• The cosmic perspective not only embraces our genetic kinship with all life on Earth but also values our chemical kinship with any yet-to-be discovered life in the universe, as well as our atomic kinship with the universe itself.

At least once a week, if not once a day, we might each ponder what cosmic truths lie undiscovered before us, perhaps awaiting the arrival of a clever thinker, an ingenious experiment, or an innovative space mission to reveal them. We might further ponder how those discoveries may one day transform life on Earth.

Absent such curiosity, we are no different from the provincial farmer who expresses no need to venture beyond the county line, because his forty acres meet all his needs. Yet if all our predecessors had felt that way, the farmer would instead be a cave dweller, chasing down his dinner with a stick and a rock.

During our brief stay on planet Earth, we owe ourselves and our descendants the opportunity to explore—in part because it’s fun to do. But there’s a far nobler reason. The day our knowledge of the cosmos ceases to expand, we risk regressing to the childish view that the universe figuratively and literally revolves around us. In that bleak world, arms-bearing, resource-hungry people and nations would be prone to act on their “low contracted prejudices.” And that would be the last gasp of human enlightenment—until the rise of a visionary new culture that could once again embrace the cosmic perspective.

October 1, 1994

17 min read

The Evolution of the Universe

Some 15 billion years ago the universe emerged from a hot, dense sea of matter and energy. As the cosmos expanded and cooled, it spawned galaxies, stars, planets and life

By P. James E. Peebles , David N. Schramm , Edwin L. Turner & Richard G. Kron

GALAXY CLUSTER is representative of what the universe looked like when it was 60 percent of its present age. The Hubble Space Telescope captured the image by focusing on the cluster as it completed 10 orbits. This image is one of the longest and clearest exposures ever produced. Several pairs of galaxies appear to be caught in one another’s gravitational field. Such interactions are rarely found in nearby clusters and are evidence that the universe is evolving.

Editor’s Note (10/8/19): Cosmologist James Peebles won a 2019 Nobel Prize in Physics for his contributions to theories of how our universe began and evolved. He describes these ideas in this article, which he co-wrote for  Scientific American  in 1994.

At a particular instant roughly 15 billion years ago, all the matter and energy we can observe, concentrated in a region smaller than a dime, began to expand and cool at an incredibly rapid rate. By the time the temperature had dropped to 100 million times that of the sun’s core, the forces of nature assumed their present properties, and the elementary particles known as quarks roamed freely in a sea of energy. When the universe had expanded an additional 1,000 times, all the matter we can measure filled a region the size of the solar system.

At that time, the free quarks became confined in neutrons and protons. After the universe had grown by another factor of 1,000, protons and neutrons combined to form atomic nuclei, including most of the helium and deuterium present today. All of this occurred within the first minute of the expansion. Conditions were still too hot, however, for atomic nuclei to capture electrons. Neutral atoms appeared in abundance only after the expansion had continued for 300,000 years and the universe was 1,000 times smaller than it is now. The neutral atoms then began to coalesce into gas clouds, which later evolved into stars. By the time the universe had expanded to one fifth its present size, the stars had formed groups recognizable as young galaxies.

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When the universe was half its present size, nuclear reactions in stars had produced most of the heavy elements from which terrestrial planets were made. Our solar system is relatively young: it formed five billion years ago, when the universe was two thirds its present size. Over time the formation of stars has consumed the supply of gas in galaxies, and hence the population of stars is waning. Fifteen billion years from now stars like our sun will be relatively rare, making the universe a far less hospitable place for observers like us.

Our understanding of the genesis and evolution of the universe is one of the great achievements of 20th-century science. This knowledge comes from decades of innovative experiments and theories. Modern telescopes on the ground and in space detect the light from galaxies billions of light-years away, showing us what the universe looked like when it was young. Particle accelerators probe the basic physics of the high-energy environment of the early universe. Satellites detect the cosmic background radiation left over from the early stages of expansion, providing an image of the universe on the largest scales we can observe.

Our best efforts to explain this wealth of data are embodied in a theory known as the standard cosmological model or the big bang cosmology. The major claim of the theory is that in the largescale average the universe is expanding in a nearly homogeneous way from a dense early state. At present, there are no fundamental challenges to the big bang theory, although there are certainly unresolved issues within the theory itself. Astronomers are not sure, for example, how the galaxies were formed, but there is no reason to think the process did not occur within the framework of the big bang. Indeed, the predictions of the theory have survived all tests to date.

Yet the big bang model goes only so far, and many fundamental mysteries remain. What was the universe like before it was expanding? (No observation we have made allows us to look back beyond the moment at which the expansion began.) What will happen in the distant future, when the last of the stars exhaust the supply of nuclear fuel? No one knows the answers yet.

Our universe may be viewed in many lights—by mystics, theologians, philosophers or scientists. In science we adopt the plodding route: we accept only what is tested by experiment or observation. Albert Einstein gave us the now well-tested and accepted Theory of General Relativity, which establishes the relations between mass, energy, space and time. Einstein showed that a homogeneous distribution of matter in space fits nicely with his theory. He assumed without discussion that the universe is static, unchanging in the large-scale average [see “How Cosmology Became a Science,” by Stephen G. Brush; SCIENTIFIC AMERICAN, August 1992].

In 1922 the Russian theorist Alexander A. Friedmann realized that Einstein’s universe is unstable; the slightest perturbation would cause it to expand or contract. At that time, Vesto M. Slipher of Lowell Observatory was collecting the first evidence that galaxies are actually moving apart. Then, in 1929, the eminent astronomer Edwin P. Hubble showed that the rate a galaxy is moving away from us is roughly proportional to its distance from us.

MULTIPLE IMAGES of a distant quasar ( left ) are the result of an effect known as gravitational lensing. The effect occurs when light from a distant object is bent by the gravitational field of an intervening galaxy. In this case, the galaxy, which is visible in the center, produces four images of the quasar. The photograph was produced using the Hubble telescope.

The existence of an expanding universe implies that the cosmos has evolved from a dense concentration of matter into the present broadly spread distribution of galaxies. Fred Hoyle, an English cosmologist, was the first to call this process the big bang. Hoyle intended to disparage the theory, but the name was so catchy it gained popularity. It is somewhat misleading, however, to describe the expansion as some type of explosion of matter away from some particular point in space.

That is not the picture at all: in Einstein’s universe the concept of space and the distribution of matter are intimately linked; the observed expansion of the system of galaxies reveals the unfolding of space itself. An essential feature of the theory is that the average density in space declines as the universe expands; the distribution of matter forms no observable edge. In an explosion the fastest particles move out into empty space, but in the big bang cosmology, particles uniformly fill all space. The expansion of the universe has had little influence on the size of galaxies or even clusters of galaxies that are bound by gravity; space is simply opening up between them. In this sense, the expansion is similar to a rising loaf of raisin bread. The dough is analogous to space, and the raisins, to clusters of galaxies. As the dough expands, the raisins move apart. Moreover, the speed with which any two raisins move apart is directly and positively related to the amount of dough separating them.

The evidence for the expansion of the universe has been accumulating for some 60 years. The first important clue is the redshift. A galaxy emits or absorbs some wavelengths of light more strongly than others. If the galaxy is moving away from us, these emission and absorption features are shifted to longer wavelengths—that is, they become redder as the recession velocity increases. This phenomenon is known as the redshift.

Hubble’s measurements indicated that the redshift of a distant galaxy is greater than that of one closer to the earth. This relation, now known as Hubble’s law, is just what one would expect in a uniformly expanding universe. Hubble’s law says the recession velocity of a galaxy is equal to its distance multiplied by a quantity called Hubble’s constant. The redshift effect in nearby galaxies is relatively subtle, requiring good instrumentation to detect it. In contrast, the redshift of very distant objects—radio galaxies and quasars—is an awesome phenomenon; some appear to be moving away at greater than 90 percent of the speed of light.

Hubble contributed to another crucial part of the picture. He counted the number of visible galaxies in different directions in the sky and found that they appear to be rather uniformly distributed. The value of Hubble’s constant seemed to be the same in all directions, a necessary consequence of uniform expansion. Modern surveys confirm the fundamental tenet that the universe is homogeneous on large scales. Although maps of the distribution of the nearby galaxies display clumpiness, deeper surveys reveal considerable uniformity.

The Milky Way, for instance, resides in a knot of two dozen galaxies; these in turn are part of a complex of galaxies that protrudes from the so-called local supercluster. The hierarchy of clustering has been traced up to dimensions of about 500 million light-years. The fluctuations in the average density of matter diminish as the scale of the structure being investigated increases. In maps that cover distances that reach close to the observable limit, the average density of matter changes by less than a tenth of a percent.

To test Hubble’s law, astronomers need to measure distances to galaxies. One method for gauging distance is to observe the apparent brightness of a galaxy. If one galaxy is four times fainter in the night sky than an otherwise comparable galaxy, then it can be estimated to be twice as far away. This expectation has now been tested over the whole of the visible range of distances.

HOMOGENEOUS DISTRIBUTION of galaxies is apparent in a map that includes objects from 300 to 1,000 million light-years away. The only inhomogeneity, a gap near the center line, occurs because part of the sky is obscured by the Milky Way. Michael Strauss of the Institute for Advanced Study in Princeton, N.J., created the map using data from NASA’s Infrared Astronomical Satellite .

Some critics of the theory have pointed out that a galaxy that appears to be smaller and fainter might not actually be more distant. Fortunately, there is a direct indication that objects whose redshifts are larger really are more distant. The evidence comes from observations of an effect known as gravitational lensing. An object as massive and compact as a galaxy can act as a crude lens, producing a distorted, magnified image (or even many images) of any background radiation source that lies behind it. Such an object does so by bending the paths of light rays and other electromagnetic radiation. So if a galaxy sits in the line of sight between the earth and some distant object, it will bend the light rays from the object so that they are observable [see “Gravitational Lenses,” by Edwin L. Turner; SCIENTIFIC AMERICAN, July 1988]. During the past decade, astronomers have discovered more than a dozen gravitational lenses. The object behind the lens is always found to have a higher redshift than the lens itself, confirming the qualitative prediction of Hubble’s law.

Hubble’s law has great significance not only because it describes the expansion of the universe but also because it can be used to calculate the age of the cosmos. To be precise, the time elapsed since the big bang is a function of the present value of Hubble’s constant and its rate of change. Astronomers have determined the approximate rate of the expansion, but no one has yet been able to measure the second value precisely.

Still, one can estimate this quantity from knowledge of the universe’s average density. One expects that because gravity exerts a force that opposes expansion, galaxies would tend to move apart more slowly now than they did in the past. The rate of change in expansion is therefore related to the gravitational pull of the universe set by its average density. If the density is that of just the visible material in and around galaxies, the age of the universe probably lies between 12 and 20 billion years. (The range allows for the uncertainty in the rate of expansion.)

Yet many researchers believe the density is greater than this minimum value. So-called dark matter would make up the difference. A strongly defended argument holds that the universe is just dense enough that in the remote future the expansion will slow almost to zero. Under this assumption, the age of the universe decreases to the range of seven to 13 billion years.

DENSITY of neutrons and protons in the universe determined the abundances of certain elements. For a higher density universe, the computed helium abundance is little different, and the computed abundance of deuterium is considerably lower. The shaded region is consistent with the observations, ranging from an abundance of 24 percent for helium to one part in 1010 for the lithium isotope. This quantitative agreement is a prime success of the big bang cosmology.

To improve these estimates, many astronomers are involved in intensive research to measure both the distances to galaxies and the density of the universe. Estimates of the expansion time provide an important test for the big bang model of the universe. If the theory is correct, everything in the visible universe should be younger than the expansion time computed from Hubble’s law.

These two timescales do appear to be in at least rough concordance. For example, the oldest stars in the disk of the Milky Way galaxy are about nine billion years old—an estimate derived from the rate of cooling of white dwarf stars. The stars in the halo of the Milky Way are somewhat older, about 15 billion years—a value derived from the rate of nuclear fuel consumption in the cores of these stars. The ages of the oldest known chemical elements are also approximately 15 billion years—a number that comes from radioactive dating techniques. Workers in laboratories have derived these age estimates from atomic and nuclear physics. It is noteworthy that their results agree, at least approximately, with the age that astronomers have derived by measuring cosmic expansion.

Another theory, the steady state theory, also succeeds in accounting for the expansion and homogeneity of the universe. In 1946 three physicists in England—Hoyle, Hermann Bondi and Thomas Gold—proposed such a cosmology. In their theory the universe is forever expanding, and matter is created spontaneously to fill the voids. As this material accumulates, they suggested, it forms new stars to replace the old. This steady state hypothesis predicts that ensembles of galaxies close to us should look statistically the same as those far away. The big bang cosmology makes a different prediction: if galaxies were all formed long ago, distant galaxies should look younger than those nearby because light from them requires a longer time to reach us. Such galaxies should contain more shortlived stars and more gas out of which future generations of stars will form.

The test is simple conceptually, but it took decades for astronomers to develop detectors sensitive enough to study distant galaxies in detail. When astronomers examine nearby galaxies that are powerful emitters of radio wavelengths, they see, at optical wavelengths, relatively round systems of stars. Distant radio galaxies, on the other hand, appear to have elongated and sometimes irregular structures. Moreover, in most distant radio galaxies, unlike the ones nearby, the distribution of light tends to be aligned with the pattern of the radio emission.

Likewise, when astronomers study the population of massive, dense clusters of galaxies, they find differences between those that are close and those far away. Distant clusters contain bluish galaxies that show evidence of ongoing star formation. Similar clusters that are nearby contain reddish galaxies in which active star formation ceased long ago. Observations made with the Hubble Space Telescope confirm that at least some of the enhanced star formation in these younger clusters may be the result of collisions between their member galaxies, a process that is much rarer in the present epoch.

DISTANT GALAXIES differ greatly from those nearby—an observation that shows that galaxies evolved from earlier, more irregular forms. Among galaxies that are bright at both optical ( blue ) and radio ( red ) wavelengths, the nearby galaxies tend to have smooth elliptical shapes at optical wavelengths and very elongated radio images. As redshift, and therefore distance, increases, galaxies have more irregular elongated forms that appear aligned at optical and radio wavelengths. The galaxy at the far right is seen as it was at 10 percent of the present age of the universe. The images were assembled by Pat McCarthy of the Carnegie Institute.

So if galaxies are all moving away from one another and are evolving from earlier forms, it seems logical that they were once crowded together in some dense sea of matter and energy. Indeed, in 1927, before much was known about distant galaxies, a Belgian cosmologist and priest, Georges Lemaître, proposed that the expansion of the universe might be traced to an exceedingly dense state he called the primeval “super-atom.” It might even be possible, he thought, to detect remnant radiation from the primeval atom. But what would this radiation signature look like?

When the universe was very young and hot, radiation could not travel very far without being absorbed and emitted by some particle. This continuous exchange of energy maintained a state of thermal equilibrium; any particular region was unlikely to be much hotter or cooler than the average. When matter and energy settle to such a state, the result is a so-called thermal spectrum, where the intensity of radiation at each wavelength is a definite function of the temperature. Hence, radiation originating in the hot big bang is recognizable by its spectrum.

In fact, this thermal cosmic background radiation has been detected. While working on the development of radar in the 1940s, Robert H. Dicke, then at the Massachusetts Institute of Technology, invented the microwave radiometer—a device capable of detecting low levels of radiation. In the 1960s Bell Laboratories used a radiometer in a telescope that would track the early communications satellites Echo-1 and Telstar. The engineer who built this instrument found that it was detecting unexpected radiation. Arno A. Penzias and Robert W. Wilson identified the signal as the cosmic background radiation. It is interesting that Penzias and Wilson were led to this idea by the news that Dicke had suggested that one ought to use a radiometer to search for the cosmic background.

Astronomers have studied this radiation in great detail using the Cosmic Background Explorer (COBE) satellite and a number of rocket-launched, balloon-borne and ground-based experiments. The cosmic background radiation has two distinctive properties. First, it is nearly the same in all directions. (As George F. Smoot of Lawrence Berkeley Laboratory and his team discovered in 1992, the variation is just one part per 100,000.) The interpretation is that the radiation uniformly fills space, as predicted in the big bang cosmology. Second, the spectrum is very close to that of an object in thermal equilibrium at 2.726 kelvins above absolute zero. To be sure, the cosmic background radiation was produced when the universe was far hotter than 2.726 degrees, yet researchers anticipated correctly that the apparent temperature of the radiation would be low. In the 1930s Richard C. Tolman of the California Institute of Technology showed that the temperature of the cosmic background would diminish because of the universe’s expansion.

The cosmic background radiation provides direct evidence that the universe did expand from a dense, hot state, for this is the condition needed to produce the radiation. In the dense, hot early universe thermonuclear reactions produced elements heavier than hydrogen, including deuterium, helium and lithium. It is striking that the computed mix of the light elements agrees with the observed abundances. That is, all evidence indicates that the light elements were produced in the hot, young universe, whereas the heavier elements appeared later, as products of the thermonuclear reactions that power stars.

The theory for the origin of the light elements emerged from the burst of research that followed the end of World War II. George Gamow and graduate student Ralph A. Alpher of George Washington University and Robert Herman of the Johns Hopkins University Applied Physics Laboratory and others used nuclear physics data from the war e›ort to predict what kind of nuclear processes might have occurred in the early universe and what elements might have been produced. Alpher and Herman also realized that a remnant of the original expansion would still be detectable in the existing universe.

Despite the fact that significant details of this pioneering work were in error, it forged a link between nuclear physics and cosmology. The workers demonstrated that the early universe could be viewed as a type of thermonuclear reactor. As a result, physicists have now precisely calculated the abundances of light elements produced in the big bang and how those quantities have changed because of subsequent events in the interstellar medium and nuclear processes in stars.

Our grasp of the conditions that prevailed in the early universe does not translate into a full understanding of how galaxies formed. Nevertheless, we do have quite a few pieces of the puzzle. Gravity causes the growth of density fluctuations in the distribution of matter, because it more strongly slows the expansion of denser regions, making them grow still denser. This process is observed in the growth of nearby clusters of galaxies, and the galaxies themselves were probably assembled by the same process on a smaller scale.

The growth of structure in the early universe was prevented by radiation pressure, but that changed when the universe had expanded to about 0.1 percent of its present size. At that point, the temperature was about 3,000 kelvins, cool enough to allow the ions and electrons to combine to form neutral hydrogen and helium. The neutral matter was able to slip through the radiation and to form gas clouds that could collapse to star clusters. Observations show that by the time the universe was one fifth its present size, matter had gathered into gas clouds large enough to be called young galaxies.

A pressing challenge now is to reconcile the apparent uniformity of the early universe with the lumpy distribution of galaxies in the present universe. Astronomers know that the density of the early universe did not vary by much, because they observe only slight irregularities in the cosmic background radiation. So far it has been easy to develop theories that are consistent with the available measurements, but more critical tests are in progress. In particular, different theories for galaxy formation predict quite different fluctuations in the cosmic background radiation on angular scales less than about one degree. Measurements of such tiny fluctuations have not yet been done, but they might be accomplished in the generation of experiments now under way. It will be exciting to learn whether any of the theories of galaxy formation now under consideration survive these tests.

The present-day universe has provided ample opportunity for the development of life as we know it—there are some 100 billion billion stars similar to the sun in the part of the universe we can observe. The big bang cosmology implies, however, that life is possible only for a bounded span of time: the universe was too hot in the distant past, and it has limited resources for the future. Most galaxies are still producing new stars, but many others have already exhausted their supply of gas. Thirty billion years from now, galaxies will be much darker and filled with dead or dying stars, so there will be far fewer planets capable of supporting life as it now exists.

The universe may expand forever, in which case all the galaxies and stars will eventually grow dark and cold. The alternative to this big chill is a big crunch. If the mass of the universe is large enough, gravity will eventually reverse the expansion, and all matter and energy will be reunited. During the next decade, as researchers improve techniques for measuring the mass of the universe, we may learn whether the present expansion is headed toward a big chill or a big crunch.

In the near future, we expect new experiments to provide a better understanding of the big bang. As we improve measurements of the expansion rate and the ages of stars, we may be able to confirm that the stars are indeed younger than the expanding universe. The larger telescopes recently completed or under construction may allow us to see how the mass of the universe affects the curvature of spacetime, which in turn influences our observations of distant galaxies.

We will also continue to study issues that the big bang cosmology does not address. We do not know why there was a big bang or what may have existed before. We do not know whether our universe has siblings—other expanding regions well removed from what we can observe. We do not understand why the fundamental constants of nature have the values they do. Advances in particle physics suggest some interesting ways these questions might be answered; the challenge is to find experimental tests of the ideas.

In following the debate on such matters of cosmology, one should bear in mind that all physical theories are approximations of reality that can fail if pushed too far. Physical science advances by incorporating earlier theories that are experimentally supported into larger, more encompassing frameworks. The big bang theory is supported by a wealth of evidence: it explains the cosmic background radiation, the abundances of light elements and the Hubble expansion. Thus, any new cosmology surely will include the big bang picture. Whatever developments the coming decades may bring, cosmology has moved from a branch of philosophy to a physical science where hypotheses meet the test of observation and experiment.

The Origins of the Solar System Essay

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Introduction

The nebular hypothesis, origin of the molecular cloud, runaway star hypothesis, formation of the sun and planets, creation of the earth, formation of the oceans: comet/proto-planet impact theory, reference list.

The origin of the Sun and its orbiting planets has been a point of hypothesis and conjecture ever since man looked upon the stars and planets and wondered about their origins. For the ancient Greek and Roman civilization the celestial bodies they observed in the sky were thought of as Gods and Goddesses, looking down up the Earth from some form of godlike platform. Today, it is an established fact that the heavenly bodies we see in the night sky are composed of planets and stars, celestial bodies of rock, gas and varying forms of elements that were formed billions of years ago. Even though such objects have been observed for hundreds of years it is only within the last 200 that humanity has begun to understand their unique qualities. While there have been conjectures, varying hypothesis and age old established theories what must be understood is that as the science of astronomy evolves humanity begins to slowly adapt to new information, new discoveries and subsequent re-evaluations of what we knew of as fact. For example, early studies of astronomy adopted the geocentric model in that they believed that the sun, planets, moon and stars revolved around the Earth, not only that there was also the belief that the Earth was in fact flat (Copernicus, 2009: 83). It is based on this that when examining the established theories on the origins of the solar system one must do so with both an open yet skeptical mind, taking into account the given data and observations yet not clearly adhering to any one theory as being definitive proof.

Another interesting topic that should be taken note of is the origin of the Earth itself for just as there have been numerous theories as to the origin of the solar system there have been a plethora of theories which have attempted to determine the origin of the Earth itself. Our home planet is unique in that it is the only planet within our solar system that has sufficiently developed to be able to support life. While there have been varying accounts of how life came to be on Earth, with religion and science vying for attention, the fact remains that the uniqueness of our planet should not be underestimated and as such bodes a certain degree of curiosity as to the origins of the unique circumstances that enabled Earth to become what it is today. It is based on the various questions presented that this paper will explore the origins of the solar system and of Earth itself in order to attain a clear picture of where it came from and what its possible end could be.

Currently, one of the most widely accepted theories regarding the formation of the solar system is that of the nebular hypothesis which states that the solar system originated from a molecular cloud wherein through the introduction of an external force caused a gravitational collapse of the fragment resulting in the creation of A pre-solar nebula that would eventually become our solar system (Glassmeier, 2006: 1 – 5). While there has been no definitive evidence as to the exact origin of the external force that caused a section of the molecular cloud to collapse rather than dispersing it into space it is theorized that the energy from a nearby supernova produced sufficient enough force to cause the collapse and help trigger the necessary events needed to create the solar system. While few studies dispute the nebular hypothesis several do call into question the theory that a supernova caused the initial collapse. Studies such as those by Woolfson (2010) state that the energies from a supernova instead of causing a section of the molecular cloud to collapse would have actually dispersed a majority of the cloud into space thus preventing the formation of the solar system (Woolfson, 2000: 1 – 15). Furthermore, while the nebular hypothesis has been well established as a guiding concept in understanding the creation of celestial bodies little is known as to the precise origins of the molecular cloud that gave birth to the solar system itself. Several scientists such as Lognonne et al. (2007) state that origin of the Sun and its surrounding planets was a molecular cloud and go to great lengths explaining how it led to the creation of the solar system yet a lot of studies neglect to mention how the molecular cloud came to be in the first place (Lognonne et al., 2007: 1 -3)

While this paper has so far expounded on the nebular theory involving the Solar system’s origins as coming from a giant molecular cloud a rather interesting question comes to mind, “if the origin of the solar system is that of a giant molecular cloud where did the molecular cloud come from?”. Studies such as those by Sorrell (2008) explain that while our own sun is 4.5 billion years old the age of the universe itself has been estimated at roughly 13.75 billion years (estimate subject to change due to varying accounts as to the proper calculation) (Sorrell, 2008: 45 – 49). Furthermore it must be noted that our sun is not the oldest sun in the universe let alone in our galaxy and in fact can be considered in the prime of its “youth” as a main sequence star (Naylor, 2009: 432). It has been theorized by researchers such as Freire (2008) that a few billion years after the Big Bang, Super Massive stars, many times the temperature of our current sun and several times its size, were among the first stars to form within the universe (Freire, 2008: 459-460). These celestial bodies were able to grow to such great size due to less “competition” for available materials in order to coalesce into stars; it must be noted though that at this point in time planets were unable to form due to the lack of heavier elements in which a sufficient enough solid mass could coalesce into a planet (Dessart, 2010: 2113-2125).

Rather interestingly, it was actually due to the inherent instability of Super Massive stars that the universe became what it is today; this is due to the theory that as a direct result of their internal instability most of the original Super Massive stars became supernovas which actually caused the original molecular clouds in the universe to form (Dessart et al., 2010: 2120 – 2125). The original state of the universe was actually more “pure” in the sense that there was a distinct lack of heavier elements, as such the question of “where did the heavier elements come from?” comes to mind. This is actually resolved by looking at the activity of our own sun wherein through a process called stellar nucleosynthesis in which the nuclear reactions within the sun itself is able to help build the nuclei of elements that are heavier than hydrogen (Chiosi, 2010).

In relation to the explanation of the origins of the molecular cloud as coming from the debris from Super Massive stars Courtland (2010) presents a new theory that details exactly how the molecular cloud that spawned the solar system came to be. In her study which involved the examination of various meteorites she discovered that sealed within the rock were calcium-aluminum rich incisions (Al-26) that could only have been formed by stars that were at least 10 times as massive as the sun (Courtland, 2010: 8). Due to the fact that Super Massive stars usually form within clusters with Al 26 usually decaying rapidly due to the intense heat within such clusters it is hypothesized by Courtland (2010) that a run away must have been tossed out of its orbit as a direct result of either an explosion of a nearby Super Massive star or due to combined gravitational push by its sibling stars within the cluster (Courtland, 2010: 8). Due to Super Massive stars having a relatively short life cycle when the star became a supernova the dispersed molecules and elements became the molecular cloud that we know of today as being the primary basis of the nebular hypothesis.

Creation of the Sun

Since this paper has now established the various theories which attempt to explain the origins of the molecular cloud that brought about the creation of the solar it is now necessary to explain the current prevailing theory on how the planets and the creation of the sun came about. As mentioned earlier, in the section detailing the nebular theory, it was explained that as a direct result of a gravitational collapse of a section of the molecular cloud this precipitated the creation of the solar system (Boeyens, 2009: 493-499). A better explanation of this would be that as section of the nebula collapsed this produced a certain degree of angular momentum wherein the nebula actually began to spin faster as it collapsed in on itself. This spinning combined within the collapse produced a great deal of kinetic energy within the core of the molecular cloud until the result was a contraction of the center of the molecular cloud, which had now become a disc shaped object, into what is known as a proto-star, namely a star that has yet to have hydrogen fusion occur at its core (Boeyens, 2009: 493-499). Within 50 million years the internal temperature and pressure of the core itself was able to build to sufficient levels resulting in the start of hydrogen fusion marking the entry of the sun into its life as a main sequence star (Boeyens, 2009: 493-499)

Theory of Accretion

The theory of accretion is currently the most widely accepted theory proposing the creation of the planets, in it the theory indicates that the leftover material from the sun’s creation continued to spin around the sun slowly clumping together piece by piece until larger dust shaped particles were created (Ogihara et al., 2007: 522-530). Gradually these dust particles also began clumping together resulting in the creation of larger and larger objects until finally the entire solar system was composed of literally dozens of moon sized objects that crashed into each over a period of several million years (Ogihara et al., 2007: 522-530). It must be noted that the reason why such a process didn’t just create a system of bits and pieces of rock is due to the fact that these moon sized objects actually had viscous outer cores in the sense that their composition was similar to lava due to the high temperatures of the sun at the time and the process of accretion itself. As such when the objects collided what resulted was not a titanic clash that mutually shattered the objects but rather a process where both objects combined to form a larger structure or surfaces were “swapped” in the sense that certain parts of either proto-planet’s surface accreted to the colliding object (Ogihara et al., 2007: 522-530).

Originally the Earth was a proto-planet no bigger than the moon yet over several million years the process of accretion was able to slowly build up the Earth to its present shape. It must be noted though that the early outer core of the planet was fluid in that due to the intense heat present at the time metals that had accumulated on the planet’s surface slowly submerged into the inner core creating the metallic core that is present today (Robin, 2008: 4061 -4075). Within 150 million years of the planet reaching its current mass the surface sufficiently cooled resulting in the creation of a primitive crust, yet unlike today the surface of the Earth is estimated by studies as being roughly 1600 degrees Celsius with numerous volcanoes dotting the landscape releasing gases into the atmosphere which formed the initial atmosphere of the planet which was kept in place by Earth’s inherent gravity (Robin, 2008: 4061 -4075).

Most scientists agree that the presence of water on the Earth was the pivotal necessity necessary in order for life to start on the planet. When examining the process of Earth’s creation though there seems to be few indicators of water actually forming directly from the process of creation or within the Earth itself (Robin, 2008: 4061 -4075). One theory that attempts to explain this is the comet/proto-planet impact theory which states that proto-planets, planetoids and comets that were composed of ice were actually prevalent in the inner system during the later stages of the process of accretion. (Robin, 2008: 4061 -4075) As such as the Earth continued to orbit around the sun it supposedly impact millions of comets along with several icy proto-planets to create the water that can be seen in the oceans today. In fact, 4.4 billion years after the creation of the sun the Earth had actually sufficiently cooled enough to actually create clouds, rain, and the even oceans on the planets surface (Robin, 2008: 4061 -4075). This particular period marks the creation of the atmosphere that is present in the world today which is a combination of oxygen, carbon dioxide and other gases.

By the end of this paper it has become apparent that the process of creation of our solar system and even of our planet has been an accumulation of fortunate incidents that culminated in humanity evolving into its present state. When examining the theories explaining the creation of the molecular cloud, how Courtland (2010) presented the notion that the molecular cloud our present system came from originated from a rogue Super Massive star that coincidentally was shot out of its group by gravitational forces, that it was able to travel far enough to an area ideal enough for uninterrupted growth, that the creation of our planet was in the right place, at the right time with readily available water literally crashing into the planet in order to support life; a combination of all of these completely coincidental factors almost leads one to believe that the creation of humanity itself was no accident but on purpose. On the other hand there are quite literally billions upon billions of solar systems within the universe and it might actually be the case that the process that created the Earth is not so coincidental and that somewhere out there life similarly exists on thousands of planetary systems with the exact same composition as that of humanity yet far away enough that we cannot see the similarities at the present.

Boeyens, JA 2009, ‘Commensurability in the solar system’, Physics Essays , 22, 4, pp. 493-499, Academic Search Premier.

‘Copernicus’ 2009, American Heritage Student Science Dictionary , p. 83, Science Reference Center.

Courtland, R 2010, ‘Runaway star may have spawned the solar system’, New Scientist , 205, 2754, p. 8, Academic Search Premier.

Chiosi, C 2010, ‘Primordial and Stellar Nucleosynthesis Chemical Evolution of Galaxies’, AIP Conference Proceedings , 1213, 1, pp. 42-63, Academic Search Premier.

Dessart, L, Livne, E, & Waldman, R 2010, ‘Shock-heating of stellar envelopes: a possible common mechanism at the origin of explosions and eruptions in massive stars’, Monthly Notices of the Royal Astronomical Society , 405, 4, pp. 2113-2131, Academic Search Premier.

Fazekas, A, (2010), Hubble telescope catches superfast runaway star . Web.

Freire, PC 2008, ‘Super-Massive Neutron Stars’, AIP Conference Proceedings , 983, 1, pp. 459-463, Academic Search Premier.

Glassmeier, K, Boehnhardt, H, Koschny, D, Kührt, E, & Richter, I 2006, ‘The Rosetta Mission: Flying Towards the Origin of the Solar System’, Space Science Reviews , 128, 1-4, pp. 1-21, Academic Search Premier.

Lognonne, P, Des Marais, D, Raulin, F, & Fishbaugh, K 2007, ‘Epilogue: The Origins of Life in the Solar System and Future Exploration’, Space Science Reviews , 129, 1-3, pp. 301-304, Academic Search Premier.

McFadden, L, Weissman, P, & Johnson, T 2007, Encyclopedia of the Solar System , Elsevier LTD., eBook Collection. Web.

National Astronomical Observatory of Japan. (N.I.). Hd 141569a’s disk . Web.

Naylor, T 2009, ‘Are pre-main-sequence stars older than we thought?’, Monthly Notices of the Royal Astronomical Society , 399, 1, pp. 432-442, Academic Search Premier.

N.I.. (2010). The Creation of the Earth. Web.

Ogihara, M, Ida, S, & Morbidelli, A 2007, ‘Accretion of terrestrial planets from oligarchs in a turbulent disk’, ICARUS , 188, 2, pp. 522-534, Academic Search Premier.

Photo Journal. (2007). Pia09967: water’s early journey in a solar system (artist concept) . Web.

Robin M., C 2008, ‘Accretion of the Earth’, Philosophical Transactions of the Royal Society A: Mathematical, Physical & Engineering Sciences , 366, 1883, pp. 4061-4075, Academic Search Premier.

Sorrell, WH 2008, ‘The cosmic age crisis and the Hubble constant in a non-expanding universe’, Astrophysics & Space Science , 317, 1/2, pp. 45-58, Academic Search Premier.

Woolfson, M 2000, ‘The origin and evolution of the solar system’, Astronomy & Geophysics , 41, 1, pp. 1.12-1.19, Academic Search Premier.

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Universe - Free Essay Examples and Topic Ideas

The universe is a vast expanse of space that encompasses all the matter and energy that exists. It includes everything from galaxies to stars, planets to asteroids, and even the tiniest particles that make up matter. The universe is estimated to be around 13.8 billion years old and is constantly expanding. It is home to countless mysteries and wonders, from black holes and supernovae to galaxies far beyond our own. Despite its incredible size, the universe remains a source of fascination and curiosity for scientists and people around the world.

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Here is an essay on ‘ Our Universe’ for class 6, 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Our Universe’ especially written for school and college students.

Essay on Our Universe

Our Universe contains 176 billion (one billion = 100 crores) constellations (group of stars) and each constellation includes hundreds of billion stars. Universe consists, constellation, in which Sun exists, is so big that from the core of constellation, light takes around 27 thousand years to reach up to sun. The solar system which is part of Milky Way galaxy is in disc-shaped spiral form.

Essay # 1. Sun:

Sun rotates round its axis from West to East. About 99.85% mass of solar system lies with sun only whereas planets constitute – 0.135%, comets – 0.01%, satellites – 0.00005%, dwarf planets – 0.000002%, shooting stars – 0.0000001% and inter planetary medium consists of 0.0000001% of the rest of mass.

Sun is not stationery and completes one rotation round its own axis in 25 days. One rotation of sun takes 25 days (of Earth) if observed from the equator while if we observe it from its poles, each rotation of sun takes 36 days. The rotation of sun was observed by Galileo first of all.

Sun is source of light, heat, energy and life on our Earth. Normally looking pale, this spherical ball of fire has 13 lakh multiples more volume than that of Earth and 3.25 lakh times more weight. Pressure of gaseous material on its centre is 200 billion multiples more than the pressure of air, Earth experiences while density of gases is 150 times more than that of water. Temperature of sun is 50 lakh degrees Kelvin (one Kelvin is equal to one degree on Celsius scale).

Hydrogen in form of Plasma turns into Helium at this temperature. This fusion gives birth to energy. The quantum of such produced energy may be imagined from the fact that fusion produced energy in one second is more than as much mankind has used on Earth till date. This fusion is continuous process on the surface of Sun.

Gravity of Sun is 28 times more than that of earth and black spots visible on sun are actually very powerful magnetic regions. Each magnetic regions of sun is more than 10 thousand times more powerful than magnetic power of Earth. Actual size of each black spot may be lakhs of square kilometers. Temperature at photosphere of sun is only 6000° Kelvin while ends of chromospheres experience it 10 thousand degree.

At corona this temperature varies from 10 lakh Kelvin to 50 lakh Kelvin. Continuous winds blow at the surface of sun at speed of 800 to 900 kilometer per second and these may prove dangerous for Earth at times. These winds have their fatal effect on Ionosphere. Solar storms disturb communication system on Earth. Many a times, power grids get destroyed or seized because of disturbance at the surface of Sun.

Optical telescope at Udaipur and Kodyekanal along with Radio telescope at Pune keep continuous watch over happenings related to Sun.

Essay # 2. Planets:

Planet is a Greek word which means, Wanderer. All the planets are spherical and are total eight in number.

We can group these planets in two, that is:­

a. Inner Planets:

Inner planets are those planets which are nearer to sun as compared to others. Secondly their relief constitution includes rocks and metals. These planets are known as terrestrial planets also. Namely these planets are; Mercury, Venus, Earth & Mars.

b. Outer Planets:

Outer planets are beyond asteroids and are constituted of gases, popularly known as Gas Giants. These are; Jupiter, Saturn, Uranus and Neptune.

The planets do not have any light of their own but these illuminate by reflecting sunlight and are visible at night. In the sequence of their distance from sun, these may be retented from initial alphabets of words in this sentence; My Very Efficient Mother Just Served Us Nuts.

i. Mercury:

This planet is not only smallest one but also lies closest to Sun. It does not have atmosphere of its own and is engulfed by blasts taking place because of Sun. Its core is made of iron and has this part larger than crust.

It is presumed that this crust reduced due to some comet accident. Mercury lies some 579 million (57crore 90 lakh) kilometer away from Sun and its average temperature varies between 420°C during day to -180°C at night.

It completes its revolution around Sun in 88 days while takes 58 days and 16 hours to complete its one rotation on its axis. Galileo founded Mercury in 1631 which has no satellite.

This is a rocky celestial body like Earth and second planet if counted serial vise from Sun. It completes its revolution round sun is 224.7 days while takes 243 long days to complete its rotation round its own axis from East to West.

All the other planets rotate around their axis from West to East. This hottest planet is second most glittering celestial body, first being the Moon. Also known as sister planet of Earth, Venus resembles to it in shape, size and gravity.

It has a number of volcanoes just like Earth and its surface has been formed because of volcanic eruptions. Its atmosphere consists of Carbon dioxide (96.5%) and Nitrogen. That is why it is called ‘Veiled planet’ also. Venus lies nearly 1082 million kilometers away from Sun.

iii. Earth:

Our mother planet’s name has not been derived from Greek or Roman language but from old English and Germanic. According to International Astronomical Union (IAU) biggest among Inner planets, Earth is only planet which has Geological activity taking place in its core.

Its atmosphere is also quite different to that of other planets as it consists of 77% Nitrogen and 21% Oxygen which gives it a name of ‘blue planet’. Earth is only planet where life exists. Situated nearly 14.96 crore kilometers away from sun.

The earth completes a rotation round its axis in 23 hours, 56 minutes and 4.09 seconds (approximately 24 hours) while to revolve around the sun, it takes 365 days 5 hours and 48 minutes. It has a satellite named Moon.

Known as the Red Planet, Mars is fourth planet of our solar system as counted from Sun. Its soil has very rich iron content and because of Ferrus content it looks red. As far its rotation on axis is concerned, it has similarity with Earth and it supports various seasons also.

Mars is a cold planet which has thin atmosphere. Its one rotation on its axis is completed in 24 hours, 37 minutes and 23 seconds while its revolution against sun takes 687 days. Having two satellites, Mars is placed around 2279 lakh kilometer away from sun.

The success of India to plant its Orbiter in orbit of Mars in its just first attempt has made it a pioneer and an exceptional one. Mars is only planet other than Earth which has ice-caps on its poles which have been named as Planum Boreum (North Pole) and Planum Australe (South Pole) or Southern Cap. The spacecraft that reached in the orbit of Mars is named 440 Newton Liquid Apogee Motor (LAM).

v. Jupiter:

First beyond the Asteroids, Jupiter is fifth planet of our solar system and is the biggest planet. This planet is one of the Gas Giants and has 1280 kilometer wide atmosphere composed of gases like Methane, Ammonia, Hydrogen and Helium.

It revolves around the sun in anti-clockwise direction and completes one revolution in 12 years. Its rotation on its axis is very fast and completes one in just 10 hours causing severely blowing winds.

These winds look like multi-coloured cloud belts. Jupiter is tilted on its axis at 3.1° and has more than 60 satellites. Most of the satellites are unknown for mankind as far information about them is concerned.

vi. Saturn:

The sixth from sun and second largest planet in solar system is Saturn. Situated some 1,431 million kilometers (More than 143 crore km) away from Sun, it is constituted of iron and nickel principally. Completing its rotation on its axis in 10 hours and 41 minutes, it makes one revolution around Sun in 29.5 years.

Its swift rotation gives rise to winds at the speed of 1800 kilometers per hour. Speed of winds on Saturn is higher than that on Jupiter but lesser than that on Neptune. There are nine rings around Saturn which from three arcs around it. These rings are made of frozen ice and rocks. It has around 62 satellites and biggest among them is Titan which is almost double the size of Moon. The atmosphere of Titan is thicker than that of Earth.

vii. Uranus:

This is seventh planet of our Solar System and third largest planet. Its size is 63 multiples bigger than earth but in weight it is only 14.5 multiples than that of Earth. Constituted of gases, Uranus has coldest atmosphere as compared to all the planets and has an average temperature of 223°C. Many layers of clouds are found on Uranus.

Higher cloud formation consists of Methane gas while lower formation consists of water. Speed of winds on this planet is 250 meters per second while it is tilted at 97.77° on its axis. Revolving round sun in anti-clockwise direction, it completes one revolution in 84 years while for completing one rotation around its axis, it takes 10 hours and 48 minutes.

viii. Neptune:

Neptune resembles to Uranus as seen in the Solar System. But it is smaller than Uranus and its surface is more condense. Presence of Methane gas makes it look green. Winds blow at speed of 2100 kilometers per hour in the atmosphere of this planet.

The planet consists of around 900 full circles and various incomplete arcs. Situated approximately 4,498 million kilometer away from Sun, it completes one rotation its axis in 16 hours and a revolution around sun in 164.8 years. Neptune has 13 satellites while Triton and Neried are two main satellites.

There are various dwarf planets in our solar system, out of which only five have been recognised.

1. Pluto (Earlier know as ninth planet, was declared dwarf in August, 2006)

4. Make make

Essay # 3. Satellites:

Satellites are of two types, manmade and natural. Satellites are actually celestial objects that revolve around some other celestial object. Natural satellites rotate on their axis also. They neither have atmosphere nor light of their own but due to reflection of sunlight, they look illuminated.

Manmade satellites are made of aluminium or plastic and are hardened with help of carbonic sheets. They travel at the speed which is 10 to 30 multiples more than that of an aircraft. Humankind has been benefitted extremely by manmade satellites in fields of telecommunications, weather forecasting, geological activities and atmospheric activities among other fields. India fired its first satellite named Arya Bhatt in 1975 and since then, we have sent more than 75 satellites into the orbit.

Moon is natural satellite of our Earth. It is around 3,84,403 kilometers away from Earth and takes 27.3 days to complete its revolution around Earth. As yet mankind has touched only this celestial body i.e. Moon on 21st July 1969. Atmosphere of Moon is so thin that it weighs only 104 kilograms and gravity is only one sixth part of the gravity of Earth.

Essay # 4. Asteroids or Planetoids:

These are too smaller than planets of Solar System but bigger than Asteroids. These celestial bodies revolve round the sun in anti-clockwise direction. These rocky bodies are numerous and most of these are concentrated between Mars and Jupiter. Five of them namely Ceres, Pallas, Vesta, Hypiea and Euphrosyne have been recognised. European Space Agency has found water vapour on Ceres on 22nd January, 2014.

Essay # 5. Comets:

The word comet is derived from Latin word ‘Stella Cometa’ which means ‘hairy star’. These celestial bodies were part of sun earlier and are made of frozen gases, ice and small rocky substances. Head of comet is 16 million kilometers in diameter and is followed by cloud of misty substance looking like a tail.

This tail is also lakhs of kilometer long. Tail is never towards sun facing side of comet and shines with rays from Sun. Comet which passed through Solar System was first seen in 1705 and it passes close to sun after every 75.5 years. English scientist Edmond Halley founded it and it was therefore named Halley’s Comet.

Comets are being traced regularly. Their total number was 5,186 in August, 2014. Halley’s Comet was seen in 1910, then in 1986 and next it shall be sighted in 2062. Nucleus of Halley’s Comet is 16 x 8 x 8 kilometers and it is the darkest object in solar system. This comet is periodical one and may be sighted at specific intervals but all the comets are not periodical.

Essay # 6. Meteors or Meteorites:

One can see a streak of star light in the sky sometimes, it gives an impression that any part of star has broken away. These are actually meteorites. Parts of meteorites that remain unburnt and reach our Earth in small parts are named as meteorites.

When these enter the atmosphere of Earth, burn out immediately and vanish in shape of ash most of times. A part of Arizona desert in U.S. is known to have come into form due to striking of some meteor. There are, however, various principles about formation of meteors. Some thinkers part them parts of planet which has vanished while others say these are parts of Sun, Earth and Moon only.

Indian Museum at Kolkata is known for preserving remains of meteors. Biggest such museum in Asia, it has 468 meteor parts. Their study has concluded that meteors are made of metals like iron, nickel, aluminium, oxygen and tin.

These get attracted towards Earth because of gravity of Earth. On April 21, 2013 a meteor shower was observed in many parts of the world in which more than 20 shooting stars were seen within an hour. This shower is known as Orionid Meteor Shower. Such wonderful sights are very common in our solar system.

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Cogitating black holes

The universe cannot always be understood through observation. instead, physicists explore by devising thought experiments.

by Michael Dine   + BIO

Albert Einstein’s theory of gravitation, known as general relativity, is intimidating, even for highly trained theoretical physicists. In his theory, matter and energy cause space-time to curve. In most situations, this warping is so small as to be unobservable, even with powerful and sophisticated instruments. In fact, for many years after Einstein put forth his theory in 1916, there were only three situations in which small corrections to Newton’s classic laws of gravity (the force we feel here on Earth) could be observed: the bending of light by the Sun during a solar eclipse; a small anomaly in the motion of Mercury; and a small shift in the wavelength of light due to gravitation. Since that time, the situation has dramatically changed. General relativity has provided us with a framework for thinking about the Universe as a whole, and plays a role in much of what astronomers understand about stars. It even plays a role in the GPS system that helps us navigate the roads.

Einstein’s equations ultimately revealed a set of previously unknown, ultradense cosmological objects: black holes. The mathematics of Einstein’s equations showed that light starting inside the black hole could get only so far. That distance, known as the Schwarzschild radius, can be thought of as the surface of the black hole; this surface is known as the horizon, beyond which light cannot escape. Near and within the horizon, space and time are modified so violently that it even becomes tricky to figure out what is space and what is time.

No one could see inside this kind of object, but speculations on their nature date to the work of J Robert Oppenheimer (famed for his leadership of the atomic bomb project during the Second World War) and John Wheeler, a Princeton theorist who provided, among other things, the name ‘black hole’.

Over the past half-century, astronomers have found black holes in great numbers around the Universe. Some are the result of stellar collapse, and have masses typically a few times larger than that of our Sun. Much more massive ones exist at the centres of most galaxies, including our own. Smaller black holes are typically ‘seen’ as they swallow matter from companion stars; the large black hole at the centre of our galaxy was discovered through its effects on the motion of stars orbiting about it. We may never be able to literally peer inside a black hole, but knowledge of the cosmos and emerging theories of physics allow us to think through their nature; the modus operandi for this kind of exploration, the thought experiment, has been a cornerstone of physics since Einstein dramatically altered our understanding of space and time.

E instein’s theory that the Universe is curved and time is relative has been subject to direct experimental and observational study for more than a century – but thought experiments played a major role, as well. One of the most famous thought experiments of all time juxtaposed Einstein’s general relativity, which looked at systems as large as the cosmos, with quantum mechanics, also referred to as quantum theory, which resulted from experimental studies of objects on the scale of atoms or smaller.

Prior to the emergence of quantum mechanics, physicists thought of atoms as something like billiard balls. In the pre-quantum or classical view, their motion was governed by Isaac Newton’s laws, which allow a person, given knowledge of the basic forces of nature, to predict the motion of the particles in the future. But quantum mechanics called this viewpoint into question. Instead, it suggested an alternative picture of reality, coded in the Schrödinger equation – which provided the probability, though not the certainty, that an electron would be located at a given spot at a particular point in time. It was the physicist Max Born who made the radical proposal that quantum mechanics predicted probabilities of various outcomes, rather than a single certain result. Critical to his assertion was a set of thought experiments. Born asked what Schrödinger’s equation would predict for the outcome of the collision between two atoms, or an atom and an electron. Newton’s billiard ball outlook holds only when the probability of one particular outcome is far larger than that of any other.

Thought experiments suggested the widely separated elements would still be entangled

The notion deeply troubled Einstein, provoking his complaint in a letter to Born in December 1926: ‘Quantum mechanics is certainly imposing… The theory says a lot, but does not really bring us any closer to the secret of the “old one”. I, at any rate, am convinced that He does not throw dice.’

In 1927, Werner Heisenberg summarised the distinctions between the physics of Newton and that of the Schrödinger equation in his uncertainty principle, which sets limits on what one can measure about a system. The location of a particle, would always be a question of probability, never a sure thing. He arrived at this principle by considering various thought experiments, where he asked how particular measurements might actually be performed. Einstein tried to demolish the quantum theory through sharp critique, continually challenging Niels Bohr , a Danish founder of quantum mechanics and a leader in the effort to interpret the theory with thought experiments similar to those of Born and Heisenberg. At first glance, these seemed to show that quantum theory and its probability interpretation did not make sense. The questions Einstein asked were often tough, but Bohr, sometimes after a prolonged period of thought, invariably found a way to resolve each paradox. One such experiment, known as the EPR paradox (for Einstein and his two assistants, Boris Podolsky and Nathan Rosen), involved the connections between two widely separated parts of a single system. Thought experiments suggested the widely separated elements would still be entangled, with one part of the system invariably providing information about the other. This was eventually turned into a real experiment, proving quantum mechanics correct.

S o what does all this have to do with black holes? A real-world experiment sets the stage.

According to the rules of classical physics, an object with electric charge, like an electron or proton, emits light as it speeds up or slows down. Einstein understood that, in a similar manner, his general relativity would lead to waves of the gravitational field – gravity waves – when mass or other forms of energy sped up or slowed down. These waves, in turn, would push and pull on matter as they passed by. Because the gravitational force is so much weaker than electricity and magnetism, these effects would be minuscule, even when huge amounts of mass are involved.

The first experimental programme with any real hope to detect these tiny gravitational waves began in the 1990s, and was known as LIGO, for Laser Interferometer Gravitational-Wave Observatory.

The programme was based on an outcome of general relativity understood early on by Einstein: when two planets collide, the mass involved would be insufficient to perceptibly impact the shape of space-time. But when two superdense objects like black holes collide, they would distort space-time enough that the effect could be detected. According to Einstein’s theory, these waves, travelling through space from their source, would stretch the space around them, ever so slightly. Objects nearby would appear slightly longer and then slightly shorter, and then slightly longer again. This stretching and shrinking would alert us that the objects had been there at all.

Now, when I say slightly, I mean slightly . The LIGO gravitational-wave detectors are long metal tubes each 4 kilometres long. Waves from colliding black holes stretch and shrink these huge bars by about 10 -18 cm, an amount 10 5 times – 100,000 times – smaller than an atomic nucleus. Put another way, as a fraction of its length, each bar changes by about a trillionth of a trillionth of its length.

Throw in tables, chairs, planets, other stars, and the black hole’s mass increases and its horizon area increases

Only over the past decade has the detector picked up gravitational waves from collisions of neutron stars and black holes. With this discovery, a whole new way to study the Universe has emerged .

Yet these experiments go only so far. Indeed, in a universe governed by quantum mechanics, there are aspects of black holes that are far from clear. Because, in Einstein’s theory, a black hole can’t emit light or transmit information in other ways, they are almost featureless. If you know their mass, their electric charge, and how fast they spin, you know everything you can possibly know about them. They may have arisen from the collapse of a complicated star, surrounded by planets with advanced civilisations, but when they formed, all of that information simply vanished. This is different from a fire or an explosion, where you might hope, with a huge amount of work, to reconstruct all the original information by looking through the ashes and the outgoing light and heat. In the collapse of a black hole, such reconstruction seems impossible.

This new visualisation of a black hole illustrates how its gravity distorts our view, warping its surroundings as if seen in a carnival mirror. The visualisation simulates the appearance of a black hole where infalling matter has collected into a thin, hot structure called an accretion disk. The black hole’s extreme gravity skews light emitted by different regions of the disk, producing the misshapen appearance. Created by NASA Goddard Space Flight Center/Jeremy Schnittman

One physicist who tried to glean more through thought experiment was the late theorist Jacob Bekenstein of the Hebrew University of Jerusalem. He noted an analogy between black holes and the second law of thermodynamics. The second law says that entropy – which is a measure of disorder – always increases. For black holes, there is also a quantity that always increases: the area of the black hole surface, its horizon. Whenever you add something to a black hole – say throwing in tables, chairs, planets, other stars – the mass increases and the area of the horizon increases. Bekenstein proposed a precise relationship between the black hole area and entropy, and suggested that black holes were actually thermodynamic systems with a temperature.

In physics, we think of temperature as a measure of the energy within some set of particles – atoms, molecules, photons. Yet, from the outside, we have no information about the black hole apart from some gross properties such as its mass, and we certainly can’t identify things like particles.

It was Stephen Hawking who, in the early stages of his career, finally discovered the sense in which black holes have a temperature. Hawking had an interest in extreme situations in general relativity, such as the earliest instants after the Big Bang and the interior of black holes. Now thinking about the behaviour of particles such as electrons and photons near the horizon of a black hole – thought experiments again – he realised that black holes are not really black; they radiate particles now known as the ‘Hawking radiation’. This is an intrinsically quantum phenomenon. The uncertainty principle permits brief violations of energy conservation in ordinary space-time. As a result, for an extremely short time, a particle and its antiparticle (in the case of an electron, for example, the antiparticle has the same mass but the opposite electric charge, known as the positron) can appear, even in a complete vacuum, and then annihilate each other and disappear again. For us, there is no observable consequence because energy is conserved.

But Hawking realised that some of these flickering particles could borrow some of the enormous energy of the black hole and become real. If produced near the horizon, one of these virtual particles could fall back into the black hole while the other escapes. Hawking found that the particles were emitted just as they would be from an object with the temperature predicted by Bekenstein. (The radiation from an object with a given temperature is called ‘blackbody radiation’ and has characteristic features; the most dramatic example is the Universe itself, whose temperature is 2.7 degrees Kelvin).

In short, the black hole appears to be a much more complicated object in a quantum world than in a classical one. In the quantum world, there’s a lot going on inside. The black hole in the quantum universe is not static. As it emits particles, it gradually evaporates, eventually disappearing altogether.

For a black hole formed in the collapse of a star a bit more massive than our Sun, the time for the entire object to evaporate is very long – about 10 67 years, far, far longer than the present age of the Universe. But we can contemplate smaller black holes, which might be disappearing today. At the end of their lifetimes, there would be a large burst of energy. Astrophysicists are currently searching for this possibility. But we’d have to be quite lucky to find such a thing and, so far, there is no evidence for black holes of this size.

H awking’s theoretical discovery of the Hawking radiation, possible through thought experiment, was a major accomplishment. It brought general relativity and quantum theory together in a remarkable way. But performing still another thought experiment, Hawking was puzzled by features of this radiation – or more precisely, its lack of features. Critical to Born’s probability interpretation of quantum mechanics was that something always happens. If you add up the probabilities for anything that may happen, you will find that the total probability is one. This can be formulated as a statement about information: if one knows everything one can know about a system at one time, one can know everything about it at later times. But this did not seem to be the case for radiation from black holes.

These ideas may be unfamiliar – indeed they are unclear to many physicists, so it is worth elaborating a bit. The fact that the probability of all outcomes is one is illustrated by a familiar pastime. If you enter your state or national lottery, you focus on your chances of winning. If you buy one ticket and there are 10 million lottery tickets sold, your chances of winning the jackpot are 1 in 10 million. That’s a really minute chance. But I either win or lose the lottery: the chance of winning or losing is 100 per cent.

What does it mean for information to disappear? Of course, we all forget things, lose records of various types, or deliberately shred or burn papers. But we believe that with enough patience and resources, we could reconstruct this information. The amount of information in a system (or the Universe) doesn’t change, though much of it may be hard to access. For a complicated system, like a collapsing star, there is a lot of information – an unimaginably large amount. In classical physics, there would be the positions and velocities of all the nuclei and electrons. In quantum mechanics, there are complicated relations between all of them; one can’t give the probability that one particle is at a point without specifying also the probability of finding all the other particles at particular places as well.

There is a situation where black holes could exist and quantum mechanics could make sense: string theory

So a collapsing star contains a huge amount of information. Thanks to Hawking, we know that, if the star is heavy enough, it forms a black hole and then slowly evaporates, emitting radiation. The vast amount of information that was contained in the initial star has been reduced to just the temperature of a warm body. Hawking, in his 1976 paper , argued that the information was simply lost. Quantum mechanics, he asserted, breaks down near black holes.

Many leading theorists have struggled to resolve the puzzles raised by this thought experiment. Some have argued that, indeed, one has to redo quantum mechanics or general relativity to resolve Hawking’s paradox. Others have been more sceptical of Hawking. Perhaps, for example, the evaporation of a black hole is like a lump of ash from the burning of a log in a fireplace. Surely the laws of quantum mechanics don’t break down when an object burns? In that case, the resolution of the puzzle is that the outgoing radiation is not exactly that of a black body because subtle connections between the outgoing photons remain intact. But it was soon realised that the answer to Hawking’s question about the black hole problem could not be so simple; the structure of space and time makes it hard to understand how such correlations might arise. There were other proposals, none very satisfying. Perhaps Hawking was right: just as Newtonian physics was usurped by quantum mechanics and general relativity on large or tiny scales, something had to give here as well.

It turns out that there is a situation where black holes could exist and quantum mechanics could make sense: string theory. String theory, also emerging from thought experiments, replaces the particles of quantum mechanics with one-dimensional strings. That concept has provided at least a partial resolution of the puzzle. Two theorists at Harvard University – Cumrun Vafa and Andrew Strominger – building on the work of the late Joseph Polchinski, of the University of California at Santa Barbara, were able to understand the temperature of certain idealised black holes in quantum mechanical terms. In other words, the information, at least for these idealised systems, somehow survives, evading Hawking’s paradox.

But while this result settled the question in an abstract way, it left many physicists dissatisfied. Because the calculation is done in a situation that doesn’t much resemble an astrophysical black hole, it is hard to figure out just what went wrong with Hawking’s argument.

There remains something important about the way general relativity works that we don’t yet fully understand. It may be that the rest of the story will be rather mundane, but it seems likely that fully resolving these questions will yield dramatic new insights into the quantum nature of space-time, and might answer some big questions we have about the Universe as we observe it. One of the biggest puzzles in our current understanding of nature is that most of the energy of the Universe – about 70 per cent – exists in a strange form with negative pressure , known as the dark energy . But it is very hard to understand why there is so little of it.

It is conceivable that a thought experiment resolving Hawking’s puzzle might provide some clues. The most radical possibility is that space-time is not the basic arena for the phenomena of nature. A being living in a crystal, for instance, would experience something like space-time, but would have a very different character. Condensed matter physicists would say that space-time is emergent. The basic underlying entity might be something else entirely. Perhaps one day our science and technology will be so advanced that actual experiments will reveal what it is – but, until then, thought experiments involving black holes, among other phenomena, will have to light the way.

Adapted excerpt from the book This Way to the Universe by Michael Dine, published by Dutton, an imprint of Penguin Publishing Group, a division of Penguin Random House LLC. Copyright © 2022 by Michael Dine

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What is the universe made of?

Matter and energy are the two basic components of the entire Universe. An enormous challenge for scientists is that most of the matter in the Universe is invisible and the source of most of the energy is not understood. How can we study the Universe if we can’t see most of it?

As our tools for observation grow more sophisticated, scientists at Center for Astrophysics | Harvard & Smithsonian will continue to be at the forefront of dark matter and dark energy research.

NASA’s Chandra X-ray Observatory and optical telescopes help map the distribution of dark matter in colliding galaxy clusters, like the Bullet Cluster. X-ray observations show a heated shock front where the gas from the clusters collided and slowed down, but gravitational lensing measurements show that dark matter was unaffected by the collision and separate from the normal matter.

It is theorized that when some dark matter particles collide, they annihilate and disappear in a flash of high-energy radiation. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) in Arizona, which can detect gamma-ray radiation, is looking for the signature of dark matter annihilation.

The South Pole Telescope in Antarctica and Chandra are placing limits on dark energy by looking for its effects on galaxy cluster evolution throughout the history of the Universe. By comparing observations of galaxy clusters with experimental models, researchers are studying how dark energy competed with gravity throughout the history of the Universe.

Scientists at CfA have led the Baryon Oscillation Spectroscopic Survey (BOSS), analyzing millions of galaxies and charting their distribution in the Universe. The distribution has been shown to trace sound waves from the early Universe, like ripples in a pond, where some regions have higher numbers of galaxies, and others have less. Looking at these distributions, we can more accurately measure the distance to galaxies and map the effects of dark energy.

On the horizon, the Dark Energy Spectroscopic Instrument (DESI) will create a 3D map of the Universe, containing millions of galaxies out to 10 billion light years. This map will measure dark energy’s effect on the expansion of the Universe. And the Large Synoptic Survey Telescope (LSST) will observe billions of galaxies and discover unprecedented numbers of supernovae, constraining the properties of dark matter and dark energy.

Dark Matter and Dark Energy

Astronomer Fritz Zwicky was the first to notice the discrepancy between the amount of visible matter in a cluster of galaxies and the motions of the galaxies themselves. He suggested that there may be invisible matter, or what he called “dark matter”, interacting gravitationally with the visible matter. Later, astronomers noticed similar incongruities when observing nearby spiral galaxies. The outer edges of the galaxies rotated much faster than expected, suggesting “dark matter” existed throughout and extended beyond the visible galaxy.

Today, we can estimate the amount of dark matter in a galaxy based on how it causes light from a background source to bend. Using this “gravitational lensing” technique, we can measure the severity of that bend to get an idea of the galaxy’s mass. When the mass we calculate from the bend and the mass we can observe directly don’t agree, we know dark matter must be present.

Modern calculations say dark matter comprises about 27% of the Universe. We don’t yet know what it is, but we are searching for answers.

We have known that the Universe is expanding since the early 20th century. But recent observations of distant supernovae and other observations show that the Universe is not only expanding, but the expansion is accelerating. This astonishing discovery came as a complete surprise because the expansion of the Universe should slow down with time because of the gravitational attraction between galaxies and clusters of galaxies. The unseen repellant force required to explain this observation has been labelled “dark energy,” and current models say it makes up about 68% of the Universe.

That leaves only 5% of the Universe that is visible to us. 

Supernova 1994D in this image from NASA's Hubble Space Telescope might look like a star, but it's the explosion of a white dwarf that nearly outshone an entire galaxy. Such supernovas — known as type Ia — are extremely similar to each other, allowing astronomers to use them to measure the rate of the expansion of the universe.

What We Know and What We Think

While we can’t see dark matter, we know it’s there. And we can investigate some of dark matter’s properties using gravitational lensing. This technique measures the gravitational pull galaxies exert on light from more distant sources. The warping and magnification of this light gives us insight into the amount, density, and distribution of dark matter in any given lensing galaxy. Theoretically, the current best explanation we have for dark matter is the existence of WIMPs, or Weakly Interacting Massive Particles. These theoretical particles should have certain predictable behaviors, but directly observing them and their byproducts so far has proved elusive.

As for dark energy, Einstein had assumed the Universe was static, neither expanding nor collapsing. However, his Theory of General Relativity predicted that the Universe was not static, and so he added a “cosmological constant,” to oppose gravity. He later called it the “biggest blunder” of his life after Hubble demonstrated that the Universe was expanding.

The discovery that the expansion of the Universe is accelerating revived the idea of the cosmological constant. The simplest interpretation of this constant is that it represents the energy of empty space. This “vacuum energy” is constant throughout space and time.

Another interpretation is that dark energy might be an energy field that varies over time and space. Or, perhaps we do not fully understand gravity. For example, maybe it acts differently on enormous scales. Astronomers are currently testing modifications to General Relativity to see if they can explain the Universe’s accelerating expansion.

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What is the Universe?

The universe is everything. It includes all of space, and all the matter and energy that space contains. It even includes time itself and, of course, it includes you.

Earth and the Moon are part of the universe, as are the other planets and their many dozens of moons. Along with asteroids and comets, the planets orbit the Sun. The Sun is one among hundreds of billions of stars in the Milky Way galaxy, and most of those stars have their own planets, known as exoplanets.

The Milky Way is but one of billions of galaxies in the observable universe — all of them, including our own, are thought to have supermassive black holes at their centers. All the stars in all the galaxies and all the other stuff that astronomers can’t even observe are all part of the universe. It is, simply, everything.

Though the universe may seem a strange place, it is not a distant one. Wherever you are right now, outer space is only 62 miles (100 kilometers) away. Day or night, whether you’re indoors or outdoors, asleep, eating lunch or dozing off in class, outer space is just a few dozen miles above your head. It’s below you too. About 8,000 miles (12,800 kilometers) below your feet — on the opposite side of Earth — lurks the unforgiving vacuum and radiation of outer space.

In fact, you’re technically in space right now. Humans say “out in space” as if it’s there and we’re here, as if Earth is separate from the rest of the universe. But Earth is a planet, and it’s in space and part of the universe just like the other planets. It just so happens that things live here and the environment near the surface of this particular planet is hospitable for life as we know it. Earth is a tiny, fragile exception in the cosmos. For humans and the other things living on our planet, practically the entire cosmos is a hostile and merciless environment.

How old is Earth?

Our planet, Earth, is an oasis not only in space, but in time. It may feel permanent, but the entire planet is a fleeting thing in the lifespan of the universe. For nearly two-thirds of the time since the universe began, Earth did not even exist. Nor will it last forever in its current state. Several billion years from now, the Sun will expand, swallowing Mercury and Venus, and filling Earth’s sky. It might even expand large enough to swallow Earth itself. It’s difficult to be certain. After all, humans have only just begun deciphering the cosmos.

While the distant future is difficult to accurately predict, the distant past is slightly less so. By studying the radioactive decay of isotopes on Earth and in asteroids, scientists have learned that our planet and the solar system formed around 4.6 billion years ago.

How old is the universe?

The universe, on the other hand, appears to be about 13.8 billion years old. Scientists arrived at that number by measuring the ages of the oldest stars and the rate at which the universe expands. They also measured the expansion by observing the Doppler shift in light from galaxies, almost all of which are traveling away from us and from each other. The farther the galaxies are, the faster they’re traveling away. One might expect gravity to slow the galaxies’ motion from one another, but instead they’re speeding up and scientists don’t know why. In the distant future, the galaxies will be so far away that their light will not be visible from Earth.

Put another way, the matter, energy and everything in the universe (including space itself) was more compact last Saturday than it is today.

Put another way, the matter, energy and everything in the universe (including space itself) was more compact last Saturday than it is today. The same can be said about any time in the past — last year, a million years ago, a billion years ago. But the past doesn’t go on forever.

By measuring the speed of galaxies and their distances from us, scientists have found that if we could go back far enough, before galaxies formed or stars began fusing hydrogen into helium, things were so close together and hot that atoms couldn’t form and photons had nowhere to go. A bit farther back in time, everything was in the same spot. Or really the entire universe (not just the matter in it) was one spot.

Don't spend too much time considering a mission to visit the spot where the universe was born, though, as a person cannot visit the place where the Big Bang happened. It's not that the universe was a dark, empty space and an explosion happened in it from which all matter sprang forth. The universe didn’t exist. Space didn’t exist. Time is part of the universe and so it didn’t exist. Time, too, began with the big bang. Space itself expanded from a single point to the enormous cosmos as the universe expanded over time.

What is the universe made of?

The universe contains all the energy and matter there is. Much of the observable matter in the universe takes the form of individual atoms of hydrogen, which is the simplest atomic element, made of only a proton and an electron (if the atom also contains a neutron, it is instead called deuterium). Two or more atoms sharing electrons is a molecule. Many trillions of atoms together is a dust particle. Smoosh a few tons of carbon, silica, oxygen, ice, and some metals together, and you have an asteroid. Or collect 333,000 Earth masses of hydrogen and helium together, and you have a Sun-like star.

For the sake of practicality, humans categorize clumps of matter based on their attributes. Galaxies, star clusters, planets, dwarf planets, rogue planets, moons, rings, ringlets, comets, meteorites, raccoons — they’re all collections of matter exhibiting characteristics different from one another but obeying the same natural laws.

Scientists have begun tallying those clumps of matter and the resulting numbers are pretty wild. Our home galaxy, the Milky Way, contains at least 100 billion stars, and the observable universe contains at least 100 billion galaxies. If galaxies were all the same size, that would give us 10 thousand billion billion (or 10 sextillion) stars in the observable universe.

But the universe also seems to contain a bunch of matter and energy that we can’t see or directly observe. All the stars, planets, comets, sea otters, black holes and dung beetles together represent less than 5 percent of the stuff in the universe. About 27 percent of the remainder is dark matter, and 68 percent is dark energy, neither of which are even remotely understood. The universe as we understand it wouldn’t work if dark matter and dark energy didn’t exist, and they’re labeled “dark” because scientists can’t seem to directly observe them. At least not yet.

How has our view of the universe changed over time?

Human understanding of what the universe is, how it works and how vast it is has changed over the ages. For countless lifetimes, humans had little or no means of understanding the universe. Our distant ancestors instead relied upon myth to explain the origins of everything. Because our ancestors themselves invented them, the myths reflect human concerns, hopes, aspirations or fears rather than the nature of reality.

Several centuries ago, however, humans began to apply mathematics, writing and new investigative principles to the search for knowledge. Those principles were refined over time, as were scientific tools, eventually revealing hints about the nature of the universe. Only a few hundred years ago, when people began systematically investigating the nature of things, the word “scientist” didn’t even exist (researchers were instead called “natural philosophers” for a time). Since then, our knowledge of the universe has repeatedly leapt forward. It was only about a century ago that astronomers first observed galaxies beyond our own, and only a half-century has passed since humans first began sending spacecraft to other worlds.

In the span of a single human lifetime, space probes have voyaged to the outer solar system and sent back the first up-close images of the four giant outermost planets and their countless moons; rovers wheeled along the surface on Mars for the first time; humans constructed a permanently crewed, Earth-orbiting space station; and the first large space telescopes delivered jaw-dropping views of more distant parts of the cosmos than ever before. In the early 21st century alone, astronomers discovered thousands of planets around other stars, detected gravitational waves for the first time and produced the first image of a black hole.

With ever-advancing technology and knowledge, and no shortage of imagination, humans continue to lay bare the secrets of the cosmos. New insights and inspired notions aid in this pursuit, and also spring from it. We have yet to send a space probe to even the nearest of the billions upon billions of other stars in the galaxy. Humans haven’t even explored all the worlds in our own solar system. In short, most of the universe that can be known remains unknown .

The universe is nearly 14 billion years old, our solar system is 4.6 billion years old, life on Earth has existed for maybe 3.8 billion years, and humans have been around for only a few hundred thousand years. In other words, the universe has existed roughly 56,000 times longer than our species has. By that measure, almost everything that’s ever happened did so before humans existed. So of course we have loads of questions — in a cosmic sense, we just got here.

Our first few decades of exploring our own solar system are merely a beginning. From here, just one human lifetime from now, our understanding of the universe and our place in it will have undoubtedly grown and evolved in ways we can today only imagine.

Next: The Search for Life: Are We Alone?

Home — Essay Samples — Science — Big Bang Theory — The Big Bang: Universe’s Birth

The Big Bang: Universe's Birth

• Categories: Big Bang Theory Space Exploration Universe

About this sample

Words: 573 |

Published: Jan 29, 2019

Words: 573 | Page: 1 | 3 min read

Works Cited

• Bennett, J., Donahue, M., Schneider, N., & Voit, M. (2014). The Cosmic Perspective (7th ed.). Pearson.
• Chaisson, E., & McMillan, S. (2013). Astronomy Today (8th ed.). Pearson.
• Guth, A. H. (1997). The Inflationary Universe: The Quest for a New Theory of Cosmic Origins. Perseus Books.
• Hawking, S. W. (1988). A Brief History of Time: From the Big Bang to Black Holes. Bantam Books.
• Liddle, A. R. (2003). An Introduction to Modern Cosmology. Wiley.
• Linde, A. (2017). Inflationary Cosmology after Planck 2016. Universe, 3(2), 49.
• Penrose, R. (2005). The Road to Reality: A Complete Guide to the Laws of the Universe. Vintage Books.
• Peebles, P. J. E. (1993). Principles of Physical Cosmology. Princeton University Press.
• Planck Collaboration. (2018). Planck 2018 results. VI. Cosmological parameters. Astronomy & Astrophysics, 641, A6.
• Weinberg, S. (2008). Cosmology. Oxford University Press.

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A Smithsonian magazine special report

What Is the Universe? Real Physics Has Some Mind-Bending Answers

Science says the universe could be a hologram, a computer program, a black hole or a bubble—and there are ways to check

Victoria Jaggard

The questions are as big as the universe and (almost) as old as time: Where did I come from, and why am I here? That may sound like a query for a philosopher, but if you crave a more scientific response, try asking a cosmologist.

This branch of physics is hard at work trying to decode the nature of reality by matching mathematical theories with a bevy of evidence. Today most cosmologists think that the universe was created during the big bang about 13.8 billion years ago, and it is expanding at an ever-increasing rate . The cosmos is woven into a fabric we call space-time, which is embroidered with a cosmic web of brilliant galaxies and invisible dark matter .

It sounds a little strange, but piles of pictures, experimental data and models compiled over decades can back up this description. And as new information gets added to the picture, cosmologists are considering even wilder ways to describe the universe—including some outlandish proposals that are nevertheless rooted in solid science:

The universe is a hologram

Look at a standard hologram, printed on a 2D surface, and you’ll see a 3D projection of the image. Decrease the size of the individual dots that make up the image, and the hologram gets sharper. In the 1990s, physicists realized that something like this could be happening with our universe.

Classical physics describes the fabric of space-time as a four-dimensional structure, with three dimensions of space and one of time. Einstein’s theory of general relativity says that, at its most basic level, this fabric should be smooth and continuous. But that was before quantum mechanics leapt onto the scene. While relativity is great at describing the universe on visible scales, quantum physics tells us all about the way things work on the level of atoms and subatomic particles. According to quantum theories, if you examine the fabric of space-time close enough, it should be made of teeny-tiny grains of information, each a hundred billion billion times smaller than a proton.

Stanford physicist Leonard Susskind and Nobel prize winner Gerard ‘t Hooft have each presented calculations showing what happens when you try to combine quantum and relativistic descriptions of space-time. They found that, mathematically speaking, the fabric should be a 2D surface, and the grains should act like the dots in a vast cosmic image, defining the “resolution” of our 3D universe. Quantum mechanics also tells us that these grains should experience random jitters that might occasionally blur the projection and thus be detectable. Last month, physicists at the U.S. Department of Energy’s Fermi National Accelerator Laboratory started collecting data with a highly sensitive arrangement of lasers and mirrors called the Holometer . This instrument is finely tuned to pick up miniscule motion in space-time and reveal whether it is in fact grainy at the smallest scale. The experiment should gather data for at least a year, so we may know soon enough if we’re living in a hologram.

The universe is a computer simulation

Just like the plot of the Matrix , you may be living in a highly advanced computer program and not even know it. Some version of this thinking has been debated since long before Keanu uttered his first “whoa”. Plato wondered if the world as we perceive it is an illusion , and modern mathematicians grapple with the reason math is universal—why is it that no matter when or where you look, 2 + 2 must always equal 4? Maybe because that is a fundamental part of the way the universe was coded.

In 2012, physicists at the University of Washington in Seattle said that if we do live in a digital simulation, there might be a way to find out . Standard computer models are based on a 3D grid, and sometimes the grid itself generates specific anomalies in the data. If the universe is a vast grid, the motions and distributions of high-energy particles called cosmic rays may reveal similar anomalies—a glitch in the Matrix—and give us a peek at the grid’s structure. A 2013 paper by MIT engineer Seth Lloyd  builds the case for an intriguing spin on the concept: If space-time is made of quantum bits, the universe must be one giant quantum computer . Of course, both notions raise a troubling quandary: If the universe is a computer program, who or what wrote the code?

The universe is a black hole

Any “Astronomy 101”  book  will tell you that the universe burst into being during the big bang. But what existed  before  that point, and what triggered the explosion? A  2010 paper by Nikodem Poplawski , then at Indiana University, made the case that our universe was forged inside a really big  black hole .

While  Stephen Hawking  keeps changing his mind, the popular definition of a black hole is a region of space-time so dense that, past a certain point, nothing can escape its gravitational pull. Black holes are born when dense packets of matter collapse in on themselves, such as during the deaths of especially hefty stars. Some versions of the equations that describe black holes go on to say that the compressed matter does not fully collapse into a point—or singularity—but instead bounces back, spewing out hot, scrambled matter.

Poplawski crunched the numbers and found that observations of the shape and composition of the universe match the mathematical picture of a black hole being born. The initial collapse would equal the big bang, and everything in and around us would be made from the cooled, rearranged components of that scrambled matter. Even better, the theory suggests that all the black holes in our universe may themselves be the gateways to alternate realities. So how do we test it? This model is based on black holes that spin, because that rotation is part of what prevents the original matter from fully collapsing. Poplawski says we should be able to see an echo of the spin inherited from our “parent” black hole in surveys of galaxies, with vast clusters moving in a slight, but potentially detectable, preferred direction.

The universe is a bubble in an ocean of universes

Another cosmic puzzle comes up when you consider what happened in the first slivers of a second after the big bang. Maps of relic light emitted shortly after the universe was born tell us that baby space-time grew exponentially in the blink of an eye before settling into a more sedate rate of expansion. This process, called inflation, is pretty popular among cosmologists, and it got a further boost this year with the potential (but still unconfirmed)  discovery of ripples in space-time called gravitational waves , which would have been products of the rapid growth spurt.

If inflation is confirmed, some theorists would argue that we must live in a frothy sea of multiple universes. Some of the  earliest models of inflation  say that before the big bang, space-time contained what’s known as a false vacuum, a high-energy field devoid of matter and radiation that is inherently unstable. To reach a stable state, the vacuum began to bubble like a pot of boiling water. With each bubble, a new universe was born, giving rise to an  endless multiverse .

The trouble with testing this idea is that the cosmos is ridiculously huge—the observable universe stretches for about 46 billion light years in all directions—and even our best telescopes can’t hope to peer at the surface of a bubble this big. One option, then, is to look for any evidence of our bubble universe colliding with another. Today our best maps of the big bang’s relic light do show an  unusual cold spot in the sky  that could be a “bruise” from bumping into a cosmic neighbor. Or it could be a statistical fluke. So a team of researchers led by Carroll Wainwright at the University of California, Santa Cruz, has been running computer models to figure out what  other sorts of traces  a bubbly collision would leave in the big bang’s echo.

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Victoria Jaggard is the science editor for Smithsonian.com. Her writing has appeared in Chemical & Engineering News , National Geographic , New Scientist and elsewhere.

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