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Ten Reasons To Trust In The Big Bang

(1) THE UNIVERSE IS EXPANDING

In 1929, Edwin Hubble at Mount Wilson Observatory in California showed that every distant galaxy was racing away from every other galaxy exactly as you would expect if the universe had started with a big bang. Galaxies fly apart like debris from an explosion. Take note, however, that the galaxies are not flying through space. They are flying along with space because space itself is expanding in the wake of the big bang. How do we know the universe is expanding? Each galaxy emits light with a particular set of wavelengths or colors. The expansion of space stretches the waves so that they're longer than expected, making the galaxies seem redder because red is at the longer end of the wavelength spectrum. This so-called red shift is greater for more distant galaxies because the intervening space between us and them has stretched to a greater extent.

(2) DIFFERENT TYPES OF GALAXIES AT DIFFERENT DISTANCES

The big bang suggests that the universe has evolved from a hot, dense state into today's universe. It would have been populated by different types of galaxies as it matured, starting with fresh-faced baby galaxies and ending with more distinguished, elderly galaxies such as our own Milky Way. Early galaxies would have had a different shape, size and composition compared with later galaxies. The big bang is vindicated because, by looking far away, we still see the young galaxies that populated the earlier universe. These galaxies no longer exist but are visible because it takes billions of years for light from distant galaxies to reach us. In other words, we see distant galaxies as they were billions of years ago. Sure enough, the distant (or early) galaxies look different from our neighboring (or modern) galaxies. For example, quasars are a type of baby galaxy, and they are found only in the most remote parts of the universe.

(3) THE ORIGIN OF HELIUM

The big bang model can suggest how temperature and density developed in the early universe. The first few minutes would have been ideal for nuclear fusion. Indeed, many of the original hydrogen nuclei would have fused into helium, and the big bang model indicates that today's universe should contain hydrogen and helium in the ratio of roughly three to one. When you look at the galaxies, roughly three quarters of the mass is hydrogen and one quarter is helium. This prediction was published in a 1948 paper written by George Gamow and Ralph Alpher, but Gamow added his friend Hans Bethe to the paper's list of authors. He liked the idea of a paper by Alpher, Bethe and Gamow, a pun on the Greek letters alpha, beta and gamma. Although the heat of the big bang was also responsible for synthesizing other light elements, it did not create the heavier elements. These elements were formed by nuclear reactions within various types of stars during different phases of their lives and deaths. When stars die they throw these elements out into space to form new stars, planets and everything else. So we might like to think of ourselves as stardust- or nuclear waste if you're less romantic.

(4) THE AFTERGLOW OF THE BIG BANG

Gamow and Alpher, working alongside Robert Herman, made a second prediction in the late 1940s. They argued that the big bang would have released a blast of radiation and predicted this radiation should still exist today in the form of microwaves throughout the universe. Unfortunately nobody bothered to check this basic test for the big bang model, partly because of limitations in technology and partly because few scientists at the time believed in a moment of creation. In 1964, however, Robert Wilson and Arno Penzias at Bell Labs in New Jersey were pointing a radio detector toward the sky and noted an annoying microwave noise. They suspected it was caused by a "white dielectric material" deposited on the detector by a pair of pigeons, but the microwaves persisted even after a cleaning. In the end they realized they had accidentally discovered the afterglow of the big bang. This is an example of pure serendipity, namely discovering something wonderful by chance. An alternative definition of serendipity is looking for a needle in a haystack and finding the farmer's daughter.

(5) THE BIG BANG IS SIMPLE

This may not seem like the most convincing evidence to support the big bang, but simplicity is valued by scientists when it comes to theories, and the big bang model is surprisingly simple Simplicity is important because the world appears to operate according to simple rules, such as Einstein's equation E=mc2, which encapsulates the relationship between matter and energy. When models become complicated they are probably wrong. For example, the Greek astronomer Ptolemy postulated that the sun orbits the earth. His model also involved several fabricated and spurious orbits in order to make sense of the night sky, which made the model inordinately complex. These ad hoc orbits were necessary to patch up a fundamentally flawed model. The importance of simplicity was proposed by William of Occam, a 14th century English theologian who stated the principle of Occam's razor. This argues that if there are two competing theories, with other things being equal, the simpler one is more likely to be correct. Doctors rely on Occam's razor when diagnosing a patient, and medical students are advised, "When you hear hoofbeats, think horses, not zebras."

(6) THE BIG BANG IS BEAUTIFUL

For some reason, beautiful theories are often accurate. Beauty in any context is hard to define, but we all know it when we see it, and there is consensus on the concept of beauty in science. Perhaps it has evolved through experience, so that whatever set of qualities can be ascribed to theories that turn out to be true becomes the definition of beauty and an indicator of truth for new ideas. "When I'm working on a problem," said R. Buckminster Fuller, "I never think about beauty. I think only about how to solve the problem. But when I have finished, if the solution is not beautiful I know it is wrong." Perhaps this is a slight exaggeration, because reality is the ultimate test for a theory, so ugly theories can sometimes be right and beautiful theories can sometimes be wrong. As Thomas Huxley observed, "The great tragedy of science: the slaying of a beautiful hypothesis by an ugly fact."

(7) OLBERS'S PARADOX

In 1823, when many scientists assumed the universe was infinite and eternal, German astronomer Wilhelm Olbers wondered why the night sky was not ablaze with starlight. In essence, an infinite universe would contain an infinite number of stars, and if the universe were infinitely old then this would have allowed enough time for an infinite amount of light to reach us. The obvious lack of this infinite light from space is known as Olber's paradox. There are various ways to explain why the night sky is dark, but the big bang explanation is the most convincing. The fundamental claim of the big bang is that the universe was created and therefore has a finite age. If the universe had been created just a few billion years ago, the starlight would have had only enough time to reach us from a limited volume of space because light travels at only 300,000 kilometers a second. In short, a finite age for the universe and a finite speed of light result in a night sky with only a finite amount of light. Therefore, evidence of the big bang confronts you every time you look at the night sky which is dark black not brilliant white.

(8) THE UNIVERSE HAS NOT YET COLLAPSED

Scientists used to assume the universe had existed for eternity in a largely changeless state. But this notion is incompatible with gravity, which provides an attraction between all objects. Hence, within a finite amount of time all the objects in the universe should have fallen toward one another, causing the universe to collapse. Hence the universe could not have lasted for eternity, it could have lasted for only a finite time, which is what the big bang states. Scientists attempted to salvage the eternity theory despite gravity, but they failed. Einstein posited an antigravity force to keep all the galaxies apart, but ultimately the universe would still be unstable. Isaac Newton was also troubled by the thought of a gravitationally collapsing universe. One of his solutions was to envisage an infinite, symmetric universe in which every object is pulled equally in all directions so there is no overall movement. Unfortunately he realized that even the turning of a page would alter the balance of the universe and trigger total collapse. Newton suggested that the only explanation for why the universe hadn't collapsed was the God intervened from time to time to keep the celestial objects apart.

(9) EVERYTHING IN THE UNIVERSE IS RELATIVELY YOUNG

In the past century the age of the universe according to the big bang model at times appeared to be less than the age its contents. This was clearly absurd. But huge errors in measurement were found. Astronomers have since been I able to refine the age of the universe and reestablish the credibility of the big bang. Remember, the big bang implies a I universe that is only 13.7 billion years old, give or take a billion years. So everything in the universe should be younger than that, which seems to be the case. The earth, for example, is between 4 billion and 5 billion years old, and the sun is about that age as well. The age of our galaxy is roughly double that. Crucially, there are no celestial objects with ages of 100 billion years, or 100 trillion years, which is what you would expect to find if the universe were infinitely old. Hence the universe is only finitely old.

(10) FLUCTUATIONS IN THE AFTERGLOW

One of the puzzles of the big bang model of creation is that the universe started off perfectly smooth yet today is highly structured, with giant galaxies in some parts and vast voids elsewhere. How did the universe evolve from smooth to structured? The tiniest imaginable fluctuations in the early universe would have gradually grown in time because regions of slightly higher density would have pulled in more matter by gravity. Hence the fluctuations would have increased, exerting more of a pull, which would drag in even more matter and so on until galaxies were formed. If the early universe did have tiny fluctuations, these should show up as slight variations in the big bang afterglow, also known as background radiation. For 25 years no variations could be found. As John Mather put it, "We haven't ruled out our own existence yet. But I'm completely mystified as to how the present-day structure exists without having left some signature on the background radiation." Then, in 1991, the Cosmic Background Explorer satellite discovered variations at the level of one part in 100,000. This effectively proved the big bang model beyond all reasonable doubt. Stephen Hawking called it "the discovery of the century, if not of all time."

Simon Singh - Author of Big Bang