15. Evidence that a big bang created the universe

(continued) Chapter 2.
Long Evolution: Universe Emerging

 

big-bang

 

Thus in the manner of scientific method, scientists made several predictions about things that should be true if the theory of a big bang is correct. As luck would have it, four important predictions have in fact been verified over recent decades as relevant observations and measurements were made possible by ever-improving technology. Briefly examining the four predictions will be good practice for understanding the “appropriateness” that qualifies facts to be recognized as credible scientific evidence.

 

1.  UNIVERSAL EXPANSION

The Prediction:  If a big bang (presumed) really happened, the primal explosion (also presumed) would have given a colossal outward push to all original matter contained in the early universe. Therefore the universe presumably might still be expanding outward. Evidence of such continuing expansion would be:   to observe that galaxies are receding away from us and from each other in all directions as the universe expands like a balloon.

 

The Evidence: In the late 1950s Alan Sandage, using the 200-inch telescope on Mount Palomar to test Hubble’s law farther and farther out, observed that distant galaxies were receding at velocities at least ten percent the speed of light. This observation of an expanding universe was the first hard evidence that expansion of the universe (an observed effect) was probably preceded by a primal outward push (the presumed cause). The cause can only be presumed, but – when you think about it – what else could cause such an effect? Gravity, throughout the universe, pulls things together. Even things on opposite “sides” of the universe (many scientists deny the universe has sides) have some gravitational influence on each other, regardless how slight it might be. Therefore anything powerful enough to overcome gravity’s vastly long reach had to be very powerful indeed. A big bang could do the trick.

 

2.  LIGHT ELEMENTS

The Prediction: Physicist George Gamow reasoned that if the universe was created by a big bang, the explosion would have been very hot indeed. He further reasoned that the extreme heat in the earliest moments of the universe’s existence would have produced only light elements with the simplest atomic structure, primarily hydrogen and helium. Therefore these two elements should be the most abundant in the universe. If it turned out that they were, then a big bang with great heat could reasonably be inferred. Gamow’s ideas ran counter to prevailing mindsets that a big bang would have been a colder (less hot) event because, he reasoned, a cooler state would have produced the more high density elements like iron, making them the most abundant – and he knew they clearly were not abundant across the universe. When Gamow dared publish his reasoning, a lot of scientific mindsets didn’t hold back from telling him how wrongheaded he was.

 

The Evidence: The light elements hydrogen and helium have in fact long been observed and reliably measured to be by far the most abundant across the universe. Elemental matter created in the big bang was about three quarters (73%) hydrogen and one quarter  (25%) helium. Those two alone total 98% of all matter in the universe still yet today.

 

A take-your-breath-away fact:  That seemingly meager remaining 2% has been enough to make all the planets in the universe, plus a great deal more gas nebulae and other stuff. Since the 2% included only traces of lithium and deuterium (and little else) which must have been produced in the big bang, we know that all the heavier elements had to have been made later, in stars. Stars cannot make significant quantities of the light elements, because hydrogen and helium are the first to be consumed after a star forms. In most stars they are in fact the primary fuel. Therefore the furiously hot big bang itself had to have forged the plasma of protons, neutrons and electrons that soon merged to make hydrogen the most abundant element, with helium not too far behind. And so Gamow’s thoughtful prediction – against many learned know-it-all mindsets – was verified as true by facts that are quite observable by anyone with modern telescopic technology.

 

3.  BACKGROUND RADIATION

The Prediction: If a big bang really occurred it would have generated such extreme heat (billions of degrees) that a background residue of hot radiation would have been left behind everywhere across the universe. This residual hot radiation would have expanded along with everything else that was precipitated by the big bang’s outward force. Therefore, the fossil residue of this radiation – though now greatly cooled (and become so-called “blackbody radiation”) – should still be present all over the universe. If it is still around, modern heat-measuring telescopes should be able to find it.

 

The Evidence: In 1964 radio astronomers Arno Penzias and Robert Wilson were using an obsolete microwave radio telescope that had been originally designed for satellite communications. Temporarily stymied by a persistent “white noise” (which they at first blamed on pigeons pooping in their open-design telescope), they soon realized the noise they were hearing was their telescope picking up the pervasive “glow” of remnant heat left over from the big bang – now known as “cosmic microwave background radiation” (CMBR). Anyone can observe this big bang evidence – it appears visually as part of the “snow” on a television screen tuned to no channel.

 

This ancient remnant glow, painted broadly across the heavens, was seen to be “isotropic,” meaning it is approximately the same in all directions. Its carefully measured temperature, only three degrees above absolute zero, is sufficient for certainty that fossil warmth literally left over from the big bang has been found. Thus the prediction was verified. It also strongly reinforced Gamow’s theory of a very hot big bang.

 

Of interest for later sections of this chapter describing other universe-origin theories that compete with the big bang, almost all scientists regard this confirmed observation of the cosmic microwave background radiation to be the death knell for any theory that lacks a super-hot, super-dense beginning. All odds are on the reality of a big bang. Remember: it’s still “just” a theory, but it’s approximately as good as the theory that human beings exist on the planet earth.

 

4.  FLUCTUATIONS

The Prediction: The factual observation that galaxies are irregularly distributed across the universe today supports an assumption that irregularities must have been present in the early universe’s fluctuating densities before galaxies first formed. It reasonably follows that such early irregular “density fluctuations” should still be present in the remnant cosmic microwave background radiation, and they should show up as tiny differences in temperature. This “fossil distribution of energy” would predictably lie in the far infrared end of the spectrum, and would now consist of extremely cold radiation at a temperature around 3 degrees Kelvin (barely above absolute zero).

 

The Evidence: In 1989 the actual temperature was found and measured to be an average 2.725 degrees Kelvin – an observational finding remarkable both for its precision and its correlation with the prediction. This first definitive measurement of temperature differentials in the microwave background was made by the Cosmic Background Explorer (COBE) satellite. Those small fluctuations in the early microwave background were the original seeds of the large-scale structure of galaxies and galaxy clusters we now see across the universe. Starting with these small fluctuations, the gravity of regions with slightly denser matter gradually attracted ever more matter, while less dense regions became gradually emptier. Those over-dense areas were the precursors that eventually evolved into galaxies. Distribution of matter in the early universe thus could not have been uniform when expansion began, or cosmic structures such as our Milky Way could never have formed. Neither galaxies nor people would exist.

 

Imagine, assume, infer, reason and deduce

The foregoing, an intriguing though typical example of both method and mindsets of modern science, merits a quick review. We observed a highly uneven distribution of galaxies, thus acquiring a few facts. Based on those few facts we assumed there must have been some irregularities in the distribution of early matter before the galaxies formed. Treating the assumption as if it were fact, we used our intellect to try to imagine how the process most likely would have worked, and then logically reasoned how to fill in the blanks. When we eventually developed technology precise enough to measure the real situation, the measurements confirmed that our assuming, imagining, inferring and logical reasoning had been correct. A big bang really happened. Or so (keeping an open mindset) we’re pretty darn sure.

 

Notice how vital was the conditional use of human imagination in the effort to attain greater understanding. Let no one disparage the dreamer who dreams about how things could be and might indeed be, because the creative mind necessarily is engaged during the dreaming. For an interesting reprise, glance back over all four predictions giving special attention to how imagining and reasoning faculties were deeply engaged as scientific understandings advanced. Consider what sort of distinction exists – or if one exists – between an Einsteinian “thought experiment” and the more observation-based devices of conventional scientific method. How important was hard observational data? How important was imagination? Did either outweigh the other?

 

The big bang theory appears to be as close to the truth as a scientific theory can be. Yet at any moment some new discovery could come along and expose a fatal flaw in the theory (recall how wrong Alan Greenspan was when after forty years of certainty he discovered his fatal flaw), forcing hundreds of scientists to scrap a century (not to mention their own lifetimes) of dedicated work, and start over. And remember this if nothing else:

            it takes only one single confirmed observational fact to completely overturn a scientific theory, no matter how long it has stood “looking like a law.”

 

If present understandings of the big bang were to be clearly disproved, there would be heartbreak, nay-saying and terrible gnashing of teeth against the new findings, but new scientific directions would inevitably have to be pursued. And it has happened more than once before. Such relentless pursuit of truth is not found in the mindsets that characterize law enforcement, or politics, or economics – or especially religion – or any other human institution. Only science has it built in. What if all the others acted with such open minds?

 

Acceleration

Before moving on to other important mileposts in the universe’s long, long evolution, one other little matter really must be mentioned. You already know the universe is expanding, has been doing so ever since the beginning. But did you know the expansion is speeding up? It was only near the twentieth century’s end when scientists observed that universal expansion is accelerating. As a result, we think we understand that the most major of the major events in the universe’s evolution occurred in the following sequence:

 

  • A big bang brought the universe into existence from out of nothing at all;
  • An micro-instant later inflation began, enormously expanding the universe’s size in an unbelievably brief flick of time;
  • Inflation quickly ended, and universal expansion settled back to a calmer steady rate;
  • Sometime around 7 billion years into the universe’s existence, expansion began to accelerate, and – slowly but steadily – it continues speeding up to this day.

 

For sheer incredulity it is doubtful that Genesis or Old Turtle could top this four-step scenario. Scientists have plenty of theories about why acceleration is occurring, but no one really knows. Maybe God’s doing it – but maybe also means maybe not. It’s quite a cosmos-class mystery, so to speak, and so we shall explore it a bit more in a later chapter. Something new:  the universe’s accelerating expansion now, after all these eons, prevents any new very-large-scale structures such as galaxy clusters from forming, because the speedup is now exceeding even gravity’s long reach. Alas.

 

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Condensing and self organizing

From here on things get increasingly interesting – at least if you aren’t all caught up in the stuff they call news these days. We have seen that evidence for the reality of a big bang has been found in several convincingly credible forms, including such odd stuff as fluctuations in the density of background radiation. These modern scientific findings tell us – by inverse reasoning – that such fluctuations were already there, in the original fireball, when the universe was much smaller and much denser. With such reasoning, it is not difficult to imagine how those originally small density fluctuations became larger, and enabled – some would say caused – the universe’s far flung matter to organize itself.

 

Self organizing is a fundamentally important aspect of evolutionary processes in the broadest sense. It applies equally to the first (physical universe) phase of long evolution as well as to the second (biological life) phase, as will be discussed in the next chapter. During the first phase self organizing is thought to have worked as follows.

 

The vast clouds of gaseous debris flying in all directions from the big bang did not spread quite uniformly. Why the process was not uniform we do not know, but of how it became non-uniform we think we know a little. Some areas “just were” slightly more dense than the average density of the whole, other areas “just were” slightly less dense. Like those big circular exploding fireworks at the county fair. Little perturbations occurred between, and rippled across, these areas of slightly differing densities. An area of space with even minutely greater density of gaseous stuff than its neighbor would have a slightly higher gravity than the neighbor, thereby inviting a perturbation to ripple across from one to the other. This took only millions of years.

 

Under such very slight differences in gravity’s tenuous pull, the hot clouds of gas gradually separated. Slightly higher gravity in slightly higher-density areas slowly pulled all matter in the area in toward a center, thereby increasing both density and gravity as the cloud shrank in size, condensing, growing more dense. The more that density and gravity grew, the faster they grew. The opposite happened in surrounding areas that had lower density and hence lower gravity. Over time, much of the matter content was gradually drawn from the low-density spaces into adjacent higher-density aggregations. After several ages, low-density “near-empty” space lay as gaps between higher density clouds. All this took quite many human lifetimes, but not much as universe time goes.

 

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…to be continued in one week…

 

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