The beginning of the Universe

I don’t think that there is anyone on this planet who is at least semi-literate who hasn’t wondered as to when and how the universe began. Christians, Jews and Muslims alike have been taught as children that at the beginning of Genesis, the Old Testament says that God created the Heaven and the Earth. Then it says that the Earth was void. There was no mention of Heaven being void.

When we look out into space with our eyes alone, the most stars we would ever see even if we positioned ourselves at different places on the surface of earth; are 3,000 of them. However, our galaxy (the Milky Way) that earth is in has approximately 300 billion stars in it and the universe has at least 100 billion galaxies in it so it follows that the universe is extremely vast.

Humans have always wondered: Has the universe always existed like we see it now, or did it somehow start all of a sudden from nothing? Until the early 1900s, most people had assumed that the universe was fixed in size. What has been known since further into the last century is that the entire universe is expanding. Imagine if you will, the universe being a black balloon and all the white flakes of paint you see on the surface of the balloon are stars. As you blow into the balloon, it expands and as it expands, the paint flecks move further apart from one another. That is what is happening in space. This has led physicists to deduce that the universe started out in the finite past with a minuscule size so small, it couldn’t be seen with the naked eye. Before I get into the ‘big bang’ theory, let me explain how we know that the universe is expanding.

An astronomer, Vesto Slipher noticed that there are more galaxies going away from us than approaching us. Astronomers know that a galaxy is approaching or receding by looking at the spectrum of its light. If the spectrum is shifted toward shorter wavelength (blueshift), then the galaxy is approaching, just like the sound of an approaching racing car has a higher pitch (shorter sound wavelength). If the spectrum is shifted toward longer wavelength (redshift), then the galaxy is receding, just like the sound of a racing car that has passed us has a lower pitch (longer sound wavelength). The degree of the shift depends on the speed of approach or recession. So in other words, Slipher observed more galaxies whose spectrum was redshifted than those whose spectrum was blueshifted, meaning that the galaxies are moving apart from one another.

If we could extrapolate backwards in time, we would see that the separations between galaxies become smaller while the density of them becomes greater. This continues until all matter is compacted into a completely shrunk volume of the universe with an incredible density—the moment of the big bang. We can estimate how long ago this was by dividing the distance to a far away galaxy by its recessional velocity. This way we estimate how long ago the distance between that galaxy and our own galaxy was earlier. Calculation shows that the big bang occurred as long 15 billion years ago, which is about three times the age of the Earth.

According to the big bang theory, the universe began by expanding from an infinitesimal volume of matter with extremely high density and temperature. The universe was initially significantly smaller than even a human cell in our bodies. With the big bang, the fabric of space itself began expanding like the surface of an inflating balloon ---- matter simply rode along the stretching space like paint specks on a balloon's surface. The big bang is not like an explosion of matter in otherwise empty space; rather, space itself began with the big bang and carried matter with it as it expanded.

Physicists think that even time began with the big bang. Today, just about every scientist believes in the big bang model. The evidence is overwhelming enough that in 1951, the Catholic Church officially pronounced the big bang model to be in accordance with the Bible.

From radioactive dating of uranium isotopes, (one of two or more species of atoms of a chemical element having nuclei with the same number of protons but different numbers of neutrons) we know that the oldest isotopes were created (through nuclear reactions in supernovae) about 10 billion years ago. The oldest things we would ever find in the universe are between 10-15 billion years old, but definitely not older. Presuming that the universe began 15 billion years ago, then it was compacted into a space so infinitesimal; it couldn’t be seen by the human eye.

The notion that the expanding universe was extremely hot in its beginning provides a reasonable explanation as to why helium and deuterium seem to have existed even before the stars were formed. Both helium and deuterium are created by nuclear fusion. Fusion of a proton and a neutron produces deuterium (also known as heavy hydrogen), while fusion of two deuterium nuclei produces helium. These reactions can occur only at very high temperatures, such as in the interiors of stars. This process, called the ‘big bang nucleosynthesis’, would have created helium and deuterium (plus trace amounts of elements like lithium and beryllium) out of an initial sea of energetic protons and neutrons.

Spectroscopic studies of local stars show that the abundance of helium is about 20-30% by mass, the rest being mostly hydrogen. Stars make their own helium in the present universe. The stars combine hydrogen nuclei (protons) into helium nuclei through nuclear fusion, releasing great amounts of energy. Some, if not most of the helium existed before star formation s occurred.

Observation of deuterium gives an additional support of the big bang nucleosynthesis. Deuterium, unlike helium, is not produced in stars at all. At temperatures above about one million degrees K, it dissociates into proton and neutron. Astronomers in the early 1970s realized that no known process in the present universe could have produced deuterium. This is because any deuterium created in stars will immediately dissociate or convert to helium due to the high temperatures in interiors of stars. However, in 1973, studies of absorption spectra of nearby stars showed that interstellar medium (material between stars) contains a trace of deuterium. Since stars could not have produced the deuterium, it must have been created either very early in the formation of the galaxy or even before. Despite the high temperature at the beginning, the big bang nucleosynthesis could create deuterium because the expansion of the universe lowered the density and temperature so quickly that there was hardly time for the deuterium to decay. Thus, the abundance of helium and existence of deuterium in space provides strong evidence that the universe began with a hot, violent explosion consistent with the big bang theory.

The most conclusive evidence for the big bang arises from the observation of the cosmic background radiation. In 1948, an astronomer by the name of Gamow made a prediction that the radiation from the big bang nucleosynthesis must still be filling the universe. In 1964, two radio astronomers Arno Penzias and Robert Wilson discovered that a constant signal was precisely uniform in every direction so they pointed the antenna toward the Sun or the Milky Way and the more empty parts of the sky. This meant that the signal was coming from far beyond our Galaxy; otherwise it would not be so uniform in all directions. The high degree of isotropy (uniformity in all directions) tells us that the signal originated from very far away, or equivalently, from very early in time. The source must have been enormously powerful for us to be still detecting it. Physicists inferred that this must have been from the immense fireball of radiation that occurred from the onset of the big bang which explains the existence of the big bang as Gamow predicted.

According to the big bang theory, the universe at the beginning must have been crowded with particles of protons and neutrons and light and for this reason, it must have been extremely hot. In that environment, the particles were constantly bumping into light, absorbing and re-emitting it. Light from such an environment would have a blackbody spectrum, and the spectrum's characteristic shape would be preserved while the light travels through the expanding space. Black-body radiation is light in thermal equilibrium, light radiation with a given temperature. It is the basic thermodynamic state of light.

It took practically the entire age of the universe for the radiation from the beginning of the universe to reach us. Astronomers now know that the expansion of the universe during this time stretched out the wavelength of the radiation by more than 1000 fold. The afterglow of the big bang comes from when the universe was only about 500,000 years old. This makes the cosmic background radiation the oldest thing we have ever observed. We are almost viewing the event of the big bang in terms of time.

The 20th century saw a giant leap in how humans perceive the universe. No longer did people assume that the universe was static in size. By looking at how distant galaxies recede from us, we learned instead that the universe is expanding in volume. Tracing the expanding universe backward in time, we can imagine a dense, hot beginning of our universe in a finite past. In the middle of the century, we learned that the nuclear reactions in this hot early universe accurately account for the previously mysterious abundance of helium and deuterium. Moreover, we detected a faint afterglow of the big bang that occurred billions of years ago. That the universe began with a big bang is essentially conclusive and may stand as the most profound discovery that humans have ever made.

The big bang, however, is merely a global description of the origin of the universe. Today, particle physicists have consistent theories about the history of the universe down to only a trillionth of a second after its birth or even earlier. They can test their theories experimentally with particle accelerators that can simulate events involving enormous energies similar to the condition of the universe at its beginning. The goal of physics today is to develop this quantum theory of gravity so that we may one day understand what exactly happened around the moment of the big bang that got the universe started.

I appreciate the fact that it is extremely difficult to accept the premise that trillions of stars and their planets were actually compressed into a speck so small, it couldn’t be seen by a human eye just before they exploded with a big bang. For example, neutron stars are massive stars that collapsed once their cores ceased nuclear fusion and energy production. A teaspoonful of neutron star matter would weigh about 100 million tons. To get all of that (multiplied a trillion times) into one tiny speck of matter is mind boggling. But it must have happened considering that the Universe is presently expanding and has been since the beginning of its existence. You notice that I didn’t say ‘since the beginning of time’. The reason for this is that what was going on before the big bang and how long was it going on is beyond my understanding, unless…..

There is a theory about this. It is believed by some, that like a balloon, the universe can only expand so far and that gravitational forces will draw all the stars and galaxies back to their original positions they were at the time of the big bang; that of a speck and that it will explode again and that this expansion and deflation (for want of a better word) has been going on for a very long time.

The Bible is not a science book however the big bang theory is the most reasonable explanation for the creation of the universe. The theory being that the universe began billions of years ago in the explosion of a single, super-dense point that contained all matter in space. Many religious people believe that God is the creator of the universe and that we are not here as the result of mere chance. It is not my intention in this essay to comment on that belief.

What I find rather disturbing however is that if the universe will eventually stop expanding and begins to return back to its original state, a minute speck of matter because of gravitational forces and then it begins expanding again, what will the future of Mankind be then? Well, since I don’t expect to be around then, I guess that concern is a bit academic. Since religious scriptures tells us that if we have been good, we will be in heaven; that raises an interesting question; Where will heaven be when all this happens? There is no way I am going to attempt to answer that question.