A Universe from Nothing

A Universe from Nothing 

by : Aria Ratmandanu

"The real bang in the Big Bang was not the beginning of the universe, but the period of inflation"

" Nothingness is unstable (According to Quantum Mechanics)"

            

                   Every civilization has had its creation stories. The Europeans came up with a doozy in the early twentieth century, and it has since been refined and elaborated upon by scholars from all over the world. It came to be called the Big Bang, but it has morphed into something called the standard model of cosmology. We consider it a theory, while we call the other explanations myths. What makes the Big Bang different from the Mayan proposition that we are all made from white and yellow corn?  What are the limits of current knowledge ?

              The idea of the Big Bang arose from Einstein’s theory of general relativity, which he completed in 1915, after over a decade of work. General relativity is a set of equations that describe the way gravity, space and time, energy and matter, all interact. With his theory Einstein was asking people to toss out the intuitively satisfying and very successful theory of Isaac Newton, and in its place to accept some very weird ideas that seem to contradict what we experience in everyday life. Metaphysics is a court of opening and closing arguments, with no requirement that evidence be presented in between. In science it is only the evidence that matters. So when Einstein said there is a hidden reality underlying and quite different from the world we perceive with our senses, no scientist would have listened unless he produced a series of smoking guns. He did.

                Though one can apply general relativity to the universe as a whole, the applications that provide the easiest tests of its validity are the ones that successfully explain simple systems such as a planet orbiting our sun, or a ray of starlight flying past it. It was these applications that provided the first physical evidence that Einstein was onto something. In the case of the planet, Einstein’s theory explained a previously observed irregularity in the orbit of Mercury, which deviated from the prediction of Newton’s laws. It was a small irregularity, so most scientists before Einstein had simply scratched their heads over it, and expected that eventually a mundane explanation would be found. Einstein showed that the explanation was anything but mundane. Because that irregularity was already known, an even more “an even more impressive test of the theory was his novel (and at the time astonishing) predic“tion that, given the effects of relativity, gravity would bend light rays, and hence that our view of distant stars would be altered when their light passed near our sun. In order to observe that effect, and not have the starlight in question swamped by that of the sun, one had to look at it during a total solar eclipse. This experiment was performed, and Einstein’s theory was found to correctly predict not just that the light would be bent, but also the amount of the bending.

                Einstein’s triumph—and the equally revolutionary triumph of quantum theory—did not mean that everything about Newton’s view of the world had suddenly been invalidated. It is not as if civilization woke up one morning and realized it had built all its buildings and bridges wrong, that Edison’s lightbulb is really a quantum laser, or that if you drive faster than the speed limit you’ll never need wrinkle cream. Newton’s theory had been tested and retested, and, except for the problem of the orbit of Mercury, never been found lacking, and Einstein’s theory didn’t challenge the fact that Newton’s theory provides an excellent description of the events we experience in our “everyday lives. In fact, when applied to such situations, Einstein’s theory yields predictions so close to those of Newton’s that only very sophisticated instruments can detect the difference. But under certain conditions, relevant for astrophysics and in certain laboratory experiments, Newtonian predictions do differ significantly from those of Einstein’s theory. So when scientists say that Newton’s theory is “wrong,” we mean it is only approximately correct. Still, Einstein’s theory is a more fundamentally true description of nature, which reveals the character of space and time on a much deeper level than what Newton had envisioned.

               The experimental support for his theories made Einstein an international celebrity, but the most astounding implications of his ideas were yet to come. In the 1920s a Belgian priest and astronomer named Georges Lemaître applied Einstein’s equations to the universe as a whole. He discovered something that at the time might have seemed both obvious and shocking. First the obvious part. Since gravity is an attractive force, when you toss an apple into the air, the pull of gravity will cause it to fall back toward the Earth. That is, the apple first moves away from the earth, then back down toward it, but does not hover in place (except for that single instant at the top of its trajectory). The shocking part came when Lemaître showed that, similarly, due to the mutual attraction of the matter and energy within it, the universe can expand, slow down, and possibly contract, but cannot remain “at a fixed size, as everyone at the time—including Einstein—believed. If the universe is expanding, that means that if you trace the history of the universe backward in time, you’ll find the universe getting ever smaller. And so Lemaître speculated further that the universe began as a single point. That theory is now called the Big Bang theory.

             The Big Bang theory was intimately connected to Einstein’s general relativity, but if it had made no testable predictions it would have been little better than saying the universe was made from corn. A critical element of the theory was confirmed shortly after Lemaître’s work, when Edwin Hubble discovered that the universe is expanding. But a more specific implication of Lemaître’s scenario is that, as the primordial fireball cooled to a billion degrees in the first few minutes after the Big Bang, various light elements should have been created in certain definite proportions. In particular, about 25 percent of the matter in the universe should be in the form of helium—and this is precisely what we find. Another implication is that the universe should have cooled a great deal more since then. According to the theory, space today “space today should be permeated with residual radiation at a temperature of, on average, about 2.7 degrees centigrade above absolute zero. Again, this agrees with what we measure.

            By the 1970s the Big Bang model had proved very successful at explaining most of the history of our universe. But there remained some apparent anomalies. For example, consider a frying pan that is at a uniform temperature except for one spot that is hotter than the rest. After a short time, the hot spot will be a bit cooler, while the nearby region of the pan will be slightly warmer. With more time, the hot spot will cool further, transferring its heat to ever larger areas of the pan. Eventually the entire pan will end up at a uniform temperature. But this transition to uniformity takes time. The universe is like the pan after a very long time—its temperature is almost uniform. The problem was that we happened to know that not enough time had passed to have allowed that to occur. So why is it so close to 2.7 degrees in every direction? Why not a hot spot here and a cold spot there? Physicists called this the horizon problem. 

               The so-called flatness problem was another puzzle. General relativity dictates that the amount of matter and energy in the universe determines the curvature of space. What does that mean? Curvature of our three-dimensional space can be difficult to visualize, but the idea is similar in two dimensions, so let’s consider that. A flat plane is a two-dimensional surface with no curvature. The surface of a sphere, on the other hand, curves in on itself, and is an example of a surface with what is called positive curvature. In contrast, a saddle is curved outward, so it is said to have negative curvature. The equations of general relativity tell us that if there is more than a certain critical amount of matter and energy per unit volume in the universe, space will curl up into a spherelike shape, and eventually collapse upon itself. If there is less than this critical density, space will curve outward like a saddle. Only if the average concentration of matter and energy is exactly at the critical value will space be flat. The critical density varies with the age of the universe. Long ago it was very high, but today it is the equivalent of about 6 hydrogen atoms per cubic meter of space.

                We can measure the large-scale curvature of space directly, and space appears to be flat, at least to the precision to which we can measure. The problem is that the equations of general relativity show “that if the density of the universe ever deviated from the critical value, that deviation would quickly get enormously amplified. That means that if, in the early universe, the density of matter had been even slightly less than the critical density, the universe would today be saddle-shaped and vastly more dilute than we find it. Or if its density had been just a bit higher than the critical value, the universe would long ago have collapsed in on itself like a balloon with the air sucked out. Due to this amplification effect, in order for the Big Bang model to account for the degree of flatness that we observed, when the universe was one second old, the concentration of matter and energy had to be tuned to the critical value within an accuracy of one part in a thousand trillion.

             One might ask, “So what? Couldn’t the universe simply have been made that way?” It could have, but this illustrates an important point in science. The key aspects of a theory should follow from some principle, and not be contrived to make the theory work. To a scientist, a theory stating that the universe depends upon being set up long ago in a very precise way is not a very satisfying theory. Scientists want to comprehend the underlying reason, the natural laws that explain the special circumstance.

            The horizon problem, the flatness problem, and some other difficulties with the Big Bang theory were all resolved in the late 1970s when physicists discovered a new chapter in the evolution of the universe, a chapter called inflation. Inflation was “discovered by Alan Guth, a young particle theorist who, by his own admission, hadn’t really accomplished very much up until then. Guth changed that when he realized that certain conditions that physicists believe were present when the universe was a fraction of a second old would have caused the cosmos to go crazy, doubling in size in less than every billionth of a trillionth of a trillionth of a second. Assuming that doubling continued for “only” a hundred cycles, a parcel of universe the width of a penny would have blown up to more than ten million times the diameter of the Milky Way.

             That, in brief, is the scientific picture of how the universe got here, and some of the evidence for that scenario. The real bang in the Big Bang was not the beginning of the universe, but the period of inflation, an expansion many times more drastic than that predicted by the original Big Bang scenario, and one that happened an instant after the universe began.

         What happened before inflation? For now, scientific answers to that question are far more speculative, and far less certain, than the picture I’ve described above. Better answers await progress in creating a quantum version of general relativity (string theory, if shown to be true, would accomplish that). Many physicists argue that the new theory, once we have it, will show that, at some point before inflation, time as we know it did not exist. But the most striking speculation about what a quantum theory that includes general relativity might tell us comes from a quantum principle called vacuum fluctuations.”

            I mentioned above that galaxies are products of the microscopic fluctuations of quantum fields. Vacuum fluctuations refer to the quantum prediction that even “nothingness”—which in quantum theory is given a precise mathematical definition—exhibits “fluctuations, and is therefore in a sense unstable. That is, even if you start with a region of space in which there is neither energy nor matter, it will not remain that way. Nothingness is instead like a boiling cauldron in which particles are always bubbling in and out of existence. That is a strange concept taken in the context of everyday experience, but to those who spend their days studying the behavior of elementary particles, it is a familiar effect. Vacuum fluctuations are one of the best-confirmed results in all of science, and have been measured to an accuracy of ten decimal places. They must be accounted for in all calculations and experiments in modern particle physics. In fact, most of your mass comes from the protons in the atoms you are made of, and most of the mass of a proton comes, not from the masses of the quarks that make up the proton, but from the energy of the “empty” space between those quarks, the turbulent brew of particles arising from nothingness, and then quickly disappearing back into it. So next time you think about how much you weigh, remember that most of your weight is due to the weight of empty space.”

            Many physicists believe that vacuum fluctuations point to an astounding prediction: the universe could have arisen spontaneously from nothing. Did it ? We don’t yet know for sure because we don’t yet understand exactly how general relativity and quantum theory can be combined. Even once we think we have figured it out, specific predictions pertaining to observable phenomena will have to be made, and those predictions tested. Physicists will do that, because that, ultimately, is the work of science. Unlike philosophical and metaphysical speculations, which are not bound by the constraint of evidence, a scientific theory of the origin of the universe must pass observational tests. The resulting picture might not satisfy those looking for a divine source for our beginnings, but it will be the answer of science.