The Universe Marches to Its Own Drummer

Blink your eyes. Are you done yet? Okay, that took about one-third of a second. For us humans, that seems like a very short time, occurring in "the blink of an eye." But by the time the early Universe was about an eye-blink old, a lot of the interesting stuff had already happened. For example, by about a millionth of a second, the sub-microscopic particles making up all ordinary matter- electrons, protons and neutrons- had been produced. But it would be a very long time- 380,000 years in fact- before the Universe contained any stable atoms. Only then would the blazingly hot Universe have cooled down enough to let those tiny building blocks stick together long enough to form atoms. And perhaps prophetically, most of those early atoms were hydrogen, the most abundant atom in our bodies.

But we need a far less anthropomorphic view of Time to think about the seminal events in the early Universe. During the first fraction of a second after its birth, the Universe was much more tumultuous and rapidly changing than at any later time.

First came the Big Bang that started it all about 13.7 billion years ago. This was of course really "big", since it was the beginning of our Universe, when space, mass-energy, and even time itself somehow appeared, apparently out of nothing. But scientists now believe that, for a time extremely shorter than a millionth of a second, the nascent Universe expanded in a rather leisurely fashion- not at all like a Big Bang. Then, according to a 1979 theory of Alan Guth, the true "Bang" began an exceedingly short time later. Guth termed his theory Inflation, a mild term indeed for the posited tremendous exponentially increasing explosion in the size of the Universe.

This proposed Inflation "explosion", occurring very early in the life of the Universe, could answer a number of otherwise very puzzling questions about our present-day Universe, 13.7 billion years later:  1. Why is the Universe (on a very large scale) the same, and in fact so smooth, in all directions?  2. Why is the Universe so "flat"? Yes, it seems strange to describe the three-dimensional Universe using a word conventionally applied to two-dimensional objects like a perfect plain. But for the Universe, "flat" simply means that the angles in any gigantic triangle add up to 180 degrees,  just like those triangles featured in our high school trigonometry classes.  3. Any magnet contains both a North and South magnetic pole, and so do the pieces we get by cutting the magnet in half again and again. But any electrical charge has only a single "pole": it's  either positive or negative. So why hasn't anyone ever found an analogous magnet (a "magnetic monopole"),  that also has only a single pole? Inflation provides the answer to that question too.

Because Inflation yields answers to all three of these profound questions about today's Universe, it is a widely accepted theory. But there are two fundamental unanswered questions about this proposed enormous explosion:

1.  We don't know know why or when Inflation might have either started or stopped. We do know that the beginning and end of Inflation (at least in our local part of the Universe) must have occurred at times unimaginably soon after the birth of the Universe, something like a trillionth of a trillionth of a trillionth second later. And during this extremely short time, the Universe doubled in size at least 90 times, growing from inconceivably small to the size of something we can actually imagine, for example a golf ball or a basketball. During Inflation, parts of the Universe expanded far faster than the speed of light- surely the greatest explosion that ever has or ever will occur. A "big bang" indeed! [For anyone concerned about a possible contradiction here with Einstein's Special Theory of Relativity: although Einstein's theory states that no information or (real) matter can travel within the Universe faster than light, there is no limit on how fast the Universe itself can expand.] When Inflation ended (if indeed it ever started), the Universe returned to a more laid-back expansion rate. 
    But curiously, this rate is being accelerated by a very mysterious form of energy discovered in the 1990s, Dark Energy . The expansion caused by Dark Energy is fairly mild today, but its rate increases as the Universe itself expands. So scientists hypothesize that, many billions of years from now, the effect of Dark Energy will become strong enough to cause a Big Rip, ultimately tearing apart the Universe and even its constituent atoms. The Universe would then turn into a vast thin dark and cold gruel, with the sad probable fate of forever becoming only ever bigger, darker, and colder.

2.  Unfortunately, we don't yet have any direct experimental evidence that Inflation ever happened. A part of the problem is that we can't detect the light of the Universe at any age earlier than 380,000 years after its birth. This is because, as noted above, only then could stable atoms form from sub-atomic particles. So light particles could finally cease incessantly bumping off of the charged sub-atomic particles; and so voyage freely through space for 13.7 billion years, finally to reach our telescopes today. What we can see today of the 380,000 year-old Universe is termed the Cosmic Microwave Background (CMB), whose discovery in 1964 provided convincing evidence for the Big Bang theory. It does seem poignant that we will very probably never pierce this barrier that prevents any glimpse of our Universe during its frenzied early infancy. 

Quite recently, there was optimism that direct evidence for Inflation had finally been obtained. Early in 2014, observations by astronomers using the BICEP2 telescope at the South Pole, of particular light patterns in the CMB, indicated that these patterns arose from the effects of Inflation. But data produced by the Planck spacecraft later that year showed that the BICEP2 data could have arisen entirely from effects of dust in our own galaxy, instead of from Inflation.

So stay tuned. It seems likely that current intense and ever more precise investigations of the CMB will determine whether Inflation- potentially able to explain profoundly puzzling aspects of our current present Universe- ever actually occurred.

(sciencequandaries.blogspot.com)