How the Universe Got Big

A team of radio astronomers, working in Antarctica, where the air is clear and dry, have found the first direct evidence for the theory of cosmic inflation. That’s the theory about the origin of the universe first stated by the physicist Alan Guth in 1980.

Here’s some background from an article Guth wrote in 1997 for Beam Line, the magazine of the Stanford Linear Accelerator Center (now the SLAC National Accelerator Laboratory):

Although it is called the “Big Bang theory,” it is not really the theory of a bang at all. It is only the theory of the aftermath of a bang. It elegantly describes how the early Universe expanded and cooled, and how matter clumped to form galaxies and stars. But the theory says nothing about the underlying physics of the primordial explosion. It gives not even a clue about what banged, what caused it to bang, or what happened before it banged. The inflationary universe theory, on the other hand, is a description of the bang itself, and provides plausible answers to these questions and more.

Guth explains that in order for the universe we observe to have begun with a Big Bang, the early universe must have been extremely uniform and have had a precise density. However:

The classical form of the Big Bang theory requires us to postulate, without explanation, that the primordial fireball filled space from the beginning. The temperature was the same everywhere by assumption, not as a consequence of any physical process….

[In addition] the initial values of the [universe’s] mass density and expansion rate are not predicted by the theory, but must be postulated. Unless we postulate that the mass density at one second just happened to have a value between 0.999999999999999 and 1.000000000000001 times the critical density [the boundary value between a universe that will expand forever and one that will eventually collapse], the Big Bang theory will not describe a universe that resembles the one in which we live…

Although the properties of the Big Bang are very special, we now know that the laws of physics provide a mechanism that produces exactly this sort of a bang. The mechanism is known as cosmic inflation.

The National Accelerator Laboratory issued a press release today:

Instead of the universe beginning as a rapidly expanding fireball, Guth theorized that the universe inflated extremely rapidly [faster than the speed of light] from a tiny piece of space and became exponentially larger in a fraction of a second.

For inflation to occur, the universe must have been in a state that allowed a sudden change to release enormous energy, creating an expanding universe almost from nothing. The process was apparently a kind of delayed phase transition, as when water is supercooled below its natural freezing point and then, because of some disturbance, suddenly freezes, generating heat.

However, as Guth immediately realized, certain predictions in his scenario contradicted observational data. In the early 1980s, Russian physicist Andrei Linde modified [the theory so that it] generated predictions that closely matched actual observations of the sky.

The new observations reported today are the first evidence of the existence of gravity waves. These are ripples in spacetime originally predicted by Albert Einstein. The radio astronomers working in Antarctica found traces of these ancient gravity waves by analyzing the cosmic background radiation left over from the Big Bang. Andre Linde reacted to the news: “These results are a smoking gun for inflation, because alternative theories do not predict such a signal. This is something I have been hoping to see for 30 years.”

Future Nobel Prize-winner Alan Guth offered this summary in 1997:

While it may be too early to say that inflation is proved, I claim that the case for inflation is compelling. It is hard to even conceive of an alternative theory that could explain the basic features of the observed Universe. Not only does inflation produce just the kind of special bang that matches the observed Universe, but quantum fluctuations during inflation could have produced non-uniformities which served as the seeds of cosmic structure [in particular, the existence of galaxies].

Physicists doubted whether Guth’s theory would ever be proven. With today’s announcement, cosmic inflation is a big step closer to becoming settled science.

What Made the Big Bang Bang?

Physicists believe our universe began with a “Big Bang” about 14 billion years ago. The evidence suggests that the universe was infinitely hot and infinitely dense before it rapidly expanded, resulting in the still-expanding universe of which we are a tiny part.

But the physicists don’t know why the Big Bang occurred or what, if anything, existed before it. Maybe an earlier universe collapsed upon itself and then bounced back in a tremendous explosion. Maybe our universe resulted from some kind of random quantum fluctuation — or from a really cool experiment carried out by a kid with blue skin and 12 eyes.

Another hypothesis, of course, is that God kicked off the Big Bang. I wouldn’t bet on that, but you never know (although you might get to know if you ever join the choir invisible).

It’s also been suggested by some physicists that a black hole in another universe may have had something to do with the beginning of ours. The latest theory along those lines is that a star in a universe with four spatial dimensions (not our familiar three) ended its life as a supernova, creating a 4-D black hole at its core and simultaneously ejecting some debris out into 4-D space. Our universe could be a 3-D sliver of this 4-D cosmic debris. Or something like that.

Something immediately struck me when I read an article about this latest theory. It wasn’t the plausibility of the theory, which I’m almost completely unqualified to judge. It was the sudden feeling that we’ve now figured out why the Big Bang occurred. And no god had anything to do with it! It’s just the cosmos and us after all!

If I were religious, this momentary reaction might be understandable. But I’m not. So why did the idea that there’s no god out there pulling strings make me feel suddenly lonely? I guess it’s hard to escape your upbringing, no matter how old you get. And all that space out there can make a person feel a little bit alone, even on a planet with 7 billion people and 3 billion internet users.

Of course, God could have created that other universe that gave rise to ours, or the even earlier universe that gave rise to that one, or the one that came before that other one, and so on and so on, but somehow it’s just not the same once universes start giving birth to new ones all by themselves.

Why Is There Something Rather Than Nothing?

There is a new book out by journalist and former philosophy grad student Jim Holt called Why Does the World Exist? It’s worth reading if you’re interested in questions like that.

Nowadays, when people ask why the world exists they are generally asking why the Big Bang occurred. Unfortunately, nobody knows. The most common answers are that either some random quantum event or some higher being made it happen. Some physicists think that our universe is just a small part of reality and that the existence of a vast, possibly infinite, collection of other universes explains why ours is here and/or why ours is the way it is. 

As soon as a particular cause or reason for our universe to exist is suggested, however, it is natural to ask why that cause or reason is the explanation, rather than some other cause or reason. Why are the laws of quantum mechanics in effect? Where did God come from? Where did all those other universes come from?

This is why the answer provided by a Buddhist monk at the very end of the Why Does the World Exist? is my personal favorite: “As a Buddhist, … he believes that the universe had no beginning….The Buddhist doctrine of a beginning-less universe makes the most metaphysical sense….A billion causes could not make the universe come into existence out of what does not exist”.

Perhaps the reality that exists beyond our universe or that preceded the Big Bang (the super-universe, the multiverse, the quantum foam, whatever it might be) always existed and always will. It simply was. Or is. It never came into existence, so no cause, reason or explanation is necessary or even possible. Perhaps it’s cyclical. Perhaps it’s not. Perhaps it’s always changing. Perhaps it isn’t. But it had no beginning and might have no end.

The great 17th century philosopher Spinoza referred to all of existence as “God, or Nature” (Deus, sive Natura): “That eternal and infinite being we call God, or Nature”. I prefer “Nature” to “God”. To Spinoza, it was the same thing and it was eternal.