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.

Isn’t One of the Damn Things Enough?

Theoretical physicists talk about parallel or multiple universes a lot these days. The interesting video below explains that there are three main kinds of theories under discussion.

My favorite version is #1. It’s the kind of scenario described by the physicist Lee Smolin in a wonderful book called The Life of the Cosmos. Smolin suggested that we live in a universe that is fit for life (molecules stick together, for example) because a black hole in universe X will tend to generate a new universe Y that is similar to universe X, but not exactly the same (like parents have offspring who are similar but not the same). So there tend to be universes that are like the one we happen to live in, with lots of black holes and natural laws compatible with life. Cosmology meets the theory of evolution and explains why our universe is such a nice place to hang out.

If you’re interested, check out other videos on Henry Reich’s MinutePhysics channel:

Big Science, Low Taxes

The physicist Steven Weinberg wrote an article in the New York Review of Books a few months ago about “big science” — the kind of science that requires large amounts of money. The two main examples of such science are particle physics and cosmology, the sciences of the very small and the very large. In each case, scientific progress has made the problems to be investigated more difficult and more expensive. One of the stories he tells is how concern over federal spending resulted in the death of the Superconducting Super Collider in the early 90s.

Instead of simply calling for the government to devote more money to particle accelerators and space-based telescopes, however, Weinberg puts spending on big science in the context of overall government spending and taxation.

In the last part of his article, he calls attention to the need for more spending on a number of important priorities (education, infrastructure, drug  treatment, patent inspectors, regulation of the financial industry, etc., etc.). Professor Weinberg concludes:

“In fact, many of these other responsibilities of government have been treated worse in the present Congress than science….It seems to me that what is really needed is not more special pleading for one or another particular public good, but for all the people who care about these things to unite in restoring higher and more progressive tax rates, especially on investment income. I am not an economist, but I talk to economists, and I gather that dollar for dollar, government spending stimulates the economy more than tax cuts. It is simply a fallacy to say that we cannot afford increased government spending. But given the anti-tax mania that seems to be gripping the public, views like these are political poison. This is the real crisis, and not just for science.”

The anti-tax mania isn’t gripping the public as a whole, but he makes an excellent point.