What happened before the Big Bang?

Contributed by
Jul 1, 2007
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What happened before the Big Bang? Does that question even make sense?

When astronomers think about the Big Bang, in general they don't actually mean that one singular moment when the Universe burst into being. It's really the name given to the model used to describe what happened an infinitesimally thin slice of time after that moment.

The problem is, right at that moment, at T=0, our laws of physics... well, they stall out. You wind up dividing by zero a lot, which causes a lot of headaches. You get things like zero volume and infinite density of matter and energy. It's not that this moment didn't exist physically, or that something impossible happened, it's just that the math we currently use can't describe it. And let me be clear: what happened after that one moment we can model fairly well. We may not have a complete picture, and the model may yet be supplanted (more on that in a moment), but we have a relatively (har har) good grasp on how the Universe behaved after T=+0.0000000000000...1 seconds. But at T=0, fuggeddaboutit. And T<0? The way the math works, that question doesn't even make sense.

The basic trouble is that Einstein's relativity gives us a good description of some things (large scale gravity, for example), and quantum mechanics tells us about other things (how particles behave), but no one has ever successfully combined the two, and they must be combined to understand that First Nanonanonanonanonanosecond. Einstein himself tried, and failed.

It's possible, now, that this has changed.

Martin Bojowald, an assistant professor of physics at Penn State University, may have broken through this barrier for the first time. He is working on a theory called Loop Quantum Gravity, and it combines relativity and quantum mechanics. Using this new math, something amazing happens: at T=0, the volume of the Universe is not zero, and the density is not infinite.

In other words, the math still works, even at The Big Moment.

Loop Quantum Gravity has been around a while, but Bojowald appears to have simplified it, using different mathematical terminology. This allows solutions to be determined for what was, before, an intractable problem. And what his solution reveals is something that's... well, it's astonishing.

It's been thought for sometime that there may have been some previous Universe that existed "before" ours. This is a difficult idea, because in the Big Bang model, space and time were created in that initial moment. But if Bojowald's solutions are correct, it leads the way to understanding this previous Universe. It was out there, everywhere, and it contracted. Eventually it became an ultradense, ultrahot little ball of space and time. At some point, it got so small and so dense that bizarre quantum laws took effect -- things like the Uncertainty Principle, which states that the more you know about one characteristic of an object (say, its position) the less you know about another (its velocity). There are several such laws, and they make it hard -- impossible, really -- to know everything about the universe at that moment.

What Bojowald's work does, as I understand it (the paper as I write this is not out yet, so I am going by my limited knowledge of LQG and other theories like it) is simplify the math enough to be able to trace some properties of the Universe backwards, right down to T=0, which he calls the Big Bounce. The previous Universe collapsed down, and "bounced" outward again, forming our Universe. No doubt the physical aspects of this previous Universe were somewhat different; the quantum uncertainties at the moment of bounce would ensure that. It may have been much like ours, or it may have been quite alien. In his equations, it's the volume of that previous Universe that cannot be determined. How big was it? It may literally be impossible to ever know.

In a sense, this uncertainty wipes the slate clean after a Universe crunches back down.

I want to stress that all of this is very interesting, and may possibly be borne out to be a better solution to the real physical situation of the Universe than anything we have now. Or, let's face it: it might all eventually be tossed into the toilet. It's a bit early to know. But it's fascinating, and provides a glimpse into the future of cosmology, where we may not be limited by the one singular Universe in which we live. Another theory, called Brane Theory, is similar-- it posits that there are other Universes as well, and they, well, they bounce back and forth, colliding every few hundred billion or trillion years. And that's not even the weird part of brane theory... it might be able to explain dark matter and dark energy, and why our Universe appears to be accelerating. It's well beyond what I can write for this blog entry (though it'll be in my next book, heh heh). There is plenty of info on it on the web if you're interested (here's a good page to start you off).

Also, and what's perhaps most exciting about these theories, is that they make predictions, predictions which can be verified or falsified based on observations. These are delicate experiments to be sure, but some will be possible to perform in just the next few years (for example, different cosmological origin theories predict different behaviors for the Universe at very early times, and these would imprint themselves on objects which can be observed).

These theories may seem like mumbo-jumbo or magic, but they have that very basic property of science: they're testable.

And of course, I have to use this to stick it to the creationists once again. One thing they love to talk about is "fine tuning", how so many physical constants (like the charge on an electron, and the strength of gravity and the nuclear forces) appear to be incredibly well-adjusted to produce not just our Universe, but intelligent life in it: us.

Well, some of us.

The creationists claim that the only way this could possibly happen is if some sort of Intelligent Designer -- and let's not be coy, they mean God -- set these values to be precisely what they are. Even just on its merits this isn't right. I talked about this in the video clip I posted last week, so I won't elaborate here. Go watch it.

But now we see another answer to the creationists: maybe this isn't the only Universe. There might have been a string of them, reaching back in time, in meta-time beyond time. In those other Universes, maybe the electron had more charge, and stars couldn't form. Or maybe it had less, and every star collapsed into a black hole. But if you get enough Universes, and the constants change in each one, then eventually one will get the mix right. Stars will last for billions of years, planets can form, life can evolve, and on one blue green ball of dust, chemicals can get complicated enough that they could look inside themselves, understand what they see, and marvel at the very fact of their own existence.

And maybe, just maybe, they can also figure out how it all came to be. This isn't fantasy, folks, it's science. It's how things work.