Expert: Courtney Seligman - 5/4/2010

Question
What caused the big bang?  I understand it to be a singularity that through gravity eventually "exploaded" Is that correct, and if so, why aren't molecules doing that all the time?  Thanks, Marc

Answer
In normal physics, empty space would be considered to have nothing in it -- neither mass, nor energy. But in quantum physics, "empty" space can be thought of having an indeterminate amount of positive or negative energy -- indeterminate in that no observation can verify its existence, because the act of making an observation would inevitably involve some uncertainty in the result, and as long as that uncertainty was larger than the "real" amount of energy, there would be no way of knowing if it was really there, or not.

Now, this idea is very strange, but it leads to an interesting result. Namely, any point in space-time can have any amount of energy, providing that it "disappears" in less time than it would take to observe it. So at some moment in time, at some particular point in space, you might have a nearly infinite amount of energy, capable of creating a whole new Universe. It just can't "hang around" long enough to be observed. But if the energy involved was large enough, it certainly wouldn't hang around, because it would create a whole new Universe, completely separate from the Universe that created it.

That's the basic idea of how the Big Bang probably occurred. If it is correct, our Universe should have certain properties, which as far as we can tell, it does. And every similar quantum physics theory that can be tested has been proven correct, so it seems likely that this theory is correct, as well. And if so, then any Universe can create an infinite number of other Universes, all completely separate from each other, because they each have their very own space-time. (This idea is sometimes referred to as a "multiverse".)

( For a discussion of this idea, you might refer to my webpage, "In The Beginning", at http://cseligman.com/text/prologue.htm )

Now, as to why we don't see this happening all the time...

When I stated that any point in space-time could have any amount of energy, so long as you can't tell that it does, that doesn't mean that it "really" has any amount of energy. There are statistical rules that have to be obeyed, about how likely it is. Piddling amounts of energy, too small to care about even if you could measure them, are fairly common. But larger amounts, say enough to lift a flea a fraction of an inch, are extremely rare. And immense amounts, such as those required to create an entire Universe, would be unbelievably rare. The odds against such a thing happening in any given point of space-time would involve more zeroes than you could shake a stick at.

The only way that you can get new Universes out of this theory is if you have an infinitely infinite number of points of space-time to try this with. Get enough points in space-time, and even though the odds than any one of them will create a new Universe are very close to zero, the overall probability becomes greater than one. It's just that you need a VERY large number of points of space-time.

How many? Imagine dividing the entire Universe into pieces a trillionth of a trillionth of a trillionth of an inch in size. Then divide each second of time that each of those pieces exists into a trillionth of a trillionth of a trillionth of a second. Even for one cubic inch of space, and one second of time, that's about 150 zeroes. Multiply that by the billions of billions of seconds in a Universe such as ours, and however many cubic inches would fit into something tens of billions of light years across, and you probably add another 50 zeroes.

In other words, we have perhaps 200 zeroes worth of space-time points to work with. Even if the odds of one of them creating a new Universe was 190 zeroes to one against, you would create ten billion new Universes.

But suppose you don't want to look at all of space and time, over the entire width and breadth and existence of our Universe, but at just a small region -- say, whatever you can intently gaze at, for the rest of your life. In such a small region, the chances of anything happening would be very close to zero. But suppose a miracle occurred, and something DID happen. You still wouldn't see it, because the energy "glitch" isn't visible in the old Universe. In the old Universe, nothing at all appears to happen. It is only in the NEW Universe, completely unconnected from the old one, that you have a Big Bang.

So you don't see anything happening because (1) the chances of something happening are so small that you couldn't possibly wait around long enough to see it and (2) even if it did happen, there is no way to tell that it did. A neat trick, eh? But a bit disappointing, too. You get the most spectacular fireworks display ever, for no cost at all. But you don't get to watch the show, or even find out that there was one.

I hope this helps, instead of being infinitely confusing. But if not, you would have plenty of company, as quantum physics is a field that sometimes leaves even quantum physicists shaking their heads.