The Big Bang theory is the prevailing theory about the “birth” of the universe.
Throughout human history, every time we think we know what the universe is, it turns out that there is not just one of those things, but a lot of them.
First we thought the universe was Earth, a sun and a moon, and a sky with a lot of mysterious points of lights. Then there turned out to be a number of planets with their own moons. Then a lot of suns, with their own planets: a lot of solar systems.
For a while the universe was what we now call our galaxy. And then, it was a number of galaxies. Maybe five. Maybe five hundred. Maybe five million. However many galaxies we think, at any given time, make up the universe, it turns out that there are a million times more!
If our universe is our planet, plus everything we can see from here with our most powerful telescopes, then there are zillions of similar universes that are not our universe. Hence a multiverse. In that sense, at least, we live in a multiverse.
But now physicists are telling us, or at least asking us to consider, that we live in a multiverse of a much different sort.
All the galaxies we have just been talking about obey the same physics; the same basic laws, and the same constant values, like the speed of light. But what is called a “type 2” multiverse consists of universes where the fundamental constants have different values. Maybe e=mc3. Maybe light moves at the speed of molasses. It’s not just more of the same sorts of galaxies. It’s bunch of alternative universes, that work in different ways.
Why in the world—or perhaps why in the multiverse—would anyone believe that? There are different reasons. One goes like this: The values of the fundamental constants that emerged from the Big Bang were such as to allow for the formation of planets, without which there would have been no life, and no humans. That seems like that was a piece of luck.
But if you suppose that there were zillions of universes, with different values for the fundamental constants, it wouldn’t be a matter of luck, but of statistics. Given enough universes, the odds are that there is sure to be one was that is hospitable to human life. We couldn’t very well say it was luck that we live in one of them, because where else would we live?
One universe, hospitable for human life—call it luck. Or maybe intelligent design. But physicists don’t like luck, or depending on a benevolent God. With enough universes, a hospitable one is an inevitability.
That’s some argument. I’m afraid it doesn’t move me much. Between Intelligent Design and a type-2 multiverse, I’d go for Intelligent Design. I’d pick luck over either of them. But maybe I am missing something.