Turtles all the way down

Infinity is a slippery idea. People talk fairly casually of “eternity” — an infinite period of time. According to the Big Bang theory, the universe came into being about 13 billion years ago. Not only was there no universe before then — there was “no before” before then. Some people worry about that, and most of them seem much happier with the idea that the universe has always existed. That is, its past has already been long.

This alternative seems to solve the difficult question of the origin of the universe, by denying that it ever had an origin. If something has always been here, it’s silly to ask why it is here now, isn’t it?

Probably. But, that doesn’t explain why it has always been here.

This can be a difficult point to grasp. To bring it into perspective, let me compare it with a rather different proposal. There is an amusing (and very likely true) that a brilliant, famous scientist — Stephen Hawking is often mentioned because he told the story in A Brief History of Time — was giving a lecture about the universe, and a lady in the audience pointed out that the Earth floats in space because it rests on the back of four elephants, which in turn rest on the back of a turtle.

“Ah, but what supports the turtle?”, Stephen Hawking asked.

“Don’t be silly,” she said, “It’s turtles all the way down!”

All very amusing and we don’t buy that explanation. A self-supporting pile of turtles is ludicrous, and not just because it’s turtles. Each turtle being supported by a previous one just doesn’t look like an explanation of  how the whole pile stays up.

Very well. But, now replace the earth by the present state of the universe, and replace each turtle by the previous state of the universe. Oh, and change “support” to “cause”. Why does the universe exist? Because a previous one did. Did all start a finite time in the past? No, it’s universes all the way back.

So, a universe that has always existed is at least as puzzling as one that has not.

Reference: A Brief History of Time by Stephen Hawking

Reference: Professor Ian Stewart’s Cabinet of Mathematical Curiosities.

More later,

Nalin Pithwa



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