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On the (Small) Number of Atoms in the Universe

norvig.com

31–40 of 171 posts

Re: On the (Small) Number of Atoms in the Universe

#31
post #26
post #25

There is a theory that states the number of atoms (well, electrons) in the universe is exactly 1. https://en.wikipedia.org/wiki/One-electron_universe

But electrons interact with each other, don't they? How'd that work?

The rules probably aren't the same as they are in Back to the Future.

Re: On the (Small) Number of Atoms in the Universe

#33

I like how Ken Jennings dealt with the 'Go complexity' analogy: "Go is famously a more complex game than chess, with its larger board, longer games, and many more pieces. Google’s DeepMind artificial intelligence team likes to say that there are more possible Go boards than atoms in the known universe, but that vastly understates the computational problem. There are about 10^170 board positions in Go, and only 10^80…

> the total number of atoms in all those universes combined would be close

Close?? Wouldn't it still be roughly 10 billion times smaller...?

Re: On the (Small) Number of Atoms in the Universe

#35

I like how Ken Jennings dealt with the 'Go complexity' analogy: "Go is famously a more complex game than chess, with its larger board, longer games, and many more pieces. Google’s DeepMind artificial intelligence team likes to say that there are more possible Go boards than atoms in the known universe, but that vastly understates the computational problem. There are about 10^170 board positions in Go, and only 10^80…

> the total number of atoms in all those universes combined would be close Close?? Wouldn't it still be roughly 10 billion times smaller...?

When you're dealing with numbers on the order of 10^80 to 10^170, I think you're entitled to calling that "close".

Re: On the (Small) Number of Atoms in the Universe

#36

I'm curious how the author found the link to this - I looked at Norvig's home page but could not find it, which made me wonder how many more goodies he's got up there that we don't know about!

Some search engines have a "link:" modifier that you might already be aware of. That can help you find paths leading to a particular page.

Re: On the (Small) Number of Atoms in the Universe

#37
post #23

Earlier quoted context omitted.

> And would such a theory have any practical use? Yes, sureley. In Computablilty Theory you have the famous Ackermann-function[1]. It is actually an operator-extension, like you just described. It is important, because it grows overexponentially, but is still computable (unlike e.g. the busy-beaver-function). [1]: https://en.wikipedia.org/wiki/Ackermann_function

Given that Graham's Number is an (over-)extension of the Ackermann-function that means that it's still computable, correct? Given the series leading up to Graham's Number, G = g_64 (g_1, g_2, ...), BB(n) will outgrow g_n, right? If so what's the smallest n such that BB(n) > g_n?

After a bit of research I found that there is a proof [0][1] that BB(12) > g_1. But that's still a ways from g_2, let alone g_64.

[0]: "A Lower Bound on Rado's Sigma Function for Binary Turing Machines" by Milton Green (1964)

[1]: https://en.wikipedia.org/wiki/Busy_beaver#Known_values_for_....

Re: On the (Small) Number of Atoms in the Universe

#38
post #11
post #9

Earlier quoted context omitted.

That actually makes the Earth seem small to me. I wouldn't have blinked if someone had told me the blueberries would fill up a sphere the size of the Solar System. Just shows how hard it is to visualize these numbers.

The earth is small. If you build a scale model of the solar system the size of a football field, with the sun and one end and Neptune at the other (Pluto has been laid off as a planet) then the sun will be about the size of a ping pong ball and the earth will be the size of a poppy seed (and it will be about ten feet from the sun). Jupiter is about the size of a pea at this scale. Alpha Centauri is about four miles a…

Planets seem like a really big waste of mass in that sense. Computational dust in a cloud around a sun would be a more efficient allocation.

Re: On the (Small) Number of Atoms in the Universe

#39

I like how Ken Jennings dealt with the 'Go complexity' analogy: "Go is famously a more complex game than chess, with its larger board, longer games, and many more pieces. Google’s DeepMind artificial intelligence team likes to say that there are more possible Go boards than atoms in the known universe, but that vastly understates the computational problem. There are about 10^170 board positions in Go, and only 10^80…

Comparing combinations with numbers of items is unfair.

In Go, the number of items is the number of pieces, and it's very small.

In the universe, the number of combinations of positions of all the atoms is, well, wonderful.

Re: On the (Small) Number of Atoms in the Universe

#40

If you believe in the axiom of choice (I don't) then you can imagine a process which has more degrees of freedom in in than anything at all.

You don't believe that the product of non-empty sets is non-empty?

You could always be a intuitionist/constructivist, and enjoy "choice" as a theorem. It seems completely reasonable to give up uncountable infinities.

http://arxiv.org/abs/math/0404335

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