There could be as many as 5^500 universes in the multiverse, according to string theory.^{1}

That's five hundred zeroes, Ladies and Gentlemen. When I heard this I had to laugh out loud. Then I paused the video, stared into infinity and cackled insanely for a good quarter of an hour.

The number derives from the variations of possible ways of compacting the extra dimensions in string theory.^{2} The way the dimensions are compacted dictate the fundamental physical laws of that universe.

In other words, the laws of physics are determined by how 6 extra dimensions are knottet up.
(yeah, I don't really, *really* get it either)

They can be knottet up a lot of different ways. Here's how many ways, here's five hundred zeroes:

500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

(yeah, I get that those are not all viable - for human life - universes, but it's a big number, and I - we - like to go "ooh" over big numbers)

Regarding the low estimate, this slide mentions 10^1000 as well ![[Pasted image 20210309214538.png]] Source: https://www.d.umn.edu/~vvanchur/2013PHYS1021/vanchurin.pdf

It seems these possible universes are not all viable, if I understand it correctly, listening to [[Michio Kaku]] on [[into the impossible]] podcast 2021-05-02. Some don't even have internally consistent mathemathics, like you could prove 2+2=5 in some of them.

via:: [[Beyond einstein - in search of the ultimate explanation]]