[snarks_when_bored]

A slight correction (to the original and to my post):  the passage which reads

An estimate of the number of distinct histories that can unfold in an O-region between the big bang and the present gives 10 to the power 10150 . This number is fantastically huge, but the important point is that the number is finite.

should instead read

An estimate of the number of distinct histories that can unfold in an O-region between the big bang and the present gives 10 to the power 10¹⁵⁰. This number is fantastically huge, but the important point is that the number is finite.

That is, Vilenkin is speaking of the gargantuan number

10¹⁰¹⁵⁰

[Erasmus]

Did you find that out by Googling it?

< }B^)