I don't say quantum - so called QI works in the big world which may be non quantum, just large enough to include many copies of the Earth.
Egan law - it is not Egan's, it is not a law and it is not true, and some one who tried to question it was extensively downvoted and leaved LW.
Most submarines are already filled with bombs.
Anyway, I think that big world immortality has small chance to actually work (in predictable way), so it would not be wise to use it as any first line defence. But it may be used it third line defence.
For example, if I build a space ship to survive impending catastrophe on Earth, I also use that fact its most likely catastrophic modes will kill all crew in one moment.
The same thing about cryonics. It is good itself, but if big world immortality works, it will be even better.
some one who tried to question it was extensively downvoted and leaved LW
Who? The last LW kerfuffle I can remember that involved Egan's law (and some other Egan things) was around Eitan_Zohar who did indeed get a lot of downvotes and does seem to have left LW. But so far as I can tell he didn't get those downvotes for trying to question "Egan's law".
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