Re: Time Machines, FTL, and P=NP

Jens Egon Nyborg <jens.e.nyborg@[EMAIL PROTECTED]
> wrote:
> Bryan Derksen skrev:
>> Michael Ash wrote:
>>> Since you don't want to wait around for 300 years, you use your
>>> wormhole and write this instead:
>>>
>>>     get x from future-wormhole
>>>     if no future information exists yet because it's the first run:
>>>         set x to first possibility
>>>     test x
>>>     if x is good, return x
>>>     else put x into wormhole
>> 
>> I assume you mean "put x+1 into wormhole"? An infinite loop could have
>> interesting consequences.

Yes, my mistake. Although I think an infinite loop wouldn't do anything. 
You end up with a self-consistent timeline which happened to involve some 
time travel in the past. You'd hit go and just get 0 out and time wouldn't

loop in any way, so you'd know something was wrong if 0 wasn't the right 
answer.

>> This is basically Hans Moravec's time loop logic
>> <http://en.wikipedia.org/wiki/Time_loop_logic>,
but you came up with
>> some really neat applications that might not immediately occur to most
>> computer scientists. :)
> 
> There are clear similarities, but it seems to me that Michael Ash is
> using paradoxes to do the work, whereas Hans Moravec is relying on
> paradoxes being prohibited by natural law.

I think I mentioned earlier that a lot depends on what sort of time travel

you believe in.

I was assuming a sort of time travel in which every time information is 
transmitted to the past, a new timeline branches off and the old one is 
destroyed.

I think that this is functionally equivalent to the sort of time travel 
postulated in that Moravec time loop logic. With the kind I was assuming, 
paradoxical timelines get destroyed, and the end result is a paradox-free 
timeline. Moravec assumes that the paradoxes simply can't happen. I think 
these are really different ways of describing the same thing, but I could 
be wrong.

-- 
Michael Ash
Rogue Amoeba Software