Microsoft Word Kurzweil, Ray The Singularity Is Near doc

Going Back in Time.
Another intriguing—and highly speculative—possibility is to send a computational process 
back in time through a "wormhole" in space-time. Theoretical physicist Todd Brun of the Institute for Advanced 
Studies at Princeton has analyzed the possibility of computing using what he calls a "closed timelike curve" (CTC). 
According to Brun, CTCs could "send information (such as the result of calculations) into their own past light 
cones."
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Brun does not provide a design for such a device but establishes that such a system is consistent with the laws of 
physics. His time-traveling computer also does not create the "grandfather paradox," often cited in discussions of time 
travel. This well-known paradox points out that if person A goes back in time, he could kill his grandfather, causing A 
not to exist, resulting in his grandfather not being killed by him, so A would exist and thus could go back and kill his 
grandfather, and so on, ad infinitum. 
Brun's time-stretching computational process does not appear to introduce this problem because it does not affect 
the past. It produces a determinate and unambiguous answer in the present to a posed question. The question must 
have a dear answer, and the answer is not presented until after the question is asked, although the process to determine 
the answer can take place before the question is asked using the CTC. Conversely, the process could take place after 
the question is asked and then use a CTC to bring the answer back into the present (but not before the question was 
asked, because that would introduce the grandfather paradox). There may very well be fundamental barriers (or 
limitations) to such a process that we don't yet understand, but those barriers have yet to be identified. If feasible, it 
would greatly expand the potential of local computation. Again, all of my estimates of computational capacities and of 
the capabilities of the Singularity do not rely on Brun's tentative conjecture. 
E
RIC 
D
REXLER
:
 I don't know, Ray. I'm pessimistic on the prospects for picotechnology. With the stable particles we 
know of, I don't see how there can be picoscale structure without the enormous pressures found in a collapsed 
star—a white dwarf or a neutron star—and then you would get a solid chunk of stuff like a metal, but a million 
times denser. This doesn't seem very useful, even if it were possible to make it in our solar system. If physics 
included a stable particle like an electron but a hundred times more massive, it would be a different story, but 
we don't know of one. 
R
AY
:
 
We manipulate subatomic particles today with accelerators that fall significantly short of the conditions in a 
neutron star. Moreover, we manipulate subatomic particles such as electrons today with tabletop devices. 
Scientists recently captured and stopped a photon dead in its tracks. 
E
RIC
:
 Yes, but what kind of manipulation? If we count manipulating small particles, then all technology is already 
picotechnology, because all matter is made of subatomic particles. Smashing particles together in accelerators 
produces debris, not machines or circuits. 
R
AY
:
 
I didn’t say we've solved the conceptual problems of picotechnology. I've got you penciled in to do that in 2072. 
E
RIC
:
 Oh, good, then I see you have me living a long time. 
R
AY
:
 
Yes, well, if you stay on the sharp leading edge of health and medical insights and technology, as I'm trying to