If we can send information even a little to the past, we can then send it a little more to the past, and by induction we can send information anywhere in time.
So we have infinite power computers. Singularity starts here.
If you can send data a little into the past, compute something, then send the result back to the beginning, you can do an infinite amount of computation in a finite amount of time, just by reusing the same time over and over again. https://secure.wikimedia.org/wikipedia/en/wiki/Closed_timeli...
It has been argued that we can avoid the notion of tachyons traveling into the past using the Feinberg reinterpretation principle which states that a negative-energy tachyon sent back in time in an attempt to challenge forward temporal causality can always be reinterpreted as a positive-energy tachyon traveling forward in time. This is because observers cannot distinguish between the emission and absorption of tachyons. For a tachyon, there is no distinction between the processes of emission and absorption, because there always exists a sub-light speed reference frame shift that alters the temporal direction of the tachyon's world-line, which is not true for bradyons or luxons. The attempt to detect a tachyon from the future (and challenge forward causality) can actually create the same tachyon and sends it forward in time (which is itself a causal event).
Your mind isn't properly blown until you read the next paragraph which ends with the thought: "Although remote, the possibility of backward causality is not a real challenge to the principle of causality, but rather a novel way of understanding an additional aspect of it."
If we can send information even a little to the past, we can then send it a little more to the past, and by induction we can send information anywhere in time.
So we have infinite power computers. Singularity starts here.