Last week on io9 was a fascinating story on how two scientists looking for time travelers searched archival texts mentioning "Pope Francis and comet ison." Two phenomena which could not have been known in the past. The results: a big zero. But why are there no time travelers? You know how if you put something out of your mind, your brain still thinks of it on the back burner? Well, I couldn't let it go. And it got me to think about Moore's Law. That the number of transistors that can fit on a computer chip doubles every two years.

Its pretty stunning to think this has happened well within our lifetimes. Now suppose, technology slows down so that instead of doubling every two years, its every five. Or even ten. What would computers look like in 100 years? A thousand? Ten thousand? The amount of processing power potentially available in the future is beyond mind boggling. If that were so, then the calculations needed to send information back to the past should exist. [In this scenario, I only discuss information as the power requirements to send physical matter backwards in time may still not exist.] But then, where are the hidden messages? Since modern humans have existed for 50,000 years, another 10,000 is not out of the question. Maybe the absence is because humanity does not survive some future cataclysmic event wiping us out before we invent the technology? Are we doomed without time travel?