There has been news recently of neutrinos traveling faster than the speed of light. While many remain skeptical of the news, I thought it would be fun to think of the real life implications of a faster than light particle. Physicists have theorized of a particle that moves faster than the speed of light since the 60's called a tachyon. Normal matter can never go faster than the speed of light but a tachyon can never go slower than the speed of light.
According to Einstein any particle going faster than the speed of light must be traveling backwards in time. This creates a lot of problems with causality so it's widely accepted that nothing can go faster than the speed of light (or more accurately nothing can go faster than the cosmic speed limit which is the speed light just happens to travel at). Imagine you had a television with an antenna that detected tachyons. You could watch television broadcasts from the future, assuming they were sending the signal in tachyons. I'd love to see what the world is like 2000, 2 million or 2 billion years from now!
More fascinating to me still would be the idea of a tachyon computer. It would need a tachyon detector to receive information from the future, but to send information to the future you could just write out questions on a piece of paper if you wanted. This seems pretty low tech so we'll just put the questions on a ROM chip. It would be very important to put a time stamp on this data because the Earth rotates around the sun. The future computer operators would have to point the tachyon beam in a specific direction in both time and space so they would need to know where the earth was when the message was sent. There would be certain times when the future Earth was positioned directly on the other side of the sun and we would likely not be able to send a beam back to the past Earth because of interference but that is no problem, they'd just need to wait until the Sun is no longer in the way. From the perspective of the people in the past, information would still be returned instantaneously.
Lets assume we wanted to know how to build a teleportation device. We could write down in our computer "Please send schematics back for teleportation device." Hoping that at some point in the future humans discover how to teleport. When/if they do they would beam the information back to us. Now the question arises, what happens to that future where the teleporter was invented? Let us assume it is erased and overwritten by the new future in which we got the information on teleportation via our computer. Where did that information come from? In this new timeline no one ever invented the teleporter since we've always known how to do it from the tachyon computer.
In order to deal with this problem I think we have to assume every time a piece of information comes back from the future a new separate timeline must be created. Now, we live in a timeline where the information for building a teleporter came to us via tachyon computer, but in the multiverse in another timeline, the inventor of the teleporter still invented it. This way we don't have information just being generated out of nothing. There are theories that every moment the universe splits into every possible outcome of the current universe, so having new timelines created from information from the future would fit in with that theory.
This would also solve another potential dilemma. What if you asked the question "How do I build a teleporter" on the ROM which travels forward in time in the regular fashion, get the answer, and then replace the ROM state with a new question. In the rewriting the current future idea of the universe, because you changed the question after you got the answer, the future never got the original question so how could you have gotten an answer? One solution would be to never erase old questions, always just adding new questions until you ran out of memory, but lets say you did erase a question, would all the teleportation devices just disappear? Would your timeline get erased like the future timeline and replaced with one where we never learned how to build a teleporter from the tachyon computer?
The alternative timeline theory again makes more sense. Once you get the info, you are in a new alternative timeline so even if you delete the original question, the first timeline still has it and still was able to answer it. The only unfortunate thing from some points of view, is the people in all the older timelines will never really get to benefit from all the information provided by the tachyon computer, they would have to just answer the questions as a favor to people in the new timelines being generated. Unless of course they ask the computer how to travel between timelines and reap the benefits of the new timelines.
At the point this computer was invented something like The Singularity (Read The Singularity is Near, or search on Youtube for some videos explaining this fascinating idea) would occur. Almost instantaneously we'd have all of the technology that will ever be invented at our disposal. The only thing that would slow us down is our imagination, which would actually be a considerable factor if you think about it. If you could ask an ancient Roman if he could have any piece of technology from the future, he would never ask for a cell phone, as a device like that is beyond his comprehension. Just 50 years ago people wouldn't be able to conceive of a portable internet connection. This factor would preventing us from getting stuff from the very distant future. I would imagine we'd never ask to know about anything that wasn't discovered within the next 50-100 years.