Travel Between the Stars
Is travel between the stars (interstellar travel) even possible?
The sun is our star, and orbiting the sun is our planetary system including the Earth. The Earth has been around for a little over 4 billion years, and during that time life has evolved. The pinnacle of that evolution (at this point in time) is humans. Humans have worked out how to travel into space and to the moon. We have learned how to send unpersoned craft to other planets, and we even have probes leaving our solar system for the great unknown.
These somewhat remarkable achievements are not so remarkable when compared to what we would like to achieve, and that is manned or even unmanned travel to planetary systems orbiting other stars. The difference in distance is vast. Whilst it would take light a little over 4 hours to travel to our furthest planet Neptune, it would take light a little over 4 years to travel to our nearest star Proxima Centauri.
We have only been venturing into space since the 1950's though. It is very possible that life living on planets around other stars (exoplanets) may have been evolving and travelling into space for much longer than we have. We can only guess at what technologies these distant lifeforms may have developed. Maybe they have the capability of travelling interstellar distances at near the speed of light. Maybe they have the capability of travelling faster than the speed of light. Is this even a possibility? Our conventional knowledge of physics says "no", but then again "maybe".
Faster Than Light
The Wikipedia article faster than light gives us a good overview of the current state of thinking on this subject, delving into such strange subjects as quantum mechanics and universal expansion. It is a long read, but it really is worth it.
Just for fun an article on Science Alert dot Com gives 4 examples of things that can travel faster than light, but this doesn't really help with our quest to be able to travel interstellar.
Faster than light travel certainly would make interstellar exploration more exciting, but our current knowledge tends to preclude this as a possibility. Nonetheless, we don't know everything, so let's hope there is something our scientists have missed here. It certainly would be nice if scientists have gotten this one wrong.
Sub Light Speed
Without light speed the journey will take a very long time, so we would need to work on ways to reach as much speed as possible. If we could travel even close to light speed it could see us reaching several interesting interstellar destinations well within a human lifetime. With a few obstacles to overcome it's even possible that a human could make the trip to some of our nearest stellar neighbours and then return to Earth. However this brings about the quandary of time dilation. According to relativity the travellers would seem to experience the trip in much less time than the people back on Earth. This is a tough one to get your head around, especially when you consider that whilst the ship would be moving away very fast relative to the Earth, it could also be said that the space ship is stationary and the Earth is moving very fast relative to the ship. If this is the case, why do the people on the ship experience time faster than people on Earth and not vice versa? I'm afraid I have no answer for this one, but if anyone knows please feel free to enlighten us.
Even if we can never travel at or beyond the speed of light we can still look at ways to travel interstellar, but we will have a lot of obstacles to overcome.
One major obstacle is propulsion and fuel. To be able to generate enough energy to travel anywhere near the speed of light we need to devise new efficient propulsion methods and ways to store, generate or collect the fuel required for such a long journey. Michio Kaku has a great thought provoking article about the physics of interstellar travel. The Wikipedia page on interstellar travel is quite good too.
Other major concerns for any such venture include the danger of collisions and overcoming cosmic radiation during such a long space flight. This Popular Science article puts a bit of a dampener on any perceived glory of interstellar travel.
With what we currently know it's doubtful that faster than light travel will ever be possible, but we we stall just short of saying this is an impossibility. We hope it is possible. Interstellar travel at sub light speed certainly looks a more promising prospect. We are cautiously optimistic that humans will one day overcome the obstacles associated with such a venture. There will always be someone trying to make the dream a reality.