Three questions

[Sophius]

I apologize for not posting these questions within a forum devoted to a specific branch of science, however these questions cover multiple fields of study, so this seemed to be the most adequate place to post them. First of all, please forgive me if these questions are sophomoric, for I am afraid that I myself am but a mere high school sophomore grappling with concepts that I can only review conceptually (Embarrasingly enough, I'm only in pre-calculus, so I'm not yet able to read some of the more technical works), however, I have been siezed by the pressing need to verify ideas that have vexed me for weeks. It seems to me that these ideas would stand to reason given the current concepts expressed in modern physics, but like I said before, I require verification(along with a potential book recomendation.).

 

My questions are:

 

Because something travelling at the speed of light is said not to age due to time dialation, would this mean that an entity travelling at the speed of light (which I am aware is considered impossible for massive objects, but let's say the entity in question is a sentient being made purely out of energy) would appear to himself/herself to reach his/her destination instantaneously?

 

Also, because light does not age, if somehow something were capable of travelling faster than the speed of light, would that not mean that they would travel backwards in time?

 

Furthermore, if Tachyons are a legitmately existing particle as they are currently theorized, would that not mean that they would travel backwards in time, and if that was so, what would that look like to an observer?

 

Also, could anyone point me out to a comprehensive and non-technical( preferably non-religious) assesment of Tachyon theory.

 

Thank you to all who respond.

[ajb]

Because something travelling at the speed of light is said not to age due to time dialation, would this mean that an entity travelling at the speed of light (which I am aware is considered impossible for massive objects, but let's say the entity in question is a sentient being made purely out of energy) would appear to himself/herself to reach his/her destination instantaneously?

 

By appear to "himself" means that one can set up an inertial rest frame and make measurements relative to that frame. However massless objects have to travel at the speed of light as measured in any inertial frame, that is there is no good definition of a rest frame for them. Thus we cannot really talk about "their point of view".

 

Massive particles however we do have the notion of a rest frame and thus can talk about proper time and proper length.

 

Also, because light does not age, if somehow something were capable of travelling faster than the speed of light, would that not mean that they would travel backwards in time?

 

So see above for light.

 

If a particle travels faster than light then it is always possible to find an inertial reference frame in which the particle is travelling backwards in time.

 

 

Furthermore, if Tachyons are a legitmately existing particle as they are currently theorized, would that not mean that they would travel backwards in time, and if that was so, what would that look like to an observer?

 

Yes, classically tachyons travel backwards in time. They would be observable, and have negative mass squared.

 

However, quantum mechanically they are believed to be unstable and decay very quickly.

 

Also, could anyone point me out to a comprehensive and non-technical( preferably non-religious) assesment of Tachyon theory.

 

Tachyons are not a religious issue.

 

Tachyons appear in string theory and quantum field theory. They can also be understood classically, which I think is what you are looking for. One of the initial papers on the subject is [1].

 

References

[1] Feinberg, Gerald (1967). "Possibility of Faster-Than-Light Particles". Physical Review 159 (5): 1089–1105