ok this is really a question and it's something that has been bugging me for ages!
my understanding of this is quite limited so it's probably not accurate but bear with me here!
So energy and mass are interchangable, and any kind of energy, heat, radiation ect absorbed by a particle is turned into movement i.e. the particle becomes excited and vibrates more. So the faster/more movement a particle has the more energy it has and in turn the more mass it has. So as a particle accelerates and moves faster it becomes heavier and more massive and it requires more energy input to accelerate it and make it move even faster. The way i see it it is impossible to reach the speed of light because at this speed any body will have infinite mass and require infinite energy to accelerate it to this speed, which is impossible. Is this correct?? Also, true/absolute zero, is this the sort of the other end of the stick? when you take energy away from something it becomes less massive until a point at which it has no mass left i.e. absolute zero. True/false??
Another thing as you accelerate time slows down until you reach the speed of light at which point time stands still. But i've heard a lot about distance and legnths decreasing or contracting and reaching nothing at the speed of light, is this correct? Or is it just that at this speed time would stand still so anything you did would be instantaneous e.g. something moving from one place to another would get there instantly whatever the distance??
If you have any knoledge on this or know any websites where i might find some answers please post them below. thnx

also just had another though, if something had zero mass, i.e. it had reached true zero does this neccesarilly imply that it ceases to exist?? of rather somehow if it were reheated it could re-apear or something??

Hi god-of-course,

"So energy and mass are interchangable, and any kind of energy, heat, radiation ect absorbed by a particle is turned into movement i.e. the particle becomes excited and vibrates more."

Well, you should take care what you mean by "movement", there are some (complicated when taken all-together) effects you must consider: If a system of particles absorbs radiation, this energy is used to let the entire system vibrate around an equilibrium position, i.e. there is no translational movement here. The momentum of the photon is used to start a translation of the entire system (assuming it was at rest first). Add to that the possibility that single particles of the entire system absorb energy to get into excited states and you'll understand that it is not evident to say where absorbed energy goes. (For the techies: yes, we can determine that by studying energy spectra and filtering out vibrational modes, excitation modes, etc etc).

[i]"So the faster/more movement a particle has the more energy it has and in turn the more mass it has. So as a particle accelerates and moves faster it becomes heavier and more massive and it requires more energy input to accelerate it and make it move even faster."

The faster a particle moves (translational movement), the more kinetic energy it has. In special relativity you can associate a "mass" with this kinetic energy. It is not true that the particle becomes "heavier": if you would move along with the particle, and would put the particle on a balance, you would not see an increase in (rest) mass.

The "weight" of a particle is determined by this rest-mass (= the mass of the particle when put on a balance when it is at rest, i.e. the idea of mass as we use it daily). This quantity remains constant (at all time, for all observers). However, there is also the idea of "mass" in relativity (the "m" in E=mc²) that indicates how difficult it will be to accelerate a particle, and in that sense you are right: the "mass" increases, and it will be more difficult to accelerate it.

[i]"The way i see it it is impossible to reach the speed of light because at this speed any body will have infinite mass and require infinite energy to accelerate it to this speed, which is impossible. Is this correct??"

When the word "mass" is interpreted right, this is exactly the explanation that the theory of special relativity offers.

"Also, true/absolute zero, is this the sort of the other end of the stick? when you take energy away from something it becomes less massive until a point at which it has no mass left i.e. absolute zero. True/false??"

This is not correct. A particle will always have a minimum amount of energy associated with it. If the rest-mass of a particle is m₀ then the minimum energy a particle can have is E = m₀c².

[i]"Another thing as you accelerate time slows down until you reach the speed of light at which point time stands still. But i've heard a lot about distance and legnths decreasing or contracting and reaching nothing at the speed of light, is this correct? Or is it just that at this speed time would stand still so anything you did would be instantaneous e.g. something moving from one place to another would get there instantly whatever the distance??"

The mixed combination of time dilatation (time slowing down) and length contraction led John Wheeler to say "We can go anywhere in the universe". As your speed increases, the distance you have to travel shortens and the time for you required to do so also decreases.

[i]"also just had another though, if something had zero mass, i.e. it had reached true zero does this neccesarilly imply that it ceases to exist?? of rather somehow if it were reheated it could re-apear or something??"

Zero mass = Zero energy = vacuum = nothing. Note that "zero mass" implies "Zero restmass" (but not the other way around, a photon has zero restmass, but it has "mass" in the relativistic sense). Theoretically, there exists a construct where you can "heat" vacuum (i.e. put energy in it) and create a particle that way. I am not sure if this is experimentally verified to be possible, since energy always needs a carrier (photon, particle, ... ) so it is not entirely clear how you would experimentally transmit energy "to the vacuum".

Bye!

Crisp