Special Relativity

Special theory of relativity is basically this:

Every observer has their own inertial frame - perspective on the universe (this is to do with them having a particular velocity)

Special theory of relativity is basically this:

Every observer has their own inertial frame - perspective on the universe (this is to do with them having a particular velocity)

In your inertial frame, time and space warp such that the speed of light always appears to be constant.

So if you go faster, time dilates (each second becomes "longer") and lengths contract (metres become "shorter"). Without diagrams, it's quite hard to explain why this would make the speed of light look like it is constant regardless of your personal velocity, so maybe look in a physics textbook or check out t'internet.

As for theories that dispute the fact that the speed of light is constant, the only type I know are Variable Speed of Light (VSL) theories. These theories don't dispute relativity out of hand i.e. they still agree that right now, if I was going faster than you, time would pass more slowly for me etc.... What they suggest is that in the early universe, the speed of light was still constant for all observers, but was different to what it is today i.e. they are challenging the numerical value of the speed of light at different times in the universe's history.

Joao Magueijo's book Faster Than the Speed of Light is about VSL and its implications for cosmology. Also has a really good introduction to special and general relativity. Well worth reading if you're doing your coursework on this.

Johnny C, I must take issue with your description of relativity.


- Most observers are not in an inertial frame! Most things in the universe are accelerating due to gravity, many orbiting. This is a bit picky, but your statement is incorrect. Special relativity is to do with observers in an inertial frame, but this is a special case...hence the "special" part!
- Your reference to a "particular velocity" is contradictory to special relativity. You are implying a preferred frame against which this "velocity" is being measured. The true essence of special relativity is that every observer who is in an inertial frame sees himself as stationary, and everything else moving about him.


- The speed of light doesn't just "appear to be" constant or "look like" it's constant: it is constant. There is nothing you can do, inside current theory, in order to measure the speed of light in vacuo as something different to c. By describing it as you do, you are implying that there is some hidden physics which is stopping us from treating light like an everyday object. This is not true: light has its own physics very different from own everyday intuition.
- Again, there's no such thing as a "personal velocity". Your reference to seconds becoming longer as you go faster is not correct. As you increase your speed relative to someone else, you will notice their time dilating, not your own, and similarly for length contraction.


Just so I don't appear vindictive, I completely agree with this!

I really wasn't trying to be picky, but I just think it's very important to use the correct language when describing such strange ideas as relativity. Basically, if you ever talk about a velocity in relativity, it has to be relative to some other specified frame. There is no such thing as absolute velocity.

thank you for your message. i do find it quite difficult to really truly grasp the theorem. But i suppose i can articulate some stuff, thankyou, i may come back to you for help! Thanks! By the way, how thick is that book? Can i read it within a couple days?