wendy wrote:If anyone is wondering where i am, i have been wandering around trying to make 'sense' of relativity.
A lot of the stuff i read simply does not make sense. But knowing me, this is not the usual way, but because while the equations look right, the meanings are wrong.
The equation x²+y²+z²-c²t² = a² does not define a kind of distance, since a=0 for everything you can see now.
I learned it by reading
Reflections on Relativity by Kevin Brown, which I highly recommend.
Let's begin with Emmanuel Kant. He noted that we do not perceive anything directly, all that we can sense are the "forces" that other things set into motion.
We now know that such influences have a finite speed. So we cannot perceive what is going on at the time on our clock. All our information comes from the past.
Relativity deals with this in the following way. Everything in the space where a=0 is our present. It's what's happening. The space a> 0 is our future, while a<0 is the past.
Different locations have different pasts, presents, and futures. There is no common present, past, or future. For different "observers" there are only intersections of these sets.
Next comes velocity. If another observer has the same velocity vector as you, then you both are traveling into the future in much the same way. If the velocity vectors differ, especially if they are not in the same direction, then the two observers have a differing angle into the future. The strange effects are well known.
Changes in that angle may have great effect. Our world is based on this. This is less well known.