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View Full Version : Relating GR and SR



m74z00219
2008-Nov-30, 10:14 PM
I have a good handle on SR, but not so much on GR. I was wondering, are GR and SR considered separate entities or are they somehow mathematically relatable?

Nowhere Man
2008-Nov-30, 10:17 PM
The simple explanation is that Special Relativity is included in General Relativity as a special case (hence the moniker "Special Relativity"), one in which there is no acceleration. Adding acceleration requires more math that took Einstein 10 years to work out.

Fred

alainprice
2008-Nov-30, 11:11 PM
They're really 2 different beasts.

In special relativity, you simply state that the speed of light is measured as a constant by everyone, and rework the laws of mechanics. This rework ends up being the Lorentz transform, which is a fairly simply concept. In terms of space and time, there is no origin(or preferred coordinate). There are no absolutes, only references. This theory says nothing about gravity. It is a rework to mechanics in terms of space, time, mass, energy, momentum, etc...

In general relativity, you state that there's no experiment which can tell the difference between an acceleration(car, rocket, roller coaster) and gravity(me sitting in my chair, the earth orbiting the sun). We later add in that the speed of light is a constant in vacuum and a few other things, and we have general relativity. Since it does away with gravity as a force, it is mathematically challenging to describe. It's so intense that it's not used unless really necessary. It looks at spacetime and just picks an origin and works out from there. This theory describes gravity, but still does not explain what causes it.