### special relativity

**(SR)**
(physics explaining how the speed of light can be constant)

**Special relativity** (**SR**) is one of two relativity theories by Albert
Einstein, and is an explanation of how the speed of light comes
to be measured at the same rate even if your measuring equipment is
moving along with the light (which might be thought to measure it
as slower) or moving in the opposite direction (making it faster).
For centuries, there has been a notion that anything you do in a
closed room that is smoothly moving at a constant velocity is exactly
the same as within a room that is motionless, a notion that seemed
largely true and possibly completely true.
After scientists succeeded in measuring the speed of light, they
eventually tested whether its measured speed adheres to this notion.
Experiment showed light's speed measurement is the same no matter
how your measurement equipment is moving, and apparently being
within a closed room is not a factor. Albert Einstein worked out
the logic of how this could be true and consistent, which was
eventually termed **relativity**, and later termed **special relativity**
after Einstein additionally worked out general relativity.

Special relativity equations involve only a bit of high school math,
and Einstein may well have worked out their principles in a single
evening, the real challenge having been taking on notions that go
against things we've "known" about how physical reality works, for
our whole life. In contrast, general relativity (which also explains
out how the manner in which things work while stationary on the
surface of the Earth is exactly identical to things done away
from Earth but accelerating just enough to feel like Earth-like
gravity) required Einstein years to devise and he used a
mathematician's assistance to learn new math to do it.

Both special relativity and general relativity are deterministic,
and they calculate a deterministic future-prediction given a current
state, just as do Newton's laws. Though this is the case, there
have been people who associated Einstein's *relativity* with the
idea that objective reality is somehow different for different
people, a notion termed **relativism**. Relativity theories are
unrelated to relativism and purport a single reality that everyone
lives in.

(*physics*)
**Further reading:**

http://en.wikipedia.org/wiki/Special_relativity

**Referenced by pages:**

general relativity (GR)

Lorentz transformation

metric

relativity

spacetime

time dilation

worldline

Index