RELATIVITY…
One principal
subject of physics is relativity, the field of study that measures events
(things that happen): where and when they happen, and by how much any two
events are separated in space and time. In addition, relativity has to do with
transforming such measurement reference frame that move relative to each other.
Transformation
and moving reference frame were well understood and quite routine to physicists
in 1905. Then albert Einstein published his special theory of relativity. The
adjective special mean that the theory deals only with inertial reference
frames, which are frames in which Newtons laws are valid.
(Einstein general theory of relativity treats that more challenging situation in which reference
frames can undergo gravitational acceleration; the term relativity implies only
inertial reference frames.)
EINSTEIN
DEMONSTRATION…
In particular, Einstein demonstrated that space and time
are entangled; that is, the time between two events depends on how far apart
they occurs and vice versa. Also the entanglement is different for observer who
move relative to each other. One result is that time does not pass at a fixed
rate, as if it were ticked off with mechanical regularity on some master grandfather
clock that controls the universe. Rather, that rate is adjustable: Relative
motion can change the rate at which time passes. Prior to 1905, no one but a
few daydreamer would have thought that. Now, engineers and scientists take it
for granted because their experience with special relativity has reshaped their
common sense.
SPECIAL relativity has the reputation of being difficult.
It is not difficult mathematically, at least not here. However, it is difficult
in that we must be very careful about who measures what about an event and just
how that measurement is made and it can be difficult because it can contradict
routine experience.
Fundamental Of Physics.
The Wall