What exactly does Einstein's theory of relativity mean?

Question

I know it has something to do with the speed of light, curved space, weird physics stuff like that, but I'm not entirely sure what it all means. I'm not looking for a lot of detail in the answers, by the way...I know next to nothing about physics.

Answer 1

Einstein's first postulate presents the Principle of Relativity. This principle originated in the observation that events occurring in a vehicle seem to occur in much the same way whether the vehicle is at rest or moving along a straight-line path at some constant ratio of distance to time. In Einstein's words,

the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest. [Thus] ... the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good. We will raise this conjecture (the purport of which will hereinafter be called the "Principle of Relativity") to the status of a postulate .... (2)

The laws by which the states of physical systems undergo change are not affected, whether these changes of state be referred to the one or the other of two systems of co-ordinates in uniform translatory motion. (3)

This postulate tells us that, if a scientific law (L) describing an event in a physical system is valid, it will be equally valid whether the system is a stationary system (S) or a moving system (M), as long as M's motion is along a straight-line path through S at some constant ratio of distance (dS) to time (tS). Briefly, "LS = LM" as long as M's dS/tS is constant.

§ III. The Second Postulate

Einstein's second postulate expresses his law of the constant velocity of light. In Einstein's words,

[we] introduce another postulate, which is only apparently irreconcilable with the former, namely that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body. (4)

Any ray of light moves in the 'stationary' system of coordinates with the determined velocity c, whether the ray be emitted by a stationary or by a moving body. (5)

According to this postulate, a little bit of light generated by a source in a stationary system (S) always travels at the same velocity (CS) relative to S. By definition, this velocity will always be the same constant ratio of distance in S (DS) to time in S (TS). In summary, "DS/TS = CS".

§ IV. The Postulates Combined

What, then, must we believe if we believe that both postulates are true simultaneously?

According to the first postulate, if one of two physical systems is stationary and the other is traveling at some constant velocity relative to the first, then a scientific law which is valid in one system will be valid in the other. Given the second postulate's assertion that the law of light's constant velocity is valid in a stationary physical system, if both postulates are true, then the first postulate is tantamount to an assertion that the law of light's constant velocity is also valid in a moving physical system traveling at some constant ratio of dS/tS relative to the stationary system. In other words, CS = DS/TS = DM/TM = CM.

Necessarily,

DS/DM = TS/TM

DS/DM = 1 when TS/TM = 1
TS/TM = 1 when DS/DM = 1

To visualize these statements, imagine M traveling along a straight-line path through S at some velocity dS/tS.

Answer 2

Basically, "E = MC squared" literally means "Energy equals MASS x LIGHT SPEED squared. That means energy and mass are virtually the same thing, and actually convert in form between each other. It predicts an object can be affected by gravity even if that object has NO MASS (which would make the object more of a unit of pure energy than mass).
The "curve in space and time" isn't hard to understand when you think of it as an object's affect on another being DELAYED by however long it takes for it's attributes to arrive from Point A to Point B at "light speed".\
Personally I think calling it "light speed" confuses the issue for most...this velocity is actually the speed of any object in the Universe with NO MASS...not just light.
It's difficult to give this an "easy answer".

Answer 3

A couple of things Einstein said was that time slows as you speed up, and that for an object to reach the speed of light it would acquire infinite mass. if you could go fast enough long enough you could return to earth and find that where you think you had been gone a day, a month would have passed on earth; if you could approach the speed of light and then return you might find all your friends who were the same age as you when you left were now grown old or dead and buried.

Relativity is really all about how things look relative to an observer who can travel near the speed of light.

Answer 4

He means that things look different to each person based on where we're standing.

For example, if you're in a car and you look out the window, and there is a car driving beside you that is going EXACTLY the same speed as you, they won't look like they're moving, because you're both moving. But both of you will see the world zipping by quickly. And the things inside the car won't be moving for you, either, even though they're speeding along with the car. And if you toss a water bottle from the front seat to the back seat, it'll look like it's moving backwards for you, but for everyone else, it's moving forward with the car.

He also says that we can't judge the speed of light if we're in a vacuum.

Answer 5

In Einstein's own words, Theory of relativity is what the relativity of a young man to time when he sits beside a beautiful girl for hours and on a hot stove for even a second!

Answer 6

SR basically says three things.
1
Information cannot travel between two points in less time than a photon of light could make the same journey.
2
Measurements made between different inertial reference frames are invalid unless corrections are made for (1)
3
You can never know all there is to be known about your own inertial reference frame as long as you are a part of it.

Some people like to add a 4'th about 'there is no preferred inertial reference frame', but 1, 2, and 3 actually imply that anyway.

HTH ☺

Doug

Answer 7

Watch the movie Matrix. Because Neo is moving fast the bullets appear to be moving slowly. The concept of 'bullet time' is relativity!

Answer 8

it is a conversion of energy to mass.......meaning that E (energy) = M (mass) x C2 (energy squared). In summation......all things are energy, including you, and there is alot of it.