In simple terms, what is the theory of relativity?

Answer 1

"A man sits with a pretty girl for an hour and it seems shorter than a minute. But tell that same man to sit on a hot stove for a minute, it is longer than any hour. That's relativity."

Albert Einstein

Answer 2

There 3 kinds of Relativities

1/ The Galilean relativity
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This one is easy to understand: if you walk inside a moving train
you have to add your "speed" to the "speed" of the train.

Another way to state it is that if you run and through a ball
the ball will go faster (seen by someone immobile) than if you through the ball while you are immobile (the speed of your race and the speed of the ball adds: Vrun+VLaunch=Vball)

It also state that if you are inside a train that has a constant speed and that does not vibrate and has no windows you have no way to know if the train moves or not and if it moves at which speed it moves.


2/ The special relativity
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Developped by Einstein it is based on the fact contrarily to the ball in the example above the light goes ALWAYS at the same speed even if the star that produce the light is rushing towards the earth or is rushing away from earth. (this was measured experimentally)

This lead Einstein to conclude that the addition of speeds is more subtle than simply summing 2 numbers.
he replaced the formula from the Galilean relativity by

Vball=(Vrun+Vlaunch) / (1+Vrun*Vlaunch/C²)

Where C is the speed of light 300 000 000meters/second
Since C is HUGE most of the time the Galilean and the special relativities give nearly identical values. but if Vrun grows to be nearly the speed of light then the difference becomes non neglectable.

3/ General relativity
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It is a much more complex theory but It can be summarized as follow:
Here Einstein noticed that there is no difference between the gravity and the acceleration of a vehicle. This lead him to conclude that mass (of a planet) is bending the space. In other words, according to this theory a satellite going around the earth is going along a straight line but on a curved space.

This lead to conclude that in case of very heavy masses the space could be curved enough to bend a light ray (this is used in astronomy to determine that an object seen in the space is not in the direction we see it but at another place) and also explains the black holes where space is bent so much the light is trapped and cannot exit anymore.

Answer 3

There are two theories of relativity, The Special Theory and The General Theory.

The Special Theory was published by Einstein in 1905. The special theory is really about time, and is most noticable with fast moving objects. It abolished old absolute notions of time. Mainly it abolished the idea that time was the same for everything and replaced it with the idea that the direction of time varies, and instead it is the speed of light in a vacuum which is constant. It does this by unifying the idea of time with that of space. The special theory implies clocks go slower as you go faster. It also implies that Mass and Energy are equivalent.

The General Theory came later and is an explanation for Gravity. The General Theory says that Mass and Energy curves space-time. And that Gravity simply is the result of our taking the shortest possible paths in this curved space/time that results.

The General Theory is used to describe massive bodies such as black holes, and it was the General Theory that made possible the science of Cosmology, which is the study of the large scale stucture of the universe.

Answer 4

General relativity or special relativity? Special relativity is the
result of two postulates.

1. The speed of light is the same for all observers despite their relative speeds.
2. The laws of physics are constant in any inertial (ie: non-accelerated) frame of reference.

From these two postulates Einstein demonstrated that classical definitions of momentum and energy must be adjusted. He also demonstrated that quantities such as length and time are dependent upon the observer. Physicists tested the predictions of Einstein's theory against observations and found them to be true. This indeed validates the two postulates that are at the heart of special relativity.

Answer 5

first off, the theory of relativity is NOT E= mc^2... that's the rest-mass energy equation.

the theory of relativity has to do with frames of reference. for example, if you're standing still and a train is passing you at 60 mph, you see the train as moving at sixty miles per hour. However, if you are travelling in a car at 40 mph in the same direction as the train... you only see the train as moving at 20 mph RELATIVE to you. basically, the theory of relativity states that the observations one can make about the world around them are entirely dependant on their reference frame.

furthermore, Einstein noticed that no matter what speed you travel, the speed of light is constant. in order for this to occur, two things had to happen... the length of a second must get longer as you go faster (time dilation) and the distance of one meter must get shorter as you go faster (distance contraction). through a somewhat complex example, you can actually find the time dilation and distance contraction as a percentage for any given speed.

Answer 6

The concept explains that the value of physical time, as it relates to a moving mass, is changeable. The object that moves is the only time changed entity. A similar illustration is found in your personal "time machine" (automobile). A person really does exchange energy for time when they move about in their car. The greater the amount of energy you use in a particular time, the less time it takes to arrive at the destination. The less energy used (gasoline) the longer the time it takes to arrive at the destination.

Keeping this in mind, in the broader sense of time change, the speeds that would cause a major time dilation approach the speed of light. It is not that a person does not really have a slight time dilation when moving in an automobile, or even walking, because they do. The value in these instances is so slight compared to the speed of light that it is negligible - similar in value to holding a candle for lighting ones way while a bright sun shines overhead at noonday. The light of the candle is not realized.

Lastly, there is what is known as the "Twin Paradox". In this instance one twin (Joe) travels to a nearby star that is three light years away, while the other (Josephine) remains on earth. The twin going on the expedition travels from earth to the star at the speed of light (this part of the illustration is impossible, because mass moving at the speed of light converts into electromagnetic energy - but for the sake of the illustration ...). When Joe arrives at the star system, he finds a note left there left by Leonardo Divinci that states just five light years further on is a planet of pure gold and platinum. Joe takes the hint and heads out. Five years later he finds the planet and loads his spacecraft up, then heads directly back to earth to spend his hoard of wealth and tell others what he had seen.

The interesting part of travel at the speed of light is that, were Joe to have begun his travels with a hot cup of coffee and a cold sandwitch, if he made the entire trip and the speed of light, being able to instantly stop and start, when he arrived at the first star, the coffee would have been as hot as when he started three years earlier and the sandwitch just as cool. Further, if Joe immediately headed toward the planet of gold and platinum, when he arrived there everything would still be the same temperature.

Leonardo Divinci had been considerate in pointing out a location for joe to park his spaceship also. All Joe had to do was open his upper hatch, where a waiting ramp would allow all he wanted to slide into his craft. Loading time: 5 minutes. The total time that Joe had spent stopped added up to one hour.

Now Joe Goes directly home. That distance is eight light years away in a direct course. When Joe arrives he shall find:

Sixteen years have passed by on earth for Josephine while one hour has passed by for Joe. Half of the sandwitch he did not eat when he had stopped would still be fresh. Joe would have no sense of any time having passed by, other than one hour.

http://360.yahoo.com/noddarc explains time travel in an easy manner. click on "view blog" and the second writing down "The Problem and Repair of Relativity" will describe why time works this way.

Answer 7

There is no theory of relativity in simple terms! LOL!

OK, it is said as this by Einstein himself:-

"When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour.
This is relativity."

Basically, time and space are the same and and all motion are relative to one another, from a persons point of view.

Answer 8

If you are on a train travelling at 100 miles an hour and your uncle Jack is fired from a cannon at 50 miles an hour, that is just what the old twit deserves.

Boredom emitted by your Great Uncle Arnold travels at the speed of light even if you push him off a cliff and he accelerates away from you under free-fall.

If your Aunt Jackie gets any fatter she will be able to bend space/time, so that her gin and tonic goes into orbit around her while travelling in a straight line.

Bobs your uncle!

Answer 9

Relativity deals with one question:

Are there any changes to the laws of motion when someone is moving, compared to when they aren't?

Galileo put forth his theory: If a table is moving at speed v1 (with respect to the ground), and a block on the table is moving at speed v2 (with respect to the table), then an observer on the ground sees the block moving at a speed v1+v2.

Einstein said that Galileo was close, but not exactly right.

Answer 10

You are traveling at 500mph, somebody fires a gun at you from behind and the bullet travels at 1000mph, at the same time somebody else fires a gun at you from an equal distance in front of you also with a projectile speed of 1000mph. Assuming no loss of speed of the bullets, you'll get hit in the face before being shot in the back. Same thing applies for light/radiation. That's relativity :)