What is the theory of relativity stating?

Question

I've heard three different explainations.....

1. Time and space areintertwined to make the Space-Time continuum. The faster you go, the slower time moves. (I think this is B-S.)

2. Everythin must be measured relative to something else. If you're doing 40 MPH in a car, you're actually going faster because the planet you're on is rotating.... so you're going as fast as the planet is rotating + 40MPH. (I guess this makes sense...)

3. It takes a certain amount of energy to move a certain amount of matter at a certain rate of speed. (This looks right, but it sounds totally dofferent that everything else...)

4. Green Nuclear Zoom Zooms!!!! Weeeeeeeeee!!!!!!

Is it one of these, or something completely different??

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Answer 1

It's all of those and more. Points 2 and 3 were well known before Einstein's theory, so it's not part of the theory, but it is important for the theory. Point 1 is true. All of it is true, and it's not BS - it's been experimentally verified.

Einstein's Special Theory of Relativity is based on two Postulates: 1) The Laws of Physics are the same in all intertial reference frames. So if you're traveling at 400mph and your friend is traveling at 800 mph, if you measure the half-life of some radioactive isotope each within your own reference frame, you'll get the same number. Makes sense. 2) The speed of light is universally constant. This is the weird one. It says that no matter how you measure the speed of light in vaccuum you get the same number. Let me explain this one more thoroughly: You are standing on the side of the road and a car passes you at 50mph (you measured it with a radar gun). You're friend is driving at 30mph ahead of the other car. When the 50mph car passes your friend, he measures the speed to me 20mph relative to him (i.e., the 50mph car is traveling 20mph faster than he is). That makes sense, and that's Newtonian physics. Do the same experiment with light. You're on a planet and light beam goes by. You measure the speed of light to be 186,000mps. Your friend is on a spaceship traveling at half the speed of light (93,000mps). When the beam of light passes him, what should he measure its speed to be? If you answered 93,000, then you'd be right from Netwon's point of view. But experimentally, it has been shown, that you would actually measure 186,000mps. That's why relativity was invented. To explain this weird result. Now once you except this postulate, other weird things are directly resulting from it. Things like the length of a ruler depends on how fast the observer is traveling relative to the ruler (so your friend would measure a slightly different number for the wavelength of the light pulse than you would based on your different speeds). And, even weirder, time slows down for a person traveling faster than someone else. So a person who leaves Earth on a rocket will travel 50 years (at close to the speed of light), return to Earth, and find that, say, 100 years would have passed on Earth (I didn't do any math, so don't quote those numbers). This has been experimentally verified by measuring the time it takes for particles to decay as they travel at different speeds.

General Relativity is even weirder, but that's another post. It extends special relativity to non-inertial frame. Just take this to mean that the theory describes gravity. It states that gravity is caused by a curvature of space-time (space and time) and that this curvature is what produces the force of gravity. Matter and energy curve space. This has been measured as well.

Answer 2

Basically relativity states that space-time and matter-energy are dual pairs. They can be interchanged with the right factors. There is no absolute time. Time is different for the observer. Gravity has an effect on time. Two very accurate clocks were set at the bottom and top of a tall building and measured slightly different times. The faster you go the more energy it takes. The more massive something is the more energy it takes to make it go fast. How is that really that surprising?

Answer 3

Einstein's theory of relativity really says two important things:

The first has to do with light. Motion is relative in all time-frames, but not the speed of light. This is best illustrated with an example.

If you're driving at 40 MPH and your friend passes you while travelling at 60 MPH, it's exactly the same as if you were still and he were going 20 MPH. Relative. No so with light. If your friend turns on a flashlight and you shoot off after that beam of light at a third of the speed of light, you will still see that beam of light moving away from you at light speed. Just the same as if you were standing still.

This is immensely counter-intuitive. And the only way to make sense of it is if other things are changing that don't normally change. Namely, the passage of time and your size (and consequently mass).

As you travel faster and faster, your internal time perception slows further and further while the external universe seems to be going faster and faster relative to you. If you could go almost the speed of light, you would effectively not personally travel through time at all. You could go from Earth to the nearest star in the blink of an eye. But it would only be for you. Everyone else would see you moving about at light speed and arriving a few years later.

Unfortunately, it's really, really hard to go the speed of light because your mass changes. Energy that you expend to accelerate is instead turned into extra mass, making it harder for you to accelerate more. At light speed, this approaches infinity, which is why light speed is cited at the 'universal speed limit'. As we understand the rules now, no amount of energy would be sufficient to accelerate even the smallest piece of matter to light speed, much less past it.

Before you doubt either of these effect, let me say that they are some of the most rigorously proved in science. Atomic clocks have been set at the top and bottom of skyscrapers, and even that small difference in velocity (with the rotation of the earth, the top moves faster) is enough to cause a difference in the times displayed. Likewise, electrons have been observed to gain mass wwhen forced to move at near-light speeds in certain atomic orbitals. These are facts.

This part in particular is one of the primary origins of the idea of 'spacetime'. Because all motion necessarily causes some (if miniscule) change in time perception, it is impossible to move in space without also moving in time.

The second major statement of Einstein's relativity is that gravity can warp space. And the more gravity is present, the more it is warped. Thus even things without mass (such as light) are affected by gravity, albeit on a much smaller scale than gravitational attraction normally works upon.

With ideas such as vacuum energy, the expansion of the universe, and other space-distorting effects, this seems less unreasonable these days than it might have once. This, like the other statements, have been very well proven too, and is even used as a means to measure distances to certain stellar objects.

Some people have taken these theories to all kinds of odd extremes to justify a number of strange ideas. I'll leave elaboration of those to them.

Answer 4

There are two theories...

SPECIAL theory which states that the speed of light is constant with respect to the observer. This has some real major implications! There is no reference point in space. Only the observer.

and the

GENERAL theory which contains your space/time/gravity thing. Also the relationship between energy and mater. E=M^2.

In effect blowing Newton out of the water. But wait! There's quantum physics too!

Answer 5

My physics textbook says:

1) Events that are simultaneous for one observer might not be simultaneous for another.

2) When two observers moving relative to each other measure a time interval or a length, they may not get the same results

3) For the conservation principles for momentum and energy to be valid in all inertial systems, Newton's second law and the equations for momentum and kinetic energy have to be revised.

I mostly understood it in terms of time dilation... the whole simultaneous events part. The first part you asked about is not exactly right I don't think. It's not the slower time moves, it's that time moves slower to you relative to time to something moving at a slower velocity.

Time dilations looks like this:

Change in Time = (Change in time naught) / (1-u^2/c^2) ^(1/2)

Where u is a constant speed an object moving relative to the object we are considering at rest. The change in time for the observer (object at rest) is change in time naught. c is the speed of light.

Answer 6

#1 is correct...sort of.

To an outside observer, time slows down when observing something moving very fast. If you were to watch a train going the speed of light, the speech of everyone on the train would be slow and garbled.

Answer 7

Gravity and acceleration are equivalent, then it can be said that motion affects gravity (like time and space), as well.

Answer 8

By the way what is your question