Theory of Relativity??

Question

What exactly is the theory of relativity?? I know it is E=mc squared, but im not entirely sure what that means. Deatils please, i need all the information possible.

Answer 1

E=MC2 has very little to do with the theory of relativity.



Einstein, who came up with the theory of relativity often said "at what time does the station reach the train?", meaning that although the train relative to almost everything else is moving, if you were on the train it seems as though every thing else is moving. It is like knowing your left and rights, what is on your left, to the person looking at you it is on their right. Left and Rights are relative meaning that they can change.

SOOO, although to the person at the station, it is the train that is moving towards them, to the person on the train, it is the station that is moving towards them.



A final example is if you and a friend were walking down the road next to each other, relative to each other you would not be moving, you would always be at the same distance apart until one of you started to speed up or slow down, how ever to the Old man sitting on the bench across the road you would both be moving away from him.



Hope that helped

Answer 2

I'll try to explain this in simple terms, but it's rather mind-twisting.

These are the basic principles of Relativity:



1. The speed of light is constant for all frames of reference.

Light goes toward you at the same rate no matter how fast you're moving away from the source. As an example, think about someone throwing a ball at you. If they throw the ball at 25 miles an hour and you run away from them at 10 miles an hour, then from your perspective, the ball will be approaching you at only 15 mph, because you are running away from it. But with light, no matter how fast you run away from the approaching light, you will always "see" it coming after you at 186,000 meters per second. But the light isn't speeding up.



2. Time can speed up and slow down.

If you were to get in a rocket and zoom off into space going really fast (nearly the speed of light), and if you were to stay up there for a couple of years (still going really fast), you would come back to Earth to find that a couple of decades had passed. In other words, even though you would have lived only two years, the people on Earth would have lived 20 years already. This is because the faster you are moving physically, the slower time moves. This is not noticeable in everyday situations, because the time change is less than a billionth of a second. It's only a noticeable difference at really high speeds or with really sensitive atomic clocks, but it has been proven to be true.



3. No matter (physical thing made out of atoms or sub-atomic particles) can move at the speed of light, or any faster.

The faster something is moving, the more mass it has. So if you were trying to accelerate something to the speed of light, the faster it got, the heavier it would get, and the harder it would be to make it go any faster. Eventually, it would be too heavy to accelerate. An object moving at the speed of light would theoretically have infinite mass. Since light waves aren't matter (they're energy), they can move at the speed of light. Same goes for gravity waves - they also move at the speed of light.



4. Space and time are meshed together in something called spacetime, which is sort of the "framework" for the universe - like the paper on which you draw a picture. Matter (mass) bends spacetime.

Picture a trampoline. If you were to place a ping pong ball on the trampoline, it would make the area below it sag a little bit, but it would hardly be noticeable, because the ping pong ball is so light. But if you were to put a bowling ball there instead, the indentation would be much larger. In the same way, larger masses cause more curvature in spacetime. This concept has two consequences:



A: The closer you are to a large mass, the slower time gets. So if you were to get really close to a black hole, then time would slow down for you.



B: Remember that going really fast gives you more mass (#3)? Well, this why #2 works. If you're in a rocket going nearly the speed of light, then your mass is going to be bigger. That in turn means that spacetime will curve more around you, so then time will pass slower.



There's a lot more to it than that, but those are the basics.

Answer 3

E=MC^2 is just an equation that qualified as a law.

The theory of relativity is a bit more complicated and involves the idea that time looks different to different users depending on where they were observing it from, and how fast they were moving.

Where they are observing from includes their location in the gravity fields. Relativity regards space and time as parts of the same thing with gravity a result of them being warped by mass.

The best writing that explains it is a book by Einstein himself that he made for the Canadian Broadcasting Corporation.

It is a pretty scarce book.

Answer 4

Einstein published two theories - general relativity and special relativity. The first describes gravity, while the second describes physics at high velocity.



E = m*c^2 refers to the energy a particle with mass m contains while at rest.

Answer 5

The Special Theory of Relativity expresses the results of measurements of physical quantities in reference systems moving uniformly with respect to each other ( i.e. not accelerated ).



The General Theory of Relativity permits the calculation of measurements of such quantities in reference systems uniformly ACCELERATED with respect to each other. It happens that gravity and acclerated systems are equivalent so The G T of R deals with gravity in a very fundamental way.

Answer 6

E = m*c^2 is indeed a formula from relativity.

This formula did not exist before Albert Einstein introduced his special theory of relativity in 1905.



E = the total energy of a particle

m = the total relativistic mass of a particle

c = the speed of light = a constant of nature



Basically stated, that formula tells us that mass and energy are (in some sense) equivalent. That is, if we converted a particle of mass m into pure energy then the amount of energy we would get is E, as given by that formula.



To describe relativity I will simply repost a response that I gave to a similar question:



An introductory explanation of relativity is often done as follows:

1) Introduce the concept of a Galilean transformation,

2) Make it clear that in the Galilean view the speed of light is either infinite or is a different value for different observers.

3) Point out that if observers are moving at constant velocity then they do not feel the motion, and hence that it is natural for every such observer to claim that they are stationary and that others are moving (i.e. the basic notion of relativity within the Galilean picture),

4) Describe the Michelson-Morley experiment and why it is taken as evidence that the speed of light is seen as the same for all observers,

5) Introduce the fact that one would like to have the laws of physics look the same in all inertial (non-accelerating) frames of reference,

6) Point out that the laws of electromagnitism do not look the same in all inertial frames if the Galilean transformation is used,

7) Point out that there is an other kind of transformation law that makes the laws of electromagnetism look the same in all inertial frames (i.e. the Lorentz transformation),

8) Introduce the work of Einstein, in which he derived the transformation equations that would be required if the speed of light were the same for all observers, and as a result he found that the lorentz transformations were the correct ones. He also took the bold step of supposing that the Lorentz transformations could be applied to moving trains and other kinematic examples, not just the Maxwell equations of electromagnism.

9) Begin going through all sorts of examples that highlight the counterintuitive differences between special relativity and the Galilean picture.

10) Point out that one cannot, in certain circumstances, tell the difference between being stationary in a gravitational field and being accelerated through empty space with no gravitational field (e.g. accelerated with rocket thrust). Because of this, Einstein was led to suspect that there is a form of "equivalence" between accelerating frames and frames in a gravitational field, in a similar manner as the equivalence of frames that are in constant motion (described in step 3),

11) Introduce the idea that making space (and time) curve (like the wavy surface of a mini-golf green) would allow for transformation laws that make this new equivalence principle mathematically rigorous.

12) etc, etc, etc, ...



This is a long path towards a somewhat rigorous understanding of relativity, but for the purposes of answering this "Yahoo Answers" question it is unnecessary (and impossible, due to the lack of space). As an alternative to such a long process towards understanding I offer the following.



Consider the formula d=v*t, which can be used to describe the relationship between "distance travelled", "velocity of travel" and "time for travel" for any object that is moving with constant velocity. Imagine that two people, Alice and Bob, are both watching a spaceship go past and would like to apply d=vt to the spaceship. Also imagine that Alice judges Bob to me moving past her at speed U and that she sees the spaceship going past at speed Va. The classical (i.e. Galilean) way of thinking about the situation is that Bob must judge the spaceship to be moving past him at velocity:

Vb = U - Va

The Galilean way of thinking would also say that if Alice and Bob had clocks that were synchronized at some point in the past, then the clocks would always be synchronized and Alice and Bob would always agree upon what time it was (i.e. they need only have one common time variable 't'). As a result, Alice would apply d=vt as follows:

Da = Va*t

and Bob would apply it (from his point of view) as:

Db = Vb*t

Now, since Vb = U - Va we can combine Alice and Bobs formulas to get:

Db = Vb*t

Db = (U - Va)*t

Db = U*t - Va*t

Db = U*t - Da

That is, the distance that Bob judges the spaceship to have travelled in a given time t is shorter than the distance that Alice would judge the ship to have travelled.

To put another way, if two cars on a highway are going nearly the same speed (with Bob going 61 mph and Alice going 60 mph) then in one hour elapsed time, Bob will seem to Alice to have only gained 1 mile on Alice. However, to people on the ground Bob will appear to have gained 61 miles in that hour.



So the point of the galilean view of the formula d=vt is that 't' is constant for both Alice and Bob (and all observers, for that matter), and 'd' and 'v' are expected to differ between observers.

Now in special relativity we have, for a photon (a particle of light), that 'v' is constant for all observers, not 't'. Thus it must be that in d=vt we have that either all observers agree on 'd', 'v' AND 't', or we have a situation in which disagreement about the value of 'd' implies disagreement about the value of 't'.

So, to modify our example above slightly, let us imagine that Alice and Bob are watching a photon travel past instead of a spaceship. Then Alice will apply d=vt for the photon as follows:

Da = c*ta {where v=c is the speed of light}

and Bob will write:

Db = c*tb

In order to combine the two equations as we did above we cannot use the Galilean velocity formula Vb = U - Va, since Vb = Va = c.

There must be some other equation that connects what Alice sees to what Bob sees, and that equation (actually up to four equations) is the Lorentz transformation -- the heart of special relativity.



So, without going into further detail about the mathematics of the Lorentz transformation, the key point of this discussion is that there is a difference between how Galileo and Einstein would view the equation d=vt and the quantities d, v and t (when applied to a particle of light in this example):

Galileo: 't' is the same for all observers but 'd' and 'v=c' are not.

Relativity: 'v=c' is the same for all observers but 'd' and 't' are not.



In other words, relativity hinges upon the experimental discovery that the speed of light is the same for all observers. The fact that constant moving frames of reference were equivalent (in the sense that every observer would "feel" that they were stationary and claim that everyone else was moving) is not unique to relativity -- it is a property of equivalence that was recognized even by Galileo and had to be kept in the new transformation equations of Einstein. Had this equivalence not been part of the new transformation equations then these equations would not describe one of the most obvious features of objects moving past each other. So (at least in my opinion), special relativity involved preserving the equivalence of frames of reference from Galilean theory, while at the same time incorporating the fact that the speed of light is constant for all observers. One might think of the Galilean way of thinking as the OLD theory of relativity and the Einsteinian way of thinking as the NEW theory of relativity, though I do not recall any standard textbooks on relativity describing things in quite this way.



As for general relativity ... well ... I will have to discuss that in another "Yahoo Answers" forum question. There is just not enough room to discuss that here due to message length limits in "Yahoo Answers".



Is Einstein's theory of relativity still considered accurate?

Yes, his theories are still the most accurate that we have for gravitational calculations and motion calculations for anything larger than a micrometer. Smaller than a micrometer we begin to enter the realm of atomic and particle physics, and at that scale the theory of general relativity exhibits some incompatibilities with quantum mechanics. The theory of special relativity, however, is still an integral part of atomic and particle physics, since one has a special relativistic version of quantum mechanics. Kep in mind that Newtonian/Galilean mechanics is extremely accurate for most everyday speeds, and (as far as I know) even the calculations for sending the space shuttle into orbit or sending the Mars probes to Mars all involve Newtonian/Galilean calculations. The extra accuracy provided by relativity is not needed for most applications.



How did Einstein's theory impact science over the last 100 years?

Special relativity has become an integral part of every physical theory that might be used to describe fast moving objects or situations with strong gravity. In fact, there are a few notable examples of modern technology that would not work without the formulae of relativity. For example, in any large particle accelerator one must use special relativity to calculate the correct magnet strengths to keep the particles confined within the accelerator (e.g. CERN in Switzerland/France). As another example, the ultra precise timing that is required for satellites (with atomic clocks) to make the Global Positioning System possible requires not only special relativity, but general relativity as well. Without the correct calculations of general relativity the GPS system would simply not allow for precise locating to within a few meters on the Earth's surface.