almost everywhere I go I always hear about Einstein's General and Special Theory of Relativity and his very famous equation e=mc^2. it bothers me u know, cos honestly I don't know what relativity means. can u please tell me what it means, in a simple way, please? cos i am just an 11 yr old boy.
120324
The special theory of relativity deals with how nature behaves when things move at very large speeds. In fact at any speeds, but things only get a lot different from what we are used to, when speeds are close to the speed of light. The theory is essentially founded on the observation that the speed of light is constant to an observer regardless of how fast the observer is moving. Which is very different from the behaviour of objects with mass such as cars an the like.\n\nThe general theory of relativity extends on the special theory of relativity and is actually a refinement of earlier theories of gravity.\n\nI would suggest that if you want to understand relativity, that you first investigate "classical physics" or "Newtonian physics".\n\nDon't worry that you are only 11, if you want to understand these things then investigate them. If you get bored with them then you can stop investigating them. And make sure you have plenty of fun too.\n\nOh, and the famous equation actually an expression of the fact that mass can be converted in to energy, and energy can be converted into mass.\n\nAfter reading a couple of the answers below I feel that they could be a little misleading, so I would like to point out that the concept, or "theory" if you please, of "relative motion" was well established, before Einstein proposed his theories named "special relativity" and "general relativity".
263585
You do have a point. Of course Schrodinger's equation was a brilliant breakthrough but these theories necessarily have a mathematical foundation and sometimes that foundation is not as secure as generally perceived. Mathematics is evolving and some of the stuff coming out is very weird, paradoxes and all, and this ends up affecting the way scientists formulate their theories. Put it this way: most physcists are not expert mathematicians and they are often a step behind with respect to rigor. As far as quantum mechanics is concerned, one has to consider its real and significant successes as a useful theory but with the realization that any developing theory  will necessarily have growing pains and it will need to be adjusted, finetuned and sometimes overhauled in the light of new info. in order to be incorporated in a more general theory of which it is a special case much like classical mechanics had to adjust to both quantum mechanics and the special and general theories of relativity. I think the greatest revision to quantum mechanics and General relativity will occur when the large and the small, and the uncertain and the deterministic, are finally 'married' in a breakthrough theory of quantum gravity. The problem with general relativity is that it is deterministic field theory and it is based on the concept of a space-time 'continuum'. I think the concept of continuum upon which the formalism of general relativity is based, is counter-productive and it needsto be replaced with a quantized 'granular' space-time structure that would allow things to get unified. On a philosophical note, you are right, in a sense, concerning questionable foundational definitions since if you keep asking the question: and what precisely do you mean by that? It doesn't take that many questions before you are reduced to axioms which are based on presumptuous perceptions of the human mind: In otherwords we could be missing a lot.
144984
To the extent that there was a conflict, it was resolved by Dirac. His was a quantum theory that directly included relativistic invariance. His equation is now the basis for our understanding of relativistic electrons. As of now, we don't have a way of reconciling quantum theory and *general* relativity, though.
1443
the formulas are what convince me.  I've had to derive so many complicate formulas myself, and most of them, especially mechanics formulas can be proven, such as measuring a quantities, solving for a missing variable, then doing an experiment and getting the same answer.  This is too much to be a coincedence or something.  Most theories and things are developed before formulas and actual mathamatical relationships are found, then they find them and it all fits together nicely.  Even with reletivity and things with spacetime, there are a lot of concrete formulas, and once you have the satisfaction of deriving them yourself from previously proven formulas... it all clicks nicely, that's why im a physics major, curiosity about everything like this.  I guess human perception can be valid once connections start being made between things, because when ideas are incorrect, they really don't connect to other things very easily.
308761
As weird as it sounds, the theory of relativity says that if you are in a car traveling at 200,000,000 m/s with the headlights on, then the light from those headlights will pass a person standing still at 299,792,458 m/s and not 499,792,458 m/s. And if that stationary person shines a light at your car, you will see his light approaching you at 299,792,458 m/s and not 499,792,458 m/s.\n\nThe theory is so weird that numerous scientists have done numerous experiments to test it. The most famous of these experiments is the Michelson-Morley Experiment. All experiments have confirmed that this strange prediction of relativity is true.\n\nBelieve it or not!
124650
You've confused the statement of the theory. Let two observers be in the same inertial reference frame with two synchronized watches. One observer accelerates in a negligibly small amount of time to some fraction of the speed of light relative to the other observer. The latter observer will be called O1 and the moving observer O2. \nO2 will measure the time in 01's reference frame to be going *slower* than the time in his frame. Likewise, O1 will measure the passage of time in 02's frame to be going *slower* than in 01's frame (the half-life of particles "increases" depending on their speeds). In other words, given two events A and B that always occur t seconds apart in O, they will occur at some separation T > t when measured from O'. The same will occur if O' is switched with O in the sentence above.\nQuestions like this usually come from confusing the relativity of simultaneity. Remember that in relativity, there are no two events that are simultaneous with respect to all inertial frames. \nI recommend you check out the text "Spacetime Physics" by Wheeler et al.
625984
Here's the equation T = T' / sqrt[1- (v^2/c^2)]\n\nT is time measured by an observer at rest.  T' (read: T prime) is time measured by a moving observer.  v is the moving observer's velocity and c is the speed of light.\n\nThe speed of light is very fast.  So if v is 100 mph or 10 000 mph when you divide it by a number like c (186000 mps that's miles per second so a huge amount of miles per hour)  the v^2/c^2 value is zero and T = T'/sqrt (1) which is T = T'/1 so there is no measurable difference.  \n\nBut plug in 9/10 c for v.  That means an object going 9/10 the speed of light.  You get T = T' / sqrt[1-(9/10c)^2/c^2]\n\nc^2 cancels out and you get T = T'/[sqrt 1-(81/100)] T would be 2.2 times T'.  More time transpired for the non moving observer.\n\nHow did we get the equation?  Einstein was really smart.
20964
Your "authority", if they was refering to relativity and time dilation, was wrong.\n\nThe special theory of relativity, including time dilation, is a well established experimental fact.  It has been tested and verified in many different ways (particle acceleators, cosmic rays, satellites, etc.).
271887
Einstein postulated that the speed of light would remain the same regardless of the inertial frame in which it is measured.  This contradicts classical physics, since if an object is moving at a velocity v, as measured in an inertial frame, and that inertial frame is moving with a velocity v2 with respect to a second inertial frame, then you should take the vector sum of the two velocities to determine the velocity of that object with respect to the second inertial frame.\n\nEinstein postulated that within an inertial frame the laws of classical physics held.  So, to make things work out Einstein calculated that time and space are distorted with velocity.  It is as though you and your brother are of different heights, but you both want to be the same height, so you take a rubber ruler and stretch it so you get the same measurement for the two of you.\n\nIn this way you always measure the speed of light as the same value, no matter how fast the source of the light is moving with respect to you.  You adjust the rubber ruler so that what you want to believe remains true.
215225
General relativity is the geometrical theory of gravitation published by Albert Einstein in 1915. It unifies special relativity and Isaac Newton's law of universal gravitation with the insight that gravitation is not viewed as being due to a force (in the traditional sense) but rather a manifestation of curved space and time, this curvature being produced by the mass-energy content of the spacetime.\n\nmore info for you :)
364108
a train runs at a speed of 10kmph and u chase it at a speed of 4 kmph , then the speed of the train will appear 10-4=6kmph to u.\n\nbut this is not the case with light rays. u chase it with any speed, its speed will always be 3*10^8 mps\n\nlong ago this boggled the scientists and they came up with relativity theory.\n\nconsider the example given above(train & u)\n\nspecial relativity: \nif both (train & u) r not changing your speeds again and  again then we use special relativity to compare motion between train & u.(ie both are non-accelerared frames)\n\ngeneral relativity\nif either-one/both (train & u) r changing your speeds again and  again then we use general relativity to compare motion between train & u.(ie either-one/both are accelerared frames)
465917
The formula expanded a bit is: E (joules or kg*m²/s²) = m (kilograms) multiplied by (299,792,458 m/s)2\n\nE is Energy, m is mass and c is the speed of light in a vacuum.  \n\nCheck out http://en.wikipedia.org/wiki/E%3Dmc%C2%B2\n\nOff the subject, but an important reply to Fresh Prince and those of the same mind:\n\nYou seem pretty mad.  It is unfortunate that "[we] people disgust [you]."  It does not diminish Einstein’s discovery to say God created the highly balanced universe which is made up of this mathematic formula as well as all formulas - discovered and undiscovered.  Einstein was doing wonderful work in unlocking the mysteries of Creation - he was a genius among geniuses\n\nEinstein himself believed in a "god / creator" - not the God of the Bible, but a Creator nonetheless.  He was not closed - he acknowledged that the universe is so finely balanced on finite mathematical principals, there is a higher intelligence governing things that we cannot comprehend.  He spent his life exploring the wonder of what has been created and set before mankind.  Please cast aside your disgust.  No one is taking credit away from Einstein - or you.  \n\nRegarding religion, Einstein said: "The most beautiful and deepest experience a man can have is the sense of the mysterious. It is the underlying principle of religion as well as all serious endeavor in art and science. He who never had this experience seems to me, if not dead, then at least blind. To sense that behind anything that can be experienced there is something that our mind cannot grasp and whose beauty and sublimity reaches us only indirectly and as a feeble reflection, this is religiousness. In this sense I am religious. To me it suffices to wonder at these secrets and to attempt humbly to grasp with my mind a mere image of the lofty structure of all that is there."\n\nWhen asked: "[Do] You accept the historical Jesus?" \n\nHe replied: "Unquestionably! No one can read the Gospels without feeling the actual presence of Jesus. His personality pulsates in every word. No myth is filled with such life."\n\nNo, Einstein did not believe in God as Christians believe.  But he recognized the order of the universe as a signpost to a higher being.  The point is, there is no cause to be "disgusted" by ideas outside your paradigm.  I am not disgusted with you.\n\nTake a hint from Einstein - the consummate scientist who believed in a Creator: "...science without religion is lame, religion without science is blind."  I will not be blind, so please do not be the former.  Take a look from another perspective; you may learn something of value.\n\nRemember, you may be angry with God, deny God, ignore God, and not care to inquire with an open mind, but God loves you anyway.\n\nHave a blessed day, my friend (that is a positive statement, please take it as such).
17792
Well\nrelativity \n\nPhysical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference. One consequence of the theory is that space and time are no longer viewed as separate, independent entities but rather are seen to form a four-dimensional continuum called space-time. Full comprehension of the mathematical formulation of the theory can be attained only through a study of certain branches of mathematics, e.g., tensor calculus. Both the special and general theories have been established and accepted into the structure of physics. Einstein also sought unsuccessfully for many years to incorporate the theory into a unified field theory valid also for subatomic and electromagnetic phenomena.\n\nEvolution from Classical Theory\n\nThe modern theory is an extension of the simpler Galilean or Newtonian concept of relativity, which holds that the laws of mechanics are the same in one system as in another system in uniform motion relative to it. Thus, it is impossible to detect the motion of a system by measurements made within the system, and such motion can be observed only in relation to other systems in uniform motion. The older concept of relativity assumes that space and time are correctly measured separately and regards them as absolute and independent realities. The system of relativity and mechanics of Galileo and Newton is perfectly self-consistent, but the addition of Maxwell's theory of electricity and magnetism to the system leads to fundamental theoretical difficulties related to the problem of absolute motion.
167221
As the others have said, all light travels at exactly the same speed.  This is even true if the observer and/or the  light source are moving very very fast.  Once this was proved by experiment, everyone was very upset until Einstein figured it out and showed that time and space can distort. If you want a real bad headache, you can read all about this.  If it doesn't give you a headache, become a physicist!
51653
Brownian motion, the photoelectric effect, special relativity, and his famous E = m(c^2) equation are four examples of things Einstein did that affect our lives.\n\nThe photoelectric effect explains how light can be converted into energy.  This is very useful for things like solar cells which are used for solar power.\n\nSpecial relativity has to do with the way space and time works and doesn't affect our modern life as much but has implications for space travel.\n\nBrownian motion was important because it confirmed the existance of atoms.  Before Einstein's time atoms were considered to be a "neat idea" but after that they were considered to be a reality.  This has many implications on our modern life because it helped to expand the outburst of technology that has greatly influenced the way we go about our lives.\n\nFinally E=m(c^2) was an offshoot of the theory of relativity and this had several implications the most influential being the atomic bomb.
73803
The equations imply that it is impossible for any object with >0 rest mass to accelerate from below the speed of light up to exactly the speed of light. This is because, as has been mentioned, that would take an infinite amount of energy.\n\nThe equations don't prohibit an object traveling faster than the speed of light from the outset though. Photons have zero rest mass, and the instant they are created they are traveling at exactly c. If it were possible for a particle to exist that was traveling faster than c from the instant it was created, this would not be a problem for relativity. I'm not sure what it would imply about it's mass though. The name for such a particle is a tachyon (although there is no evidence these actually exist as far as I'm aware).
568320
there is a important factor that appears in the theory of relativity:\nit's called "gamma" (we use the greek letter usually).\nFor a body moving with the velocity v, we have \ngamma=1/squareroot(1-v^2/c^2) , where c is the velocity of light.\nas you can check, as v increases (but always being lower than c), gamma becomes bigger and bigger, tending towards infinity as v tends to c. You can also check than when v=0, gamma=1.\n\nIn non relativistic theory, the mass of a rod for example is called "m" and its length "L". In the point of view of the rod, m and L are constant. For an outside observer also...\nBut what the theory of relativity shows is that for the outside observer, the mass and length of a rod moving with a velocity v is no more m and L, but gamma*m and L/gamma.\nThus, if the velocity is much smaller than c (everyday experience), gamma~1 and nobody can see the difference, if the velocity increased a lot, gamma->iinfinity, and thus the mass also tends towards infinity and the length tends towards 0...  for the outside observer!    If you are the rod, your velocity compared to yourself is 0, so your "own gamma" is 1 and your length and mass, in YOUR point of view, is constant.\n\nthe theory of relativity shows that "basic" things such as the length, the mass (and even the time between two events) of an object depends on the observer. \n\nI hope I've been a bit helpful. Go on with your reading, don't be afraid if you do not understand everything at the first and even the tenth reading, that comes with experience...