What did Einstein really mean by the theory of relativity?
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There are plenty of good websites that answer this question, for any knowledge level. The concept is complex enough that you won’t get a meaningful answer here.\n\nIn horribly oversimplified terms Relativity simply states two things.\n\nOne that there is no universal ‘at rest point’, it all depends on how you choose to define it. You sit in a car doing 100mph and I stand beside the road. Normally we assume that you are in motion and I am at rest. Relativity states that we can just as accurately say that you and the car are at rest and I am moving at 100mph. Alternatively, we normally believe that the Earth orbits the sun and the Moon orbits the Earth. Relativity states that it is just as accurate to say that the Earth orbits the moon and the sun orbits the Earth, or we could say that we all orbit some imaginary point in between all three. It is all a matter of choice what we define as being the fixed point.\n\nThe second is that the speed of light is constant regardless of whether you are at rest or moving, and regardless of how fast you move. If you are sitting in a car doing 9/10 of lightspeed and are going past me standing still beside the road and we both look at exactly the same light beam shining down the road we will both see that light beam travelling away from us at exactly the speed of light relative to both of us. You don’t see it slowed down just because you are travelling almost as fast as it is. It will move away from me just as fast as it moves away from you.\n\nThose are the basics, and they aren’t all that hard to understand, even if they don’t seem to make much sense. What Einstein did was sit down and think really hard about the logical consequences of those two points.
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One man by the name of A. Einstein believed that a unified theory is possible. As you know he did a pretty good work on general theory of relativity.  His explanation of gravitation perhaps was not complete (we need that unified theory to figure exactly what gravitation is) but it was much better then say the older Newtonian idea.  At the same the, as Albert was developing the general theory of relativity, the Quantum Mechanics (QM) became to emerge as serious science. The QM scientist beloved that the behavior of subatomic particles is probabilistic. Einstein heard that ad protested with a statement: “I do not believe God play dice with the Universe” to which Niels Bohr answered “Albert, do not tell God what to do” (Or something like that). So the fit between deterministic macro world and probabilistic micro world has begun.\n\nToday physicists s are trying to marry the macro world, where very week gravitational force act, to the micro subatomic world of QM.  The string theory seems to have the mathematical tooling to allow both of these worlds to exist within a single model.\n\nYou can find more info in \nThe Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory by Brian Greene http://en.wikipedia.org/wiki/Brian_Greene \n\nWho by the way I heard had an excellent documentary on NOVA, PBS.\nhttp://www.pbs.org/wgbh/nova/elegant/greene.html
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Einstein has 2 theories of realivity.  The Special theory of relativey and the General theory of realtivity.  \n  The first simply means this in layman's terms.  All laws of physics laws are valid given that the state of object is in Uniform motion.  (uniform motion means a constant state of acceleration)\n  The General theory of relativity is all about gravity.  Basically it is a theory to explain the force of gravity.  \n   Although Neither theorys specifically mention time travel, many people have used the specifics of these theorys to try to show whether time travel is indeed possible.  \n    One of the principals of the general theory is that no object can travel faster than the speed of light.  Although this seems like qquite a simple statment it really isn't.  If you think about light and the things you are seeing "lets say your looking at the stars"  The light coming from those stars has traveled billions of miles to get to earth.  You are in fact seeing the light that a certain star has emmited in the past.  Now if you were to travel faster than light you could in effect travel through time and reach light events that people have yet to see.  \n   Now at face value you would say well since the theory of relativly states you can't travel faster than light this is impossible.  Here lies the catch.  The speed of light is always the speed of light (meaning if you were in car traveling at the speed of light down the road and you turned your headlights on the speed of the light from the headlights would still travel away from the car at the speed of light).\n   Now let's say your a person standing on some point and were watching the car travel at the speed of light.  The light that is coming from the cars headlights would to you seem to be traveling at 2times the speed of light. Get it?  \n   So when speaking relativisticly the frame of refrence is the most important factor.  Now one thing to note that time is NOT a constant.  It has been proven that the faster an object moves the slower time is for that object.  This indeed does work for everyday activities such as your car driving down the road.  Time for you is accually an extremely tiny bit slower than it is for the tree that you past on the road. \n    SO if we "could" get an object to move the speed of light or greater time could either stop or go in reverse for that object.  We cannot get matter to the speed of light at this time.  We have gotten close, but right now the laws of physics seem to prevent that.
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Nobody really knows.  Einstein's special theory of relativity posits gravity as a warp of space-time caused by the object's mass, but that only pushes the question one layer further down.  All we know for sure is that gravity exists, is pervasive, and can be important.
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A.) In his General Theory of Relativity, Einstein developed a mathematical description of gravity—one that links space to time and mass to energy in a fundamentally geometrical fashion. In other words, mass(-energy) shapes space(-time) instead of acting like a “force” in the traditional Newtonian sense.  (Thus, in Newton’s description of gravity, one would say that all bodies exert an attractive gravitational force on one another. In Einstein’s conception, one would say that all bodies change the underlying geometry of space-time in a way that causes them to be attracted to one another.)  Thus, our best understanding of gravity is that it’s a fundamental property of space-time to be “warped” by the presence of mass(-energy). So gravity is simply a property of space-time, and most likely, it came into existence at the same time.  (One caveat: curvature or warping really only provides an analogy to what the equations tell us. If you want to imagine the effects of an object on its surrounding space-time, then you can think of it as changing the shape of space-time in its vicinity. The distortion is real—we can measure its effects—but the images that are often presented of flexible sheets of space-time with bowling balls or marbles rolling around on them, for example, simply present analogous situations.)\n\nB.)  Spinning is a common attribute of objects in the Universe because the way things form virtually always leaves them in rotation, and once things get started rotating, it’s hard to make them stop.  It’s not intuitively obvious, but if you take, say, a cloud of gas and dust collapsing to form a planetary system, then averaging all the random motions of the particles will leave you with some tiny element of rotation.  As the collapse takes place, any rotation will be magnified, so you end up with planets revolving around their parent stars, and planets themselves rotating on their axes.\n\nC.)  It’s doubtful that we’ll ever acquire much in the way of interstellar real estate, simply because the distances involved are so great.  Our best hope is to carry on radio communication with them, but even at the speed of light, it would take decades or centuries for radio signals to travel between us and the stars currently within our range of communication.\n\n\nRyan Wyatt\nRose Center for Earth & Space\nNew York, New York
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Simple..\n\nU know why Einstein is so-called the most genius man in the world.\nEveryone who didn't study modern physic would say. the famous equation E=mc^2 bought his fame. No Einstein is genius becoz of his work on relativity.\nOne of the postulates made by the Einstein is that gravitational force is the curvature of space-time. U probably don't realize the importance of that statement. \n\nBut here i want to stress on the word space-time. Before Einstein, every scientists treat space and time as 2 separate distinct. But Einstein is genius enough to find that space and time as single entity. \n\nthe universe is all about energy and gravitational force.\nPeople says the universe start when a dense material exploded. Thus the universe was born. Remember to treat space-time as single thing. So, when universe was born, so the space and time was expanded and run. when there is no time, there is no space. so when the universe perish, the time also disappears and so the space...\nBcoz there is no mass, lead to no gravitational force and lead to no space and time.\n\n\nSo, God is really Almighty. there is no start and there is no end to Him
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No.  The theory of relativity states that an object moving at a high enough velocity will appear to shrink along the direction of motion and increase mass from the point of view of a non moving observer, so much so that, if a physical object would be to travel at the speed of light, its dimension will be zero and its mass infinite.
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Energy equals mass times the speed of light sqaured. It is a theory discovered by Einstein known as the theory of relativity in 1905. It says that iff you go faster than the speed of light you can have advantage over time and space is related to time.
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There are actually two theories of relativity: special relativity and general relativity. \n\nIn a nutshell, relativity was Einstein's way of saying that nature always appears to have the same laws, no matter where or what you are. And it does this without having to have some sort of base reference place in the universe, or a base time. If you are on a plane going real fast, the speed of light always seems to be the speed of light. Special relativity accounts for this by things like time dilation (time moves at a different rate for you on the plane than for me on the ground.) Your size is different. Your weight is different. But to you it always seems the same.\n\nAnyway, it is a complex subject, and the easiest way to understand special relativity, the first of the two theories is this:\n\nhttp://en.wikipedia.org/wiki/Special_relativity_for_beginners
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To answer your question literally - Yes! I'm quite sure\nsomeone knows what the theory of relativity is.
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Isaac Newtwon laid down the ground work for modern day physics.  Then Einstein came along and published the most recent great discovery in physics, the theory of relativity.  The problem is, these two contradict each other.  Steven Hawkings and others have since been working with string theory, which would explain these contradictions.
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In Einstein's Theory of Relativity, he proved that space and time are relative properties of our material universe, not absolutes, independent of matter, as Newton believed...
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The general theory of relativity is much more complex and difficult to understand than the special theory. It proves the force of Gravitation, as proved by Sir Isaac Newton, wrong. According to Newton, gravity was a force between two bodies, which depends on their respective mass and the distance between them. \nThe basic idea of general relativity can be illustrated with the help of an imaginary experiment as performed by Einstein.  Suppose a lift is at rest in space.  If a ball is released within the lift, it will float in space and not fall.  If the lift accelerates upward, an observer within the lift will see the ball fall to the floor exactly as it would under the pull of gravity.  The ball appears to fall because the floor of the lift, as seen from outside the lift, it accelerates upward toward the ball.  All the effects we associate with gravity would be seen by the observer in the lift.  Einstein called the phenomenon shown in this experiment the Principle of Equivalence. This principle states that it makes no difference whether an object is acted on by a gravitational force or is in an accelerated frame of reference.  The result in both cases will be the same.  From this principle, Einstein reasoned that matter in space distorts or "curves" the frame of reference of space. The result of this curvature is what we experience as gravity. The Euclidian or flat geometry was unable to explain the curve, so Einstein used geometries called Riemannian geometry to explain the effect. \nAccording to Newton's theory, a planet moves around the sun because of the gravitational force exerted by the sun.  According to the theory of general relativity, the planet chooses the shortest possible path throughout the four-dimensional space- time, which is deformed by the presence of the sun. This shortest possible path is called a geodesic.  This may be compared to the fact that a ship or an aeroplane crossing the ocean follows the section of a circle, rather than a straight line, in order to travel the shortest route between two points.  In the same way, a planet or light ray moves along the "shortest" line in its four-dimensional world. \nSo far, three things have been discovered in which Einstein's theory of general relativity receives experimental proof as opposed to the theories of Newton.  These differences are not great, but are measurable.  In the first place, according to Newton's theory, the planet Mercury moves in an ellipse about the sun.  According to Einstein's theory, Mercury moves along an ellipse, but at the same time the ellipse rotates very slowly in the direction of the planet's motion.  The ellipse will turn about forty-three seconds of an arc per century (a complete rotation contains 360 degrees of an arc and 360 X 60 X 60 seconds of an arc).  This effect is rather small, but it has been observed.  Mercury is nearest to the sun and the relativistic effect would be still smaller for other planets.  \nIf we take a picture of part of the heavens during an eclipse of the sun and near the eclipsed sun, and then take another picture of the same part of the heavens a little later, the two photographs will not show identical positions for all the stars.  This is so because, according to general relativity, a light ray sent by a star and passing near the rim of the sun is deflected from its original path because the sun's gravity curves space.  The effect of gravity on light is also the reason why black holes are invisible.  The gravitation in a black hole is so strong that light cannot escape from it. \nPhysicists have known for more than a hundred years that when some elements are heated to incandescence they give off a pattern of spectral lines (coloured lines), which can be examined through a spectroscope.  According to the Einstein theory, the wavelength of light emitted from a massive object will become longer because of gravitation.  This results in a shift of the spectral lin
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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!
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Part of the Beauty of Einstein's work on relativity is how easy it applied all the existing work, including Newton's work. When it comes to calculating forces necessary to bend light around a sun relativity does come into play.  And you are right early attempts were thwarted by weather and such. As I recall the first such measurements were carried out by a party that journeyed down to South Africa to make observations during a solar eclipse.  They were doing it, not to prove Newton's work, but to test the need for Einstein's corrective formulas.  The measurements were a roaring success and Einstein's ideas concerning Spacetime was quickly excepted by the larger scientific community.\n\nAppended thoughts - Before we get all sanctimonious here, let us keep in mind Newton and Einstein were 300 years apart, both men were geniuses, both men were deeply religious and both men DEFENDED errors in their thinking.  This is what Kuhn talked of when he put forth his ideas on Paradigm Shifts.  It was Maxwell who punched holes in Newton's thinking on Aether and it was Bohr who ushered in Quantum Mechanics. And it was hundred other people making a hundred other contributions that have gotten us where we are today.  And there will probably be a hundred more in the future trying to sort out these difficult questions.
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What does it mean to be "true"? The quantum theory (I suppose that's what you're asking about) can explain a lot of physical experiments, so, up to a certain extent, it has been proven true. It is also the truest physical theory for small scales up to today.\nScience isn't about finding absolute truths, it's about providing a description of reality that suits your needs. Take newton's gravity laws for example: while proven false in absolute by einstein's relativity, they are still really useful and tought in many places.\nOf course the goal is to one day provide a theory (a description of reality, not "a guess") that explains everything, but for now that's still a dream.
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His definition is a little odd, and does not seem to follow from his example (which is more about motion than position on the earth).  Technically, his motion relative to stationary students would make time pass at a different rate according to all that Einstein stuff (though there's no way he could ever notice the tiny difference).  But that would be true without any reference to the earth and the sun.  Is he trying to make a different point -- that his days would be longer because the sun would set later for him because he is walking toward the west where the sun sets?  If so, he's right that his days (defined as revolving around the Earth's axis) would be longer, but that would not mean time was moving at a different speed for him; it would only mean that the sun would set a little later from his visual perspective -- just like you can gain or lose hours when you cross time zones in an airplane; you reset your watch, but that has nothing to do with the passage of time.  Unless you are defining time only by calendars and clocks and common agreement.