Relativity is an example.  Einstein developed his theories as a pure mathematical exercise.  Once the equations had made predictions those predictions were validated by observation.  There are many, many other examples.  So why should this be so?  What is the connection between abstract maths and reality?
132750
Your question is basically a philosophical  "Why is there math?"\nIt even borders to something massive as "Why is there a universe, why do we exist and what is the meaning of life?"\n\nThese are big questions and yes they probably have an answer tucked in the folds of the cosmos.  \n\nWithin our own realm of humanity we have such diversity and variety with crossover of culture.  Linguistics for example; so many languages, some like others but all different is a subject that describes humanity and different areas of the world.   But mathematics is a universal language, it is the same everywhere.  It is understandable to explain simple tasks of counting and measurement to the properties of physics.  Yes you know it does but you're asking why it does.  \n\nMathematics is about ideas: ideas of space, of time, of numbers, of relationships.
590909
GOOD QUESTION: well done! There is not really any such thing as time, it is merely our way of describing a particular abstract concept. If it was a solid physical reality it surely couldn't be relative. Lets all go and read Einstein and try to figure it out!
321572
They're strange because no model is definite. Models such as those for the atom and for light are merely theories to explain the observations we've made about them. As soon as something comes along that doesn't follow the model, a new model is proposed.
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.
423962
Who says it cannot?  \n\nSure it cannot be tested completely, in a lab, using the technology we currently have.  Be we sure can test aspects of the theory, and they absolutely confirm.  One day we may devise a method to test the theory completely, without the need for an entire world and a billion years to duplicate the real conditions.  But it can't be done today.\n\nBut simply because we cannot test the theory today does not invalidate the theory, exactly in the same way Einstein's theory of general relativity held in Newton's day the same as it holds today, even though Newton had absolutely no chance of confirming the theory scientifically using 17th ca technology.  \n\nThe important point is that certain aspects of the theory can and HAVE been proven, and can be retested and reproven.  Plus the theory fits within the existing scientific evidence that has been confirmed through experiment and test.  It's the only theory to meet those two criteria.
642337
As mentioned in other replies, physicists don't yet have all of the "how" questions answered. Einstein, in the General Theory of Relativity, pretty much nailed the underpinnings of the current theoretical understanding of gravity. Here is my attempt at the "nutshell." I'll start with an analogy. Let's say you are driving somewhere in the midwest or plains states--essentially flat ground, with a few rolling hills. Let's say you stop your car at the top of a slight rise. As you look around you, you see flat land in every direction. You're sitting on essentially a two-dimensional plane. Taking your foot off the brake, you notice the car starting to roll forward. Your initial observation about the 2-dimensional "space" you were sitting on isn't quite accurate. The 3rd dimension (altitude) has come into play, and gravity is pulling your car into the swale. What Einstein said (and how he came up with this back in the early 1900's is incredible) was that our THREE dimensions are really a slightly inaccurate description of the world (and universe) we inhabit. A fourth dimension, time, is part of the "fabric" of our surroundings. As in the case of that slight "warp" in the 2-dimensional farmland that led to a noticeable effect on your car, Einstein said that warps in the space-time continuum are experienced as gravity. As you know, Einstein was into the "energy = mass" thing big time, and you know that mass is tied up with gravity as well. If you want to get more cozy with these related concepts, I strongly recommend David Bodanis' book, "E=mc2: A Biography of the World's Most Famous Equation" -- available as a "BooksOnTape." It's exciting, full of cool anecdotes about the heroes of 20th century physics, and... NO MATH, just concepts. Best of luck!
590106
None.  That is the point.  If they exist is not proved, and hypothetical tests to see if they exist are flawed.  \n\nOn your other question of visualizing multiple dimensions, I have a few hints.  Have you read Flatland yet?  Start there, its good, and not overly mathematical.  Multiple dimensions can mean different things to different scientists.  We use them all the time for their mathematical properties.  But mathematics is just a description, the real world is something observable.  In terms of observation, you would not be able to detect a separate dimension by any means pedantic.  We may be able to prove that physical space has more than three dimensions, but that does not mean that those other dimensions are physical space.  Just like time.  Some particle interactions appear to go backward in time briefly.  What if there is more than one time dimension?  \n\nSo the classic three dimensional physical picture of multiple dimensions will always be flawed by the observers expectation of the properties of the unseen dimension.  Which is why we describe those dimensions using 'imaginary' constructions.  Hope this helps a bit.
252571
it is a conception of Space, made not only of 3 dimension, but 4. The fourth is Time. The relativity equations are made in this 4 dimension Space-time "Space".\nThe idea was not from Einstein, but he was the one who hd spread it.
569016
I figure that a theory that predicts 6-7 extra dimentions may be true, but it is really easy to explain things with 9-10 degrees of freedom..\n\nTHink about it, you have data... you try to make a linear fit, most often you don't get a good correlation... Now try a 4th power polynomial fit... you get something better... 11th power can describe any data, but it makes no really valid predictions. \n\nAs Einstein said, "Any fool can make things bigger and more complicated" (don't remember exact words so this is paraphrasing) "but to explain things in simple manner truly takes a genius"\n\nBut there are things about it that are likely true, for instance the "strings" themselves... Yes, everything is made of a fundamental unit of energy (double slit experiment demonstrated that matter is localized energy) \n\nLast point: to have a valid theory it should predict measurable results, string theory does not.\n\nSo no, I doubt its tue, but only time will tell.
659685
This "nothing" is what we perceive without the laws of physics. Our universe is limited by the knowledge we have about it. Recent theories (the "M" theory) suggest that endless universes exist, and sometimes they even collide one into other. Probably, out there, beyond the boundaries of 12 billions light years, others dimensions, other plan of existence exist.
112252
yeah, you get a bit off on a deep tangent towards the end there... but I don't think Einstein asserted anything more than the idea that time, space, and matter are related and not independant.  two systems of matter travelling in wildly different velocities relative to one another also have different processions of time and different masses, from the perspective of the other.  It only applies to things moving close to the speed of light- I think it's the Schroedinger Equation that covers the inter-relation.  But there's no real analogy to it in the observable world, unless you work at a particle accelerator, so I leave it to the doctorates of physics to debate.
4624
There is indeed a thread in philosophy that treats mathematical truth as representing some kind of eternal fixed world.  However, there are plenty of mathematical objects other than numbers that have a rich field of mathematics associated with them.\n\nFor example, one defines a group as being a set of elements and an operation between them, denoted '+' (a bit like 'addition', but not restricted to acting on numbers) such that:\n1) If a and b are elements in our group then there is an element c such that a + b = c\n2) There exists an element of our group O such that for every element a in our group, a + O = a.\n3) For every element a in our group, there is also an element b such that a + b = 0.\n4) If we pick three elements in our group, then (a + b) + c = a + (b + c).\n\nThis is an abstract definition, and doesn't prescribe what the underlying elements actually are.  All it says is that they must satisfy (1)-(4) to be called a group.  You can probably check for yourself that numbers do satisfy these rules, although there are many particular examples of groups where numbers don't provide enough flexibility to be considered as the underlying elements.\n\nNow, mathematicians spend a lot of time studying these, and other, mathematical objects, and there are many beautiful theorems associated with them.  These objects, and the theorems about them, should be considered as eternal as the numbers whilst at the same time being different to the numbers.
616354
Math is used all the time in the engineering sciences.  Many physical phenomena, including fluid flow, heat transport, and diffusion can be described by appropriate partial differential equations.  In order to solve these equations and make predictions, you need to be good at calculus.\n\nIf you limit yourself to addition, subtraction, multiplication, and division, you would be stuck with linear models for everything.  This means that any more complicated relationship between two variables could not be modeled continuously, and you would never be able to extrapolate with any confidence.  Thus development of new technology would be strictly trial and error (and you wouldn't even have a good trial and error system without statistics).\n\nHang in there!  Get through that math.  You don't have to like it, but you will inevitably appreciate the developments that math has enabled.
508895
Maybe.  But the question is hypothetical -- infinity is a mathematical concept, and does not exist in the real world.
7300
because, it meant that energy and mass are basically the same thing.  this is pretty contrary to our everyday experience, and in fact it is only a noticeable effect when there are very large energies involved.  so, at the time there was basically no experimental evidence to show that this equation was correct!  nevertheless einstein derived this equation, and the rest of the theory of general relativity, based on mathematical principles alone.  only afterwards were experiments done and he was shown to be right!  \n\nthis is part of the reason einstein is so celebrated as a genius - his correct prediction of the equivalence of energy and mass.
119372
Einstein was a genius, no doubt, but he was wrong on a lot of counts-even in physics.  He denied the possibility of quantum physics to his dying day, and yet quantum physics is the basis of more discoveries than relativity.  There are a number of examples of brilliant men and women, Nobel laureates, who were absolutely wrong in many things.  No human is infallable.
33
First, I would never say that a theory has been proven. There may be a lot of evidence that supports a theory, and as a result it may no longer be on the list of theories that are being challenged, but theories are always theories and should always be open to adjustment by new evidence. A good theory is just a collection of hypothesis, experiments and deductions that survives repeated challenge and can therefore be used to predict untested outcomes.\nNow to your question (sorry for the tangent)... I think that most physicists consider Arthur Eddington's observations of the bending of light during the 1919 solar eclipse as the first solid evidence to support Einstein's theory of General Relativity. Einstein's theory predicted that gravitational fields would bend light, and Eddington's measurements supported that prediction, thus making it the first empirical data to support the theory.