speed of light does not depend on any conventional frame of reference.is it connected to any vibration of space?is it related to gravity wave propagation?it may be possible that there are other sources of information travelling faster than light.
136919
http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/fast_light.html\n\nhave a look at this website
149561
Your example is actually a good one for how we know no one can travel faster than the speed of light.  The people on the boat would measure the same speed for the beam of light as those standing on the shore.\n\nEinstein's theory of special relativity states that, regardless of your motion, light's speed remains constant.  Space and time warp in order to make light's speed constant from all perspectives.  As matter gets closer and closer to the speed of light, space stretches and time contracts, requiring infinite energy to reach the speed of light.  Only things with no mass (i. e. energy only) can travel at the speed of light, and nothing we know of can go faster.\n\nHowever, Einstein's theories do suggest that we could bend space and time to allow us to get around the speed of light.  We can't travel a trillion miles per second, but, with enough energy, we could shift some spot a trillion miles away to right next to us.
419320
As matter approaches the speed of light, the properties of change, and since E=MC2, we know that there's a relationship between energy and matter.\n\nEinstein's theory of special relativity dictates that since all motion is relative (for example, you in your chair may be at rest, but the Earth is rotating, the galaxy is moving, and the universe is expanding).  However, the speed of light will be measured by anyone anywhere to be the same.  \n\nIf an object undergoing constant change (like, say a human aging) is accellerated to close to the speed of light, the environment around it, (like say, his family on earth), would experience time at a different rate.  If you go on a 6-month space flight traveling at near the speed of light, you would find that people on Earth had aged several years.\n\nIn this way, it is like that person traveled into the future.  However, I can't think of any plausible way of matter reversing time, since it must be positive, or zero.
364134
the speed of light, c, is measured to be the speed in vacuum......\nall other mediums (or media?) have greater index of refraction n, (for all other meduims n>1), thus, slower speed of light...\n(for vacuum n=1, for air n=1.003, for water n=1.33 )\nthere can not be a medium where n<1....\n\nif, however, there is a discovered medium such that n of the medium is less than the n of vacuum, the speed of light known to be c is not anymore valid...there will be a new speed of light measured....
600608
Moving faster than light isn't really the real issue for space travel as traveling AT the speed of light solves all the distance problems(unless you are interested in time travel!). Of course that in itself is a big challenge. If one could demass the vehicle then surely one could achieve the speed of light!!! Afterall photons do travel at this speed.\nBut we would do very well even with speeds like .99999c because time dilation will reduce the time required drastically. Have the science, just need the technology!
213973
This is the kind of question I like ... :-)\n\nNo, this is not information transfer. I will try to enlighten the problem by formulating it more precisely.\n\nBut first, I'd like to show that if you could tranfer information faster than light, you'd get a contradiction with special relativity.\n\nSuppose A can communicate some information faster than light to B. Let A sending the information be event 1, B receiving it event 2. If the message is travelling faster than light, it can be shown that in the reference frame of A, event 1 happens _before_ event 2, while in the reference frame of B event 1 happens _after_ event 2, which is a contradiction because Bob cannot receive the message before Alice sends it. If a light-signal cannot travel between events 1 and 2, we call them spacelike separated (at least in some other languages than English we do :-) ). Spacelike separated events don't have a definite temporal order (the order depends on the reference frame).\n\nOf course, in your example there is a correlation between the outcome of Alice's and Bob's measurement, but it cannot be considered information transfer. They always knew that they would get opposite results, but they didn't know who would get |up> and who would get |down>. Information transfer would mean that Alice already has a piece of data she knows, eg. a bit of 1, and she would like to transfer it to Bob. Bob's gaining knowledge of this information is the result of Alice's sending it. So there is a definite temporal order (and causal relationship) between these events. In the entagled particle-pair example she doesn't have this piece of information before she does a measurement.\n\nHowever, you could say that A can transfer information like this: she does a measurement, and as the result of the measurement the wave function of both particles collapses, and B can measure to see if his particle is in a collapsed (|up> OR |down>) or superposed (|up> + phase_factor*|down>) state. So B will know if A has already measured or not! But B cannot decide which state the particle was in with only one measurement! And he can make only ONE measurement, because the measurement collapses the state. As a result he will always get either UP or DOWN, so he cannot tell if the original state was |up>+|down> or one of |up> or |down>.\n\nOf course if B could copy the state of his particle, he would be able to make multiple measurement on the same quantum-spin-state, but he cannot copy the state because of the no-cloning theorem (Zurek-Wootters, Nature, 1983 if I remember well, but anyway, see it on Wikipedia). Of course, if he would be able to copy the state, we would get a contradiction with special relativity.\n\nAs satanorsanta pointed out there are still problems with the _interpretation_ of quantum mechanics (especially with the measurement postulate), but I wouldn't consider this specific question unsolved.\n\nI know my English is not the best ... I hope you will understand my reasoning. If you's like to chat about these thing, send me a mail.
4945
It's true that the speed of light is constant no matter what speed at which you or the source is moving.  This is a fundamental postulate of relativity, and there is no explination.  It's just accepted because our experiments indicate that it is true.  You used the formula "lights speed + X = actual speed"  this type of velocity addition is called "Galilean".  It turns out that speeds don't actually add that way.  Far out.\n\nWhere is the rest of the energy? Good question.  The frequency of the light you observe from the sun DOES depend on how fast you and it are moving.  The energy of each photon is given by E = hf, where f is the frequency of light.
568438
You have the old Newtonian physics, which is called classical physics.  It is built on the premise that space and time are absolute fixed entities, and cannot change.  This is the physics that you learn in High School, and is true and works for our everyday life.\n\nHowever, when one begins to approach the speed of light, and apply the classical physics to that situation, we see violations of physical law: such as an object can go faster than the speed of light.  For example, let's say a car is traveling at half the speed of light, and you shoot a bullet that is traveling at .6 times the speed of light (all hypothetical of course).  An observer would see the bullet traveling at 1.1 times the speed of light, which is obtained by adding the speed of the car and the bullet together.  That is the classical method of finding the bullet's speed.\n\nEinstein correctly surmised that nothing can travel faster than the speed of light, or even be seen traveling faster than light, such as our bullet.  Therefore, he considered how classical physics would look if space and time were not fixed entities.  In doing so, he developed a more comprehensive physics, called relativistic physics, which fixes our bullet problem.  \n\nThe cool thing is, the relativistic equations are almost exactly the same as the classical equations, with one exception: the have what I call a relativistic adjustment.\n\nFor example, to find the bullet's speed as seen by an observer, requires the following equation:\n\nV = Vc + Vb\n\nWhich in our problem would be:\n\nV = .5c + .6c = 1.1c\n\nThe relativistic equation is almost the same:\n\nV = (Vc + Vb)/(1+Vc*Vb/c^2)\n\nThe numerator is the same as the classical equation.  The denominator is the relativistic adjustment.  So, the equation becomes with our example:\n\nV = (.5c + .6c)/(1 + .5c*.6c/c^2) = .846c\n\nThe bullet would be seen traveling at almost 85% the speed of light.  \n\nThe cool thing here is that when you use speeds that are very small, like everyday speeds, the relativistic adjustment bascially equals one, so it reduces to the classical equation.
514460
Simultaneity in Special Relativity is based on 2 assumptions:\n\n- the laws of physics apply equally to all inertial reference frames\n- the speed of light in empty space is constant and independent of the relative motion of its source\n\nThis implies that there is no absolute simultaneity, meaning that two events that happens at the same time in one inertial frame may not happen at the same time in another inertial frame.\n\nSo Einstein is NOT defining Simultaneity based on the invariance of the speed of light in all inertial frames, but instead the failure of absolute Simultaneity is a consequence of the invariance of the speed of light in all inertial frames.\n\nSo why does the invariance of the speed of light in all inertial frames imply the lack of Simultaneity? The argument for this is exactly the same as why there can be no absolute reference frame if we assume that the speed of light is constant in all reference frames.\n\nThe only way for the speed of light to be constant in all reference frames is for distance and time to be relative and be a function of speed of the reference frame, i.e. speed = distance/time implies that distance must contract and time must dilate if the reference frame is moving with a certain speed.\n\nSo if distance and time is different in one reference frame than another, then there is no way that two observers, each in separate reference frames, can agreed on when some event has happened. Thus simultaneity is violated.
675663
the speed of light as we know it is based on the structure of the space around us but may actually vary in different parts of the universe. the age of our sun and the processes that it goes through determine the make-up of our region of space.\n\nother star systems at varying levels of development and size convert elements into heavier elements. heavy elements are unstable to us and decay but may be the norm around other systems, especially the ones that have gone nova and seed the space around it with this exotic material which eventually forms new stellar and planetary systems.\n\nread the link below and you will see that light is manipulated when it goes through exotic materials. therefore the speed of light is determined by our placement in the universe and how light reacts as it crosses the spacial material from it's source to our eyes.
483815
Why shouldn't they be the same?  The distance between the Earth and the Sun doesn't change much in one day.  And even if you argue that the rotation of the Earth gives is a relative speed that should be added to (or substracted from) the speed of light, you're forgetting that the speed of light is a constant.  You can't add or remove anything to it.  If you're on a train going at the speed of light and you turn on a flashlight, the "total relative speed" of that light won't be twice the speed of light.\n\nAs for how can this speed me mesured, there's an experiment that uses mirrors and a laser.  Those flat mirrors are glued around a cylinder and they rotate.  (It could also be a rotating screen with holes in it.) When the mirror is positionned right, the light comes back to the laser.  Knowing the distance between the mirror and knowing the frequency of the rotation, we can calculate the speed of light by mesuring how much times it takes for the light to go to the mirror and come back.  TRY FIZEAU OR FOUCAULT ON GOOGLE.  He's the guy who did that.
437498
It is exactly that question that inspired Einstein to formulate his theory that nothing can ever travel faster than light. I am not saying the Einstein had a goal to make a theory saying nothing can travel faster than light. I am saying that the question made him think about how to explain what would happen in such a case and then the math lead him to a theory of motion in general which says nothing can travel faster than light.
104855
Light speed is constant but can be warped by objects or black holes gravity. Science can only assume on such matters by use of mathimatical functions. Unless of course someone could travel to a black hole and make it back to tell the story, hundreds of years from the time they left.
14428
this is somewhat similar to a question I answered realative to time travel. The short answer is no, there was never a time, nor will there ever be a time when matter (massive fermions) travel faster than light (massless bosons). This is because massive objects need energy to accelerate and regaurdless of how much energy was released in the big bang, it could not have been infinite, and that is what is required to move a massive particle faster than light. Light speed is not a derived measurement, it is a fundemental constant that is the same in all reference frames. Here's the cool exception though.....and this is how a theoretical warp drive would work..... the actual expansion of space itself might have been faster than light. There has never been a limit imposed on the speed at which space expands although because gravity is a result of the deformation of space and gravitons are the theoretical force carrier, it has been assumed that the expansion of space would occur only as fast as gravitons can travel....which is most likely light speed. One of the many postulates asserted by string theory is that gravitons may not be bound to our spatial demensions, that they might radiate through extra demensions (which would account for gravity's lack of strenght compared to the other forces). If this is the case that the gravitons travel through other demensions it is quite possible that within a given reference time, a graviton could pop into a superior demension and back into our at some other point and essentially beat light to some defined location.\n\nI know thats a little confusing.....but its fun to think about.
313989
No known force could push you faster than light.  The only exception might be quantum entanglement, but we're nowhere near the technology to use that.  At the speed of light, nothing could catch up to you from behind, but plenty of stuff will hit you from the side or head on.  Just like any propulsion, light propulsion might get you close to but not quite to the speed of light.
447755
Yes, it is true that there are stars and galaxies whose light has not yet reached Earth. This is because light travels at a finite speed (about 3.00E8 km/s). It does not lose energy to space either... and the only thing in space that disrupts light's path by any real amount is gravity.\n\nWhen we look into the sky at night we are seeing the past. When we look at our Sun we are looking 8 minutes into the past (light from the Sun takes about 8 minutes to reach us)... The nearest stars to our Solar System are hundreds, even thousands of light-years away (a light-year is the measure of the distance that light travels in a year)... So, when you look at the stars in the sky, you are seeing them as they were 100's, 1000', if not millions or billions of years ago. Scientists, using our most advanced telescopes have looked as far back as when our Universe was only a baby (about 450 million years old). As the Universe is about 15-20 billion years old right now thats very far back in time.\n\nTo answer your question about faster-than-light travel. As we know physics today, that is impossible. Einstein and many other relativistic theortists have shown time and time again that faster-than-light travel has a high probablity of impossibility. Also, light speed and (if possible) faster than light speed travel would affect the traveler's perception of time relative to the inertial frame.\n\nThis is a basic theory in relativity and I really don't want to get into that.
450654
well there r lot of major scienctists nowday ... working on it... for myself i do belive that time travels faster than light because we are living in alternate dimension.. inside vortex of time, we can be frozen in time and still time moves past us,the light travels is pretty slow.. when we look up in sky ans there r stars and next day same place, for about 3 days later it will be moved bit forward.. and that star is probably dead or giant black hole.. think about it