Why can't we travel faster than light?
117448
From our current undestanding of physics, we cannot. That does not mean in 500 more years or 5000 more years we will not have a better understanding of physics that includes methods for travelling faster than the speed of light in a vaccuum. However, at the moment it looks very doubtful. \n\nWe have substantial evidence that special relativity is true from years of operating particle accelerators. From special relativity, it appears that it would require an infinite amount of energy to accelerate to the speed of light. The glib manner people here are discussing an infinite amount of energy tells me that people do not understand what infinite means. \n\nAn infinite amount of energy is more energy than the sun produces. It is more than the energy produced by a billion suns. It is more than the energy produced by a billion galaxies full of hundreds of billions of stars. It is more energy than would be produced if every particle in the universe (about 10^70, the Eddington Number) was converted into a star like our sun. In fact, it is an INFINITELY greater amount of energy than 10^70 suns would produce. \n\nIf something is going at a speed greater than the speed of light in a vacuum (tachyonic speeds), then presumably the formulae we have for special relativity would not apply. There has been some occasional attempts to look for tachyons (particles going faster than the speed of light), but they have never been reliably discovered. \n\nThere are postulated entities called wormholes that might enable this kind of travel. Of course, we have no evidence for them at all.\n\nHowever, our understanding of physics is still very crude. We do not understand dark matter. Unifited field theory is still unproven. Even if it is proven, we do not understand the consequences of it (a lot of technology came from unifying electricity and magnetism). We do not understand what happens in black holes. We do not understand how the quantum world and gravity fit together. Even in quantum electrodynamics, which is viewed as settled and accepted, we end up performing illegal mathematical operations to get answers that agree with experiments. The role of the observer in quantum mechanics is not understood. We do not understand quantum teleportation very well. We do not understand BCS theory and its instantaneous coupling very well. We do not understand the apparent accelerating expansion of the universe (a sort of anti-gravity). There are immense holes in our understanding. Therefore, I would not be too confident that our current physics means very much here. \n\nThe only way to address this, is to continue to enhance our basic understanding of the way the physical universe operates. This might not be as romantic as it appears in the movies, but the hard work has to be done.
69084
only in black holes, which have an escape velocity greater than the speed of light, so light can't escape.
678688
It's not a yes or no question.\n\nCan one travel faster than the speed of light?  No.\n\nCan objects be moving away from each other at a relative rate faster than the speed of light?  Yes.\n\nMeditate upon this, and you may become enlighted, or enspeeded, or something...
214684
No massive object can move at the speed of light, so the question is ill-posed. Sorry.\n\nAs a physicist, please let me give you a little advice: don't loose your time with this nonsense, try instead to focus on the mathematics of the relativity theory, that's the way to understand it. The rest is pseudo-science.
72176
If you're asking about some mass being accelerated up to and beyond the speed of light, no it is NOT possible. Einstein theorized that the faster an object moves, the greater will become its mass. This increased mass would require more energy to accelerate it even more, which in turn would increase its mass, which would require more energy to go faster, etc., etc.,. Ultimately to get this object up to the speed of light would require infinite energy, and that's impossible. This isn't just theory anymore either; mass increase versus velocity has been observed countless times in modern particle accelerators.\n\nOf course there are plenty of sci-fi novels, TV shows and movies (like Star Trek and warp drive) where things move faster than light, but unless someone can find a way around Einstein and all the evidence that he was right we'll never be able to attain FTL travel.\n\nBy the way...worm holes don't provide a way to MOVE faster than light. So-called worm holes, if they exist at all, are nothing more than short cuts; going through a worm hole you'd still have to obey the speed limit imposed by Einstein.\n\nPersonally I hope that some day some radically new branch of physics is found that would allow us to get around Einstein, but right now it doesn't look too good.
410964
i think its very much possible to travel at the speed of light, its just that we would need an extremely strong processor (like a fax machine) to break down the matter that we are made of into energy (E=MC^2) and then after reaching the destination just convert the energy back into matter. (not possible with the technology we have today)
1001554
According to Einstein and Stephen Hawking, travelling at the speed of light (for anything with mass, ie not photons) is impossible.  But travelling near the speed of light is theoretically possible.\n\nIf you were to travel close to the speed of light you would go into the future a lot quicker than those who don't travel close to the speed of light.  It would require huge amounts of energy.\n\nUnfortunately it would be a one way system.  To travel back it time it would be necessary to bend the whole universe.  Or you could find a way of travelling to parrallel universes (if they exist) and that would solve problems for both forward time travelling and back time travelling.
689820
Neither you, nor the train, could ever travel at the speed of light since both of you have some non-zero rest mass.\nIn order to accelerate something with a non-Zero rest mass, an infinite amount of energy would be required....and in the whole universe, there is not an infinite amount of energy.\n\nBut lets say you were traveling just under the speed of light...at 99.99999999999999% of c and you began to run toward the front of the train, \nyou would still NOT be traveling at or above the speed of light (as seen from an outside, "stationary" observer) since at relativistic speeds such as this, velocities do not add in the normal Galilean way, you would still be traveling slower than the speed of light.
148002
It's technically impossible for something with mass (like a spacecraft) to go the speed of light in our universe under the laws of physics.  As something approaches the speed of light, it gains mass.  In theory, if something were to actually go the speed of light, it would have infinite mass, which is impossible.  \n\nOf course, no one can say for sure.  Science fiction on television and in books have gotten around these rules by using wormholes, subspace, etc., none of which are known to actually exist.
1061558
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!
317753
Space is very vast and the distances are in the order of millions of light years to the farthest reaches of the universe. Even if we learn to travel at the speed of light, it will be impossible to travel for millions of years for one person or one generation. Some have proposed that there may be holes in the fabric of space-time which would enable us to reach such places without going throught the distance in between. This remains to be proven.
478673
Looks like a controversy here....but no, gravity does not travel faster than light, it would take eight minutes before the earth's orbit changed.\n\n(If gravity was instantaneous, then it would be possible to use that to send messages faster than light!)
758936
One of the fundamental assumptions of relativity is that there is a finite speed of causality.  Usually this assumption is stated "the speed of light is a constant", but I think the finite speed of causality statement is a better way of looking at it.  So if something could travel faster than the maximum speed of causality, then it could make events happen before it caused them.  That is assuming that relativity is true and that causality is a flexible concept.  If you assume that causes must preceed effects then there are two possibilities for the hypothetical object going faster than light.  1. there is a maximum speed for the object that is going faster than light, so just raise the speed of causality to that new speed and keep relativity  2. there is no maximum speed limit for the object and influences can travel instantly, thus one of the fundamental assumptions of relativity is false and we need to throw out the theory
490004
According to Einstein, no object can go faster than the speed of light, approx.186,000 miles a second.
596319
There is a big difference between predictions that the speed of sound could not be broken and that the speed of light cannot. It was always known that *some* things can go faster than sound. Bullets for example. The question was whether we would have the technology to get people to that speed.\n\nThe speed of light is very different since we haven't seen *anything* go faster than light in a vacuum. Nothing. Ever. Furthermore, the predictions of special relativity have been verified in particle accelerators when the particles are going to within a hundred thousandth of the speed of light.\n\nAs an example, at Fermilab protons are accelerated to energies of 2TeV. This is over 2000 times the rest mass of those protons. To accelerate something the mass of a *gram* to an equivalent speed would take about the energy of the largest hydrogen bomb ever exploded. This amount of energy would be needed for each gram to get to that speed, so multiply it by 75000 for a medium sized human. And that doesn't count the spaceship they would have to travel in!\n\nNow, this is how much energy is needed to get to speed we *know* about. To go faster would require even more. Unfortunately, we have never seen a wormhole of any type. But the predictions are that the energy requirements would be even more prohibitive than what I just described.
168923
>>>>why can nothing excede the speed of light?\n\nLots of things can and do exceed the speed of light.\n \nNo information or mass can exceed the speed of light. Why? Because the speed of light is our one reference point. If anything exceeded the speed of light it would arrive at its destination BEFORE it was sent.\n\nIt's exactly like recieving a letter the day before it is written. It's impossible and  it makes no real sesne to ask why it can't happen. Cause has to preceed effect.\n\n>>>>if radio waves are slower than light\n\nRadio waves are just electromagnetic radiation. They travel at lightspeed just like all other EMR.\n\n>>>>>then wouldnt gama and X rays be faster?\n\nNo, they also travel at C. They just have higher freqencies.\n\n>>> or do all waves travel at the same speed and the light >>> part is just a term\n\nWaves have all sorts of speeds. \nOcean waves travel at variable speeds, often les than 10  kms.hr. \nSound waves travel at a bit over 1000km/hr. \nLight waves travel at the speed of light.\n\n_______________\nInfinity said:"By the way, the quote "Lots of things can and \n>>>>>>do exceed the speed of light" is entirely false.\n\nI really, really wish people would do some basic research before attempting to adress points they clearly don't understand.\n\nThe expansion of the universe itself is faster than the speed of light (see the link below).\n\nAnd as wd5gnr and Hound both said it is perfectly possible for non-information bearing events to propagate faster than lightspeed. We recently had an in depth discussion on the experiments which have managed to produce pahse vlocities hundreds of times faster than light.\n\nAnd of course there are many many other events that travel at speeds well in excess of C.\n\nReally Infinity, you should at least take the time to do some research before correcting others. It saves you embarassment of this kind. More importantly it prevents you misleading others and spreading your ignorance.
15559
Light travels roughly 186,000 miles per second. Einstein once said that nothing can move faster than light, and this previously was an accepted truth because visible light was considered to be just a wave of energy. However, when studying how light reacts to strong gravitational pulls, such as one from a black hole, we can see that it bends under gravity. This indicates that it shares some characteristics with matter. It could even have a minute amount of mass. If light shares characterisitcs with matter, then we can harness it and use it the same way we do air in a jet engine. Can we not go faster than the wind naturally blows with a jet engine? Yes. Then I do not see why we can't go faster than light when harnessing light itself as energy.  There have been several questions like this, and I really feel that traveling faster than lightspeed is only decades away.