speed of light question?
344500
Yes the difference between the two are still the speed of light -- it's because at speed of light, or even just factions of the speed of light "normal" Neut on physics stops and only relativity theory explains what happens.  At speed of light time no longer move at the same rate, so the two object will not have same reference in time, and since speed is distance over time, the comparison make little sense to the normal perception of how things work.\n\nAn that ultimately explain why the difference between the two is not 1000 miles per hour.
40471
E=mc^2 \nEnergy = mass * (speed of light)^2, c = the speed of light (approx. 186,000 miles per second).
230716
Two observers with different frames of reference will measure time and distance differently in such a way that the speed of light is the same in all frames of reference.  Try this site and see if it helps.\n\nhttp://www.glenbrook.k12.il.us/gbssci/phys/Class/relativity/reltoc.html
566668
No object that has mass can be accelerated to move at the speed of light. If you were somehow moving at 0.99c and then shown a flashlight, the velocity of the photons would not be 1.99c, it would just be c. The speed of light is invariant. The true formula at relativistic speeds is the following:\n\nV = (v+u) / (1 + vu/c²)\n\nWhen the velocites are not relativistic (i.e. throwing a ball out of a moving car) this approximates to V = v+u. So if you are moving toward something that is emitting photons at c, and you yourself are somehow also moving at c, the velocity you observe the photons to be moving is still just c. Try it in the formula: V = (c+c) / (1 + cc/c²) = c\n\nIt can be derived from special relativity or the Lorentz transformations.
763848
you couldn't drive at the speed of light.  But if you could drive near the speed of light, and turned on your headlights, light would leave your car at the speed of light relative to the car.  Einstein asked this very same question (except I think he used a train).  ANYWAY......this seems paradoxical and impossible.  But it's not....because TIME and SPACE (and distance and mass and all other measly "constants") change in order to make this possible that the speed of light still remain a constant.\nP.S. - Don't expect to understand all of this at once.  I'm pretty bright and it took me quite awhile to catch on to just how it works.
144613
light rays do not move faster or slower than the speed of light.  the speed of light is the speed of light, period.\n\nthat said, light often travels *slower* than c, which is a constant defined as the speed of light IN A VACUUM, approximately 3x10^8 m/s.  here is a way you can actually observe some honest-to-god light traveling slower than c:\n\nstep 1.  find a window.\nstep 2.  look at it.\n\ncongratulations, you have observed light traveling slower than c.  in ANY medium (air, glass, water - you name it) the speed of light is slower than the speed of light in a vacuum.  \n\nin fact, the so-called index of refraction (n, which equals 1.4 for glass) is defined as the ratio of c to the speed of light in that material.  generally, denser materials have a higher index of refraction, and people have been able to make light go REALLY slow by making some very dense materials.  all of this is perfectly consistent with general relativity.\n\nas for FASTER than c:  under certain conditions, it is possible to make photons with a "phase velocity" that is greater than c.  however, when people speak of the speed of light, they usually refer to the "group velocity".  the distinction between phase velocity and group velocity is kind of technical; but phase velocity refers to the speed at which the individual phase fronts propagate through space.  \n\nit is possible to make these phase fronts go faster than c; but because the energy or information or whatever carried by the light travels at the group velocity, the actual speed (as far as stuff like general relativity is concerned) is still less than c.\n\nanyway, all of these results are entirely consistent with general relativity.  in fact, i don't know of any published results of a scientific experiment which are not consistent with GR.  \n\nthe fact that einstein's theory, largely concocted out of the blue from basic principles and logical reasoning, has stood the test of time for so many years is a testament to the genius of the man's work.\n\nhere are some links to learn about phase velocity, group velocity and the speed of light:\nhttp://en.wikipedia.org/wiki/Group_velocity\nhttp://physicsweb.org/articles/news/4/7/8/1
13174
Hi Writholeen, the only flaw in JayNick's answer is the accuracy part. As per the National Institute of Standards and Technology, the exact value of Speed of Light in vacuum is 299,792,458 m/s. By exact, I mean there is no uncertainity till the last digit. \n\nTo be precise, what we usually call the "speed of light" is really the speed of light in a vacuum (the absence of matter). In reality, the speed of light depends on the material that light moves through. Thus, for example, light moves slower in glass than in air, and in both cases the speed is less than in a vacuum. However, the density of matter between the stars is sufficiently low that the actual speed of light through most of interstellar space is essentially the speed it would have through a vacuum, so we don't make much error by ignoring the difference.\n\nTo make it easier for you to convert, here is the speed in alternative units :\n\n(1) 983,571,056.4304461 foot/second\n(2) 11,802,852,677.165352 inch/second\n(3) 1,079,252,848.8 kilometer/hour\n(4) 299,792.458 kilometer/second\n(5) 582,749,918.3585312 knot\n(6) 880,991.0899527 mach\n(7) 670,616,629.3843952 mile/hour (mph)\n\nThese values are accurate to the 7th digit of decimal. \n\n\nFlaw in JayNick's answer:\n\nThe speed of light in kilometres per second is 279,600 kilometres/sec. Even if you approximate the actual value , 299,792.458 kilometer/second by round off the last three digit, the value would have been 300,000 kilometers per second.
122048
Peple I know you want the points, but can you please not just make up answers out of whole cloth like that?\n\n>>>>>Massive objects cannot go the speed of light.\n\nYeah, they can. They can't accellarate to the speed of light but they can be created at lightspeed and continue on.\n\n>>>>>> However if they could, no you could not see, becuase the light could not go furthur then the builbs at the front of your car\n\nNonsense. The speed of light is constant for all frames of reference. From the FOR of the bulbs the light would be seen travelling away from it at lightspeed. \n\n>>>> You'd be seeing the light go by your side.\n\nNo, you would not be seeing the light by your side. You would still be seeing all light in the universe travelling away form you or towards you at the speed of light, just as you do at your current velocity\n>>>>>The light would not shine out in front of you because you are going the same speed.\n\nIncorrect. Light always sines out in front at lightspeed in the observers FOR. It makes no difference if that FOR is stationary or lightspeed itself.\n\nYou quite obviously made that answer up.\n\nws, this question seems to get asked here every couple of days. You can go back and have a look and see it answered quite well several times.\n\nIn brief,\n\nLight is funny stuff. Light always travels at the same speed relative to you, it doens't matter how fast you travel. \n\nIf you are sitting still and a person is going past you at light speed you can both look at exactly the same light beam, and it will be travelling at lightspeed compared to both of you.\n\nIf you are going at lightspeed and turn on the headlights the light will move away fomr you at lightspeed. If it strikes something it will be refelected back at lightspeed. If someone is sitting completely still beside you he will also see that light move away form him at lightspeed, and get reflected back at lightspeed.\n\nIt's weird stuff light, it doesn't behave like anything else. The answer to any question that asks how fast light is moving towards you or away from you is always "lightspeed". It doesn’t matter what else we add to the question, the answer is always 'lightspeed".\n\nSo if the light leaves the bulbs at lightspeed and gets reflected back at lightspeed does that mean you could see?\n\nProbably not. \n\nAlthough light doesn't change speed relative to the observer it does change wavelength. The faster you travel towards a light source the bluer it will look. \n\nAny object that your headlights strike will reflect the light back to you at lightspeed, that's OK. But because you are travelling towards the object at lightspeed the light will be shifted way, way towards the blue end of the spectrum. It would all be ultraviolet an X-rays. The human eye simply can't see those wavelengths. So plenty of light would be reflected back, but it wouldn't be visible to you. As a result it would all look dark.\n\n\n>>>>> if the interior light inside your car was on at\n>>>>> the time would you see that?\n\nYes. Because both you and it are travelling at the same speed it woulnd't be red shifted at all. Similarly because you and the interior of the car are travelling at the same speed you would be able to see the light reflected off that just fine as well.\n\nEverything in the universe that is travelling as fast as you will look normal.Everything outside will appear black.
532772
nothing but light can travel at light speed.  the faster you go, the more energy it requires to accelerate.  at speeds that are close to the speed of light, you would need what is basically an infinite amount of power to accelate.  with current technology, it is impossible.  the only reason light can travel that fast, is because when it is created it is already traveling that fast.  it doesnt have to accelerate.
418308
The speed of light in a vacuum is exactly 299,792,458 metres per second (or 1,079,252,848.8  km·h-1, which is approximately 186,282.397 miles per second, or 670,616,629.4 miles per hour).
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.
426222
The speed of light is the same no matter where it is. It is 299,792,458 meters per second.
506771
Actually by what Einstein explained, da light will still be in  front of da car, it won't go behind u no matter how fast u r going even if u r faster dan da speed of light. Weird? rit. I too thought so, It was explained in discovery channel. Well I'll try 2 explain it 2 u, But it wud hav been easier if I cud actually show it by som animations. When u r travellin at da speed of light, time stops. Ya it does. Time is somthin like per user setting, it is unique for u & each & every one. Think dat ur carrying an Einstein's clock, which is a simple devise with 2 mirrors facing each other with a photon bouncin of the mirror. Each time it bounces from a mirror u'll hear a tic sound, that will b 1 second for u. Say u travel at a speed little less dan light u r movin forward but da photon has 2 move a lot more distance than it initially had been, which was in a straight line, but now it's motion will b som what like a hypotenuse, so it has 2 travell more distance dependin on ur speed. So ur 1 sec will not be da same as 1 sec is for som 1 on earth. So actually ur headlight will be actually movin faster dan u no matter what
1085739
OK!! Ignore the people who are saying that nothing physical can travel at the speed of light.  Light is physical and does actually travel at the speed of light!!  \n\nOnto your hypothetical train.  If the train is travelling at the speed of light and you try to run from one end to the other, logic dictates that you'd be travelling faster than light, but this time logic fails us.\n\nIt is impossible, according to einstein to travel faster than light.  But, according to einstein, it is possible to run from one end of the train to the other!!  This is done because they would be in the same place!  This is due to a part of the Theory of relativity call Lorentz contraction! \n\nAccording to you, the train would be the same length as it would be if stationary, and you would feel like you were running as if it were stationary.  But relative to the observer that is 'stationary' (actualy no such thing according to einstein) you would be at both ends of the train at the same time because you and the train would be zero.  The formula for lorentz contraction is L=L(0) x (square root of(1-(v/c)^2)).  Where L is the length of the train according to an observer, L(0) is the length of the stationary train, v is the speed of the train, c is the speed of light.\n\nIf you make v=c then you'll see that the train and you have absolutely no length.
718668
Neglecting the fact that it would be imposible to accelate a train (non-zero rest mass) to the speed of light,\nif you did, an observer in the train would still see light moving away from them at the speed of light.\nThe speed of light is constant in all frames of reference.
983322
frequency = C / wavelength.  c is speed of light
63805
Actually there is no speed of dark.\nBut according to me it should be the same as the speed of light because as soon as the light goes the dark appears.So it must be as the speed of light i.e. 3* 10^8 meters/seconds