Does a laser beam REALLY go on forever? I wonder because the little keychain ones don't seem to..?
541125
Light only travels until it is absorbed, dissipated to other types of radiation (no longer referred to as "light"), or expended as some other form of energy.\n\nThis can mean "forever". Of course, that depends on various important factors of light which rely on concrete proof. At the moment, there are differing theories about how light works, why, and what it is.
711259
I have always been a fan of this discussion. I propose that ANYTHING can travel faster than the speed of light (SOL). I also believe that was the driving force behind Einstein's assumptions. When we start talking about time slowing down as we approach SOL, we are talking about time RELATIVE to something else...If two people are together on a SOL spacecraft, then the time they experience is the same as if they were standing still. \n\nBefore I ramble on too much, What stops light from going any faster? If we had a theoretical spacecraft that could travel at 1/2 SOL, and we shot a laser off the front of it, how fast would the light be travelling? To the observers on the SOL-craft, the light would be travelling at absolute SOL, but to someone standing next to the craft when the laser was activated, would the light NOT be travelling at 1.5 SOL?
125793
basic principles of wave propigation. a body in motion tends to stay in motion. if what you're saying is the vacuum is deviod of all matter, including subatomic particles, the wave would continue forever, with one exception. if the beam reflecting around the room collided with itself (say it caught itself in a corner), it would cause sufficient refraction to scatter the beam eventually. photons expend no energy to travel, so the room would stay lit up forever. and man, that would have to be some badass 100% reflective material! ;->
297433
false, but the rumor probably started I believe one of Edison's bulbs is still burning in Menlo park (his lab).\n\nIt's never been turned off, which helps it last longer.
831271
Dear Madame,\n\nYou could try testing wave-particle duality nature of photons, and report on how the theory corresponds with Schodiger's findings in the early 20th century. \n\nAnyone can put a light bulb in a potato. Also, the above response about commercials is about as unscientific as you can get. I don't trust emus.\n\nPianoguy
372946
Actually, If you shine light on a steel door, the atoms that make up the surface of the door will absorb the photonic energy, and if they absorb enough photonic energy, they will emit the energy. Sometimes the newly emitted energy is outward away from the door, and sometimes the energy is emitted inward and propagated to atoms further into the doors structure.\n\nTo make thing more complicated, the energy is only emitted as photonic energy sometimes, when the atoms have the right amount of energy built up to release a quanta of photonic value. Other times the energy is emitted as heat energy. \n\nThe door is trying to propagate the photonic anergy through to the other side, however the atoms that comprise the door are capable of retaining a great deal of energy, and when they do release it, based on quantum mechanics, there is only a probability that it will be directed into and not out of the door.\n\nIf you quickly heat the atoms in a specific region ,(fill them up with energy), without giving them time to transfer the energy away, (blow torch) you can see the glowing red door on the other side.\n\nIn short, it is due the the energy retention strength of the atoms that make up the solid.
921136
Um, not sure why you need a laser gun.  If it's to shoot things, a standard ballistic gun is more practical.  FYI, it's against international law to develop lasers weapons to shoot people.\n\nIf you mean a toy, you can always pick one up at the local toy store (see link).  You won't see the beam.  If you did, it would be dangerous.\n\nhttp://www.target.com/gp/detail.html/sr=1-4/qid=1164226650/ref=sr_1_4/602-3152398-8374206?ie=UTF8&asin=B00023C3ZU\n\n\n\nNot a satisfying answer?  OK, you can always buy this:\n\nhttp://www.engadget.com/2005/11/03/handheld-laser-gun-available-for-purchase/
977539
On the contrary, a light beam would merely percieve that it travelled instantly inbetween origin and destination. Space would be warped to Zero distance in the direction of travel, not Zero space. I know it seems like a sleight-of-hand trick with the mathematics, but the distinction is important.
353005
No. But, from the POV of the photon, they are everywhere along the path of the photon at once. See the answer on "lorentz contraction", because it's right, but I just wanted to clarify that photons are not, in fact, *everywhere* at once.\n\nOh, and from the POV of any subluminous velocity, no, they propagate at the speed of light, naturally.
294491
My son has a cheap red laser pointer (well under $10)\nwhich has a few "lenses" that he can screw on the\nfront to make different patterns.\n\nI don't know if these things are strictly "lenses",\nbut they distort/focus/shape the laser dot to\nlook like a star, a line, or a couple of other\npatterns.\n\nIn any case, one causes the laser pointer to produce a\n"line" rather than a "dot", and that seems like it would\nsatisfy some of your needs.  The width isn't readily\nadjustable, but the the length would be (by covering\npart of the "line" just past the light source).
44359
a red l.e.d. laser is currently used.  Very soon, blue lasers will be generally on the market, but they will be a bit pricey for a while until the technology matures a bit.
181006
I cannot tell you whether or not it has been done...\nBut I will never be truly "trapped" even with a mirror with a fairly high finish (aka 1-2 microns) there is still a loss every time it "bounces" off the mirror + if you do not do it in a vacuum there will be atomspheric losses as well.\nHenceforth if it is "trapped" it wouldn't stay there for long..
983543
what exactly do you want to know?\nThe lazer beam burns data into the specially coated layer in the CD.\nNot quite like the grooves in a vinyl record, but in such a way that the other laser can read it and return the same data that was stored.\nIf you're really worried about someone finding data on a CD that you have 'erased', break or burn it.
996272
There is a little research and some guy even wrote a book claiming that teleportation is feasible.  But don't buy your home teleportation machine yet.  As yet the only thing that has been transported is a few laser beams.
830869
A Photon being a particle of light would never be at rest.  It is energy in motion.
777449
It's not a matter of great energy to travel a large distance. In a vacuum, there is nothing to stop objects. Once in motion, any object will keep going until some for acts on it. A photon(s) of light will travel untill someting absorbs it or reflects it or refracts it. Tissue paper DOES absorb light, depending on the intensity of the light, it will absorb all or a fraction of it. Pretty much anything physical absorbs light, even glass, though the absorption is very small for glass. Of course this is dependent on wavelength, some wavelenths are absorbed more than others and if you go to shorter wavelengths like x-rays, they pass right through the paper. Longer wavelenths like radio waves also pass right through.
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