Why does light have a FIXED speed????

dark_star · Aug 13, 2006

Most of that just made my head hurt but I understanded some of it, apart from all the figures you guys rattled off. I am not very Knowledgeable about physics, seeing as its my 5th year at higher, but I think that the reason that light can only go at 299 792 458 m / s is that in our universe a certain set of laws are born during the birth of our universe and in diffrent universes (biverses etc or somthing), there would be diffrent laws of physics, hence diffrent speeds. I am quite probably wrong but well... But I don't understand why it is fixed, does light use up energy getting to earth from a distant star, and if so does it slow down fractionaly. I have a small question as well, does a photon have mass, if so it must create a microscopic amount of friction.

Saiph · Aug 13, 2006

why06: #1: Not sure what you mean by wave spectrums. There are all sorts of different frequencies of light (electromagnetic waves) which make up the EM spectrum. There are also different types of waves, but only light has a constant speed. Other waves are compression waves in air (sound) and in the ground (earthquakes), waves in water, etc. #2: A field is a static "thing" that exerts a force upon all objects within it. A wave is a moving disturbance in a medium. For light, the EM fields are the medium, and so light is it's own medium. A bit more specific example: Two stationary electrons are placed next to eachtoher, the forces they field form eachother are due to their fields. Now, once one accelerates (due to any force applied) the fields change in position right? This change travels/ is communicated at a finite speed, and forms a wave. Only when the wave has reached the surrounding atoms will they know that the originating electron has moved. This wave is a light wave. #4) There are gravitational, strong, and weak fields and their variations can be represented as a spectrum. A spectrum is merely a way of measuring and organizing data on a system that changes. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

toothferry · Aug 14, 2006

"really, time dilation is a consequence of the speed of light being absolute, i.e. not a relative speed like all other cases. Time dilation does not inheritly fix the speed of light at 3x10^8 m/s. " Sure, the speed of light is constant. It's absolutely infinitely fast if you can accelerate to C! Try doing that with an ultra imaginary rocket.. mark a target a lightyear away somewhere in outter space, if you had enough energy you certainly could reach that target within a years time, or even less ..according to your clock, but not those on the ground who would clock you at less than c. without c time wouldn't even exist.. it takes infinity and applies a duration to it.. measuring the speed of light is the closely thing to measuring the speed of TIME, in its lowest common denominator form.. sort of. We measure C at 300,000 KM per sec ALWAYS because of time dilation on infinity. c requires an infinite amount of energy to reach and hypothetically if you did reach it you would have an infinite amount of kinetic energy.. and you would reach your target infinitely fast. c is infinite, but the outside observer always measures the constant. c I'm saying the glass is half full, your saying the glass is half empty, but were both saying the same thing, correct??

nova_explored · Aug 14, 2006

what saiph pointed out is a very good description, using his analogy of the passing of information between two electrons. as for your fourth question: what causes fields... Charge causes fields. opposite charges of elementary particles, subatomically interacting. Proton and neutron for strong. nucleus (positive) and electron (negative) for weak force. It's all about the relationship of charge and spin ratio of the particle (known as fermions or bosons). The ratio of spin and charge in relation to mass determine the strength of a field. one question that was debated was just what you asked, do the fields have a speed? it turns out they do. Newton thought a gravitational field would be an instantneous transmission of information if part of it changed in any way. it turns out, it is finite speed at which the information gets transmitted (the change in the field). And it propagates at the speed of light. the speed of the wave function of electromagnetic energy. if the sun were suddenly to change mass by exploding it would take eight minutes, give or take, for that information to reach us and alter our relation to the sun (the time it takes the wave function of light to reach us). think about a pool of water- what constitutes the speed of a wave. it follows the same laws as electromagnetic propagation. as the wave spreads outward it looses energy, but its speed remains constant, as does every ripple in the concentric flow. the closer you are to the source, the stronger the field. but strength is the only thing that changes, not speed. i think it was saiph who earlier pointed out to the reason for the fixed speed within a field. the strong force does exhibits a different spectrum than an EM field. the fields interact, but now we get into QM and scalar fields the show how their interactions affect the system as a whole. <div class="Discussion_UserSignature"> </div>

detriech69 · Aug 16, 2006

I have a question and I'll be surprised if anyone can answer it. What powers photons internally to get them back up to maximum or unhindered velocity after passing through, let's say, water? To us humans, light speed is fantastically fast. Electricity moves as fast, em waves collectively move that fast. Even the our nervous impulses move through our bodies that fast, not accounting for losses due to mediums. But the basic motive means that keeps photons moving at THAT speed and even jumping instantaneously back to that speed after being slowed down is almost miraculous. It is true and a fact, but what makes them go. I don't mean the energy source that created them in the first place. I mean the energy that powers them ever onward through millions and billions of light years of space from a distant galaxy or quasar. I know someone will try to explain this, but I want an answer akin to what powers the magnetic field forever in a bar magnet? I believe Gravity, photons and magnetism all share a common trait. I just don't understand why or how any of them really work, just that they do. Now, I am aware of expansion theory and want no part of that. Just a new can of worms that are equally unexplainable. If you don't know about this theory, trust me, you don't want to. That will make your head hurt, too. Just explain what makes a photon keep going and going and going without any bunny references.

toothferry · Aug 16, 2006

wish I could answer all of that.. "Even the our nervous impulses move through our bodies that fast" Actually, nervous signals are chemical messengers and travel very slowly compared to light. For instance, the feeling of touch is carried by a different neuro-transmitting chemical than pain. the pain signal happens to be very slow, even compared to the feeling of touch. he's an experiment I don't advise, but could prove it. one person experiment: 1 /> Stump your toe on something. 2 /> note that you feel the impact immediately 3 /> count the number of seconds until the "pain hits" two person experiment: 1 /> have two people stump their toe at the same time. One is very short, the other is very tall 2 /> wait until the pain hits before yelling out 3 /> the taller person will feel the pain a second later because it takes longer for the chemical messenger to reach the brain. <img src="/images/icons/shocked.gif" />

Saiph · Aug 17, 2006

well, an easier experiment is to get say, ten people, in a circle and all hold hands. Have someone squeeze one persons hand, then the instant that's felt, they're supposed to squeeze the next. Once it goes around once, or twice or so, stop a timer (guess you need another person with a timer). Divide by the number of people (and by the number of cycles you did) go get the response time of a single persons nervous system. It'll be fastish (especially with practice) but nowhere near light speed. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

derekmcd · Aug 17, 2006

What powers photons internally to get them back up to maximum or unhindered velocity after passing through, let's say, water? They actually do not slow down. The wave still always propogates at C. When the lightwave hits an atom, the electron absorbs and re-emits the stored energy via another photon. The type of material the lightwave is passing through is what determines how much the electrons ****** the advancement of the wave. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

liquidspace2k · Aug 17, 2006

The Speed of the Light is connected to Time. When you are traveling really fast and shine a flashlight, the light you see is in your Time frame, and it seems to be travel at the speed of light. But if someone else was traveling slower and was watching you shine that flashlight, to them that light would be traveling at the speed of light. Not the speed of light and the difference of the two traveling speeds.

derekmcd · Aug 17, 2006

Time dilation is a consequence of relativistic speeds... I understand that completely. How does your statement correlate with my statement? <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

Saiph · Aug 17, 2006

derek: Your explaination of electrons absorbing and re-emitting light is the valid explaination in the photon model. However, the wave model is equally valid in this case, and is merely explained as the presence of charged particles alters mu and epsilon in the region. This differing value, gives a different speed. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

detriech69 · Aug 17, 2006

OK, OK. Nerve response is chemical, I understand that, but there is some electricity at work in the brain, yes?, But, no matter. My point is that our understanding of the underpinnings of the Universe is incomplete in the extreme if we can't explain these topics specifally and to everyone's understanding and satisfaction, or a consensus of majority, anyway. Whatever. Einstein was brilliant as were his forebearers, Faraday, Maxwell, etc... But the picture is like a puzzle with a majority of pieces yet to be found, let alone placed in their proper places. Knowing that certain equations explain what we have observed is fine, but doesn't necessarily explain why things are this way. I'm not content to fall back on a Creationist view, either and say God made it this way so let's just accept that and be forever in awe. I have no easy answers, either, or complicated formula, or an alternative that is any more viable than what we think we understand all ready. But is seems that there must be connections between all of the forces we perceive in this existence, hence the quest for a Unified Field Theory that includes Gravity. But, to me, any model that is close to being correct would work on all scales equally well. Light exibits wave and particle properties and we have accepted one or the other at any given time to suit the results we find. Too cluttered. Sometimes it seems like the universe is a song and the record it is recorded on is the Rulebook of Physics. But we didn't write the "book". The Universe itself wrote it, or what caused the Universe to come into existence did. Curious. I'm reminded of a saying, and I'll paraphrase, "If we ever figure out the Mystery of the Universe and believe we understand it all, the Universe will instantly transform itself into something else to keep itself mysterious."

Saiph · Aug 17, 2006

was that quote from Douglas Adams? Seems familiar. Anyway...I don't really understand the purpose of your reply, but I'll say this: Ditto. Oh, and your specific example of photon vs wave pictures of light: Both approaches are known to work in nearly all situations. However, it is usually the case that one technique is far easier than the other when it comes to describing any given situation and making predictions, thus the general perception that it's one or the other depending upon the circumstances. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

aidan13791 · Aug 18, 2006

My take on why light has a constant speed is to do with time dilation in relativity. Since time slows down as you approach the speed of light, and stops when you reach it, if one were to travel at a super luminal velocity, they would be travelling back in time. There is, however, a particle in one form of the string theory ( bosonic, i think) which can travel faster than light called the Tachyon.

derekmcd · Aug 18, 2006

The tachyon is merely in the hypothetical stage of its evolution. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

aidan13791 · Aug 18, 2006

Ok, but there is one recorded observation of the tachyon. It is somewhere on wikipedia. 'In 1973, Philip Crough and Roger Clay reported a superluminal particle apparently produced in a cosmic ray shower ' http://en.wikipedia.org/wiki/Tachyon Although, because string theory is in its early stages, there will probably be a way to get rid of the tachyon in future versions of it, because it doesnt make sense for a particle to be able to travel faster than light, as it is a fundamental constant, and is meant to be an upper limit to speed.

harmonicaman · Aug 18, 2006

I believe the real question is why does time seem to have a fixed speed. I think it's all due to our peculiar relative perspective of the universe. We live in a world stuck between the infinite advance of time and the finite and static state of matter. From the perspective of time itself, the universe is instantaneous and infinite -- time started and it will never end, but time itself views the whole universe as occurring in an instant. Matter, on the other hand, views itself as an inert singularity. It's the interaction of time on static matter which gives us the relative perspective of observing matter as possessing dimensionality. We exist in this peculiar realm caught between the static unchanging matter and the instantaneous flow of time. From our unique vantage point, we observe instantaneous time as an orderly flow and experience the singularity of matter as having dimensionality! Our existence is in a serendipitous balance caught between the "1" and the infinite. Our view of the universe is a blend of the perspectives the components of the universe have on themselves.

derekmcd · Aug 18, 2006

'In 1973, Philip Crough and Roger Clay reported a superluminal particle apparently produced in a cosmic ray shower ' That observation has neither been confirmed or reproduced. The wikipedia site isn't work for me right now, but whomever wrote it may have neglected to mention that very important step. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

aidan13791 · Aug 18, 2006

Ah, ok. As you seem well informed on the subject, if the tachyon were real, as it is travelling back in time due to the superluminal velocity, am I right in thinking that it would decay exceptionally fast as it went from the future to the past?

Why does light have a FIXED speed????

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