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Is there a 'Minimum' Speed of Light?

by Wave's_Hand_Particle
Tags: light, minimum, speed
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Chaos' lil bro Order
#37
Feb8-05, 11:06 PM
P: 683
Interesting conversation so far, thanks for the comments.

1) When a photon is emitted from and electron due to deexcitation, the photon spirals outwards in a shape similar to a stretched out toy 'slinky'. The photon takes this shape because its parent electron spinning around an atom at the time the photon is emitted. Therefore, the photon is accelerated outwards in a spiral like pattern of radiation. The wavelength of the emitted photon of radiation is dependent on the input of energy into the initial electron excitation.



2) There is also the photoelectric effect where an incident photon will eject electrons from a metal plate and in turn this creates an electric current. Of course, there are limitations to this effect, for instance it is frequency dependent, not amplitude dependent.

Meaning, a metal like gold for example, will have a critical threshold whereupon if you send a photon of a given frequency incident on the metal plate no electrons will get ejected. Even if you increase the amplitude of the incident photon beam on the gold plate, no electrons will get ejected. However, if you raise the frequency of even 1 photon above the critical threshold of the gold plate and send it incident, an electron will get ejected from the gold plate.

Also, metals have a 'work function' which is given in units of eV (electron volts) and is equal to the amount of energy lost when the photon is converted into electricity (from heat i'm guessing, but i'm not sure exactly why there is a loss).



3) Question. What is this lag you speak of, 'When "photons" are absorbed, there is a delay, before light is given off from the particle which absorbed it.' Please explain this to me, I would like to know about it and who it works. Thanks.



4) Also you said, 'ever think that maybe, the light is stationary, the particles are all moving frames of references, since they have temperature, and the momentum we perceive is just, the distortion of that motionless medium. ( well not motionless, but keep things simple for now)'

This idea sounds interesting, can you expand on it with more examples and clearer writing so I can understand it, thanks.


Chaos' lil bro Order
#38
Feb8-05, 11:19 PM
P: 683
1) 'Wow, could this be one of those TD threads where people actually learn something instead of having knowledge and crackpottery collide'

Yes I agree with your comment, there is so much garbage to filter through on these message boards. If we all write concisely we can learn more in a shorter time.



2)'It turns out that the speed of longitudinal waves, or sound/impulses propagating through the metal, is limited by the speed of light.'

Ok, I see your point, my idea does not circumvent light speed in any respect. Question. What is the force involved here? Use a steel pole for example, is the limiting speed due to iron atoms being sequentially pushed sideways into other iron atoms, and the ensuing Coulomb repulsion domino effect carries the signal to the receiving end? If so, I can see how this must be slower than light speed considering the mediating particle of the Weak (Coulomb) force are bosons, which certainly are bound by light speed as particle acceleration tests can evidence.
If you can elaborate on this and help me understand it more, i'd appreciate it.

Thanks.



P.S. What is 'TD'? I hate acronyms I don't know :)
elas
#39
Mar10-05, 12:46 AM
P: n/a
Light travels at the speed of light. Period. And speed and energy are two completely different things:

So that's why E=M(cc)

Mass/energy equivalency has also been thoroughly proven

Perhaps Mass/energy/speed relationship is also thoroughly proven?

That was first proven by the Michelson Morley experiment in the late 1800s

This experiment could also be interpreted as showing that light travels faster than anything we can measure, therefore it is always recorded at the fastest speed we can measure (hence the c squared constant?). A similar error was made in reading ozone levels, but in that instant it was possible to build a new measuring device.
cincirob
#40
Mar10-05, 07:58 PM
P: 24
"If light travels a certain distance in space in a given time, is it possible that if space were contracted, light would travel over this "shortened" distance over the same time. i.e. to an outside observer it would appear to slow down."

According to relativity thoery every observer will measure light at the same speed, c. This would be true for an observer watching a contracted frame. It might seem to him/her that the observer in that frame should measure v>c. But this doesn't happen because time for the observer in motion is dilated (slowed down) at just the right rate to result in a measurement of c for him/her also.

"As gravity changes space, as one approaches a black hole, light would be slowed, but never stopped. Maybe that's why black holes are black, not because light can't escape but rather that light slows down on the way in and speeds up on the way out. We just haven't yet seen the light that is slowly coming out? So maybe there are black holes that are bright also; ones that the light has escaped."

Again, light travels at c in this case also. Light trying to "climb" out of the gravity of a black hole loses energy, not speed. Since Planck tells us that E=hv, where E=energy, h is Planck's constant, and v =s the frequency of light, loss of energy means lower frequency or redshift.

This all goes back to Maxwell whose equations of electromagnetism show that light speed is governed only by the permeability and permitivity of the meduim through which it travels.
Nacho
#41
Mar10-05, 09:49 PM
P: 170
Not trying to hijack this thread .. but this one has me puzzled about the invariance of the speed of light.

I don't see how it can hold true in an expanding Universe, expecially one with accelerating expansion. Take an extreme case:

You're observing an object at the very limit of the observable horizon, one that will wink-out shortly. Wouldn't you measure the speed of that light progressively approaching zero?

I guess maybe the answer might be, that what you really observe, is the wavelength progressively being redshifted and the SOL always the same, and at the point of wink-out you would observe a close-to-infinite redshift, but always the SOL the same?
Beyond-Numbers
#42
Mar10-05, 11:40 PM
P: 8
Nacho: In short, I think the answer is NO. You would simply be observing the edge of the OBSERVABLE universe. And since you state (hypothetically) it will "wink out soon", this object must be on a course away from you so it will be disgustingly red-shifted. You answered your own question and I back it up.
However, if the universe is infinite then it cannot expand. You can't really get more from the most can you? You have to either assume the universe is infinite and moves like deep ocean currents or it IS bound and expanding. Both theories support red-shift, stellar drift and the like, by the way.
Chronos
#43
Mar11-05, 01:46 AM
Sci Advisor
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P: 9,366
Quote Quote by Chaos' lil bro Order
1) 'Wow, could this be one of those TD threads where people actually learn something instead of having knowledge and crackpottery collide'

Yes I agree with your comment, there is so much garbage to filter through on these message boards. If we all write concisely we can learn more in a shorter time.



2)'It turns out that the speed of longitudinal waves, or sound/impulses propagating through the metal, is limited by the speed of light.'

Ok, I see your point, my idea does not circumvent light speed in any respect. Question. What is the force involved here? Use a steel pole for example, is the limiting speed due to iron atoms being sequentially pushed sideways into other iron atoms, and the ensuing Coulomb repulsion domino effect carries the signal to the receiving end? If so, I can see how this must be slower than light speed considering the mediating particle of the Weak (Coulomb) force are bosons, which certainly are bound by light speed as particle acceleration tests can evidence.
If you can elaborate on this and help me understand it more, i'd appreciate it.

Thanks.



P.S. What is 'TD'? I hate acronyms I don't know :)
Compressibility is very easy to demonstrate. A high speed video of a golf club impacting a golf ball clearly shows a time delay before the side of the golf ball opposite the impact side moves. Relativity explains why there is no such thing as a totally rigid [i.e., inelastic] object. Pushing a steel rod is merely a slower version of striking it with a golf club. BTW, TD is Theory Development - this thread. Having your thread moved here means it is deemed scientifically unsupported by the moderators.
Antiphon
#44
Mar18-05, 01:27 PM
P: 1,781
Wow. Here goes.

Even in vacuum, there is a line of thinking which allows a photon to travel faster
and slower than the speed of light somewhat like a quantum tunneling effect.
In this line of thinking, c is only the *macroscopically* observed speed of light.
skeletonic
#45
Mar27-05, 04:02 PM
P: 7
Quote Quote by Tom McCurdy
Lights speed is constant... it does vary in mediums though... our physics teacher talked about where he was able to run past light when he was on the outside of an experiment and light was slowed to just a few m/s
scientists took two extremely acurate atomic clocks, one stayed on the ground while the other was in a plane flying arround (i dont know the details). when the scientist reviewed their findings they saw that the one that was flying arround was off by a few nanosecs (plz excuse my crudenes). from what the rest of the article said, that proved that the speed of light was actually slower than what it used to be.
personaly i cuold never understand that mumbojumbo about whiping arund the sun to travel back in time, but maby it is not so ubsured. although i believe that time only exists in our minds, the fact that the one clock slowed down raises some unusual points to ponder.
Loren Booda
#46
Mar27-05, 10:39 PM
Loren Booda's Avatar
P: 3,408
skeletonic,

I think in that classic verification of general relativity the speed of light remained constant for each observer reference frame; it was the spacetime paths the airplanes circuited which varied.
ExecNight
#47
Apr4-05, 05:17 AM
P: n/a
I have a poor high school graduate,pathetic logic view about the speed of light..It is as poor as my grammar and vocabolary


When someone says the speed of light is constant, then of course i think "no way should change according to my velocity"

Though the explanation probably lies within the words that are used..The first question should be is speed of light a velocity?

Therefore my logical conclusion is that it shouldn't be..But well,what else can you tell 300.000 km/s? that is definetly a velocity..

But i prefer thinking speed of light reacting according to my velocity by its frequency..Ok it is formed by photons but it is also very well known that it has wave characteristics therefore i think light should have a frequency.


As you can imagine, if i would reach the speed of light with my flying elevator, i would see the universe like a picture as the frequency reaches 0..Think about it like this, you are in a standstill position and can view a virtual world by turning around using your mouse..If the frame rate is 0, then as you turn all the image will become nonsense, as it doesn't update..That is of course when it is 2 dimensional..

Unlike that while we exist within 3-D then, i would see the universe as it is..A picture, which is absolutely in a stand still..Not even an electron moving..

On the other hand if frequency changes according to my vectoral movement, then there is another consequence..The light coming towards me, and i am travelling forward becomes updating much more faster, while the light i am running away becomes updating much more slower or at a stand still situation..

Therefore from my flying elevators window i would see a weird universe.Where there is a stand still universe behind my vectoral movement..Slow motion as the angle becomes less than 180degrees from both sides..Same movement rate at 90 degrees and faster movement rate where the angle is less than 90 degrees..

Well, as i said my stupid logic...
TheUnknown
#48
Apr4-05, 10:55 AM
P: 85
Nothing in the universe is constant, not even light.
TheUnknown
#49
Apr4-05, 11:04 AM
P: 85
also, i saw on some other site, the question "will traveling faster than light open up time travel?"... my view. traveling faster than light is simply that... traveling faster than light. Example. The Sun and I start at point A, we are racing towards Earth, point B. 1...2...3.. GO, the Sun shines it's light, but i can travel faster, i can reach Earth.. let's say roughly 3 and a half minutes before the light from the sun can... reaching point B before light can does not make me a time traveler... many people are stuck on this idea that if we can travel faster than light then we can distort time in some way, can someone explain to me why this is? i am studying phylosophy and physics, i just wanna hear some real genuine answers if you could help... thanks all! :) i am new here, and it has given me a great deal of information, i love this stuff.
AWolf
#50
Apr4-05, 12:03 PM
P: 178
Here's a link that may be of interest.

http://http=www.earthtech.org/public...Conference.pdf


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