Is there a 'Minimum' Speed of Light?

[Wave's_Hand_Particle]

And would this be a candidate for DarkMatter? or Zero Point Energy?

Tecnically if there was a Light Minimum, then this would be hard to detect, using Photons for instance.

 

[LURCH]

Not sure I understand the question, but I've read some experimients in which light has been stopped.

 

[KingNothing]

http://news.bbc.co.uk/1/hi/sci/tech/1124540.stm

 

[russ_watters]

Light travels at the speed of light. Period. And speed and energy are two completely different things: those other questions are utterly meaningless. Word salad.

 

[Wave's_Hand_Particle]

Light travels at the speed of light. Period. And speed and energy are two completely different things: those other questions are utterly meaningless. Word salad.

E-hum!

Feynman Fudge Factor?

https://www.physicsforums.com/showthread.php?t=57092

Pinch yourself and eat a little meat now and again!

 

[John King]

It would depend upon the reisstance it encounters, would it not?

 

[anti_crank]

Real photons travel at the speed of light. Period. As for virtual photons, we can't observe them by definition, so they can in principle do anything consistent with QED.

 

[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

 

[Mk]

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

Since light has no rest mass it is infinitely light, pardon the pun, meaning an infinitesimal amount of force is needed to accelerate it to the speed of light in the specified medium. Could you freeze a photon? Keep it still? Or would this interfere with the 3rd Law of Thermodynamics?

 

[sweetcaroline6]

To Russ Waters
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. 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.

 

[russ_watters]

Well, you could measure the distance from one frame and the time from another and get a number other than C, but that doesn't really fit the definition of "speed."

 

[lucien86]

Since light has no rest mass it is infinitely light, pardon the pun, meaning an infinitesimal amount of force is needed to accelerate it to the speed of light in the specified medium. Could you freeze a photon? Keep it still? Or would this interfere with the 3rd Law of Thermodynamics?

Light reaches a speed of zero all the time when it hits something.
I think you are seeing light wrongly, it is better to see it as a ripple in space time rather than as a massed object. Light is actually an oscillating electro-magnetic field - a wave, and in lots of ways it doesn't even exist. Above all though light is energy, E = m c^2 and for light everything is on the E side, this is because it is moving at the speed of light (obviously).

One aspect of this is that at the 'speed of light' you are at a point where time dilation is total : so to a photon time does not exist - it is destroyed the instant it is created.

An interesting idea is that matter may be formed in the same way, as a condensate of energy - not moving outside but moving at the speed of light inside.

 

[lawtonfogle]

If E=MC^2 and C=0 then matter could be converted into energy but the energy is not there for M*0=0 so E=0

in reverse matter could come from nothing in a place where the speed of light is zero

 

[lawtonfogle]

when a ball bounces off an object there is an amount of time where the ball has no speed

now replace the ball with light, so when light hits an object light stops for an amount of time. During that amount of time matter can be created with no energy imput

this means that matter only exist because light must bounce off of it and that light only bounces off matter that is exsiting

this forms an continuing effect that never ends and cannot have an beginnig (at leat a beginning caused by normal energy or matter (anti or not))

 

[Gamish]

E=mc^2

If E=MC^2 and C=0 then matter could be converted into energy but the energy is not there for M*0=0 so E=0

in reverse matter could come from nothing in a place where the speed of light is zero

When "E=mc^2" is used, c must be the speed of ligh in a vaccume.

Im the master at time!

 

[lawtonfogle]

Does not C depend on where the matter chaning into energy is at.

 

[Wave's_Hand_Particle]

If E=MC^2 and C=0 then matter could be converted into energy but the energy is not there for M*0=0 so E=0

in reverse matter could come from nothing in a place where the speed of light is zero

Interesting?..when Light is Parametrically Downconverted, say for instance at the Horizon of a Blackhole, then as you state, the process of Matter Creation is viable. Hawking Radiation is the invisible product of Light turning into Dark?..maybe?

 

[hypermorphism]

now replace the ball with light, so when light hits an object light stops for an amount of time. During that amount of time matter can be created with no energy imput

Photons that "hit" particles are either absorbed or ignored. They don't bounce.

 

[lawtonfogle]

Mr. Hypermorphism, you are saying there is not a point of time where light has a speed of 0. What about at the moment that the photon is absorbed or released or ignored.

 

[hypermorphism]

Mr. Hypermorphism, you are saying there is not a point of time where light has a speed of 0. What about at the moment that the photon is absorbed or released or ignored.

Before the photon is absorbed, it is moving at c. A real photon released from a particle travels at c, since it is massless. The real photon doesn't accelerate from rest like a massive particle would.

 

[lawtonfogle]

So then you are saying no.


Well on to the subject that scientist are slowing down the photons, if they stopped them would not the E=MC^2 where C=0 problem still happen.

 

[Keromane]

Slowing down photons c.q. different light speeds in different media has nothing to do with the speed of light itself. The measured speed tells something about the 'fabric' of spacetime, its density. Density differences due to mass, temperature and who knows what interesting things to be discovered. Experiments like these map our universe a bit further, give us clues.

A photon cannot be compared to a complex entity like a ball. Besides that, Newtonian physics is not valid regarding quantum mechanics. When a photon 'hits' a surface it's speed is not set to 0. As said earlier in this topic, consider light as ripples in spacetime.

 

[lawtonfogle]

So you are saying that C is a constant?

If it is we have one thing.
If it isn't we have another.

Has the E=MC^2 ever been proven, or has it not yet been disproven.

 

[sweetcaroline6]

surely when light hits an object it's energy is absorbed into that object and if light returns in kind it is new light manufactured by the object using the energy of the light that it has just absorbed. so light's speed is never zero.
also (and this is to russ re my last question) how, in the scenario of the black hole described am i measuring time and speed from different frames?
many thanks

 

[russ_watters]

So you are saying that C is a constant?

If it is we have one thing.
If it isn't we have another.

Has the E=MC^2 ever been proven, or has it not yet been disproven.

C is a constant. That was first proven by the Michelson Morley experiment in the late 1800s and there were indications of it (from Maxwell's equations) before it was proven. It was just assumed to be a flaw in Maxwell's equations, but it turned out they were right.

Mass/energy equivalency has also been thoroughly proven: its the basis for, among other things, nuclear power. It's also tested every time a particle accelerator is operated.

surely when light hits an object it's energy is absorbed into that object and if light returns in kind it is new light manufactured by the object using the energy of the light that it has just absorbed. so light's speed is never zero.

All correct.

also (and this is to russ re my last question) how, in the scenario of the black hole described am i measuring time and speed from different frames?
many thanks

Black holes (and all other objects with mass) do indeed sap energy from light traveling away from them. That is manifested by a red-shift in the light: the energy of the light is reduced, while the speed stays the same. One of the ways of detecting the black holes is by observing the red-shift of light emitted by matter orbiting or falling into an unseen object.

Also, with time dilation being frame dependant, its important not to mix frames when calculating speed: if you consider the time dilation of a frame near a black hole and distance as measured from earth, you may calculate the wrong speed of light.

 

[DB]

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. 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.

Light is not slowed, it is redshifted. When light enters gravitational fields, it uses up energy to continue traveling at c. When it loses energy its wavelenght is increased and is therefore "more red". Light can be refracted, absorbed, emited etc. but all at c.

 

[DB]

Oops, russ got their first.

 

[ElectroPhysics]

I bet u people can't stop or lower the speed of light in vacuum.

 

[hemmul]

And would this be a candidate for DarkMatter? or Zero Point Energy?

Tecnically if there was a Light Minimum, then this would be hard to detect, using Photons for instance.

he-he a slightly different question born after a severe hangover:
if there is a maximal speed of information transfer (speed of light) is there a corresponding minimal speed? :)

 

[ElectroPhysics]

Hemmul:
Yes it is possible in nature...

 

[joery]

you know light is just like energy, and you will never lose it, the second law of Newton...

 

[lawtonfogle]

I was taught that the law says energy is never lost in a chemical reaction. Please tell me if this is another law that I have mixed up.

 

[Loren Booda]

What about minimal acceleration? Some speculation.

The "Hubble acceleration," a_H=c²/R_H=cH₀=6 x 10^-8 cm/s², demarcates a critical radial acceleration for galaxies and larger bodies where the influence of so-called dark matter begins. Following the rotation curve for a given galaxy, one notices the departure from conventional luminous matter dynamics at approximately the rotational velocity v with radius r so that a_H=v²/r. This asserts that the radial universal expansion parameters, i. e., the Hubble acceleration, also affect rotational dynamics.

The concept of "dark matter" may arise in large part to a quantizing of a_H. If so, this would indicate a characteristic of baryonic matter's inertia to overcome an "ultraviolet catastrophe" (similar to the blackbody's). Consequently, it tends to maintain the acceleration, and likewise the velocity, of galaxies' outlying halos. The effects of "dark matter" on large-scale structures are predominantly due to compliance with discretized minimal acceleration, given by the ratio between speed of light squared and the cosmological horizon radius. The behavior of quantized acceleration might be measured in an atom trap.

From "Matters of Gravity" on my website, below.

 

[Chaos' lil bro Order]

Light's Velocity varies depending on the medium it is in.

To say light's velocity is constant is silly. The Index of Refraction of various mediums (eg. crown glass, air, water, diamonds, etc.) was created to show that light does in fact move slower in these mediums than it does in a perfect vacuum speed of about C = 300,000 km/s.

For example, water's Index of Refraction value is n=1.33, this means that when light enters water its speed becomes C / 1.33 which equals 225,000 km/s.

As a point of interest, it is possible for light to exceed the 'speed limit' of a medium that it is in and when it does the result is a bluish glow called 'Cheryenkov Radiation'. Of course this does not apply to the medium of a perfect vacuum where light's velocity is fundamentally limited to 300,000 km/s.

Remember, light,or more appropriately, photons, come from atoms who have an excited electron in their outer orbitals, and when the excited electron falls back down to a ground state orbital (called 'deexcitation') a photon is released. The energy of this photon is precisely the amount of energy lost by the electron as it went from excited to deexcited orbitals. This amount of energy corresponds to the wavelength of light the emitted photon will have via two simple equations: E = hf and Wavelength = C / f

So when you look at your computer screen and see a blue 'Windows XP' scrollbar, the pixels that are emitting those blue photons contain many many atoms that are constantly having their electrons excited by an electrical current (energy input) and then when the electrons deexcite, poof, a photon of blue color is emitted whereupon it enters your eye.

As a side note, the greater the 'energy input' you put into exciting an electron above its ground state, the greater the 'energy output' you will get when the electron deexcites and outputs a photon. For this reason, extremely energetic light (or, more correctly thought of as 'Electromagnetic Radiation') like gamma-rays can only be created by extremely energetic sources like neutron stars and black holes. Radio waves are the lowest energy EM emitters, unless you want to include the famed gravitational waves which are still in the realm of theory.


P.S. I have an idea that I need shot down by more knowledgeable minds than mine, here it goes. If you could build a pole that was ten light years long, extremely thin, and extremely durable and strong, would it be possible to send communications faster than the speed of light if the sender tapped one end of the string in morse code and the receiver recorded the morse code? Besides the obvious feasibility issues of creating this pole, what physical laws would prevent this communication method? Even if the pole weighed a trillion trillion trillion ...etc. kilograms, you would only need to accelerate it to say 1 km / hour every time you tapped its end, so in essence Relativity is not violated from an energy nor from a exceeding C's velocity standpoint. However, I am aware that the atoms comprising the pole would have to mediate the force of the tapping and that this is likely the limiting factor that makes my idea nullified. If anyone knows how to scientifically explain this limiting factor please reply. I'm very curious to know.

Thank you.

 

[anti_crank]

Wow, could this be one of those TD threads where people actually learn something instead of having knowledge and crackpottery collide into painkillers? The problem with the idea is that rigid bodies that retain their shape when one exerts a force on one end do not exist in SR; in fact their existence would contradict SR as you have discovered for yourself. It turns out that the speed of longitudinal waves, or sound/impulses propagating through the metal, is limited by the speed of light.

 

[timeformation]

ok ok, hold up a second...

"light" which in itself is interesting by wording because it is infact light ( not heavy)
continued... When "photons" are absorbed, there is a delay, before light is given off from the particle which absorbed it. If photons do not bounce off, then explain how a charged particle does not accept incoming photons? test, take a laser, shoot it at a particle, particle = charged, then what happens to the other light coming at the particle? there is a delay between conduction band fall to valence band, and there are cases of other orbits achieveable by electrons, so that they can accept more energy than usual, however...

ok ok... so can photons bounce off, wonders...
now then... what process can take some light, then convert it to a form which "matter" feeds from.. yes it feeds, caue why is the light absorbed in the first place.. but enough of that... there will be no recoil action of an electron if it gives off light, since light is "light", so no momentum echange force to be balanced.

ever think that maybe, the lgiht 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) Forces are distuebances in the light medium, and why we do not see light giviong a recoil action when it is emitted is because, in fact it is just our matter moving, but since matter is our frame of reference we detect no movement, only light moving away at its light speed.

Does temperature of particle, affect the wave of light being emiited, either longitudianlly or transverse, ( sorry bout spelling) because if it does change with temperature, then it will definitely show how the oscillations of matter caused by temperature occur so rapidly, that it explains why there is an osscilation of light, and not just a staright line, as would be logical.
OSCILLATIONS ARE CAUSED BY MOVING POINT SOURCES.
which we all know is true.

more on this later...

 

[Chaos' lil bro Order]

Light cycles due to the spin of electrons

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]

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]

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]

"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 theory 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]

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]

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]

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]

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]

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 don't know the details). when the scientist reviewed their findings they saw that the one that was flying arround was off by a few nanosecs (please 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]

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]

I have a poor high school graduate,pathetic logic view about the speed of light..It is as poor as my grammar and vocabolary :shy:


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 definately 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 traveling 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]

Nothing in the universe is constant, not even light.

 

[TheUnknown]

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 want to 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]

Here's a link that may be of interest.

http=www.earthtech.org/publications/Mitre%20Conference.pdf