Is there a 'Minimum' Speed of Light?

In summary, the conversation discusses the speed of light and its relationship with energy and matter. The idea of a light minimum and stopping light is mentioned, along with the concept of matter being formed from light. The conversation also delves into the possibility of black holes being sources of both light and dark matter. The role of time in this process is also discussed.
  • #1
Wave's_Hand_Particle
134
0
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.
 
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  • #2
Not sure I understand the question, but I've read some experimients in which light has been stopped.
 
  • #4
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.
 
  • #5
russ_watters said:
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! :wink:
 
  • #6
It would depend upon the reisstance it encounters, would it not?
 
  • #7
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.
 
  • #8
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
 
  • #9
Tom McCurdy said:
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?
 
  • #10
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.
 
  • #11
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."
 
  • #12
Mk said:
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.
 
  • #13
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
 
  • #14
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))
 
  • #15
E=mc^2

lawtonfogle said:
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!
 
  • #16
Does not C depend on where the matter chaning into energy is at.
 
  • #17
lawtonfogle said:
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?
 
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  • #18
lawtonfogle said:
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.
 
  • #19
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.
 
  • #20
lawtonfogle said:
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.
 
  • #21
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.
 
  • #22
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.
 
  • #23
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.
 
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  • #24
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
 
  • #25
lawtonfogle said:
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.
sweetcaroline6 said:
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.
 
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  • #26
sweetcaroline6 said:
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.
 
  • #27
Oops, russ got their first. :rofl:
 
  • #28
I bet u people can't stop or lower the speed of light in vacuum.
 
  • #29
Wave's_Hand_Particle said:
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? :)
 
  • #30
Hemmul:
Yes it is possible in nature...
 
  • #31
you know light is just like energy, and you will never lose it, the second law of Newton...
 
  • #32
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.
 
  • #33
What about minimal acceleration? Some speculation.

The "Hubble acceleration," aH=c2/RH=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 aH=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 aH. 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.
 
  • #34
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. :smile:
 
  • #35
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.
 
<h2>1. What is the minimum speed of light?</h2><p>The minimum speed of light is the speed at which light travels in a vacuum, which is approximately 299,792,458 meters per second. This is also known as the speed of light in a vacuum, denoted by the symbol c.</p><h2>2. Why is there a minimum speed of light?</h2><p>The speed of light is a fundamental constant in the universe, and it is determined by the properties of space and time. It is the maximum speed at which any object or information can travel, and it is a fundamental limit that cannot be exceeded.</p><h2>3. Can the speed of light be increased or decreased?</h2><p>No, the speed of light is a universal constant and cannot be changed. It is the same for all observers, regardless of their relative motion or position in the universe.</p><h2>4. Is the minimum speed of light the same in all mediums?</h2><p>The speed of light is slightly slower in mediums such as air, water, or glass compared to a vacuum. This is due to the interaction of light with the particles in the medium. However, the speed of light in a vacuum remains the maximum speed at which light can travel.</p><h2>5. How was the minimum speed of light determined?</h2><p>The speed of light was first accurately measured by the Danish astronomer Ole Rømer in the 17th century using observations of the moons of Jupiter. Since then, it has been measured and confirmed through various experiments and observations, including the famous Michelson-Morley experiment and the study of electromagnetic radiation.</p>

1. What is the minimum speed of light?

The minimum speed of light is the speed at which light travels in a vacuum, which is approximately 299,792,458 meters per second. This is also known as the speed of light in a vacuum, denoted by the symbol c.

2. Why is there a minimum speed of light?

The speed of light is a fundamental constant in the universe, and it is determined by the properties of space and time. It is the maximum speed at which any object or information can travel, and it is a fundamental limit that cannot be exceeded.

3. Can the speed of light be increased or decreased?

No, the speed of light is a universal constant and cannot be changed. It is the same for all observers, regardless of their relative motion or position in the universe.

4. Is the minimum speed of light the same in all mediums?

The speed of light is slightly slower in mediums such as air, water, or glass compared to a vacuum. This is due to the interaction of light with the particles in the medium. However, the speed of light in a vacuum remains the maximum speed at which light can travel.

5. How was the minimum speed of light determined?

The speed of light was first accurately measured by the Danish astronomer Ole Rømer in the 17th century using observations of the moons of Jupiter. Since then, it has been measured and confirmed through various experiments and observations, including the famous Michelson-Morley experiment and the study of electromagnetic radiation.

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