Speed C is Dependant Upon Source?

[omin]

1. The speed of light is constant.

2. Light may reflect off objects.

3. The speed of light is not determined by it's source.

If the speed of light is constant and this speed is unaffected by it's source, then the expression, the shape light is, is it's natural shape and it's speed simultaneously. Light's inertia is it's shape, it's physical expression and vice versa. Light speeds itself, objects don't speed the light.

But, light can be reflected. For something to change directions, acceleration must occur. For acceleration to occur, a change in velocity must occur. For velocity to occur, a change of speed and/or direction must occur. Can it be proven that only direction occurs when light is reflected? What rules out a change of speed assuredly during reflection? Is a mirror that reflects light a new source compared to the source where light last emerged?

If the source does not determine the speed of light, then why does the speed of light always acclerate away from a source at the speed of light consistently? How does the light know that the source is there to speed away from at the constant speed?

If two mirrors are traveling at different speeds compared to each other and light is reflected from one to another, shouldn't now light change speed dependent upon source or what happens?

Since light is constant, it must have an exact quantity between the mirrors at any given state, and this quantity of light definitely changes with the distance the mirrors are from each other. When the mirror's distance is compressed, where does this extra light go? Does it begin to reflect faster?

-Still trying to understand relativity.

 

[quantumdude]

1. The speed of light is constant.

2. Light may reflect off objects.

3. The speed of light is not determined by it's source.

So far, so good.

If the speed of light is constant and this speed is unaffected by it's source, then the expression, the shape light is, is it's natural shape and it's speed simultaneously. Light's inertia is it's shape, it's physical expression and vice versa. Light speeds itself, objects don't speed the light.

To be blunt, this makes no sense. What is the shape of light, and why do you think that this shape is identical to the inertia of light?

But, light can be reflected. For something to change directions, acceleration must occur. For acceleration to occur, a change in velocity must occur. For velocity to occur, a change of speed and/or direction must occur. Can it be proven that only direction occurs when light is reflected? What rules out a change of speed assuredly during reflection?

All you have to do is measure the speed of the incident beam and of the reflected beam. In every case, you'll find that they are the same. Actually, this has nothing whatsoever to do with relativity. If you bounce a tennis ball off a rigid wall, and the collision is elastic, then the speed of the tennis ball will be the same before and after the collision.

Is a mirror that reflects light a new source compared to the source where light last emerged?

Yes it is, because the photons are absorbed and re-emitted by the mirror.

If the source does not determine the speed of light, then why does the speed of light always acclerate away from a source at the speed of light consistently?

You've just answered your own question: The very fact that the light always moves (not accelerates) away from the source at the speed of light consistently is precisely why we say that the source does not determine the speed of light. That's what it means for the speed of light to be independent of the speed of the source.

How does the light know that the source is there to speed away from at the constant speed?

It doesn't know anything.

If two mirrors are traveling at different speeds compared to each other and light is reflected from one to another, shouldn't now light change speed dependent upon source or what happens?

No, it shouldn't. You said it yourself, the speed of light is independent of the speed of the source.

Since light is constant, it must have an exact quantity between the mirrors at any given state, and this quantity of light definitely changes with the distance the mirrors are from each other. When the mirror's distance is compressed, where does this extra light go? Does it begin to reflect faster?

What "exact quantity" are you talking about?

 

[chroot]

When a photon is reflected from a surface, it is not actually stopped and turned around. Instead, it is absorbed, and a new photon is emitted in the opposite direction.

- Warren

 

[Alkatran]

When a photon is reflected from a surface, it is not actually stopped and turned around. Instead, it is absorbed, and a new photon is emitted in the opposite direction.

- Warren

Ah, you beat me to it.

Sounds like someone needs to brush up on their relativity.

 

[russ_watters]

To put a finer point on what warren said:

For something to change directions, acceleration must occur. For acceleration to occur, a change in velocity must occur.

Light doesn't accelerate in the way you think it does. It doesn't change speed. It doesn't slow down to a stop, then reverse its course. It is absorbed and re-emitted, and never travels at any speed other than C.

 

[Chronos]

No acceleration. Photon's are forbidden to travel at any speed other than c.

 

[pmb_phy]

No acceleration. Photon's are forbidden to travel at any speed other than c.

Note: A photon can accelerate in a gravitational field.

Pete

 

[urtalkinstupid]

Note: A photon can accelerate in a gravitational field.

Note: That is why light changes frequency. Doppler affect.

 

[Integral]

Note: A photon can accelerate in a gravitational field.

Pete

The direction light is traveling can and will change in a gravitational field, thus an acceleration, but the magnitude of the velocity will remain a constant c.

 

[rayjohn01]

light momentum

Perhaps someone can answer this related question. In the original 'train with mirror' relativity demonstration the traveller supposes his light to travel perpendicular to the train whilst the observer sees it travel a triangular path,from which the time relations are derived.
The hidden assumtion is that the DIRECTION of light has changed with the source ( not it's speed).
There then arises a question -- if light is absorbed by a mirror and then re-emitted it is assumed that it's momentum did not change ( hence the angle of reflection and reception are equal )
But in the above scenario the momentum did change -- so the question is does a moving mirror have equal angles or not ?

 

[grounded]

Yes it is, because the photons are absorbed and re-emitted by the mirror.

When a photon is reflected from a surface, it is not actually stopped and turned around. Instead, it is absorbed, and a new photon is emitted in the opposite direction.

- Warren

Ah, you beat me to it.

Sounds like someone needs to brush up on their relativity.

Is the above true?

When light strikes a mirror, almost all of it is reflected, a small amount is absorbed but it would only heat the mirror and not emit photons.

the energy of the oscillating electrons does not go back to the light. The energy instead goes toward increasing the motion of the atoms, which causes the material to heat up.
Microsoft® Encarta® Reference Library 2002. © 1993-2001 Microsoft Corporation. All rights reserved.

 

[urtalkinstupid]

What does your quote have to do with the reflection of light on mirrors? All your quote is doing is taking chroot's explanation a little further by saying a very small amount is not reemitted and heats up the mirror.

chroot, how exactly is a photon absorbed and a new photon emitted in the opposite direction?

 

[Hurkyl]

When light strikes a mirror, almost all of it is reflected, a small amount is absorbed but it would only heat the mirror and not emit photons.

That's not entirely accurate; all of it gets absorbed, and then almost all the energy is reemitted.

You have to be careful to distinguish between the macroscopic and microscopic terms.

 

[quantumdude]

Perhaps someone can answer this related question. In the original 'train with mirror' relativity demonstration the traveller supposes his light to travel perpendicular to the train whilst the observer sees it travel a triangular path,from which the time relations are derived.
The hidden assumtion is that the DIRECTION of light has changed with the source ( not it's speed).
There then arises a question -- if light is absorbed by a mirror and then re-emitted it is assumed that it's momentum did not change ( hence the angle of reflection and reception are equal )
But in the above scenario the momentum did change --

Right, some momentum is imparted to the mirror itself.

so the question is does a moving mirror have equal angles or not ?

Yes, the angles are equal.

 

[Entropy]

how exactly is a photon absorbed and a new photon emitted in the opposite direction?

When the photon is absorbed it exerts a force equivalent to all of it's energy. Then according to Newtons laws for every action (force on the mirror) there is an equal and opposite reaction, this being the emission of another photon in the opposite direction. Then when the mirror uses its own momentum to create a new photon in the opposite direction. I don't want to confuse the mircoscopic with the macroscopic but this is the same principle that causes a ball will bounce off a wall instead of just stopping once it hits the wall.

 

[urtalkinstupid]

So, photons are created by momentum? How is that possible?

 

[Entropy]

So, photons are created by momentum? How is that possible?

Well not exactly. You see since it absorbed the first photon it needs to exert an equal and opposite force back on to the photon. But since the photon is no longer there (it was absorbed) it simply emits a photon in the opposite direction. But photons do have momentum if that's what you mean.

 

[urtalkinstupid]

No, what I meant is what you previously said.

Then when the mirror uses its own momentum to create a new photon in the opposite direction.

How is a photon created in that process? If the photon is not created, where does it come from?

 

[beatrix kiddo]

stupid makes a good point. u say that the photon gets totally absorbed then a new photon is made from the mirror? that doesn't make sense... or are u saying that the mirror absorbs the photon then emits it?

 

[beatrix kiddo]

and if the mirror absorbs the photon and emits it then doesn't that mean the photon had to be slowed down, then accelerated in the opposite direction?

 

[quantumdude]

stupid makes a good point. u say that the photon gets totally absorbed then a new photon is made from the mirror? that doesn't make sense... or are u saying that the mirror absorbs the photon then emits it?

It makes plenty of sense. It's quantum mechanics at work (have you not taken chemistry?). A photon is incident on an atom. The atom absorbs the photon (IOW, the photon is destroyed) and an atomic electron is promoted to a higher energy level. The resulting state is unstable, and it quickly decays. In the decay, a new photon of the same wavelength is created and emitted.

 

[Alkatran]

stupid makes a good point. u say that the photon gets totally absorbed then a new photon is made from the mirror? that doesn't make sense... or are u saying that the mirror absorbs the photon then emits it?

and if the mirror absorbs the photon and emits it then doesn't that mean the photon had to be slowed down, then accelerated in the opposite direction?

E=mc^2

You can turn matter into energy and vice versa, so you can change a photon into momentum and momentum into a photon.

 

[urtalkinstupid]

Thank you for explaining, Tom. I thought matter or energy could not be created nor destroyed? Yes, I have taken chemistry. I owned at chemistry! I'm taking Chemistry II AP this coming school year. So the excitation of an electron causes decay. What kind of decay is this called? When an electron goes into decay it produces photons? Is that the only product of this decay?

 

[Alkatran]

Thank you for explaining, Tom. I thought matter or energy could not be created nor destroyed? Yes, I have taken chemistry. I owned at chemistry! I'm taking Chemistry II AP this coming school year. So the excitation of an electron causes decay. What kind of decay is this called? When an electron goes into decay it produces photons? Is that the only product of this decay?

The photon isn't destroyed, it's absorbed.

 

[urtalkinstupid]

Well, Tom told me it was destroyed. Wouldn't the conversion from momentum to energy or mass involve something other than E=mc^2? Like maybe E=pc, since light is theorized to have no rest mass? Or would you just use the whole total energy equation if you were to convert a photon to mass?

 

[beatrix kiddo]

tom, yes i have taken chemistry (i posted that in the thread u so graciously ended) and I've know how a photon is produced, but thanks for the reiteration. for the mirror to make a whole new photon, that means the other photon was destroyed and that doesn't make sense because everyone knows that energy cannot be created or destroyed. but u, mr. mattson said that the photon gets destroyed. and entropy says that the mirror creates a new photon, which also doesn't make sense. quote me if u must, but the description u're giving for this process contradicts what einstein said..

 

[Alkatran]

tom, yes i have taken chemistry (i posted that in the thread u so graciously ended) and I've know how a photon is produced, but thanks for the reiteration. for the mirror to make a whole new photon, that means the other photon was destroyed and that doesn't make sense because everyone knows that energy cannot be created or destroyed. but u, mr. mattson said that the photon gets destroyed. and entropy says that the mirror creates a new photon, which also doesn't make sense. quote me if u must, but the description u're giving for this process contradicts what einstein said..

ABOSRBED, not destroyed. You know that's what he meant.
and EMITTED, not created. Same Reason.

 

[beatrix kiddo]

how am i supposed to know what someone meant, alkatran? u told me that when we discussed that equation. mattson said destroyed and entropy said created. there's a difference...

 

[Alkatran]

how am i supposed to know what someone meant, alkatran? u told me that when we discussed that equation. mattson said destroyed and entropy said created. there's a difference...

"Creating" a photon might as well be the same as "emitting" one, except that emitting better represents what is actually happening. Now, if he said "a photon is confused by the mirror" we would have a similar situation to the disregards of PEDMAS in said equation.

 

[urtalkinstupid]

Where does this newly emitted photon come from, if it travels in the opposite direction of the absorbed photon?

 

[Alkatran]

Where does this newly emitted photon come from, if it travels in the opposite direction of the absorbed photon?

It doesn't necessarily travel in any direction. When you shine a light on a wall the photons get absorbed then emitted any which way (which is why the whole room lights up).

And you were already told it comes from the energy given to (whatever the incident photon hit).

 

[beatrix kiddo]

no, alkatran. creating isn't the same as emitting! according to tom, the mirror absorbs the photon and then that energy is given back off in the form of another photon. there is conservation, not creation. to create the photon, the mirror would have to create the energy itself, and it doesn't. it just gives it back off.

 

[Alkatran]

no, alkatran. creating isn't the same as emitting! according to tom, the mirror absorbs the photon and then that energy is given back off in the form of another photon. there is conservation, not creation. to create the photon, the mirror would have to create the energy itself, and it doesn't. it just gives it back off.

You just keep on twisting those words, alright?

My point was that you're arguing your point based on an obvious mis-wording.

 

[beatrix kiddo]

what words am i twisting, tran? u're the one who told me that we can all look at creation and emission as the same thing. i was arguing u on that, not tom's mis-wording...

 

[Alkatran]

what words am i twisting, tran? u're the one who told me that we can all look at creation and emission as the same thing. i was arguing u on that, not tom's mis-wording...

I said they could be seen as the same thing. But fine, you know what? Just to end this argument: I was wrong. There, now get on with the main topic.

 

[Chronos]

Hopeless. Quantum transactions are not the same as logical operators.

 

[stewarta]

the guy said that the photon was absorbed... he also said the it was destroyed in the absorbtion... he said that this exites the electrons, causing one to raise to a higher field, thus becoming unstable, and emmiting a new photon...

what a buch of confusing nonsense... if the speed of light cannot be changed, then tell me what is happening in a prism.

the speed of light CAN be changed as long as it is returned to it's original speed. the photon passes through the glass, hits the silver backing and is stopped. the ENERGY not the PHOTON is absorbed. the energy is then emmited back to the photon and it travels back through the glass at speed c...

there is no need to nuke this... no need to over explain. occhams razor will stand strong

 

[quantumdude]

Kiddies,

When a photon is absorbed, it is destroyed. It ceases to exist. It is no more. It is an ex-photon.

Conversely, when a photon is emitted, it is created at the moment of emission.

Thank you for explaining, Tom. I thought matter or energy could not be created nor destroyed?

All the energy is accounted for at all times. An unperturbed atom has energy E₁ at time t₁. A photon of energy E_γ comes in and promotes an atomic electron to a higher energy state
E₂. Conservation of energy demands that E₂=E₁+E_γ.

Yes, I have taken chemistry. I owned at chemistry! I'm taking Chemistry II AP this coming school year.

OK, so check out the solar system model of an atom. It's a very crude approximation, but it will at least give some mental image of the promotion and de-excitation of an atomic electron (it goes from a lower orbit to a higher one, and back again).

So the excitation of an electron causes decay. What kind of decay is this called? When an electron goes into decay it produces photons? Is that the only product of this decay?

It is an electromagnetic transition of the atom. By the way, it is the atom that decays, not the electron. Electrons are stable. And yes, the photon is the only new particle that is created.

 

[Entropy]

I'm taking Chemistry II AP this coming school year.

I hope its not as hard as AP Chem II at my school! I didn't take it, but my friends (they use to like chem) who did told me it made their lives a living hell. They had complete labs with full lab write ups due every other day. Not that its a hard subject, I think its just the teacher.

 

[urtalkinstupid]

Haha, that Chem II AP at your school sounds like the BIO II AP I just took this year. Full labs with a write up on each one. Only grades were labs and tests. Haha, average of class was like 60 or 70, but I managed to keep an A. Chem II AP at our school is supposed to be hard as *%(#.

Tom:
Anyways, How does the new photon know exactly which direction to go in order to reflect the image? Does it take the vector of the destroyed photon and reverse it? I know about electrons and them absorbing energy. I was simply saying what you were saying. So, I'm assuming it is just photon and energy that is created. Are you also saying that anything that is completely absorbed, all of its energy is destroyed? Essentially the photon isn't destroyed, just it's energy is passed on. I don't know.

 

[beatrix kiddo]

tom, it hurts my feelings when u call me kiddie... atleast make it kiddo..

u really shouldn't use words like created or destroyed, though, because it gives a false representation of what is occurring on the mirror. a photon is energy release. since no energy gets created or destroyed, then, technically, the photon really isn't destroyed either. absorption and emission cannot be viewed as destruction and creation.
entropy, chem II ap at our school is pretty hard. the teacher is nice and all, but she gives really hard tests, and labs, etc. (i am taking it next yr... but this is what I've heard from her former students)

 

[russ_watters]

Anyways, How does the new photon know exactly which direction to go in order to reflect the image?

A photon doesn't "know" anything. Conservation of momentum dictates in which direction the atom will emit the photon.

So, I'm assuming it is just photon and energy that is created. Are you also saying that anything that is completely absorbed, all of its energy is destroyed? Essentially the photon isn't destroyed, just it's energy is passed on. I don't know.

The photon is destroyed when it is absorbed, but the energy doesn't vanish, its incorporated into the atom that absorbed it. It manifests itself by the electron jumping to a higher energy level.

 

[quantumdude]

Anyways, How does the new photon know exactly which direction to go in order to reflect the image?

Ignoring the creation and destruction of photons for a minute, and just focusing on the photon states before and after the reflection, there is a total momentum and total energy in each state. In other words, this annihilation and creation of photons has to take place under the same constraints as a collision. The conservation of momentum in the direction parallel to the mirror imposes one constraint, and conservation of energy imposes another (the photon energy is unchanged in the reflection). That means that the momentum of the photon normal to the mirror can only be equal and opposite to the original normal component.

So now your question can be reduced to "Why are energy and momentum conserved in the process of reflection?"

And the answer is: "Because that's the way it is."

Are you also saying that anything that is completely absorbed, all of its energy is destroyed?

Not destroyed, but converted. It is transferred to the atom in the form of a promoted electron.

Essentially the photon isn't destroyed, just it's energy is passed on. I don't know.

The photon is destroyed. For as long as the excited atomic state exists, there is no photon. A new photon is emitted when the atom de-excites.

 

[quantumdude]

tom, it hurts my feelings when u call me kiddie... atleast make it kiddo..

Lighten up, kiddo.

u really shouldn't use words like created or destroyed, though, because it gives a false representation of what is occurring on the mirror.

No, it doesn't. And I use those words because those are the words that are used in quantum field theory, which is the best theory we have for the interactions between photons and electrons.

Actually, it's the best theory we have, period. (It has been verified to 10+decimal places).

a photon is energy release. since no energy gets created or destroyed, then, technically, the photon really isn't destroyed either.

No, the photon "technically" is destroyed. If it were not, then the atom could not be promoted to a higher energy level.

absorption and emission cannot be viewed as destruction and creation.

Can too.

 

[beatrix kiddo]

Lighten up, kiddo.

hehehe...

i still disagree. i mean a photon is energy right? well if the energy isn't destroyed then the photon isn't destroyed. maybe stewarta is correct. maybe the photon gets stopped by the mirror and then the photon is accelerated at c, back off the mirror.

 

[urtalkinstupid]

Oh, no, Janna, that is contradicting with the constancy of light's velocity. Let's not do that! It's bad to go against theories, even though they aren't full proof. I'd have to agree with you! The photon can not be destroyed. Well, I believe matter and energy can be destroyed and created, but I thought there was some kind of law stating that they can not be destroyed or created? Maybe I'm just hearing things. *looks around really quick*

I believe the photon is stopped. The energy that is emitted to an electron excites that electron. Once that electron returns to it's original energy state, it emitts the energy back out accelerating the photon in the opposite direction. WOO, another one of my outrageous ideas!

 

[beatrix kiddo]

hahahaha.. there we go. now let's really get the ball rolling and just come and say that anyone who says the photon is destroyed contradicts einstein! i don't agree with sir Albert (on many levels), but tom does. so make a choice. either the photon gets destroyed or the velocity of light changes.

 

[urtalkinstupid]

Now, we know the velocity of light can't change unless there is a shift in frequency!

 

[russ_watters]

I believe the photon is stopped.

See, this is what I was talking about in the other thread. That's just not how science works. You can't just pull things out of the air and choose to believe them (or not believe them). You're setting yourself up to take a huge fall here. An active imagination is a good thing, but don't let it get the better of you. Your imagination isn't reality.

 

[urtalkinstupid]

NOTICE HOW I CORRECTED MYSELF BY SAYING FREQUENCY SHIFT! That compensates for the decceleration.