More on Light's Mass, Energy, Frequency - Science Forum

Addict Joined: Aug 04, 2005 Posts: 69

I'd like to ask another interesting question, in reply to a statement I made earlier about light having greater energy if you are moving toward it via increased frequency.

I'm beggining to see that I don't have as firm of a grasp on all this as I believed. E=hf and f shifts due to doppler effect depending on how fast we are traveling toward or away from the source.
However, we know (at least classically and I have a feeling this is where I get in trouble) that light is released with x amount of energy and unless a force acts on the light it cannot gain or lose energy.

Therefore I made the comment earlier that the effective difference in the energy of the light wave or photon was not changing, simply our frame of reference changed so that our KE is added to that of the light to create the appearance of increased energy in the light wave.

However, according to TGR, light is traveling at c regardless of what frame of reference we are in (am I stating that correctly?). So even if we were traveling toward the sun, the light traveling from the sun at us should still appear to travel at c. How does one account then for the energy/frequency shift?

I'm probably confusing myself and everyone else, but then these questions need to be asked. HEMETIS?

Moderator Joined: Jun 21, 2005 Posts: 264

Light's energy is directional. If you are moving toward it its energy goes up. If moving away from it it goes down. Constant motion does not affect the speed of light but the energy. It affects the wave.

The wave is not a form of mass but of energy alone. Just look at matter and you will see that mass is concentrated energy. Take a C squared amount of energy and concentrate it and what do you have?
The answer is mass.

Light's energy isn't concentrated therefore it isn't "mass."
The nature of light is in its name: It is light. It isn't heavy.

Addict Joined: Aug 04, 2005 Posts: 69

Someone other than Nick who apparently knows how to do nothing but regurgitate a bunch of junk to attemp to raise his standing above expert because of the number of replies and words he can type?

Nick I asked a question that was way deeper than the reply you gave. Spouting crap is just that. If you would like to engage in a discusion of how all of what you believe can be explained or proven by all means reply to this message. If not please stop filling the forums with your rants, I would like a serious reply to this posting.

Moderator Joined: Jun 21, 2005 Posts: 264

Light has no kinetic energy. Its energy aint in its velocity but in its wave. And the wave's energy is relative to matter's motion. If light did have kinetic energy it would be the same for all photons because light's motion is a constant. The motion of light is always the same. So the kinetic energy/mass would be always the same for all photons. All photons would have identical mass.

So you see light's kinetic energy would be a constant. And this is easily seen not to be true. It's relative energy is in its wave.

Light has no rest mass because it doesn't even apply. If light can't be brought to rest you cannot talk of it having any amount of rest mass at all and that includes Zero.

Why not show me where I am wrong cwes?

Moderator Joined: Jun 21, 2005 Posts: 264

Addict Joined: Aug 04, 2005 Posts: 69

This is what I don't understand. How could one thing be considered to move relative to another and yet the inverse not be true? Isn't everything relative?

I.E. if I'm moving, yet I say that my frame of reference is moving with me, (in the case that I'm carrying a device that can measure the speed of light) then why doesn't the speed of light appear different depending on how I'm moving? I know about the Michelson-Morely experiment.

Moderator Joined: Jun 21, 2005 Posts: 264

Novice Joined: Sep 09, 2005 Posts: 6

Hi everyone !

I'm new here and I came from the "space.com" forum. A local member invited me to this thread so I'm joining the discussion.

I think that the key for that "higher energy" question is in the bases of Einstein's Relativity. The basic axiom there is that in the Universe of the Matter the only absolute thing is the speed of light in vacuum.

From there deduce that: "there is no absolute amount of energy". That means that the "total energy" of a given piece of Matter could have different Values depending on what space-time frame we use to measure it.

In the given case:
- the light beam's energy measured respectively to the emitter's space-time frame remains constant
- if you move respective to emitter the light beam's energy measured respectively your space-time frame is different and also remains constant

It's my try to explain things so you can tell how it looks like from your points of view

Bye Very Happy

Addict Joined: Aug 04, 2005 Posts: 69

So you're trying to reason, possibly accurately cause I still don't understand all there is to know about the "theory" of relativity, that much like time dilation or length contraction, energy is simply percieved differently depending on the frame of reference.

I have a further question for that idea. If light's speed is identical in every frame of reference, then shouldn't it's energy be identical in order for E=pc to hold true, or is h different in different frames of reference, which can't be because the laws of physics must be the same for every frame of reference.

Moderator Joined: Jun 21, 2005 Posts: 264

The energy is in the wave and the wave is relative. The Doppler effect comes from the motion of matter not the motion of light.

When light enters a black hole it heats up. Light boils there. In other words it becomes radically blueshifted in the slower time frame. -- Light Falls --

Novice Joined: Sep 09, 2005 Posts: 6

Hi there !

If we take the "E = hf" equation where f is the frequency, here is what we've got:
By definition "frequency" is how many identical events happen for one unit of time. We must ask is "the pace of Time" identical for the emmiter and the observer of the light.
If we observe different frequencies in different space-time frames it means that the Time flows with different paces for these frames.

All The Best Cool

Addict Joined: Aug 04, 2005 Posts: 69

I think that is what I was trying to point at in my earlier post Dan, thanks for wording it better. But the thing is, most scientists would say that if the light is blue shifted by a star traveling relatively fast toward us, then the actual photons of light reaching us have more energy than light emited by a similar sodium atom is our sun.

Novice Joined: Sep 09, 2005 Posts: 6

Nope

The "most scientists" could'n make such a statement, because it will be equal to saying:

I run compared to that car faster than you run compared to this bus

This is not an usefull statement.
When we measure something - it has to be compared to one basis. Otherwise we are wasting time Smile

Addict Joined: Aug 04, 2005 Posts: 69

thanks again for making my point. I don't agree with the statement. I don't see how saying blue shifted light contains more energy than the light emitted from a non-blue shifted source.

I understand the photo-electric effect. I understand E=h*nu. I'm saying that there must be some relativistic effect yet to be understood (possibly just by me) about nu, or I call it the failure of relativity.

Novice Joined: Sep 09, 2005 Posts: 6

I think cwes you missed some points.

If a red photon is emitted from our sun
-> it appears to us as a red photon with energy E1
If a red photon with energy E1 is emitted from a star that races toward us with 1/2c
-> it appears to us as a blue photon with energy E1+dE

Both photons travel toward us with c.

So where from comes the dE.

When the emitter moves respective to the observer that could not change the speed of light propagation (because it's an axiomatic constant). What that motion does is to shrink/enlarge the wave lengths, respectively the dE appears.

· Encyclopaedia · Wikipedia

· Encyclopaedia
· Wikipedia