Why should Light experience a Doppler Effect?
Rabb
To my knowledge, there is no direct experimental evidence that the
Doppler effect applies to light. It has just been assumed to explain
frequency shift in light from distant objects. Correct me if I'm
wrong.
If light is transmitted as photons, individual packages of vibrating
energy, whose velocity is source independent, then why should their
frequency be affected by movement of the source? Why, for instance ,
should the photon energy hv defining a particular spectral line vary
with source velocity. I would have thought that doppler shifts only
applied to waves that are transmitted through a fixed medium.
Source movement should only affect the density of photons and
therefore the brightness of a signal.
If there is a Doppler shift, why doesn't its presence suggest an
'aether'?
Now I know what many of you are going to say and I will anticipate an
answer. The length and time scales in the transmitting system will be
different from that of a relatively moving receiver. But I cannot see
how that can explain the relationship. E should = hv, no matter what
the source was doing at the time the photon was emitted.
Besides, I think I am correct in saying that the MMX, in essence,
assumes a Doppler shift in order to account for the expected but non
eventuating fringe movement. That is, the numbers of wavelengths in
the split beams varies with apparatus velocity, essentially because of
the Doppler effect. (That is similar to saying that the beams take
different times to rejoin eachother, if you think about it)
If there is actually no doppler effect for light, then we would expect
a null result.
Mattias Pierrou
Rabb wrote in message <356bdad7...@News.bigpond.com>...
>To my knowledge, there is no direct experimental evidence that the
>Doppler effect applies to light. It has just been assumed to explain
>frequency shift in light from distant objects. Correct me if I'm
>wrong.
>
- snip -
You are wrong, very wrong...
Try looking up something about 1997 Nobel Prize in Physics.
/M
Bryan W. Reed
In article <356bdad7...@News.bigpond.com>,
<Rabb...@removeacr.net.au> wrote:
>To my knowledge, there is no direct experimental evidence that the
>Doppler effect applies to light. It has just been assumed to explain
>frequency shift in light from distant objects. Correct me if I'm
>wrong.
>
Ever hear of Doppler radar? We've got a laser vibrometer in the lab
I work in that works on the Doppler effect. The Doppler effect contributes
to the line width of a laser. There's no shortage of evidence for it.
>If light is transmitted as photons, individual packages of vibrating
>energy, whose velocity is source independent, then why should their
>frequency be affected by movement of the source? Why, for instance ,
>should the photon energy hv defining a particular spectral line vary
>with source velocity. I would have thought that doppler shifts only
>applied to waves that are transmitted through a fixed medium.
>Source movement should only affect the density of photons and
>therefore the brightness of a signal.
If you can accept that it will affect the density of photons, why not
also accept that it will similarly affect the density of wave crests?
>If there is a Doppler shift, why doesn't its presence suggest an
>'aether'?
>
You can derive the Doppler effect entirely within the realm of relativistic
electrodynamics, which doesn't require an ether.
>Now I know what many of you are going to say and I will anticipate an
>answer. The length and time scales in the transmitting system will be
>different from that of a relatively moving receiver. But I cannot see
>how that can explain the relationship. E should = hv, no matter what
>the source was doing at the time the photon was emitted.
>
Kinetic energy is dependent on frame of reference. This is true for baseballs
as well as photons. Head-on collisions are a lot more painful than
sideswipes. In the frame of reference of the atom that sent out the
photon, the photon will have an energy equal to the energy difference
between the two atomic quantum states that produced the photon. In another
frame of reference, the energy will be different.
>Besides, I think I am correct in saying that the MMX, in essence,
>assumes a Doppler shift in order to account for the expected but non
>eventuating fringe movement. That is, the numbers of wavelengths in
>the split beams varies with apparatus velocity, essentially because of
>the Doppler effect. (That is similar to saying that the beams take
>different times to rejoin eachother, if you think about it)
>If there is actually no doppler effect for light, then we would expect
>a null result.
MMX to me describes a feature of a microprocessor.
You mean Michelson-Morley experiment?
Anyway, there is a Doppler effect for light. We can derive it, measure
it, and use it in practical devices.
Have fun,
breed
me...@cars3.uchicago.edu
In article <356bdad7...@News.bigpond.com>, Rabb writes:
>To my knowledge, there is no direct experimental evidence that the
>Doppler effect applies to light. It has just been assumed to explain
>frequency shift in light from distant objects. Correct me if I'm
>wrong.
>
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
Rabb
br...@HARLIE.ee.cornell.edu (Bryan W. Reed) wrote:
>In article <356bdad7...@News.bigpond.com>,
> <Rabb...@removeacr.net.au> wrote:
>>To my knowledge, there is no direct experimental evidence that the
>>Doppler effect applies to light. It has just been assumed to explain
>>frequency shift in light from distant objects. Correct me if I'm
>>wrong.
>>
>
>Ever hear of Doppler radar? We've got a laser vibrometer in the lab
>I work in that works on the Doppler effect. The Doppler effect contributes
>to the line width of a laser. There's no shortage of evidence for it.
Doesn't so-called 'doppler radar' actually compare phase difference
between one set of pulses and another set, a short time later? It
doesn't really measure frequency change, at all, and does not actually
utilize the doppler effect. The phase difference experiences a type
of doppler shift but not the EM itself.
It therefore provides no indication as to whether or not light
signals actually experience doppler effects.
>
>>If light is transmitted as photons, individual packages of vibrating
>>energy, whose velocity is source independent, then why should their
>>frequency be affected by movement of the source? Why, for instance ,
>>should the photon energy hv defining a particular spectral line vary
>>with source velocity. I would have thought that doppler shifts only
>>applied to waves that are transmitted through a fixed medium.
>>Source movement should only affect the density of photons and
>>therefore the brightness of a signal.
>
>If you can accept that it will affect the density of photons, why not
>also accept that it will similarly affect the density of wave crests?
>
>>If there is a Doppler shift, why doesn't its presence suggest an
>>'aether'?
>>
>
>You can derive the Doppler effect entirely within the realm of relativistic
>electrodynamics, which doesn't require an ether.
>
>>Now I know what many of you are going to say and I will anticipate an
>>answer. The length and time scales in the transmitting system will be
>>different from that of a relatively moving receiver. But I cannot see
>>how that can explain the relationship. E should = hv, no matter what
>>the source was doing at the time the photon was emitted.
>>
>
>Kinetic energy is dependent on frame of reference. This is true for baseballs
>as well as photons.
I didn't know that photons possessed K.E. or momentum, just intrinsic
energy hv.
> Head-on collisions are a lot more painful than
>sideswipes. In the frame of reference of the atom that sent out the
>photon, the photon will have an energy equal to the energy difference
>between the two atomic quantum states that produced the photon. In another
>frame of reference, the energy will be different.
>
>>Besides, I think I am correct in saying that the MMX, in essence,
>>assumes a Doppler shift in order to account for the expected but non
>>eventuating fringe movement. That is, the numbers of wavelengths in
>>the split beams varies with apparatus velocity, essentially because of
>>the Doppler effect. (That is similar to saying that the beams take
>>different times to rejoin eachother, if you think about it)
>>If there is actually no doppler effect for light, then we would expect
>>a null result.
>
>MMX to me describes a feature of a microprocessor.
>You mean Michelson-Morley experiment?
Of course. and since special relativity depends crucially on the
interpretation of the MMX then your argument above, that doppler
effects in light can be derived from relativistic considerations, is
entirely circular. ie relativity depends on light experiencing a
doppler shift and doppler shift can be predicted by relativity!
nikolai fedoroff
me...@cars3.uchicago.edu wrote:
>
> In article <356bdad7...@News.bigpond.com>, Rabb writes:
> >To my knowledge, there is no direct experimental evidence that the
> >Doppler effect applies to light. It has just been assumed to explain
> >frequency shift in light from distant objects. Correct me if I'm
> >wrong.
> >
>
> Mati Meron | "When you argue with a fool,
> me...@cars.uchicago.edu | chances are he is doing just the same"
nik
Nick Turnock
It should be remembered that a photon does not have an intrinsic
frequency - that depends solely on the observer. If a photon had a mind it
couldn't say if were an x-ray or a radio wave. All photons are identical.
Regards Nick Turnock
jian...@bj.col.com.cn
> Doppler effect applies to light. It has just been assumed to explain
> frequency shift in light from distant objects. Correct me if I'm
> wrong.
>
> energy, whose velocity is source independent, then why should their
> frequency be affected by movement of the source? Why, for instance ,
> should the photon energy hv defining a particular spectral line vary
> with source velocity. I would have thought that doppler shifts only
> applied to waves that are transmitted through a fixed medium.
> Source movement should only affect the density of photons and
> therefore the brightness of a signal.
> 'aether'?
>
> answer. The length and time scales in the transmitting system will be
> different from that of a relatively moving receiver. But I cannot see
> how that can explain the relationship. E should = hv, no matter what
> the source was doing at the time the photon was emitted.
In society, a person more willing to do sth or to reach a state(relative to
another person) is similar to a particle moving toward a direction relative
to another particle. If a person wants to do sth, if he is perfect, he will
do more(similar to a particle outputing more field toward the direction), so
his energy output is higher. Light is just a form of field.
In nature, a particle's field is influenced by its motion state and
receiver's motion state; in society, price of a supply(rigorously speaking,
happiness gained from an exchange) is influenced by its supplier and
receiver. A receiver getting more happiness from a supply(relative to another
person) is similar to a particle receiving photon with higher energy. A
person outputing supply with less cost relative to another person(i.e. a
person loving his job) is similar to a particle moving toward the direction
the field propagating to with a speed. In a PPS, a person's total ability is
conserved, when he loves to do sth more than another particle, he loves to do
some other things less than it, so it outputs less field to the opposite
direction.
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/ Now offering spam-free web-based newsreading
Aleh
On Wed, 27 May 1998, it was written:
> To my knowledge, there is no direct experimental evidence that the
> Doppler effect applies to light. It has just been assumed to explain
> frequency shift in light from distant objects. Correct me if I'm
> wrong.
If you do a measure of spectra of some excited gas, the width of the lines
you obtain changes with the temperature: this is a common result of
Doppler effect, since the molecules that produce the photons are moving
around the space in all directions.
Aleh
scha...@gold.tc.umn.edu
> Doppler effect applies to light. It has just been assumed to explain
> frequency shift in light from distant objects. Correct me if I'm
> wrong.
>
The Doppler effect is seen is gas lasers as a broadening of the emission
linewidth.
Steve
Kilroy Jones
NASA Scientists regulary have to adjust their radio tuners because the
movement of their planetary space probes causes a shift in frequency as they
orbit Mars for instance. Movement of the solar surface is measured by the
ammount of doppler shift that is caused by the movement.
But you don't have to take such exotic examples. Have you ever got a ticked
because you were faster than allowed? How do you think does RADAR work? Right,
that is nothing else than doppler shift used for everyday work. It does not
matter, whether you take radio waves, radar, laser or just an ordinary light
bulb. The doppler effect is so widely used that we got used to it without
further thinking about why something works.
Robert
Aleh wrote:
> On Wed, 27 May 1998, it was written:
>
> > To my knowledge, there is no direct experimental evidence that the
> > Doppler effect applies to light. It has just been assumed to explain
> > frequency shift in light from distant objects. Correct me if I'm
> > wrong.
>
mj1...@janus.swipnet.se
ntur...@globalnet.co.uk (Nick Turnock) wrote:
A photon does have an intrinsic frequency, that's the frequency
measures when the observer is at rest with respect to the source.
Mathias Ljungberg
Jim Carr
... note followups ...
me...@cars3.uchicago.edu wrote:
}
} Rabb writes:
} >To my knowledge, there is no direct experimental evidence that the
} >Doppler effect applies to light. It has just been assumed to explain
} >frequency shift in light from distant objects. Correct me if I'm
} >wrong.
}
} You're wrong.
ial...@sprintmail.com writes:
>
>So tell him why he is wrong.....
Mistake 1: cross posting between sci.physics and alt.s.p.new-theories.
To me that sends up an immediate red flag, and Mati has been around
long enough to notice the same thing. That, coupled with the assertion
above is just asking for an "uncle al" correction.
Mistake 2: it is generally incorrect to assume that an experiment that
is easy to do in the laboratory has never been done, particularly when
it involves some effect of interest to others (like astrophysics). Thus
it would be better to ask what has been done rather than assume it has
not been done.
Mistake 3: most people should know that radar and light are both
electromagnetic radiation, and that police radar works on the doppler
effect. OK, maybe not most people, but certainly anyone who asserts
something about light in a physics newsgroup. Thus we are talking
about something that is a part of daily life, not an esoteric laboratory
effect. It might even be treated correctly in an encyclopaedia. ;-)
In any case, the doppler effect for electromagnetic radiation is seen
in the laboratory for everything from microwaves (radio region) to
" visible light" (optical) to gamma rays.
--
James A. Carr <j...@scri.fsu.edu> | Commercial e-mail is _NOT_
http://www.scri.fsu.edu/~jac/ | desired to this or any address
Supercomputer Computations Res. Inst. | that resolves to my account
Florida State, Tallahassee FL 32306 | for any reason at any time.
David Rabanus
Rabb wrote:
>
> To my knowledge, there is no direct experimental evidence that the
> Doppler effect applies to light. It has just been assumed to explain
> frequency shift in light from distant objects. Correct me if I'm
> wrong.
>
> energy, whose velocity is source independent, then why should their
> frequency be affected by movement of the source? Why, for instance ,
> should the photon energy hv defining a particular spectral line vary
> with source velocity. I would have thought that doppler shifts only
> applied to waves that are transmitted through a fixed medium.
> Source movement should only affect the density of photons and
> therefore the brightness of a signal.
> If there is a Doppler shift, why doesn't its presence suggest an
> 'aether'?
Some remote sensing satellites measure line emissions (for example
OH-emissions in the UV) while staring in limb geometry. That means:
Observed emitting molecules move along line of sight of the instrument.
Compared to line emissions in the laboratory the observed frequency
shift of the same line yields a velocity of about 8 km/s (just the speed
of the spacecraft).
How do You explain that without Doppler-effect?
marisa
David Rabanus wrote:
You are not answering the original question. The fact that you can't think
of a better solution to the line emissions problem that you mention does not
solve the question of whether a Doppler effect is linked to an ether or not.
In fact, if this was the case, the evidence you mention represents a big
problem rather than a solution. :-)
CRepublic
In article <357F9006...@kabelfoon.nl>, marisa <mar...@kabelfoon.nl>
writes:
> You are not answering the original question. The fact that you can't think
>of a better solution to the line emissions problem that you mention does not
>solve the question of whether a Doppler effect is linked to an ether or not.
>In fact, if this was the case, the evidence you mention represents a big
>problem rather than a solution. :-)
>
>
>
Gee, I thought the Doppler effect was frequency shift in light, sound,
whatever.
If you throw a series of rocks in space one every second at a constant
speed say one M/S and the target is stationary they will hit at one second
intervals. Now move the target away from the source at a speed of 1/2 m/s and
the frequency of it's being hit by rocks will decrease to 1 every 2 second
because each rock will have to go farther to hit the target.
Now if the waves of light are a pattern of more photons then less photons
then more photons. Then moving away from the source of the light is going to
have the same effect moving away from the source of the Rocks will have. The
frequency will decrease and there for the wave length will increase.
Gorg
Ken Carrigan
Lasers of a coherent frequency can be used to sense
vibrations of objects.. the return signal mixed with the
fundamental coherent sent signal and then demodulated.
The audio properties are then calibrated to the fundamental
frequency and walla! You can then sense the exact velocity
of the vibrating object.... be it a car (laser radar detectors)
for an office window (laser listener).
So.. true the coherent light source does change in velocity..
therefore the photons do speed up or slow down relative
to the velocity of the coherent light.
Ken Carrigan
Jim Carr
... relativity newsgroup added with followups there ...
David Rabanus wrote:
}
} Rabb wrote:
} > To my knowledge, there is no direct experimental evidence that the
} > Doppler effect applies to light. It has just been assumed to explain
} > frequency shift in light from distant objects. Correct me if I'm
} > wrong.
You are wrong.
The Doppler effect with light is well established in the lab. It
is also the basis for police radar. Go out and get a speeding
ticket, and they will happily explain it to you in court. ;-)
} > If light is transmitted as photons, individual packages of vibrating
} > energy, whose velocity is source independent, then why should their
} > frequency be affected by movement of the source?
It is not. It is the relative motion that matters, and this is
the same for everything: photons, atoms, people, rocks, ...
} > Why, for instance ,
} > should the photon energy hv defining a particular spectral line vary
} > with source velocity.
Because the observer is not moving with the source velocity.
} > I would have thought that doppler shifts only
} > applied to waves that are transmitted through a fixed medium.
} > Source movement should only affect the density of photons and
} > therefore the brightness of a signal.
} > If there is a Doppler shift, why doesn't its presence suggest an
} > 'aether'?
}
} Some remote sensing satellites measure line emissions (for example
} OH-emissions in the UV) while staring in limb geometry. That means:
} Observed emitting molecules move along line of sight of the instrument.
} Compared to line emissions in the laboratory the observed frequency
} shift of the same line yields a velocity of about 8 km/s (just the speed
} of the spacecraft).
}
} How do You explain that without Doppler-effect?
marisa <mar...@kabelfoon.nl> writes:
>
>You are not answering the original question. The fact that you can't think
>of a better solution to the line emissions problem that you mention does not
>solve the question of whether a Doppler effect is linked to an ether or not.
That's OK, none of those questions have defined which of the many
kinds of "ether" was meant. Several of the original questions were
so confused about simple facts that it is hard to decide what sort
of ether was intended or what tests the questioner had in mind.
Questions about the ether are solved more directly, by looking for
other predicted effects of the classic luminiferous aether, or asking
for a more precise definition of the physical theory being proposed.