I have a new model that explains the red/blue shifting of light caused by the motion of stars, and galaxies, relative to us. This model is built upon a theory that I posted earlier on the "Physics and Math" forum. You can find an explanation of my theory in the "Alternative to Special Relativity" thread:

http://www.sciforums.com/showthread.php?s=&threadid=16733

To summarize by theory, it basically states that the omnidirectional speed of light is only equal to c relative to the local gravitatational field that the light finds itself in at the moment, and an observer will only measure the omnidirectional speed of light to be equal to c if the observer is stationairy relative to this local gravitational field.

In other words, if you measure the speed of light on the surface of Jupiter, you will find that the omnidirectional speed of light is equal to c relative to Jupiter. If you measure the speed of light on the surface of the Earth, you will find that the omnidirectional speed of light is equal to c relative to the Earth. However, this doesn't mean that the omnidirectional speed of light on the surface of Jupiter is equal to c relative to the Earth, or that the omnidirectional speed of light on the surface of the Earth is equal to c relative to Jupiter.

Now to get to my red/blue shift theory:

Let's say you have the star moving towards the Earth at a speed of c (see illustration). In the illustration, m1 is the mass of the Earth, and m2 is the mass of the Star.

As the star is moving towards the Earth, it releases photons. When the photons are released, they are moving at a speed of c relative to the star (because they they are in the star's gravitational field). However, their speed relative to the Earth is:

c(Earth)=c + v

Where v is the velocity that the star is moving towards the Earth.

As the photons continue to move away from the star, and begin to move towards the Earth, the star's gravitational field grows weaker, while the Earth's gravitational field grows stronger (relative to the photons). Since the photons are travelling faster than c relative to the Earth's gravitational field, the Earth's gravitational field attempts to slow them down to c in its field. However, the star's gravitational field is still influencing the photons, and it's trying to force them to travel at c in its gravitational field. This tug-of-war between the two gravitational fields is causing the speed of the photons, relative to the Earth, to decrease.

As the photons finally approach the Earth, the stars gravitational field has such a small influence on them, and the Earth's gravitational field has such a large influence on them, that their speed, relative to the Earth, is approaching c. Finally, when the photons hit the Earth, their speeds are very, very close to c since the stars gravitational effects on the photons are almost non-existant.

In summary, relative to the Earth, the speed of the photons when they are emmited from the star is c+v, where v is the speed at which the star is moving towards the Earth. As the photons approach the Earth, their speed decreases, until they finally reach c (or very close to c) when they strike the surface of the Earth. The slowing down of the speed of the light, causes the light to blue shift. If the star was moving away from the Earth, then the Earth's gravitational would speed up the incoming light, causing the light to red shift.

Any comments are appreciated.

Tom

Show me your derivation of the relativistic Doppler shift formula using your theory. (The formula is verified by experiment.)

James,

Show me your derivation of the relativistic Doppler shift formula using your theory.

I didn't get to that point yet. I was hoping that someone could point out any logical contradictions in my theory before I attempt to do the math.

(The formula is verified by experiment.)

Which experiment are you referring to? And what is the conventional scientific explanation for the Doppler shift (relating to the relative motion of stars and galaxies)?

<i>...what is the conventional scientific explanation for the Doppler shift</i>

You mean, you're putting forward a new theory and you don't even know what the current one is?

James,

You mean, you're putting forward a new theory and you don't even know what the current one is?

I understand the "basics" of the current theory, but not the specifics.

Here is my problem: If a source of a soundwave is stationairy and the observe is in motion, then the observer will here the pitch of the soundwave change because the soundwave slows down, or speeds up, relative to the observer. I don't see how the same effect can be applied to light since relativity states that the speed of light is constant for all observers.

Tom

The frequency of light or sound depends not on the speed of the wave but on the number of wavefronts you intersect per unit time. Move into a wave and the frequency increases; move away and it decreases. The basic idea is the same whether you're talking about light or sound.

James,

The frequency of light or sound depends not on the speed of the wave but on the number of wavefronts you intersect per unit time. Move into a wave and the frequency increases; move away and it decreases. The basic idea is the same whether you're talking about light or sound.

I don't agree.

If I'm moving away from a soundwave, then the soundwave is moving slower relative to me. This means that number of wavefronts that pass me, per second, decreases, thereby decreasing the "perceived" frequency of the soundwave.

The same mechanics can't be applied to a light wave since relativity states that light always travels at c relative to all observers.

Tom

Ideally we should set up multiple obeservation points in our solarsystem more or less subjected to earth gravity or one on mars to see if the difference in red/blueshift is consistent with differences in gravitational force to test this theory.

The sound wave doesn`t increase or slow down, it`s the wavelength that gets stretched or compressed...same as light (if you regard it as a wave). This gives the red/blue shift.

The speed if light is independent of the speed of the object that it interacts or emits from.

However light IS influenced by gravity (a relic of the time when all the forces were one?).

Vortexx,

Ideally we should set up multiple obeservation points in our solarsystem more or less subjected to earth gravity or one on mars to see if the difference in red/blueshift is consistent with differences in gravitational force to test this theory.

Actually that wouldn't work. The size of the gravitational field doesn't matter, only the speed of the field matters.

In other words, if you are sitting on Jupiter you would notice the same blue/red shift as if you were sitting on Earth, as long as the difference in speed between the emitting source and the observer remain the same.

Tom

blobrana,

The sound wave doesn`t increase or slow down, it`s the wavelength that gets stretched or compressed...same as light (if you regard it as a wave). This gives the red/blue shift.

The speed of the sound wave through the air (generally) does not change. However, if you are also moving, towards or away from the wave, then the speed of the sound wave changes RELATIVE to you. So if you are moving towards the source of the sound wave, the sound wave is travelling faster than sound in your frame of reference. Because the sound wave is moving faster, relative to you, the wavefronts of the sound wave strike you at a faster rate making it appear that the frequency of the sound wave has increased.

Due to relativity, the Doppler effect should be nonexistant in the case of light, since the speed of light always remains constant regardless of how fast you are moving towards, or away, from the source of the light. The same time dilation and length contraction that keeps the speed of light constant in a moving frame of reference, should keep the frequency of the light constant as well.

Tom

Tom:

The Doppler effect occurs whenever there is a relative velocity between a source of waves and a receiver, whether the waves be sound, light or something else.

The only difference between sound and light is that in the Doppler effect for sound there is a preferred frame of reference, namely the frame of the medium carrying the wave. That's why there are two different versions of the Doppler formula, depending on whether the source or receiver is moving relative to the medium.

Light needs no medium, so only relative velocity counts, and there is only one Doppler formula. We can't say absolutely whether the source or receiver is moving, and the effect is the same for both cases.

The Doppler effect does not rely on the wave speed changing. It is entirely due to relative motion between the observer and the source.

May these animations will help in showing how the Doppler-effect works for light.

The first shows two observers (red and Blue) with a light source between them and at an equal distance from both. The source is not moving in this example. The source emits a pulse of light consisting of a number of waves, which pass over each observer. As can be seen, the light radiates outward as a spherical front and strikes both observers at the same time and the same number of waves passes each observer per time unit.

http://home.teleport.com/~parvey/doppler1.gif


The second shows what happens from the perspective of the observers if the source is moving towards the blue observer while emitting the same pulse.

The front of the pulse behaves exactly the same. It expands as a sphere, and strikes each observer at the same time. But by the time the next wave of the pulse is emitted, the source has moved some distance closer to the blue observer. Each part of the wave expands out from its point of origin spherically at c, but each point of origin is closer to the blue as time goes by. As a result, more waves pass over the blue observer in the same time than pass over the red observer, and they are of shorter wavelength. Both the observers still measure the waves as passing by them at c, But one will see the light shifted blue and the other red.

http://home.teleport.com/~parvey/doppler2.gif

http://members.chello.nl/~n.benschop/contents.htm


Got Ether?

James,

The only difference between sound and light is that in the Doppler effect for sound there is a preferred frame of reference, namely the frame of the medium carrying the wave.

For sound there is an absolute frame of reference (the air). If an observer is moving through the air, the speed of a soundwave will change relative to the observer. This change in the speed of the soundwave will change the number wavefronts of the soundwave that hit the observer per second, which will result in the observing "perceiving" a change in the frequency of the soundwave.

Relativity states that there is no absolute frame of reference for light. As a result, the speed of a light wave doesn't change relative to the motion of the observer. Because the speed of the light doesn't change, the wavefronts of the light wave that hit an observer per second shouldn't change as a result of the observers motion. Since the number of wavefronts of the lightwave that hit the observer doesn't change, the frequency of the wave shouldn't change either.

Edit: Please read the post right after this one. Is it true that the Doppler effect can only explain blue/red shifting of light if the source is moving and the observer is stationairy? If the source is stationairy and the observer is moving, shouldn't time dilation and length contraction in the observers frame of reference keep both the speed, and the frequency, of the light constant?

Tom

Janus58,

Here's the problem:

With regard to soundwaves, the Doppler effect can explain frequency shifts, whether the observer is stationairy and the source is moving, or whether the source is stationairy and the observer is moving.

Unfortunately, the Doppler effect can only explain frequency shifts in light if the source is moving and the observer is stationairy (as you showed in your demonstration). If the source was stationairy and the observer was moving, then time dilation and length contraction in the observers frame of reference would keep the speed and the frequency of the light constant. You see, time dilation and length contraction will not only influence the speed of the light wave, but will also influence the distance betweeen the wavefronts which dteremine the frequency of the light wave.

This appears to be a problem with relativity since in order for it to assume that the Doppler effect is occuring, it must assume that the source is moving and not the observer. This asymmetry in relativity is the reason why I'm attempting to explain blueshifting and redshifting using a different model than the one proposed by relativity.

Tom

Originally posted by Prosoothus
James,



For sound there is an absolute frame of reference (the air). If an observer is moving through the air, the speed of a soundwave will change relative to the observer. This change in the speed of the soundwave will change the number wavefronts of the soundwave that hit the observer per second, which will result in the observing "perceiving" a change in the frequency of the soundwave.

Relativity states that there is no absolute frame of reference for light. As a result, the speed of a light wave doesn't change relative to the motion of the observer. Because the speed of the light doesn't change, the wavefronts of the light wave that hit an observer per second shouldn't change as a result of the observers motion. Since the number of wavefronts of the lightwave that hit the observer doesn't change, the frequency of the wave shouldn't change either.

Tom

Recheck out my post with the animations.

The second animation also describes what the blue and red observers see if you considered them moving rather than the source. For the very reason you mention; the light emitted by the source has to be seen as moving at c with respect to both observers, by the observers. So from the observer's point of view, it doesn't matter whether or not it is the source or them that is moving, as long as the distance between them changes with time.

Janus58,

So from the observer's point of view, it doesn't matter whether or not it is the source or them that is moving, as long as the distance between them changes with time.

You're not applying time dilation and length contraction to the space (and time) between the crests of the light wave. Let me break the problem down into its simplist components:

Let's say that I shine two pulses of light toward an observer that is moving away at a speed of v. Let's pretend that each pulse of light is the crest of a wave, and the space between the pulses is the wavelength. Let's say that the time between the pulses is t1 and the space between the pulses is d1.

In this example, relativity states that the speed of the pulses will remain constant in the observer's frame of reference. Intuition would suggest that if the speed of the pulses remain constant, and the observer is moving away from the source of the pulses, then the time difference between the pulses will increase. This assumption is WRONG.

Why is it wrong?? First we must ask ourselves what causes the speed of the pulses to remain constant to the moving observer. Einstein claimed that time dilation and length contraction are responsible for keeping the speed of light c in all frames of reference. If time dilation and length contraction do exist in the observer's frame of reference, then we must not only apply them to the speed of the pulses of the light, but we must also apply them to the space between the two pulses, and the time between the two pulses.

Conclusion: Length contraction and time dilation will keep the speed of the two pulses constant. Length contraction will also contract the space between the pulses, and time dilation will dilate the time between the pulses. This will result in the time between the two pulses remaining constant, regardless of the speed of the observer. In other words, time dilation and length contraction should not only keep the speed of a light wave constant, but it should keep the "percieved" wavelength, and frequency, of the light wave constant as well.

Tom

Originally posted by Prosoothus
Janus58,

²

You're not applying time dilation and length contraction to the space (and time) between the crests of the light wave. Let me break the problem down into its simplist components:

Let's say that I shine two pulses of light toward an observer that is moving away at a speed of v. Let's pretend that each pulse of light is the crest of a wave, and the space between the pulses is the wavelength. Let's say that the time between the pulses is t1 and the space between the pulses is d1.

In this example, relativity states that the speed of the pulses will remain constant in the observer's frame of reference. Intuition would suggest that if the speed of the pulses remain constant, and the observer is moving away from the source of the pulses, then the time difference between the pulses will increase. This assumption is WRONG.

Why is it wrong?? First we must ask ourselves what causes the speed of the pulses to remain constant to the moving observer. Einstein claimed that time dilation and length contraction are responsible for keeping the speed of light c in all frames of reference. If time dilation and length contraction do exist in the observer's frame of reference, then we must not only apply them to the speed of the pulses of the light, but we must also apply them to the space between the two pulses, and the time between the two pulses.


Read what you just said:

1.The time dilation and the length contraction are responsible for making light a constant speed in any frame."

2.Then you talk about applying the these effects to the "speed" of the Pulses.

3.Then you say that we must also apply them to time and distance.(again?)

That's applying the same dilation and contraction three times in the same situation. (or at least two, depending on whether you consider instances 1 and 2 as the same.)

You only can apply them once , all other effects are a result of that one applicaton.




Conclusion: Length contraction and time dilation will keep the speed of the two pulses constant. Length contraction will also contract the space between the pulses, and time dilation will dilate the time between the pulses. This will result in the time between the two pulses remaining constant, regardless of the speed of the observer. In other words, time dilation and length contraction should not only keep the speed of a light wave constant, but it should keep the "percieved" wavelength, and frequency, of the light wave constant as well.

Tom

Your conclusion is incorrect. The light will travel at a constant speed with respect to the observer. Each pulse will be emitted from a closer or further point from the observer than the previous one, thus will follow closer to or lag further behind than the previous one. (Regardless of whether you consider the source or observer as moving, In fact, the mere distinction as to whether the it is the source or observer that is moving is meaningless. That's what "no prefered frame of reference" means)

Your are misapplying Relativity All you need to apply is the Theorum for the addition of velocities,

W = U+V/(1+UV/c^2)

which already incorporates the Lorentz transformations. In fact, it is derived from the Lorentz transformations.

Which shows that if an object B emits light relative to itself at c, then an observer B will measure that same light as moving at c relative to himself, regardless of what relative velocity A and B have to each other. (Or how you "divide up" that relative velocity.)

You will not find a single authorative source that will state that Relativity disallows the Doppler effect. You will find many sources that will refer to "Relativisitic Doppler shift" Which is the Doppler effect taking into consideration the Lorentz Transformations applied the Source.

Tom:

<i>Unfortunately, the Doppler effect can only explain frequency shifts in light if the source is moving and the observer is stationairy (as you showed in your demonstration).</i>

Do you really think that if this was a problem, somebody wouldn't have noticed it in the last 100 years?

You're wrong about relativity (again). Since you can't say who is "really" moving (source or receiver), the Doppler shift of light is exactly the same for both situations. Note that this is not true for sound, because in that case you CAN say whether the source or receiver (or both) is moving relative to the air.

The relativistic Doppler formula explains observations for a moving source, or a moving observer or both. The only velocity which appears in the formula is the relative velocity between source and receiver.

Janus58,

1.The time dilation and the length contraction are responsible for making light a constant speed in any frame."

2.Then you talk about applying the these effects to the "speed" of the Pulses.

3.Then you say that we must also apply them to time and distance.(again?)

That's applying the same dilation and contraction three times in the same situation. (or at least two, depending on whether you consider instances 1 and 2 as the same.)
You only can apply them once , all other effects are a result of that one applicaton.

You didn't understand me. I applied time dilation and length contraction only once. I applied it to the pulses AND I applied it to the space and time between the pulses. You are incorrectly stating that time dilation and length contraction ONLY affect the pulses but ignore the space and time between the pulses.

Tom

Janus58 and James,

Close your eyes, and visualize an electromagnetic wave. Now imagine this wave hitting an observer that is moving away. Without length contraction and time dilation this wave will appear elongated to the observer. This "elongation" makes it appear to the observer that the frequency of the wave has decreased.

Now imagine that there's length contraction and time dilation in the observer's frame of reference. How will length contraction and time dilation influence the wave? Length contraction will contract the elongated wave making the distance between the crests of the wave decrease (causing a perceived increase in the frequency of the wave). Time dilation kicks in and it makes the crests of the elongated wave hit the observer at a faster rate (causing another perceived increase in the frequency of the wave).

In summary, length contraction and time dilation have contracted the elongated wave back to its original length (and frequency). The perceived increase in the frequency of the wave caused by length contraction and time dilation have compensated for the perceived decrease in the frequency of the wave caused by the relative motion of the observer. You can confirm my conclusion by using the Lorentz boost transformations.

Note: Notice that I have only used time dilation and length contraction once on the entire wave.

Tom

Originally posted by Prosoothus
Janus58 and James,

Close your eyes, and visualize an electromagnetic wave. Now imagine this wave hitting an observer that is moving away. Without length contraction and time dilation this wave will appear elongated to the observer. This "elongation" makes it appear to the observer that the frequency of the wave has decreased.

Now imagine that there's length contraction and time dilation in the observer's frame of reference. How will length contraction and time dilation influence the wave? Length contraction will contract the elongated wave making the distance between the crests of the wave decrease (causing a perceived increase in the frequency of the wave). Time dilation kicks in and it makes the crests of the elongated wave hit the observer at a faster rate (causing another perceived increase in the frequency of the wave).



Hold on, Applying the transformations to the Wave?!! If to do that, you must take the wave's relative speed to you into account, which is c. In that case, the wavelength would collapse to zero in all cases, which is nonsensical.

It only makes sense to apply the transformations to the source. Maybe this is what you mean, but as stated it doesn't make sense.




In summary, length contraction and time dilation have contracted the elongated wave back to its original length (and frequency). The perceived increase in the frequency of the wave caused by length contraction and time dilation have compensated for the perceived decrease in the frequency of the wave caused by the relative motion of the observer. You can confirm my conclusion by using the Lorentz boost transformations.

Note: Notice that I have only used time dilation and length contraction once on the entire wave.

Tom

If you apply the Lorentz contractions to the problem you get the relativistic Doppler formula:

(Delta w)/w = sqrt(1+v/c)/sqrt(1-v/c)

The application of the Lorentz transformations to the classic Doppler formula adds a correction, it does not cancel it out altogether. The two functions don't follow the same curve.

Janus58,

Hold on, Applying the transformations to the Wave?!! If to do that, you must take the wave's relative speed to you into account, which is c. In that case, the wavelength would collapse to zero in all cases, which is nonsensical.

Before the time dilation and length contraction the relative speed of the wave to the observer is not c (if the observer is moving). Only after you take the effects of length contraction and time dilation into affect, does the relative speed of the light wave equal c.

The application of the Lorentz transformations to the classic Doppler formula adds a correction, it does not cancel it out altogether. The two functions don't follow the same curve.

I'll take a closer look at your statement, and get back to you later.

Tom

Tom:

<i>Length contraction will contract the elongated wave making the distance between the crests of the wave decrease (causing a perceived increase in the frequency of the wave).</i>

Yes.

<i>Time dilation kicks in and it makes the crests of the elongated wave hit the observer at a faster rate (causing another perceived increase in the frequency of the wave).</i>

No. Time dilation would decrease the frequency.

<i>In summary, length contraction and time dilation have contracted the elongated wave <b>back to its original length (and frequency)</b></i>.

No. That's where you're wrong. When the time dilation and length contraction are taken into account, you get the relativistic Doppler shift.

<i>The perceived increase in the frequency of the wave caused by length contraction and time dilation have compensated for the perceived decrease in the frequency of the wave caused by the relative motion of the observer.</i>

Not true.

<i>You can confirm my conclusion by using the Lorentz boost transformations.</i>

Show me.

James,

No. Time dilation would decrease the frequency.

To be honest, the Lorentz transformations are confusing me. I don't know whether the time dilation would increase, or decrease the frequency.

Remember a few months ago when you used the Lorentz transformations to calculate the speed of two beams of light that are travelling in opposite directions to each other relative to a moving observer (it was the two flashlight experiment). You used two seperate time dilations for the two beams of light (I believe they were 0.229 seconds for one beam, and 4.35 seconds for the other). As you pointed out, for one beam the time slowed down, and for the other time sped up. I believe that in the case where the light is moving in the same direction as the observer, the time would speed up for the observer causing the frequency to increase(but I'm not sure).

Tom