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Aberration of starlight

  1. Feb 19, 2004 #1
    I was thinking of something and maybe somebody can explain....
    If rain is coming straight down at a rate of 4 meters/second and I'm walking along at a rate of 3 meters/second then the rain is hitting me at an angle at a rate of 5 meters/second. So, then why doesn't the same sort of reasoning apply to starlight? The aberration of starlight is what I'm referring to specifically. I mean if the speed of light is always the same then there wouldn't be any aberration of starlight correct? The light would always come down at the same angle regardless of the motion of the earth with respect to the star. Correct or not?
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  3. Feb 20, 2004 #2


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    Relativity does predict the abberation of starlight. The difference is that in Relativity you would not see a change of velocity in the light, but a slight increase of frequency. The angle of deflection is the same.
  4. Feb 20, 2004 #3
    You can’t have a “change of frequency” in the starlight seen at the earth if the star is not moving toward or away from the earth, or if the earth is not moving toward or away from the star, so aberration of starlight coming from directly overhead has nothing at all to do with “a change of frequency," and it has nothing at all to do with "Einstein relativity" either. It was discovered and described long before he lived.
  5. Feb 20, 2004 #4


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    It was discovered, by Bradley, in the 18th century, and explained by him in terms of a "wind of light" by naive corpuscles in the style of Newton's Opticks. When the wave nature of light was discovered early in the 19th century, there was a problem because the easy wind explanation could no longer be applied, and it wasn't easy to motivate the phenomenon with waves. But relativity cleared the problem up. Aberration is truly a relativistic phenomenon, and it's not a shift of frequency, it's a change in the observed direction of the star.
  6. Feb 20, 2004 #5

    Didn’t Einstein adopt the “photon particle” nature of light, rather than the “wave” nature? Isn’t that what his photoelectric effect was all about? Why is it that when Newton says it's "particles", that's "out of date", but when Einstein says it's "particles", that's considered "brilliant"?

    Bradley discovered the phenomenon and he explained it. If you know of a specific different explanation, I’d like to hear it. Exactly what did “relativity” “clear up”, and how?
  7. Feb 21, 2004 #6


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    SR made the "aether wind" unnecessary by explaining how the M&M experiment could produce a null result.
  8. Feb 21, 2004 #7
    Exactly how did SR explain how M&M got the null result?
  9. Feb 21, 2004 #8


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    Is this a trick question? You talk about this stuff all the time.

    The postulate of a constant light speed and its implications on time and space dilation predict a null result.
  10. Feb 21, 2004 #9

    The “constancy” postulate was just a guess that turned out to be wrong, as he admitted in his 1911 paper. He was able to guess at the constancy postulate in 1905, because back then astronomers didn’t realize that stars and galaxies were moving around in space at relatives speeds of thousands of miles a second. There are high-z galaxies known today that have redshifts that indicate they are traveling at 1, 2, 3, and even 4 times the speed of light, relative to the earth. The SR theory doesn’t explain this phenomena at all. The new concept is that light travels through each separate galaxy at approximately “c”, and it changes speed as it moves from galaxy to galaxy, with a local medium inside each galaxy controlling its local speed to about “c” inside each galaxy. Currently, this local medium is called, simply, the “comoving space” of the galaxy.

    Anyway, he altered the “constancy” postulate in his 1911 paper and he tied the local speed of light to an astronomical body’s local gravity field.

    A logical alternative explanation of the M&M results was that their apparatus was resting inside the earth’s own local ether (the earth’s local light-speed regulating medium) and not moving through it at all.
  11. Feb 23, 2004 #10


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    SR doesn't explain it because it has nothing to do with SR. The galaxies aren't moving so much as the space between them is expanding.
    Who'se new concept and where can I find it?
  12. Feb 23, 2004 #11


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    You could not be more wrong.

    The "guess" as you call it was the single biggest issue of Physics for the last 50 yrs of the 19th century.

    You really need to study up on the REAL history of these things before you start spouting such nonsense.

    Have you ever heard of "Maxwell's Conundrum"? You need to do a bit of research, that would be a good starting key word.
  13. Feb 24, 2004 #12


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    Consider a ray of light with a velocity according to (ct, x, y, z) coordinates of [tex]\vec{u} = -c\hat{z}[/tex]. You want to transform this velocity to a (ct', x', y'. z') coordinate system for an observer moving in the [tex]+\hat{x}[/tex] direction with respect to the first with speed v to find out what how he observes this ray. Simply apply the Lorentz velocity transformations to ray's velocity vector's components. Use [tex]u'_{x} = \frac{u_{x} - v}{1 - \frac{u_{x}v}{c^2}}[/tex] and [tex]u'_{z} = \frac{u_{z}}{\gamma (1 - \frac{u_{x}v}{c^2})}[/tex] to arrive at
    [tex]\vec{u'} = -v\hat{x'} - \frac{c}{\gamma}\hat{z'}[/tex]. The speed of the light according to the (ct', x', y', z') frame is then
    [tex]u' = \sqrt{u'_{x}^2 + u'_{z}^2} = \sqrt{v^2 + \frac{c^2}{\gamma ^2}}[/tex]
    [tex]u' = \sqrt{v^2 + c^{2}(1 - \frac{v^2}{c^2})}[/tex]
    [tex]u' = \sqrt{v^2 + c^{2} - v^2}[/tex]
    [tex]u' = \sqrt{c^2}[/tex]
    [tex]u' = c[/tex]

    As a side note, this aberration disproves aether dragging. And that in combination with c speed invariance disproves its existence all together.
  14. Feb 24, 2004 #13

    The “space is expanding” story is silly. Space is three-dimensional physical emptiness. Nothing. Space is filled with both matter and fields. The galaxies that are moving, are moving through space. The only thing that is “expanding” in space is their gravity fields that are, sort of, in effect, “stretching” and becoming weaker in the space in-between the galaxies.

    This idea that all the galaxies are “stationary” and are being “carried along by expanding space” is absurd.

    If you run away from me at 5 mph, you are “moving through space” away from me at 5 mph. But, if you get into a car and the car carries you away from me at 5 mph, you are STILL moving away from me at 5 mph. It doesn’t matter if you are being “carried along” or if you are running yourself. You are MOVING away from me, and that’s what the galaxies are doing.

    There are no scientific papers on “expanding space”. There is no physical reason for “space to expand”. There is no such thing as “expanding space”. There are no reports on where this “new space” comes from to augment “pre-existing space”, and there are no reports on how pre-existing space can physically “expand”. So, there is no such thing as “expanding space”.

    If you drive from Chicago to New York, you can’t say the “space” between you and Chicago is “expanding”. That’s nonsense. You are MOVING THROUGH SPACE as you drive, and the DISTANCE between you and Chicago is expanding, but not the “space”.
  15. Feb 24, 2004 #14

    It will some day. For some reason, quite a lot of people in physics like to pretend that “light speed is always the same everywhere”, but of course it is not. Einstein proved that in his 1911 gravitational redshift paper.

    If we have a light beam in our galaxy emitted by the sun, in the direction out toward the edge of our galaxy, that beam will move out toward the edge, and it will take about 20,000 years to reach the outer limits of our galaxy. In the meantime, that beam will be slowly moving sideways, revolving with the sun around the center of our galaxy.

    If we assume the laws of physics are the same everywhere, then light travels through a distant galaxy at, let’s say, an average speed of “c”. If that galaxy is moving away from our own at greater than the speed of light, then obviously the light beams inside that galaxy that are aimed in our direction are not moving toward us at all, but they are moving away from us. So how do the light beams eventually get to us? Davis and Lineweaver explain it in this famous paper of theirs:


    Their term “comoving space” is very misleading. But, they do not want to use the term “ether” or “local ether”, not yet. There is something inside each galaxy and in between the galaxies that acts as a light-speed-regulating medium. For now, Davis and Lineweaver, and most of mainstream cosmology, simply call that something “comoving space”, since they don’t want to call it a “medium”, a “light propagating medium”, or an “ether”. But, as you read their paper, if you just think of it as some kind of “propagating medium” for light, then their paper will make a lot more sense. This “medium” inside a galaxy is a kind of “local” phenomenon, and local mediums travel through space with local galaxies, just as our own local atmosphere travels through space with the earth.
  16. Feb 24, 2004 #15


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    O Great One, please, please note that what David is posting does not correspond with accepted physics.

    The answer to your question lies in the constancy of the speed of light and its implications on space and time: space and time are not constant. In order for different observers to agree on the speed of light (and they always do), they must sometimes disagree on the distance and time over which the measurement was taken (and they do).
  17. Feb 24, 2004 #16
    Sure it does. The Davis Lineweaver paper is mainstream physics. Einstein himself said in his 1911 gravitational redshift paper that the speed of light is variable. He said in his 1916 book that, “the velocity of propagation of light varies with position”. See Chapter XXII.

    What I think you mean is that what I say here often doesn’t conform to junior high school textbook versions of “relativity”, but that’s because the books are written for kids, like when some textbooks still say that electrons “orbit” around atomic nucleuses, even though that concept went out in the 1920s.

    Different observers don’t “always agree” on the speed of light being “constant”. Einstein said it slowed down when it passed near the sun and Shapiro’s experiments proved it did. This is mainstream physics. Look up Shapiro’s papers from the 1960s.

    What you need to do is read more than just that 1905 paper over and over again.
  18. Feb 25, 2004 #17

    I suggest that you read the paper of Davis & lineweaver over and over again.

    They believe in expansion of universe
    They believe that when you measure the speed of light you will always get the same value.
  19. Feb 25, 2004 #18
    Actually, there is a trick to that, that results from a peculiarity of nature. Seems that local atomic clocks slow down in a gravity field just as the local speed of light slows down in a gravity field. So, a slow-ticking atomic clock will measure “c” as the speed of a slow-moving beam of light. So, locally, you will measure “c” for the local speed of light were ever an atomic clock is located.

    Read the Davis Lineweaver paper again and you will see that a photon aimed in our direction, coming from a star inside a superluminal galaxy, is moving away from us at a negative speed, relative to the earth, while it is still traveling through that galaxy. As it gradually leaves that galaxy, it gradually speeds up relative to the earth, and eventually it is received on earth at an earth-relative local speed of “c”, as measured by an earth-based atomic clock.
  20. Feb 25, 2004 #19


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    In short, I agree with Russ.

    David - what are your thoughts on cosmological redshift? (redshift of light associated with the expansion of space)

    Not an appropriate analogy. Galaxies move through space based on gravitational attractions as well as move apart due to the expansion of space. That analogy only mentions the movement part and then uses that as the basis to discount the expansion part. Now, if it takes you X hours to get to New York on a non-expanding highway, it would take you X + Y hours to get there on an expanding highway.
  21. Feb 25, 2004 #20

    What is the “expansion of space”?

    What causes it?

    Does “new space” fill in the gaps between “old space”, or does “old space” just “stretch” and “expand”?

    What are the physical attributes of this “space” that can cause it to “expand”, and what exactly “expands”?

    Are you saying that “nothing” expands and becomes “more nothing” in between the galaxies?

    Gee, I’d call that “motion of the galaxies”.

    When I drive from Chicago to New York, I notice that “space” seems to “expand” between me and Chicago, but I know that is because I’m “moving” toward New York.

    Give us some links to some papers about the physical mechanism of “expanding space”. What causes it and how exactly does space “expand”?

    What ever happened to the initial “big bang” that started all the stuff of the galaxies to moving outward radially from a point? This was what all the astronomy textbooks were saying in the '30s, '40s, '50s, '60s, ‘70s, ‘80s, and ‘90s. They said the galaxies were “moving”. They assured students that the galaxies were absolutely moving.

    So now you say they are not moving, but are being carried along by "expanding space". Come on, man, give us a break. Moving is moving, no matter how you are moving.

    So what physics laws is this “expansion of space” based on?

    There are no such things as “expanding highways” or “expanding space”. There is motion along highways and motion through space.
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