Is there red shift evidence for light?

In summary, there is laboratory confirmation for red shift for light, with examples such as speed guns, laser Doppler velocimetry, and GPS. The Sputnik satellite and satellite orbit experiments also provide evidence for red shift. Additionally, cooler stars being more red is not the same as a red shift, as the latter refers to the location of spikes on a spectrogram. Red shift is caused by the motion of its primary source, and there is no other explanation for the patterns seen in far away stars.
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bartrask
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I'm aware of the doppler effect for sound waves. But light waves are different, e.g., light travels through a vacuum but sound does not. Has there been any laboratory confirmation for red shift for LIGHT. I could find only ONE paper by Bélopolsky, A. in 1901 using rotating mirrors. But there were no photos; only numerical data. Thank you.
 
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Have you ever seen a police "speed gun"? It works by comparing the frequency of the outgoing electromagnetic waves with the ones reflected back from the moving car. The difference in frequency caused by the Doppler shift tells you how fast the car is going. Does this satisfy you, or does it have to be visible light? If so, try reading about laser Doppler velocimetry. It works the same way but uses laser light to measure the velocity of fluids. Another example is that GPS receivers use the Doppler shift to calculate your velocity. There are many, many more examples.
 
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Speed guns and laser doppler velocimetry refer to doppler shift caused by the REFLECTION of light. GPS is by trilateration of radio signals. Red shift of stars is taught as caused by movement of light from its primary source i.e. not shifted by reflection.
Is there empiric laboratory evidence that light can be red shifted by the movement of its primary source?
 
  • #5
bartrask said:
Speed guns and laser doppler velocimetry refer to doppler shift caused by the REFLECTION of light. GPS is by trilateration of radio signals. Red shift of stars is taught as caused by movement of light from its primary source i.e. not shifted by reflection.
Is there empiric laboratory evidence that light can be red shifted by the movement of its primary source?

Yes. See the following link for an explanation of the experiment. (About 1/3 of the way down the page)

http://spiff.rit.edu/classes/phys314/lectures/doppler/doppler.html
 
  • #6
bartrask said:
Speed guns and laser doppler velocimetry refer to doppler shift caused by the REFLECTION of light. GPS is by trilateration of radio signals. Red shift of stars is taught as caused by movement of light from its primary source i.e. not shifted by reflection.
Is there empiric laboratory evidence that light can be red shifted by the movement of its primary source?
It's true that the first two are a reflected signal, although I'm not sure why it matters. But for GPS, the radiation is emitted by the GPS satellite, and your receiver looks at the frequency it receives and compares it to a reference to determine your velocity. Also, try looking up the Doppler shift in reference to the Sputnik satellite. Observers were able to calculate the satellite's speed by the shift in frequency of the detected radiation. Also, here is a nice study of using satellite Doppler shift to measure a satellite's orbit. Since in all of these cases, the satellite is emitting the radiation, they should meet your criteria.

What is your point? Are you trying to argue that the Doppler shift, which is clearly in the category of well established science, might not occur? If so, I urge you to re-read the rules of this site, since you are close to violating them.
 
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In addition to those experiments, there is really no other explanation for what we see when we look at far away stars. How else could we get familiar patterns of spikes on a spectrogram, but at the wrong frequencies?
 
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In the Book Big Bang by Simon Singh, he mentions that cooler stars are more red. How is this different from a red shift? i.e., if all spectra are red shifted, how can we tell whether it's due to the star receding or from being cooler?
 
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When we say that a star is "red shifted", we are not talking about the color it appears to the naked eye, but to the location of the spikes I was just talking about. The sun looks redder at sunset, but if you did a spectrograph at sunset the spikes would be in exactly the same places. Nothing else but motion can move the spikes.
 
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  • #10
bartrask said:
In the Book Big Bang by Simon Singh, he mentions that cooler stars are more red. How is this different from a red shift? i.e., if all spectra are red shifted, how can we tell whether it's due to the star receding or from being cooler?

If you look at the spectra of two stars, one blue and hot, the other red and cool, the emission and absorption lines for each element are in the exact same spots in each spectrum. Redshift causes these lines to move.
 
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You can have some minor variance due to gravitational redshift, but, is not much a factor for most stars.
 

1. What is red shift evidence for light?

Red shift evidence for light is a phenomenon observed in the light from distant objects in space. It is the result of the Doppler effect, where the light waves are stretched out and appear redder when an object is moving away from us. This is due to the expansion of the universe and is a key piece of evidence for the Big Bang theory.

2. How is red shift evidence for light measured?

Red shift evidence for light is typically measured using a spectrometer. This device separates the light into its different wavelengths and can detect any shift towards longer, redder wavelengths. The amount of red shift is then used to calculate the object's velocity and distance from us.

3. Is red shift evidence for light only observed in visible light?

No, red shift evidence for light can also be observed in other parts of the electromagnetic spectrum, such as radio waves and infrared light. This is because the Doppler effect affects all types of waves, not just visible light.

4. What is the significance of red shift evidence for light in cosmology?

Red shift evidence for light is significant in cosmology because it provides evidence for the expansion of the universe and supports the Big Bang theory. It also allows us to measure the distance to faraway galaxies and study the history of the universe.

5. Are there any other possible explanations for red shift evidence for light?

While the most widely accepted explanation for red shift evidence for light is the expansion of the universe, there are other possible explanations. These include the tired light theory, which suggests that the light waves lose energy as they travel through space, and the gravitational red shift, which is caused by the bending of light near massive objects like galaxies.

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