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Questions tagged [redshift]

Redshift refers to the difference in frequency of an electromagnetic wave as measured by a source versus a receiver in relative motion.

Redshift typically refers to the difference between the frequency of an electromagnetic wave as measured by its source and the frequency as measured by a receiver when the source and the receiver are in relative motion. When differentiated from "blueshift", it refers to a decrease in frequency, while "blueshift" refers to an increase in frequency.

The name "redshift" derives in the context of astronomy in comparison of spectral lines in the humanly visible range of electromagnetic waves; concerning distant (and, generally, receding) stars as senders, and human observers on Earth as receivers (with the sun as a reference star).

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Red shifted to what?

I searched and found a lot of questions and answers about red shift here but none with the answer to mine. (sorry if it is there somewhere and I did not find it.) Everyone is saying the light from the far away galaxies is red shifted and I could…
OCTAV
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Can gravitational waves be red-shifted?

Whenever the Doppler effect is mentioned, it's typically in the context of sound waves or electromagnetic radiation. On the cosmological scale, red-shifting is also important because of the enormous speed of receding galaxies, thanks to the…
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Wouldn't Miller's planet be fried by blueshifted radiation?

In Interstellar, wouldn't Miller's planet be fried by blueshifted radiation? The 61,000x time dilation multiplier would make even cosmic background radiation photons into extreme UV photons. I was told that this is off-topic for Science Fiction &…
blademan9999
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How can the rest-frame spectrum of redshifted light be determined?

The redshift effect must work on all frequencies, so blue would be shifted down to some lower frequency, and ultra violet would be shifted down also, into the visible area. How would you know what part of the (pre-redshifted) spectrum you were…
peter
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Redshifted Photon Energy

A photon emitted from a receding source (Doppler redshift) has less energy when detected at an observer's location. Please explain the energy loss from the perspective of energy conservation.
Michael Luciuk
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Does red shift evidence necessarily imply that the universe started from a singularity?

We are taught that the universe began as a singularity - an infinitely small and infinitely dense point. At the beginning of time there was a 'Big Bang' or, more accurately, 'Inflation'. The main evidence for this is the observation of the red shift…
david4dev
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If space is "expanding" in itself - why then is there redshift?

The "kid's" way of understanding the expanding universe is that: "space" is totally "ordinary", and all the galaxies are expanding through it (like an explosion). Of course, that's wrong. The usual better explanation is that "space itself is…
Fattie
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Does the Earth's rotation affect redshift measurements?

How do you account for the spin of the earth in the mechanical sense, when measuring redshift? Does the relatively slow speed of the earth have a major change in the measurement because of distance?
Charlie Currie
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Why isn't the De-Broglie wavelength of massive particles redshifted in an expanding universe

It is pretty straight forward how light is redshifted in an expanding universe, yet I still can't understand why the De'Broglie wavelength of a massive particle isn't redshifted in an expanding universe. There is no proper notion of conserved mass…
R. Rankin
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Galaxy getting closer faster than light

In cosmology, we speak of galaxies racing away from us due to the expansion of the universe. The light from these galaxies appears red-shifted. If the galaxies are far enough, then the space between us actually expands faster than light, and light…
Alon Navon
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With redshift, energy is lost. Where does it go?

A photon emitted by a distant source billions of light years away arrives here with a lower frequency hence less energy than it started with. What happened to the energy?
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Why doesn't the escape of electromagnetic waves from a microwave depend on the reference frame, because of the Doppler effect?

If an observer traveling towards a microwave oven at almost the speed of light blue shifts the microwaves enough to be visible light, how can the mesh on the oven door still stop to waves from escaping the oven? And conversely, if an observer…
samwa
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Is it possible to create a mirror that redshifts light?

Mirrors are able to reflect light but are not perfect and after a number of reflections, light loses intensity. However I wonder, during the reflection by a different type of mirror, could the light photons lose some energy and thus be red shifted…
Winston
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Is there a thermodynamic heuristic argument on why a redshifted blackbody spectrum is a blackbody at a new temperature?

Without calculating it, it isn't obvious to me that if you take Planck's Law for the spectral radiance as a function of temperature of a black body and shift all the frequencies by the same factor, you will get a curve that is also a blackbody…
Mark Eichenlaub
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When will the CMB reach radio wavelengths?

How long will it take for redshift to turn the microwave-frequency photons from the CMB into radio frequency? Into the CRB, if you will.
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