Science
1 lurker |
36 watchers
Nov 2023
3:54pm, 17 Nov 2023
48,511 posts
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HappyG(rrr)
So the benefit of this thread is that you get ambulances and weee-waaww explanations, instead of that sciency-wiency stuff that Google gives you?  G
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Nov 2023
3:54pm, 17 Nov 2023
48,512 posts
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HappyG(rrr)
And TOTP!
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Nov 2023
3:56pm, 17 Nov 2023
48,513 posts
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HappyG(rrr)
I think faster towards you would be compressing the wave, so increasing the frequency, so my guess is red shift is slower towards / moving away faster, but that's a guess. I refuse to Google.
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Nov 2023
4:11pm, 17 Nov 2023
15,920 posts
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jda
Not bending but stretching of light waves. HG has it. (Bending due to gravity does come into astronomy in other ways, the wikipedia page on "gravitational lensing" explains...) |
Nov 2023
4:17pm, 17 Nov 2023
41,568 posts
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Nellers
I was about to post what you just did HappyG(rrr), more or less. It's called redshift exactly because of that: As an object moves away from you it elongates the frequency of the light waves and makes them appear more red. I think that the degree of red shift is directly proportional to the relative speed that you and the observed object are moving apart. I've not heard "blueshift" as a thing but I assume it's the same effect in reverse. I understood it to be the same effect as Doppler shift but I don't know if there's a difference in how each of the terms are applied. Is Redshift only light waves? Is Doppler Shift an umbrella term and Redshift is a type of Doppler effect? I don't know. I understand that this is one of the ways astronomers can confirm that the universe is expanding. |
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Nov 2023
4:33pm, 17 Nov 2023
48,514 posts
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HappyG(rrr)
I assumed redshift is only light (what would red sound be?!) so a light specific subset of Doppler effects? Or perhaps Doppler name only applies to sound?
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Nov 2023
4:40pm, 17 Nov 2023
21,092 posts
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rf_fozzy
Doppler shift is the umbrella term for the effect for all wave types (including pressure waves - e.g. sound) Redshift/Blueshift is for EM radiation only. |
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Nov 2023
4:42pm, 17 Nov 2023
21,093 posts
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rf_fozzy
To just complicate things a tad, there is also a relativistic Doppler effect too. Which is where special relativity gets involved. |
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Nov 2023
5:02pm, 17 Nov 2023
41,571 posts
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Nellers
Let's stick to the non-relativistic explanations please, Fozzy. It's been a long week!
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Nov 2023
3:09pm, 19 Nov 2023
3,647 posts
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Steve NordRunner
Red shift is a type of Doppler effect, but not all Doppler shifts are red shifts. The Doppler effect is the apparent shift in frequency or wavelength of a wave that is perceived by an observer when the source of the wave is moving relative to the observer. This effect can be observed in both sound and light waves. When an object is moving away from us, the light waves emitted by the object are stretched out, which makes them have a lower frequency and moves them towards the red end of the electromagnetic spectrum, where light has a longer wavelength. This is called «redshift» and is an example of the Doppler effect. However, redshifts observed in distant objects are not exactly due to the Doppler phenomenon, but are rather a result of the expansion of the universe. Conversely, blueshift occurs when an object is moving towards us, the light waves are bunched up, and are moved towards the blue end of the electromagnetic spectrum, where light has a shorter wavelength.
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