Editing Talk:2926: Doppler Effect
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:Edit - There appears to be a "just" in there that I missed, changing the meaning of the sentence somewhat. Never mind. [[Special:Contributions/172.68.22.151|172.68.22.151]] 19:58, 29 April 2024 (UTC) | :Edit - There appears to be a "just" in there that I missed, changing the meaning of the sentence somewhat. Never mind. [[Special:Contributions/172.68.22.151|172.68.22.151]] 19:58, 29 April 2024 (UTC) | ||
::My understanding is that there is relative motion between the galaxies, but there is also redshift caused by the expansion of space while the light was traveling, which would occur even if the galaxies were at rest. And IIUC for most galaxies this is the dominant effect -- the Doppler shift caused by the motion of galaxies when the light was emitted is small, but the cosmological redshift caused by the light traveling for a long time is large. [[User:Vyzen|Vyzen]] ([[User talk:Vyzen|talk]]) 21:54, 29 April 2024 (UTC) | ::My understanding is that there is relative motion between the galaxies, but there is also redshift caused by the expansion of space while the light was traveling, which would occur even if the galaxies were at rest. And IIUC for most galaxies this is the dominant effect -- the Doppler shift caused by the motion of galaxies when the light was emitted is small, but the cosmological redshift caused by the light traveling for a long time is large. [[User:Vyzen|Vyzen]] ([[User talk:Vyzen|talk]]) 21:54, 29 April 2024 (UTC) | ||
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The bit about the Doppler effect being similar to a bullet fired from a moving car is simply incorrect. That's vector addition of velocities. Sound traveling from a source is going to travel at the speed of sound in the medium, and the only addition of velocities would be to the extent that the car is moving the air around it. Also, the Doppler effect doesn't make sounds louder, that's simply a function of the distance between you and the source changing, independent of velocity. Edited the text accordingly. [[Special:Contributions/172.70.42.213|172.70.42.213]] 20:00, 29 April 2024 (UTC) | The bit about the Doppler effect being similar to a bullet fired from a moving car is simply incorrect. That's vector addition of velocities. Sound traveling from a source is going to travel at the speed of sound in the medium, and the only addition of velocities would be to the extent that the car is moving the air around it. Also, the Doppler effect doesn't make sounds louder, that's simply a function of the distance between you and the source changing, independent of velocity. Edited the text accordingly. [[Special:Contributions/172.70.42.213|172.70.42.213]] 20:00, 29 April 2024 (UTC) | ||
:Although firing an automatic firearm from a moving car can make a pretty decent analogy, as the bullets will pass a person the car is moving toward more frequently or a person the car is moving away from less frequently. Though I think drive-by shootings are probably not the ideal metaphor to use in classrooms. Perhaps a nerf gun? [[Special:Contributions/172.69.246.148|172.69.246.148]] 20:38, 29 April 2024 (UTC) | :Although firing an automatic firearm from a moving car can make a pretty decent analogy, as the bullets will pass a person the car is moving toward more frequently or a person the car is moving away from less frequently. Though I think drive-by shootings are probably not the ideal metaphor to use in classrooms. Perhaps a nerf gun? [[Special:Contributions/172.69.246.148|172.69.246.148]] 20:38, 29 April 2024 (UTC) |