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We observe from a far distant star the red shifted spectrum. This is explained by the expansion of the galaxy and the expanding room between us and this star. S
by WeniTheElder 8y ago
We observe from a far distant star the red shifted spectrum. This is explained by the expansion of the galaxy and the expanding room between us and this star. So the photons coming from there have a red-shifted and hence lesser engery. What has happend to the energy of the photon? Where's it gone to?
- scruple 8y agoWhat happened to the calories that you burned while writing this comment?
- FakeComments 8y agoThat’s a nonsense reply. Those calories are known to dissipate via motion, light, and heat. By contrast, the energy lost to expansion is simply lost, not emitted by the traveling photon through some mechanism. There is no conservation of energy in such a system, so it’s completely unlike the case of burning calories.
- scruple 8y agoShould I add a /s?
- Dylan16807 8y agoIt doesn't seem to make any sense as sarcasm either, so while you're free to do that you'd be better off explaining.
- scruple 8y agoWhy does it have to make any more sense than the original question? I didn't mean anything by it, it was flippant. And all the same, I have a hard time understanding what could otherwise be meant by the GP question. I heard that question in high school physics. It doesn't have an answer today (nor did it in 1998 when I took high school physics) that I'm aware of (which admittedly doesn't mean much). But, it especially doesn't have an answer today (or, in 2013, since that's when the OP article was written) if our notion of what happens to red-shifted photons and their energy depends on the expansion of the universe. Maybe you'd like to postulate a theory to the original question with your own energy expenditure instead of deriding me for mine?
- deleted 8y ago[deleted]
- Dylan16807 8y agoThe question is why the red shift happens, and the proposed answer is that the photons were actually emitted with less energy. It's not a nonsense question. You shouldn't treat it like one. And your weird sarcastic question is just off-topic, not nonsense, so it's very confusing as a counter to begin with.
- scruple 8y agoWell, in my defense, I never intended it as a counter. Like I explained, I was being flippant. I responded with nonsense to something that I originally perceived as being nonsense. I can accept that I was wrong. And, absolutely, in retrospect, at the very least, it was all in bad taste. > The question is why the red shift happens, and the proposed answer is that the photons were actually emitted with less energy. I didn't get that from TFA or the GP question at all. What are you basing that on? What am I missing? A more careful reading?
- jplayer01 8y agoIf you think there's something wrong with his question, this is the kind of place where you formulate that in a clear way, instead of dismissing it flippantly.
- brodsky 8y agoisn't /s a reddit thing, and a really annoying one at that?
- scruple 8y agoSure, yes, this was all in bad taste. I accept that. My apologies.
- greendestiny 8y agoI think the theory is suggesting that the photon was emitted with less energy.
- FakeComments 8y agoDoesn’t this require the photon to be emitted differently depending on where it ends up, as it would experience different amounts of redshift depending on the length of flight? That’s some serious retro-causality if a photon from 13B ly hits us instead of Andromeda.
- michaelcampbell 8y agoWould the star then appear to be a different color to "someone" its own solar system than it does us? Does OUR star thus appear to be moving TOWARD them since it's "our" color vs what "they" would consider to be the correct color for a star our size?
- jajag 8y agoI think the question is that if the current accepted theory for the redshift is correct, then where has the energy gone?
- aroberge 8y agoForget about the expansion of the universe; you could ask the exact same question for an observer moving away from a source and detecting a different frequency (hence energy) of the light emitted due to "normal" Doppler effect in a non-expanding universe. Energy (on its own) is not an invariant in (special/general) relativity. You have the same situation for measurements of lengths (i.e. Lorentz contraction). Energy is one coordinate of a four-vector whose "length" is the true invariant. This is similar to a situation where you draw a set of perpendicular axis on a plane and use them to give coordinates (x, y) to a point. You then rotate the set of axis, keeping the point fix. Your question about the energy amounts to asking "what happens to the x-coordinate of that point?".
- Geee 8y agoThe energy of a photon doesn't go anywhere, it just seems to us to be lower. The observed energy of a photon depends of the relative motion. If you move at the same velocity as the observed object, the redshift disappears and the energy of photon is there.