Do photons wear out? An astrophysicist explains light’s ability to travel vast cosmic distances without losing energy
https://theconversation.com/do-photons-wear-out-an-astrophysicist-explains-lights-ability-to-travel-vast-cosmic-distances-without-losing-energy-252880
11 Comments
Uh…..no. Do electrons wear out?
Next question!
Does light really travel ‘cosmic distances’? I mean, considering length contraction?
or
If photons experience no time or distance due to traveling at light speed, can we really say they ‘travel’ across the universe – or is that just our perspective?
– Oh, never mind – that’s what the article is about. 🙂
They do lose energy due to Hubble expansion as they travel, downshifting from higher frequencies like ultraviolet to lower like infrared. AKA redshift.
Veritasium just did a very good video on energy conservation, highly reccommend
Cepheid variable stars help us determine the distance of galaxies because we know the intrinsic brightness of those objects, then we measure the apparent brightness to come up with the distance. The implication is that Cepheid variable stars, and all objects, lose apparent brightness over long distances. Is that because they lose energy due to loss of energy, or is it because of that photon’s interaction with intergalactic space?
I was just asking a physicist about this a week ago! Cool answer!
Does gravitational lensing by intermediate heavy objects in any way slow downPhotons? I think the answer is that the shortest distance is not a straight line when gravitational wells interfere. That is, geodesic distances maintain the speed of light of a photon.
It will always blow my mind that, from the photon’s perspective, the photon was “created” and landed on my eyeball at the same time. Meanwhile it took X-amount of light years to reach me.
Energy is not conserved over long distances:
https://youtu.be/lcjdwSY2AzM?si=ScgCON6_7F7dOpjz
If protons have a mass we cannot yet measure and gains or loses energy along the way based on its interactions with its surroundings. Definitely wear out and gain energy along its path.
This is probably me just being annoying rn but I kind of don’t understand the value of these articles outside of just sharing basic physics facts to a lay audience that are completely separate to the question being posed (“do photons wear out”).
The truth is we have no fucking idea *why*, just that that is indeed the case. Explanations that relate to some other aspect of physics that gives rise to this, such as being massless and thus not experiencing x,y,z types of interactions which would wear it out, is not an explanation of why, per se. It is a series of connected facts that contextualised the properties we assign to photons but they do not actually explain “why”. Science doesn’t interact with “why” for the most part.
The answer is literally “just because”. Why don’t they do X or y? Because we measured them and they didn’t do X or y. That’s the closest we may ever get to a real explanation – it is this way because the universe said so.
It is the same argument as for the various fundamental constants. You could explain “why” the fine structure is 1/137 by appealing to all the situations where it needs to be this number for the universe to work or by appealing to some underlying phenomena that sets it at 1/137. But the former example is a truism and the latter example just kicks the can down the road by making it so you need to explain “why” the underlying formula that leads to 1/137 is the way it is to be able to truly explain “why” the fsc is then 1/137. And at its base there is no reason why that can be proven or disproven by physics, the underlying constants are just … There.