Where do the photons that hit my retina go when I finish with them?<p>If they have infinite lifetimes then does each one carry a memory of it's creation event? When I burn a log in my fireplace and a cinder flares and pops creating a spark, does the photon exist after the spark energy flares out and the cinder is no longer illuminated enough to be detected by my eyes?<p>If photons are infinite then harvesting light would be the first step in deciphering the complete history of the universe. All that would be left for us to do would be to derive the algorithms to unravel and categorize each photon into discrete groups based on their historical particle paths.<p>If we wanted to harvest light to test whether photons have infinite lifetimes we would need to design a structure that forms a light trap using materials with different refractive indices so that photons entering are forced onto paths from which they perfectly reflect in a lossless manner.<p>If photons are infinite then mirrors may have a memory if we can trap and monitor the photons that pass through them and force them to unravel their travel paths. Why can't I step in front of the mirror and have it replay every event that the mirror has seen? It would be a better replacement for photo or video mementos of lost loved ones if we could simply take the mirrors from their homes and spin back to watch their happiest moments forever by reconstructing the photon impingement history of the glass and mirror substrate.
From the perspective of a photon, there is no such thing as time. It's emitted, and might exist for hundreds of trillions of years, but for the photon, there's zero time elapsed between when it's emitted and when it's absorbed again. It doesn't experience distance either.
Interesting. I had no idea that the universe would eventually be basically just photons. I wonder if that is why Stephen Baxter had his 'photino birds' as the final form of life in his Xeeleverse?
Isn't it a meaningless question? Photons aren't things, but loosely localized areas of motion energy that's temporarily assumed the shape of a photon. Upon collision with other similar waves, it may change shape and become another partickey like an electron. But the light itself is a motion itself, which is a pure abstraction. At the end of the universe, photons probably will keep spreading over larger and larger areas, slowly turning into a uniform sea of that pure motion.
Here, a second time, I point to this measured exchange of gravitational waves for photonic waves. If photons come from gravity, can photons end as gravity; and then do they have an infinite lifetime?<p><a href="https://news.ycombinator.com/item?id=40090332">https://news.ycombinator.com/item?id=40090332</a>
Huh? Light has zero lifetime, along with all massless particles. When you travel at <i>c</i> your clock doesn’t tick. From the viewpoint of a photon it is emitted and absorbed at the same instant. You cannot decay if you don’t experience time. I’m not sure exactly how index of refraction works with this.
Since there is no time from the perspective of a photon, there is only one photon everywhere at anytime. Our perception of multiple photons is incorrect. Its just multiple timelines with the same photon.
I feel like this article could be condensed into a simple answer. I got tto annoyed looking for it to find more than the answer, "yes, if the standard model holds"<p>So at the risk of venting unconstructively, I wish I had a way of screening physics writing that is not a physics paper. Articles like this are frustrating because they only have one or two interesting tidbits for me, but they hide them in a whole lot of highschool level hand waving.<p>Honestly HN would be perfect if it only allowed physics papers - no pop-physics - and if it banned any blogs or news sites with paywalls or newsletter nagware (looking at you, medium, new york times).<p>Alas. I'm wishing for something I will have to build if I really want it.