Recent comments in /f/space
Anonymous-USA t1_jcnhzpq wrote
Reply to Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
First off, yes to the part about photons (as waves) traveling indefinitely until absorbed. However, no to the second part — a photon will never reach the “edge of space” for two reasons. First, space itself expands faster than light speed. And second, since space expanded everywhere at once and is isotropic, any random photon has (today) 46B light years of its own observable event horizon in all directions, and there’s plenty of matter filling that space just as within our own observable universe. Whether our own galaxy is within that photon’s event horizon or not.
Snushine t1_jcnhmct wrote
Reply to comment by ReadditMan in Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
They go on forever way up in the sky, and you'll see even more on the fourth of July.
ZealousidealClub4119 t1_jcnhbmz wrote
Reply to comment by Cutecumber_Roll in Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
This is one of the things that periodically blows my mind: look up, and that photon from that galaxy has traveled for millions of years and for a jiffy, and just here its wavefunction has collapsed on one cell in my retina.
ZealousidealClub4119 t1_jcngki0 wrote
FMLAdad t1_jcnga7l wrote
Reply to comment by jmarkmorris in Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
My understanding is that redshift is caused by expansion, and one possible outcome is that photons will indeed redshift into nothing. At that point we would not see other galaxies and they may as well not exist to the observer.
ReadditMan t1_jcnft7u wrote
Reply to Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
🎶 Where do photons go when they die? They don't go to heaven where the angels fly. 🎶
^(I'm sorry)
Cutecumber_Roll t1_jcnfrdo wrote
Reply to Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
From the frame of reference of the photon, time moves infinitely quickly, so it arrives at its destination immediately after departing its origin. If it were to travel forever without ever being absorbed, it would still experience that infinite journey in a single moment of time.
alexkent_200 t1_jcndt08 wrote
Reply to Pillars of Creation - cropped them differently and rotated to show their "frame" by Rockclimber88
Personally, the original Pillars photo is the most metal thing in all of astrophotography for me.
I get goosebumps every time I see the photo.
decrementsf t1_jcncnlk wrote
Reply to Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
Space is round. It eventually travels around and comes back from the other side.
jmarkmorris t1_jcnbw8p wrote
Reply to comment by extra_specticles in Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
I've also wondered about Op's question. What happens as photons continue to redshift? Is there some ultimate redshift where the photon just fades away? Or is this a case of we don't know because we can't observe photons below frequency f. By the way, what is the lowest frequency longest wavelength photon that is observable by state of the art equipment?
extra_specticles t1_jcnas87 wrote
Reply to Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
A photon only has particle like behaviour when interacting with matter, otherwise it behaves like waves and spreads out and is essentially excitations in the electromagnetic field which permeates all spacetime. If there is no interaction, then it's just travelling energy in the field. In effect all travelling photons are in superposition in the electromagnetic field.
Triabolical_ t1_jcmr7nz wrote
The problem with hibernation for space travel is that you need to figure out a way to test it on humans, and I don't see how you can get approval to do that in the west.
[deleted] t1_jcmgwms wrote
Reply to comment by YawnTractor_1756 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
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YawnTractor_1756 t1_jcmg2tq wrote
Reply to comment by s1ngular1ty2 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
>things happening that could not be explained without extra mass or energy
Of course there are ways to explain observations without extra exotic mass or energy, there are several of them including as simple ones as "we've just miscalculated the actual mass of the gas in the universe" to differences in constants through time and/or space. Possibility of different explanations is the whole point of this thread.
Sure, extra mass from exotic particles was the easiest knee-jerk explanation to additional gravitational pull, but it does not make it the right explanation, and decades later we still have no idea if that exotic matter/energy is even there, yet the name continues to confusingly assume it is, and articles that say "dark matter is real" are inherently confusing because they can mean "exotic unknown matter is real" or "observations discrepancies we labeled 'dark matter' are real". And authors know it but still do it for clicks.
InformalPermit9638 t1_jcmfma3 wrote
Reply to comment by s1ngular1ty2 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
https://youtu.be/mvmwqx5vjps?t=328 She handles the data fairly well. You're both rude and dated.
s1ngular1ty2 t1_jcmdxwl wrote
Reply to comment by InformalPermit9638 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
I'm not interested in where you picked up your incorrect understanding. The video I posted is from a PHD in the field. Dark Matter is the accepted theory.
InformalPermit9638 t1_jcmcf5d wrote
Reply to comment by s1ngular1ty2 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
I'm watching now, this article is the genesis of my own belief: https://iopscience.iop.org/article/10.3847/1538-4357/abbb96
Edit: that's a really basic video, I was hoping for something a little more direct lol
s1ngular1ty2 t1_jcmbxtf wrote
Reply to comment by InformalPermit9638 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
Gravitational lensing, CMB analysis, the bullet cluster, etc all prove dark matter exists and MOND doesn't prove how any of these work.
So it's pretty clear MOND is not the answer.
InformalPermit9638 t1_jcm9nlw wrote
Reply to comment by s1ngular1ty2 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
Care to convince me? My mind is open to facts. Everything I've watched and read so far make me favor MOND over the currently favored cosmology.
s1ngular1ty2 t1_jcm8i6e wrote
Reply to comment by YawnTractor_1756 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
The names were invented for REAL observations. They observed things happening that could not be explained without extra mass or energy. The names are made up but the phenomena is real.
All names are made up by the way.
s1ngular1ty2 t1_jcm8b5q wrote
Reply to comment by InformalPermit9638 in In defence of dark energy | Nobel Laureate and dark matter pioneer James Peebles answers critics of dark energy. by IAI_Admin
How though when it doesn't explain all observations? Most scientists don't believe MOND is the answer because of this.
[deleted] t1_jclo50n wrote
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[deleted] t1_jcldx83 wrote
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Anonymous-USA t1_jcni8or wrote
Reply to comment by decrementsf in Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye
Assuming that’s true, a photon could never circumnavigate the universe because the event horizon for that random photon is expanding faster than light speed. It can’t ever catch up. Any random photon anywhere in the universe at this moment has a 46B light year event horizon in all directions. And the universe itself (regardless of its geometry) is larger than the event horizon anyway.