Photon Questions: Atom-Atom Travel & Purpose

  • Context: Undergrad 
  • Thread starter Thread starter Darken-Sol
  • Start date Start date
  • Tags Tags
    Photon
Click For Summary

Discussion Overview

The discussion revolves around the nature of photons, their behavior in relation to atoms, and various hypothetical scenarios involving their travel and interaction. Topics include the emission and absorption of photons, the implications of photon entanglement, and the effects of gravity on photons, with a focus on conceptual understanding rather than established facts.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question whether photons travel from every atom to every other atom in the universe and if one could see another atom from a given atom's perspective.
  • There is uncertainty about the number of photons emitted by atoms and whether the number remains constant, with some suggesting that photons are emitted randomly and not directed towards specific atoms.
  • Participants discuss the vast number of atoms and photons in the observable universe, with estimates suggesting a significant disparity between the two.
  • Some participants propose that photons absorbed by dust are re-emitted in random directions, complicating the path of photons traveling to an observer's eye.
  • Questions arise about the behavior of photons at rest, their interaction with gravity, and the possibility of orbiting non-black hole objects.
  • Entanglement is mentioned, with participants expressing curiosity about its implications and limitations, particularly regarding information transfer.
  • There are humorous analogies made about photons needing to keep moving to "live," with discussions on energy loss and redshift in expanding space.

Areas of Agreement / Disagreement

Participants express various viewpoints on the behavior and properties of photons, with no consensus reached on several key questions, particularly regarding the nature of photon travel and entanglement.

Contextual Notes

Limitations include the lack of clarity on definitions of terms used in the discussion, assumptions about the behavior of photons in different environments, and unresolved questions about the implications of gravity on photon behavior.

Darken-Sol
Messages
160
Reaction score
0
are there photons traveling from every atom to every other atom in the universe? hypothetically, if i were standing on an atom and i looked in any direction at another atom would i be able to see it? also what purpose does a photon have besides carrying information?
 
Space news on Phys.org
should have went to wiki first. last question answered. i can't find an answer to the first question though. and the second was just to describe my line of thinking.i didnt understand the absorbing and emitting. is there always the same number of photons? it seems unlikely since most of them are heading away from everything.
 
Photons are emitted in finite quantities, generally in a random direction from an atom, and not towards any specific atom.
 
Drakkith said:
Photons are emitted in finite quantities, generally in a random direction from an atom, and not towards any specific atom.

an atom was a poor choice i was trying to simplify my thought. i have trouble getting answers because i lack the terminology everyone uses. from any frame of reference, does every atom send photons my way?i mean i can see every thing in this room. i find it absurd to think one big table photon is how i see a table.
 
There are ~1080 atoms and ~1089 photons in the observable universe. Your scenario would require ~ 10160 photons.
 
BillSaltLake said:
There are ~1080 atoms and ~1089 photons in the observable universe. Your scenario would require ~ 10160 photons.

how did u come across those numbers?
 
Darken-Sol said:
does every atom send photons my way?i mean i can see every thing in this room. i find it absurd to think one big table photon is how i see a table.

If the room were completely dark, then there would be no external source of photons impinging on the atoms of the table. If the table were near absolute zero, then it would be emitting virtually no photons in the form of black body radiation.

Normally though, neither of the those conditons are true.

The table has been irradiated with heat from a room tempature environment, so it is continually abosrbing and remitting photons, a portion of which are in the infrared range.

The table is also in a lighted room, meaning it is constantly being bombarded by photons from the lgiht source, and is merely reflecting those photons. Turn up brightness of the lights, and more bombardment by photons and more re-emission of them from the object (i.e. it is easier to see).

How many photons?

Here's an article that talks about it.
http://zfacts.com/p/791.html

Basically, a candle, even at .0017 watts, emits enough light for millions to billions of photons to enter your eye every second.

And here's another that says in the room you're in right now (assuming it has a single bulb emitting 25-watts of visible light) there are on the order of one hundred billion photons.
http://scienceblogs.com/builtonfacts/2009/03/counting_photons.php

Photons are massless, chargeless and bosonic - many can occupy the same volume of space simultaneously.
 
Last edited by a moderator:
a photon from a star is traveling to my eye. if this photon gets absorbed by a speck of dust on the way, it then reemits as a (speck of dust) photon? or it wings of in a random direction and i never see it.
 
Darken-Sol said:
a photon from a star is traveling to my eye. if this photon gets absorbed by a speck of dust on the way, it then reemits as a (speck of dust) photon? or it wings of in a random direction and i never see it.

If an atom in that dust absorbs the photon, it will most likely emit another photon (not the same one) in a random direction. It is POSSIBLE that emitted photon from the dust could continue in the same direction, but very very unlikely. The ways that atoms absorb and emit light is fairly complicated and you would need to get into quantum mechanics to accurately describe them.
 
  • #10
Darken-Sol said:
a photon from a star is traveling to my eye. if this photon gets absorbed by a speck of dust on the way, it then reemits as a (speck of dust) photon? or it wings of in a random direction and i never see it.
Effectively, the absorption and emission are to be treated separately. Regardless of how it absorbs photons, it will simply emit photons in a random direction as blackbody radiation.
 
  • #11
  • #12
after a bit more studying i have more questions.
what happens to a photon at rest? or they don't rest?
if they are affected by gravity can we cause one to orbit something? besides a black hole?
if a photon is entangled what is the limit of messing with it and getting results for its partner?
 
  • #13
Darken-Sol said:
after a bit more studying i have more questions.
what happens to a photon at rest? or they don't rest?
if they are affected by gravity can we cause one to orbit something? besides a black hole?
if a photon is entangled what is the limit of messing with it and getting results for its partner?

1] Photons always travel at c.
2] It is sort of possible to get photons to orbit a BH, but the orbit is not stable. (Photons aren't subject to losing velocity as they climb away from a gravity well, so an elliptical obrit won't work. You'd have to make it circular.)
3] Entanglement is a whole nother kettle of wax...
 
  • #14
DaveC426913 said:
1] Photons always travel at c.
2] It is sort of possible to get photons to orbit a BH, but the orbit is not stable. (Photons aren't subject to losing velocity as they climb away from a gravity well, so an elliptical obrit won't work. You'd have to make it circular.)
3] Entanglement is a whole nother kettle of wax...

i read somewhere photons travel at c in a vacuum, but they can be slowed in a medium.
i was wondering if we could send an entangled photon into a black hole and collect data from the other one.
 
  • #15
A photon has to keep moving or it dies, just like sharks. [OK not exactly like sharks.]
 
  • #16
BillSaltLake said:
A photon has to keep moving or it dies, just like sharks. [OK not exactly like sharks.]

but where does the energy go?
 
  • #17
Bit of a joke above. The momentum is proportional to the energy of a photon in free space. These are proportional to 1/a, where "a" is the expansion parameter. In free space, a photon always travels at c with respect to any local frame regardless of how much stretch has occurred (i.e., how big a has become). The energy just disappears in that it does not flow anywhere. The energy loss is equivalent to putting a group of blackbody photons in a perfectly reflective cube with (increasing) side length "a". The increase will redshift the photons inside.
 
  • #18
Darken-Sol said:
i was wondering if we could send an entangled photon into a black hole and collect data from the other one.
Entanglement cannot be used to transmit information.
 

Similar threads

High School Confused About the Source of CMB Photons: Two Possibilities
  • · Replies 7 ·
Replies
7
Views
3K
Undergrad Does a photon travel freely through the CMB photon gas?
  • · Replies 10 ·
Replies
10
Views
2K
High School Expansion of space affecting photon's energy
  • · Replies 11 ·
Replies
11
Views
4K
Undergrad Some questions about Cosmic Microwave Background radiation
  • · Replies 13 ·
Replies
13
Views
7K
Undergrad What atoms are we made of, how much is from the big bang?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Do atoms recoil when emitting a photon?
  • · Replies 38 ·
2
Replies
38
Views
7K
Undergrad Is the supply of the observable CMB radiation limited?
  • · Replies 50 ·
2
Replies
50
Views
5K
Undergrad Photons being blueshifted when crossing evolving voids?
  • · Replies 0 ·
Replies
0
Views
2K
Undergrad What are the implications of this "Negative Time Experiment"?
  • · Replies 19 ·
Replies
19
Views
3K
Undergrad How Does a CMB Photon Travel Through Expanding Universe?
  • · Replies 39 ·
2
Replies
39
Views
6K