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Tags space , lost , photons

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Old 6th December 2005, 08:49 PM   #1
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Photons lost in space

Just a quick dumb question for those Physics minds in-the-know.

All of the billions and billions of stars are emitting light, and other, energy constantly and continously (for the most part). Some of this we receive here on our nice planet earth. Obviously most of this tremendous amount of energy we never receive but is traveling to all of the other stars and planets in the Universe. What effect does all of this energy traveling or "photons lost in space" have on current theories of the Universe or does it not count much because it has no mass?
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Old 7th December 2005, 08:24 AM   #2
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Is this thread in any way related to this thread
http://www.internationalskeptics.com...ad.php?t=48603
or is this some spooky quantum entanglement thingy?

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Old 7th December 2005, 09:55 AM   #3
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Old 7th December 2005, 10:25 AM   #4
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Talking slip of the anti-finger

slip of the finger/anti-finger
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Old 7th December 2005, 11:41 AM   #5
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In an attempt to address your anything-but-dumb question, at the easy level, if massless photons hadn't done what they have done over the last 14 billion yrs +-, and continue to do today, we wouldn't be discussing things.

At the other level, someone conversant with, say, supersymmetry could help with the big picture; quantum electrodynamics math would assist in more mundane matters.

And I could be wrong ...
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Old 7th December 2005, 04:54 PM   #6
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The first thought that comes to mind is a consideration of Richard Feynman's transactional interpretation of quantum mechanics. Specificaly the point that no photon can depart from an electron unless it knows that it will be 'caught' by another electron at the 'end' of it's journey. If there is no electron in to catch it in a particular direction -- no photon will every be emmited in that direction.

This makes the universe a closed system where no photons are 'lost'.
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Old 7th December 2005, 05:24 PM   #7
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That's an interesting thought Molinaro, however I just can't accept that is true. Sounds as if electrons should apply for Randi's millions dollars if they always know that the photon will always be captured or else they will not emit them!

If it is true then I ask if Richard defined any time limit from emition to reception? In the mean time, with all of those photons floating around the Universe looking for a place to land my original querry still stands.

I suppose my question may not be dumb but I am asking it in a dumb way because I just don't know a better way to ask. It just seems as if there is a tremendous amount of energy that we don't see when we look into space, but it is there nontheless. It has no mass but once it lands it will have an effect. Is it having any effect on the grand scheme of the Universe without landing on anything?
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Old 7th December 2005, 05:52 PM   #8
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Originally Posted by Molinaro View Post
The first thought that comes to mind is a consideration of Richard Feynman's transactional interpretation of quantum mechanics. Specificaly the point that no photon can depart from an electron unless it knows that it will be 'caught' by another electron at the 'end' of it's journey. If there is no electron in to catch it in a particular direction -- no photon will every be emmited in that direction.

This makes the universe a closed system where no photons are 'lost'.
I think that only applies to virtual photons, which are mediating the electric force. Other photons can be generated for all sorts of reasons, like when a particle/antiparticle collide.
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Old 7th December 2005, 10:52 PM   #9
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Actualy it aplies to all photons. The mathematics that you get from this interpretation is identical to the Copenhagen interpretation and that governs all photons.

It goes like this...

When a photon is emited, it actualy radiates sphericaly through time AND space. That is to say, a portion of the photon travels forward in time while another portion travels backwards. The forward seeking portion of the photon is actualy 1/2 of the wave that an observer would see. This photon travels until it hits another electron. At that time, the 1/2 photon reflects backward -- in time -- along the same physical path back to the emiting electron. It also continues on forward.. but more on that in a moment.
Since the outgoing 1/2 wave follows the same path as the reflected 1/2 wave, and they are both going at C, an observer only sees their constructive interference that is seen to be traveling forward in time as a 1/2 + 1/2 = 1 wave of the photon.
When the backward traveling 1/2 wave reaches the emiting electron it continues back in time. This backward traveling 1/2 wave will then be creating destructive interference with the original backward traveling 1/2 wave from the emiter. A similar destructive interference occurs at the reciever. It consists of the original 1/2 forward traveling wave from the emiter, and the newly created 1/2 wave traveling forward from the receiver. As the receiver also creates a pair of 1/2 waves at the reflection event. One traveling back in time the other forward.
The net result is that the constructive interference only occurs between the emiter and the receiver and a whole wave is only ever observed traveling forward in time from emiter to receiver, at a speed of C.

Interestingly, from the point of view of the photon, it exists as a standing wave extending between the 2 electrons -- instantaneously -- since the journey takes 0 time when moving at a speed of C. This also leads to the view that it is the electrons reflecting back and forth, in time, off of the static photons.

I find this interpretation much more pleasing than the collapsing probability waves of the Copenhagen interpretation. It also has the pleasing effect of offering a much simpler interpretation of the Aspect experiment without requiring any paradox involving foreknowledge of the layout of the experiment by the photon. It also negates the need for an observer.

The photon, sends out a 'sphere' of 1/2 waves in all directions (forward and backward in time), and the one following the most probable path (path of lowest energy) is the only one that reflects back along that one path to re-enforce itself and instantiate that path as the true path followed by the photon.

Hence, a photon will only be emited if it 'knows' that it will be caught.


Now, as far as my own ideas go.. I think if this realy is what is going on, the momentary constructive and destructive interference of differing source photons that would momentarily occur throughout all of space could play a role in the source of the creation/destruction of virtual particles. But that's just a guess.
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Old 8th December 2005, 06:51 AM   #10
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I probably misunderstand this topic, but that's not going to stop me from asking a question:

If only the photons that will get caught are ever emmitted, doesn't this affect the energy output of stars?

By this I mean, we calculate the amount of energy that a star generates and we assume it sends out this energy in a reasonably uniform sphere, but if only those paths that ends up in another particle the photon can be absorbed by, actually get a photon, this means that we observe a disproportionately large part of the photons emmitted by e.g. the Sun. The "sphere" of light emmitted isn't a sphere but rather a porcupine.

If this is correct, the stars emmit a lot less energy then previously thought, and this would make some drastic changes to some theories.


Mosquito - waiting for the "lies to children" that will confuse me into comfort on this subject.
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Old 8th December 2005, 08:56 AM   #11
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If the undetected photon (probability wave?) radiates spherically, then it will inevitably be intercepted eventually.

No?
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Old 8th December 2005, 12:10 PM   #12
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When I talked about the spherical spread I was not refering to a collection of photons, but rather an individual photon -- or better yet -- each individual photon.

The photons, who appear as both particle and wave to us, are actualy the moving region of intersection of the 2 wavefronts. One is moving forward in time, the other backwards. From both the emmission and absorption points the 2 waves emminate, and their points of intersection along the path of least energy is that which we see as a photon moving forward in time at C. Everywhere else off that path the waves combine destructively and nothing is measured -- within the limits of the uncertainty principle.
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Old 8th December 2005, 12:24 PM   #13
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What if there are two points in the sphere that are equidistant from the photon? Does it split into two and each electron gets half the energy? Is another photon spontaneously converted in the same spot to go off to the alternate destination?
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Old 8th December 2005, 12:39 PM   #14
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I don't mean to say anything more than that if a photon is observed, that photon is part of a triplet consisting of emmision, travel, and absorption. I am not saying anything about why it left. For those emiting and absorbing electrons, the path of least energy between them is the one the photon will have been observed to travel.

The single event of the emission of a single photon involves the shere expanding out from the electron -- in space and in time. When that intersects an electron who will absorbe it, at some point in the future, another is then emmited from that second electron. The backwards traveling portion of it's emission reinforces the orginal event's forward traveling wave along the path of least energy. Elsewhere they cancel. Because elsewhere they cancel at every point in time as well, there is no oportunity available for any other 3rd party electron to have absorbed it instead.
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Old 8th December 2005, 02:26 PM   #15
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Originally Posted by Molinaro View Post
The first thought that comes to mind is a consideration of Richard Feynman's transactional interpretation of quantum mechanics. Specificaly the point that no photon can depart from an electron unless it knows that it will be 'caught' by another electron at the 'end' of it's journey. If there is no electron in to catch it in a particular direction -- no photon will every be emmited in that direction.

This makes the universe a closed system where no photons are 'lost'.
That was John C. Cramer, not Feynman. Look here for the entire paper:
www.npl.washington.edu/tiqm/TI_toc.html

Basically, it's a time thingy. A photon is not emitted from an electron until it receives a "handshake" from it's future ineraction partner. Good reading.
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Old 9th December 2005, 06:37 AM   #16
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OK, so from a this QM perspective of photons, there are no such things as "photons lost in space" because if they are not ultimately captured then they are not emitted. It still sounds as if the emitting electrons should apply for the million dollar prize as the description of the process involves time travel backwards
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Old 9th December 2005, 06:58 AM   #17
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The idea that they should not be emitted unless known to be absorbed sounds absolutely absurd (but so do other things in QM). But how does an electron "know" anything? An electron is an electron is an electron. How can an electron contain information if it is supposed to be identical to all other electrons (down, Kumar, down!)?

Now, this may be a stupid answer, but isn't it that those photons that have been emitted and have not been absorbed are simply still out there someplace? They are just racing on into the infinite. And since there is matter distributed in the universe, and it is infinite, then they will hit matter, sooner or later.

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Old 9th December 2005, 09:17 AM   #18
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Originally Posted by John Bentley View Post
That was John C. Cramer, not Feynman. Look here for the entire paper:

[EDIT)
**URL removed since I can't post them yet**
[/edit]

Basically, it's a time thingy. A photon is not emitted from an electron until it receives a "handshake" from it's future ineraction partner. Good reading.

From your link:

"The basic element of TI is the transaction describing a quantum event as an exchange of advanced and retarded waves, as implied by the work of Wheeler and Feynman, Dirac, and others."

Feynman is the one who started it all, others expanded on it. Cramer is the guy given credit for the theory as it stands under the name Transactional Interpretation.

I always think of it as Feynman's... personal prejudice I guess.. since he's my favorite!
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Old 9th December 2005, 09:22 AM   #19
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Originally Posted by CrossHair View Post
OK, so from a this QM perspective of photons, there are no such things as "photons lost in space" because if they are not ultimately captured then they are not emitted. It still sounds as if the emitting electrons should apply for the million dollar prize as the description of the process involves time travel backwards

The math in all other interpretations of QM have already suggested negative energy and negative momentum solutions to the equations that have up to now simply been discarded and ignored as being not part of reality. In their place, for example in the Copenhagen interpretation, it is said that a probability wave expands out from the emmiting electron. That probability wave is said to have no physical substance or energy to it. That is not exactly a more realistic view.

Instead, in the Transactional interpretation, the emmiting electron sends out 2 'real' fields of energy.. one forward and one backward in time. The forward seeking field upon interacting with a receiving electron will cause it to emit it's own pair of forward and backwards seeking fields.

There is no advance knowledge needed by the emitting electron because the backward traveling field from the receiver arrives at the EXACT MOMENT of emmission! It is that receipt of a 'handshake' that allows that moment of emmission to take place in the 1st place.
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Old 9th December 2005, 01:52 PM   #20
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Originally Posted by Molinaro View Post
From your link:

"The basic element of TI is the transaction describing a quantum event as an exchange of advanced and retarded waves, as implied by the work of Wheeler and Feynman, Dirac, and others."

Feynman is the one who started it all, others expanded on it. Cramer is the guy given credit for the theory as it stands under the name Transactional Interpretation.

I always think of it as Feynman's... personal prejudice I guess.. since he's my favorite!
Well, of course! Isn't he everyones? But IIRC Feynman's work showed that retarded waves (hard to even write that without smiling) were accounted for and predicted by the math, but Feynman didn't pursue that aspect precisely because it would mean that waves were travelling backward in time. I could be wrong about that, it has been a long time since I read about it.
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Old 9th December 2005, 05:17 PM   #21
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Question

Thanks to all that have replied! I am clearer about certain things but I am still bothered by something. As with many thing about QM the solution is similar to the old "dead cat in a box" canundrum. The photons are not there unless you look at them, essentially. However, my question deals with the Universe and in this case study (humor me here) I could suppose that photons might be emitted directly out and never recieved by anything back in this Universe (for now we will ignore if the photon could, or would, be pulled back by gravity). If this synario happens then would the Universe, as we obserse it, be losing energy? (loss of photons)
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Old 9th December 2005, 05:32 PM   #22
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With regards to our universe, a photon in it has no access to "outside".

And in a sense a photon is everywhere in the universe until it is 'observed', although 'undergoes decoherence' is perhaps a better way to say it.
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Old 9th December 2005, 06:05 PM   #23
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It seems to me (not that I've really got a clue) that everything is fixed until you choose to measure it through a dimension.

Thus, every photon's path through time and space is in the wider sense, fixed. In no dimensions it appears as a solid model of its journey.
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Old 9th December 2005, 07:09 PM   #24
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Originally Posted by hodgy View Post
It seems to me (not that I've really got a clue) that everything is fixed until you choose to measure it through a dimension.

Thus, every photon's path through time and space is in the wider sense, fixed. In no dimensions it appears as a solid model of its journey.
Not sure what you're getting at here, but I think you've got it backwards - at least to most interpretations of QM.

1. Nothing is fixed until it is measured in the quantum world, as everything exists as a probability wave until then. Thus Schrodinger's cat is both alive and dead until you look. Classical or Copenhagen interp.

2. All possibilities for every single quantum event occur. Each possibility is a different universe unto itself. Many Worlds interp.

3. Then there is the Transactional interp which we have been discussing above, of which Molinaro gave a good summary.

I personally like #3 because it eliminates the need for an observation to be made before an event occurs. It also eliminates the proposition of infinite universes. And it eliminates the particle/wave duality, as every quantum particle is declared as both. It's only drawback is requiring travel backwards through time - but that's easier to get my head around than the others.
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Old 9th December 2005, 07:24 PM   #25
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Originally Posted by John Bentley View Post
It's only drawback is requiring travel backwards through time - but that's easier to get my head around than the others.
What relieves me from worry there is that solutions to Maxwell's equations always give you the -ve side that everyone throws away.
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Old 9th December 2005, 08:49 PM   #26
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Originally Posted by Molinaro View Post
When I talked about the spherical spread I was not refering to a collection of photons, but rather an individual photon -- or better yet -- each individual photon.

The photons, who appear as both particle and wave to us, are actualy the moving region of intersection of the 2 wavefronts. One is moving forward in time, the other backwards. From both the emmission and absorption points the 2 waves emminate, and their points of intersection along the path of least energy is that which we see as a photon moving forward in time at C. Everywhere else off that path the waves combine destructively and nothing is measured -- within the limits of the uncertainty principle.
You're quite right, except that it isn't exactly the path of least energy (I assume that you're referring to a Laplacian framework). It is most of the time. It's the path of highest absolute value of amplitudes integrated over all possible paths as if it were a classical particle (which, of course, it isn't). There are a number of interesting cases where this isn't the path of least energy.
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Old 9th December 2005, 09:19 PM   #27
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I'm sure that there's plenty of room for correction. It's hard to decide how far to go when trying to keep it clear and simple for someone not familiar with the subject. I purposefully didn't look anything up while making the posts and instead relied on 'how I remember it', in general terms.
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Old 9th December 2005, 10:07 PM   #28
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I've been trying to think through this (and thanks for all the simplified summaries), and I've got a question. Since in this framework, all photons will interact with something, would this let us test for stuff "out there"? Suppose we have a positron source, so we get electron-positron production of 2 x-rays, which will have roughly opposite momentum. By detecting one of these x-rays we can say that the other x-ray must be going off in the opposite direction, or else momentum isn't being conserved.
So supposing the universe were non-infinite (say, we happen to be convinently close to the edge of all matter), would we detect no x-rays being sent inwards, because they can't be sent outwards, since there would be nothing to interact with?
I suppose it doesn't really matter with an infinite universe (or a finite universe is impossible, I don't know a lot of astrophysics), although I wonder if the finite-light cone of the universe could affect that. Information can't be transmitted faster than light (as far as I understand special reletivity), so for an photon to be sent towards something the electron has to have had the chance to "see" the other electron (they would have to be inside the light cone of each other, I'd think).
So, crazy? Wrong interpretation? Not a possible distinction from other models?
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Old 10th December 2005, 09:57 AM   #29
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Originally Posted by Molinaro View Post
I'm sure that there's plenty of room for correction. It's hard to decide how far to go when trying to keep it clear and simple for someone not familiar with the subject. I purposefully didn't look anything up while making the posts and instead relied on 'how I remember it', in general terms.
Fair enough. I just think that it's important to point out that the highest probability is at a local minimum, and there are a number of interesting cases where there are several local minima e.g. frosted glass.
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Old 10th December 2005, 10:10 AM   #30
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I've often thought of a similar test. Have the device on some satelite, point it right at the earth or out into distant 'voids' in our view of the distribution of galaxies and see if anything correlates.


And Epepke, yes that is a good clarification to refer to it as a local minimum rather than 'the minimum'.
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Old 10th December 2005, 10:15 AM   #31
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Originally Posted by epepke View Post
Fair enough. I just think that it's important to point out that the highest probability is at a local minimum, and there are a number of interesting cases where there are several local minima e.g. frosted glass.
Yeah, IIRC, this also explains the rainbow effect on CD's and the same effect from oil on top of water. Feynman's "QED" explains it well.
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Old 10th December 2005, 01:47 PM   #32
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Originally Posted by Dilb View Post
I've got a question. Since in this framework, all photons will interact with something, would this let us test for stuff "out there"? Suppose we have a positron source, so we get electron-positron production of 2 x-rays, which will have roughly opposite momentum. By detecting one of these x-rays we can say that the other x-ray must be going off in the opposite direction, or else momentum isn't being conserved.
So supposing the universe were non-infinite (say, we happen to be convinently close to the edge of all matter), would we detect no x-rays being sent inwards, because they can't be sent outwards, since there would be nothing to interact with?
OK, I am going to keep flogging this horse we all agree is dead! But this still seems like an interesting question.
Maybe I am just trying to attract more flies.
Same synario as quoted above but stated differently. Say that you could simple point a flash-light to someplace with nothing to receive the photons. The excited electrons in the filament will not emit photons. Does the energy simply go to heat only? or do they just get more and more excited? (could lead to funny jokes here...) Maybe this is why some flash-lights have to be beaten first before they work, they aren't excited enough yet to emit...
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Old 10th December 2005, 05:08 PM   #33
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Originally Posted by John Bentley View Post
Not sure what you're getting at here, but I think you've got it backwards - at least to most interpretations of QM.

1. Nothing is fixed until it is measured in the quantum world, as everything exists as a probability wave until then. Thus Schrodinger's cat is both alive and dead until you look. Classical or Copenhagen interp.
Unless you count measurement as a dimension. I can well imagine that everything exists as a wave. 2d through 3d, 3d though time, time through 4d etc.... That suggests to me that the probability (uncertainty) is the result of not knowing all the dimensions. In a world where all dimensions are perceived a photon's route is a solid artifact.
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Old 10th December 2005, 07:15 PM   #34
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Originally Posted by CrossHair View Post
Does the energy simply go to heat only? or do they just get more and more excited?
Heat is photons too. just a different wavelength than visable light.

BTW, this seems similar to Schrödinger's cat. The cat exists in both states until observerd. The photon radiates everywhere until captured.

ETA: oh darn it, someone else made the Schrödinger's cat reference already.
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Old 11th December 2005, 01:37 AM   #35
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Originally Posted by kevin View Post
Heat is photons too. just a different wavelength than visable light.
I thought heat could be described as something along the lines of "average kinetic energy" or something like that, of the particles involved. (of course I think my wording is even more off than my understanding!).

Anyway, from what I understand, some wavelengths of light are emitted by most forms of matter due to the fact that they are in a state of high kinetic energy (maybe when particles collide? I don't know). This represents some of the energy of that heat being dissipated in the form of photons, which, when they are later absorbed, will tend to increase the kinetic energy of whatever absorbs them.

Meaning that hot things emit photons, and whatever absorbs those photons becomes hotter.

But that's different from saying that heat is photons.

Do I understand this in any way resembling reality?

edited to fix quote
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Last edited by Roboramma; 11th December 2005 at 01:39 AM.
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Old 11th December 2005, 11:01 AM   #36
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Originally Posted by Roboramma View Post
I thought heat could be described as something along the lines of "average kinetic energy" or something like that, of the particles involved. (of course I think my wording is even more off than my understanding!).
The words get very confused here. Temperature is related to the average kinetic energy of an ideal gas. Even this neglects some important factors, such as the angular motion of molecules and the band structure in metals.

Heat is more complex. Two objects can be at the same temperature, but much may have more heat than the other. I cooked a turkey yesterday. The turkey was actually at a lower temperature than the air in the oven but had a lot more heat.

Quote:
Do I understand this in any way resembling reality?
I think so.

Obviously, the bit about photons is about radiated energy, which is sometimes also called heat, though it's really a way that heat gets transferred. For much of our experience, hot things radiate in infrared, but of course a hot light bulb filament also radiates in visible light.
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Old 11th December 2005, 01:32 PM   #37
John Bentley
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Originally Posted by hodgy View Post
Unless you count measurement as a dimension. I can well imagine that everything exists as a wave. 2d through 3d, 3d though time, time through 4d etc.... That suggests to me that the probability (uncertainty) is the result of not knowing all the dimensions. In a world where all dimensions are perceived a photon's route is a solid artifact.
Still not sure what you're getting at. How can measurement be a dimension? And your argument about a world where all variables are known is impossible in the real world, although even Einstein denied it. It's pretty much a fact that our reality comes with unmeasurable uncertainty. Look up Heisenberg uncertainty principle for the details. http://zebu.uoregon.edu/~imamura/208/jan27/hup.html
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Old 12th December 2005, 12:53 AM   #38
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Thanks epepke, especially for the clarification of the distinction between heat and temperature! I feel dumb for not seeing that.
It sounds like heat is more of a measure of the total energy of a body whereas temperature is a measure of the average energy?
(in very broad terms? and of course realising that we're only talking about one specific type of energy.)
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Old 12th December 2005, 01:08 AM   #39
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Stick your hand into the 350 degree oven. Does it burn you? OK, now do you dare touch the side of the oven? Of course not. That's the difference between temperature and heat; the air and the side are at the same temperature, but the air is far less dense and therefore can hold a lot less heat.

Essentially, temperature is a measure of the average kinetic energy per molecule; heat is a measure of the total kinetic energy of all the molecules together (note- not the vector sum- if the vector sum of the kinetic energy of the molecules of an object is not zero, the object is moving!).
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Old 12th December 2005, 11:17 AM   #40
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Originally Posted by Roboramma View Post
Thanks epepke, especially for the clarification of the distinction between heat and temperature! I feel dumb for not seeing that.
It sounds like heat is more of a measure of the total energy of a body whereas temperature is a measure of the average energy?
(in very broad terms? and of course realising that we're only talking about one specific type of energy.)
In very broad terms, yes. Specifically, for ideal gases.

Heat, however, can be stored in other ways than temperature. For example, if you put heat into a piece of ice, it will warm up. Same with water. However, if the ice melts, it takes a lot of heat but doesn't change temperature (ideally, not at all; in practice, a little).
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