How can photons be localised if the universe is expanding?

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Offline DoctorBeaver

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My little beaver brain is working overtime again. This is what its murky depths have churned out this time.

As has been explained elsewhere, for a photon travelling at c time has no meaning. In fact, time doesn't really exist for it. It therefore follows that a photon could be everywhere in the universe at the same time. But the universe is expanding, so there is now more "everywhere" for it to be in than there was at any time in the past. How can the photon be everywhere at once if everywhere is getting bigger?

 [???]
« Last Edit: 21/12/2008 10:20:19 by chris »
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Offline Soul Surfer

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Its not just photons beaver quanum mechanics implies that every particle and quantum is everywhere in the universe over all time.  its just that the probability of being in most places other than where it is, is rather small!!!
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Offline DoctorBeaver

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Ian - I am aware of that, but I think you have missed my point; to whit, the infinite time dilation aspect of travelling at c.
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lyner

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its just that the probability of being in most places other than where it is, is rather small!!!

Could we change that to "its just that the probability of appearing in most places other than where conventional Science would predict, is rather small!!!"

?


The existence of a quantum particle 'everywhere' is fine by me. Anything to avoid trying to specify where it 'is, exactly' rather than where it has an effect. At c, a photon is, effectively anywhere because it can 'choose to' reveal itself, instantly in any one of a number of places, depending on its probability function (the diffraction pattern with which it's associated), because it exists independently of time.

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Offline Soul Surfer

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To answer your question the universe is not getting bigger from the edges its getting bigger from all over and that is why the cosmic microwave bacground radiation which was like starlight when it was generated is now srtetched right out into the microwave region.
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Offline Soul Surfer

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Sophie I think you've got it a bit wrong there It depends a bit who's time you are talking about the photon doesn't "know anything about time between it being created in an interaction and it being destroyed in another interection.  from our point of view it can have been created as part of the cosmic microwave background flash a few hundred thousand years after the big bang travelling a long way from a specific direction and arriving at our detector and being absorbed at a clearly definable location.
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Offline DoctorBeaver

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I know about the expansion not being from the edges.

Let me try saying this a different way. If nothing stops a photon from travelling then, theoretically, it could eventually actually have been at all points in the universe. Time has no meaning for a photon. Therefore it would have been at all those points simultaneously. But as the universe is expanding (and for this thought experiment it doesn't really matter how that expansion is happening) there are more points being created all the time that the photon could be at.
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lyner

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SS
You don't appear to be disaggreeing with what I wrote. The production and destruction of a photon will be observed in 'our' space / time. The conditions which determine when and where are determined by the experimental setup (including, if you like, the BB). Because it is not 'experiencing time' the photon can know instanly (from our viewpoint) where it needs to have started and where it needs to finish its journey between source and detector. CBR would behave just the same as light from a light bulb in this respect.

In fact what I am saying is that many of the difficulties and 'paradoxes' can be resolved by looking at the problem this way and not thinking of a photon as being at a point, ever.
DrB
Your problem with points in between being generated by expansion is dealt with because the only thing that matters is where / when the ends of the experiment are. The photon doesn't have to 'be' anywhere in between.
« Last Edit: 20/12/2008 11:30:55 by sophiecentaur »

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Offline DoctorBeaver

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SC - there is no experiment involved in what I'm saying; just a photon - any photon - travelling at c. It doesn't get measured in any way. Put yet another way, how does that photon "view" the expansion of the universe if time doesn't exist as such?
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lyner

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If you're observing anything it can be an experiment. You can't have a photon unless it's produced by something and you have no idea where it is or when it is unless it is absorbed by something.  Of course it is 'measured' at both ends. The atom it interacts with has measured it, effectively, when it decides if it has the right energy for an interacton  and the one which chucked it out used a 'measured' amount of energy to make it with. We are considering a testable hypothesis in this discussion!


How does it 'view' the expansion? That's almost not a valid question because it would have to see a rate of change of displacement which implies dividing a distance by time. Dividing by, effectively, zero will give the impression of an 'infinite' or indeterminatly rapid step change between the emission and absorption events. But, as the photon doesn't really need to exist except at each end of the process, why should it (or we) care?

How's that, Dr B?

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Offline DoctorBeaver

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Re: How can photons be localised if the universe is expanding?
« Reply #10 on: 20/12/2008 23:34:11 »
SC

What you said...
Quote
If you're observing anything it can be an experiment.

What I said...
Quote
It doesn't get measured in any way.

Right, forget that intelligent observers exist. Early enough in the universe's history there weren't any anyway.

A photon gets created somewhere, somehow - could be the CMBR or something else; it doesn't matter. Off the photon goes on its journey through the universe without interacting with anything else (unlikely, but theoretically possible). If spacetime is closed then there is the possibility that it will travel through every point in space - actually travel through every point. From the perspective of the photon, such a journey would take zero time. But, in fact, by the time the photon has indeed made its journey, the universe has expanded. So, is it true to say that from the photon's point of view, the universe has expanded in zero time?

Or, if you prefer to think of it this way, take a photon emitted from the Sun and heading towards the Earth. It takes roughly 8 minutes in our time, but zero time to the photon due to the infinite time dilation. In the 8 minutes of our time that elapse, the relative positions of the Sun and the Earth has changed. How does that change "look" to the photon in zero time? How can something happen if there is zero time for it to happen in?
« Last Edit: 20/12/2008 23:35:42 by DoctorBeaver »
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lyner

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Re: How can photons be localised if the universe is expanding?
« Reply #11 on: 21/12/2008 00:50:25 »
I can see that you are still insisting that, somehow, the photon (like a bullet) is speeding on its way from a to b. If you look at it that way then I can see there may be a problem. But why does it have to exist between a and b? The only places and times that you can prove it's there are at each end of 'its' journey.
There is a great difference between a photon and all other so-called particles. An electron can make a journey and make its presence felt by many systems on the way - giving a little (in principle, measurable)  nudge to every charge it passes. But a photon only interacts at each end of its 'journey'. As far as I can see, then, it is not necessary to consider what it is getting up to on the way - it gets up to nothing, in fact. I also hold that the 'it', to which we refer , is just the energy, which will behave according to the wave with which it's associated. It can't  / needn't be considered as a particle except where it is interacting.

You seem to be over concerned about the changing distance between source and detector - why should that concern an object which doesn't really exist on the journey? What about the situation where source and detector happen to be approaching each other at the same speed that the space between them is expanding - wouldn't that situation be just as difficult to explain?

My way of looking at it is not to say "Off the photon goes on its journey through the universe without interacting with anything else" because, for a start, you can only say that it hasn't interacted yet. I say it is potentially everywhere at all times between its creation and its absorption. It's journey is only described once it has actually completed the two interactions.

There is, of course, a very finite time involved in the interactions at each end because they are, essentially, resonances which take time to build up. As far as the photon is concerned, the two ends could be one atom's width or the whole universe apart.

The bullet picture makes it extremely difficult to reconcile the effects of diffraction - requiring a message to travel instantly all around the Universe to tell all other atoms that the photon has arrived 'here' and can't be seen anywhere else. But, even in the simplest, two slits, experiment, something has to tell each photon that it is part of a number of others which must, somehow sort themselves out into an interference pattern - which will always occur when there are 'enough of them'. It's a nightmare this way round; stick to the wave interpretation.

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Offline DoctorBeaver

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Re: How can photons be localised if the universe is expanding?
« Reply #12 on: 21/12/2008 08:47:46 »
For what I'm trying to get at, it doesn't matter whether it's a particle or a wave. So, let's say that "...the wave could propogate through every point in space..." and be throughout the whole of space at the same time. Space is still expanding and there is still zero time for the photon.
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lyner

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How can photons be localised if the universe is expanding?
« Reply #13 on: 21/12/2008 12:48:25 »
OK but so what?
Are you after finding out what the photon 'experiences'? What do you mean by 'the photon'?
If ,as I suggest, it doesn't exist except where it interacts then it's not 'like anything' for the photon. There isn't a photon for it to be like for.

It's a bit like sending a TV picture over a link. The picture exists at each end but it doesn't travel across the link in the form of a picture. It would not make sense to talk in terms of the picture during the transit time of the signal - all you could say would be that the link characteristics could affect what the picture turned out like.

Or. I have this idea and you are receiving it (and understanding what I say - or gnashing your teeth about that idiot the other end). The text, the binary signal from the keyboard, the wi fi signal from computer to router, etc etc are not the IDEA, they only carry a representation of the idea.
For me, the photon is just what 'goes on' during the interactions each end. It would be meaningless to discuss its existence except where / when it exists.

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Offline DoctorBeaver

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How can photons be localised if the universe is expanding?
« Reply #14 on: 21/12/2008 13:11:51 »
That sounds as if you're saying that in between the photon being emitted and being detected it doesn't exist anywhere. From everything I've read, that is simply not the case. Also, I've seen it proposed in physics text books that an electron can be everywhere at once.
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lyner

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How can photons be localised if the universe is expanding?
« Reply #15 on: 21/12/2008 14:54:41 »
Yes - I'm saying just that. Or, rather, that it has no meaning or reason for considering it as existing. I suppose it's a bit a a Zen thing - like "when a tree falls in the forrest, does it make a sound if there's no one to hear it?". But that is a bit of Zen nonsense because there are plenty of things for a falling tree to interact with and there is no interaction for a photon to have on the way.

Yes- I've read the same thing but that doesn't mean it's the best way to look at things. There isn't a 'right answer' to any of this stuff. All you can do is get a theory together which predicts most events as accurately as possible.
The wave theory gives the right answer about where to expect light to turn up (it gives a probability distribution) and the particle theory gives a good answer about how the quanta of energy in the wave will interact (the quantum of energy and the momentum).
Until I thought out this way of looking at it I had a terrible problem reconciling the two approaches. I have yet to hear a coherent (no pun intended) way of explaining what happens, in terms of photons, during diffraction. And you have to remember that every 'photon' follows the rules of diffraction in every circumstance! Diffraction is always there.

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Offline DoctorBeaver

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How can photons be localised if the universe is expanding?
« Reply #16 on: 21/12/2008 22:29:28 »
So the expansion of the universe has no effect on photons?
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Offline Bikerman

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How can photons be localised if the universe is expanding?
« Reply #17 on: 21/12/2008 23:34:23 »
Yes expansion has an effect.
If you consider the point the photon was emitted and the point it is detected (presuming that the two are separated by large (intergalactic) distances) then the red-shift of the photon is a measure of the expansion between the two points (after we subtract the gravitational red-shift/blue-shift).

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lyner

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How can photons be localised if the universe is expanding?
« Reply #18 on: 22/12/2008 00:44:29 »
Yes. That is an energy matter. Another problem for the 'traveling photon' model. The photon would need to have both energies at the same time because it could not be changing 'with time'.
« Last Edit: 22/12/2008 01:09:19 by sophiecentaur »

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Offline Bikerman

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How can photons be localised if the universe is expanding?
« Reply #19 on: 22/12/2008 05:11:44 »
The problem with photons (I think) is there is no non-mathematical language which can
be applied. You cannot construct a spacetime diagram for a photon (well, you can, but you just end up with the y-axis, or you have to construct a Minkowski diagram with ct as the y-axis and the photon as a 45 degree plot). Therefore it is meaningless to talk about time from a photon's POV, unless you are doing a translation...

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Offline 3lviis

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How can photons be localised if the universe is expanding?
« Reply #20 on: 22/12/2008 08:11:37 »
As has been explained elsewhere, for a photon travelling at c time has no meaning.
Your basic premise is flawed. Time has no meaning without the observable context of mass. Photons have mass(albeit infinitesimally small mass). This is the reason why black holes can capture light....if photons had no mass they would pass by black holes. Also effects like gravitational lensing would not be observed if photons had no mass.

"It therefore follows that a photon could be everywhere in the universe at the same time."

Time does exist for photons (because they have mass) which is why they cannot accelerate past the speed of light in a vacuum.

"But the universe is expanding, so there is now more "everywhere" for it to be in than there was at any time in the past."

Is it really? All of this conjecture is based on the Big Bang theory, the red shift and the premise that the Doppler effect of sound translates into the Doppler effect of light. In fact it doesn't and cannot be proven to. Why you ask? Because we have yet to discover a way to accelerate light past the speed of light.

When you decelerate sound the frequency becomes lower. When you decelerate light the frequency becomes lower (observable shift toward the red spectrum).
When you accelerate sound waves the frequency becomes higher. When you accelerate the speed of light what happens? The answer is no one know because you cannot accelerate the speed of light.

This explains why we see a red shift in the universe and no corresponding blue shift. And it explains why scientist incorrectly came to the conclusion that all matter originated from one point.

What science hasn't explained is why we have yet to discover the universe's edge. The point at which we can no longer see mass. Everywhere we have looked there has been mass.

newbielink:http://www.youtube.com/watch?v=fgg2tpUVbXQ [nonactive]

I believe that the reason we haven't discovered the edge of the universe is because there is no edge and that the universe is infinite.

Other problems with the big bang theory is that the rate of expansion of the universe according to theory had to be improbably precise in order for the atoms to coalesce into the galaxies we have today. Any infinitesimally small increase would have resulted in  a universe of scattered atoms. Any infinitesimally small decrease would have resulted in all the matter coagulating into one massive lump. Many groups point to this improbability as evidence of a Prime mover. I point to it and say that it is evidence of a flawed theory.

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Offline DoctorBeaver

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How can photons be localised if the universe is expanding?
« Reply #21 on: 22/12/2008 09:20:18 »
As has been explained elsewhere, for a photon travelling at c time has no meaning.
Your basic premise is flawed.

It's not my basic premise. Please take up the issue with Richard Feynman, Stephen Hawking & Lisa Randall as it was in books by them that I read it first.

Quote
Because we have yet to discover a way to accelerate light past the speed of light.

That statement is a total nonsense. If you accelerate light past the speed of light then the speed of light has increased and you would have to accelerate it again to get past it which will increase it... ad infinitum.
« Last Edit: 22/12/2008 09:22:54 by DoctorBeaver »
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Offline DoctorBeaver

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How can photons be localised if the universe is expanding?
« Reply #22 on: 22/12/2008 09:24:07 »
I should also like to point out that the title of this thread has been changed and no longer reflects my initial question.
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Offline DoctorBeaver

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How can photons be localised if the universe is expanding?
« Reply #23 on: 22/12/2008 09:28:37 »
Yes expansion has an effect.
If you consider the point the photon was emitted and the point it is detected (presuming that the two are separated by large (intergalactic) distances) then the red-shift of the photon is a measure of the expansion between the two points (after we subtract the gravitational red-shift/blue-shift).

But, surely, that is only from an observer's POV. The photon itself won't "notice" it.
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lyner

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How can photons be localised if the universe is expanding?
« Reply #24 on: 22/12/2008 11:23:09 »
If, indeed, it's "there" to notice anything.

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Offline DoctorBeaver

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How can photons be localised if the universe is expanding?
« Reply #25 on: 22/12/2008 12:13:33 »
If, indeed, it's "there" to notice anything.

Well, yes.
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Offline yor_on

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Re: How can photons be localised if the universe is expanding?
« Reply #26 on: 24/12/2008 16:50:33 »
I can see that you are still insisting that, somehow, the photon (like a bullet) is speeding on its way from a to b. If you look at it that way then I can see there may be a problem. But why does it have to exist between a and b? The only places and times that you can prove it's there are at each end of 'its' journey.
There is a great difference between a photon and all other so-called particles. An electron can make a journey and make its presence felt by many systems on the way - giving a little (in principle, measurable)  nudge to every charge it passes. But a photon only interacts at each end of its 'journey'. As far as I can see, then, it is not necessary to consider what it is getting up to on the way - it gets up to nothing, in fact. I also hold that the 'it', to which we refer , is just the energy, which will behave according to the wave with which it's associated. It can't  / needn't be considered as a particle except where it is interacting.

You seem to be over concerned about the changing distance between source and detector - why should that concern an object which doesn't really exist on the journey? What about the situation where source and detector happen to be approaching each other at the same speed that the space between them is expanding - wouldn't that situation be just as difficult to explain?

My way of looking at it is not to say "Off the photon goes on its journey through the universe without interacting with anything else" because, for a start, you can only say that it hasn't interacted yet. I say it is potentially everywhere at all times between its creation and its absorption. It's journey is only described once it has actually completed the two interactions.

There is, of course, a very finite time involved in the interactions at each end because they are, essentially, resonances which take time to build up. As far as the photon is concerned, the two ends could be one atom's width or the whole universe apart.

The bullet picture makes it extremely difficult to reconcile the effects of diffraction - requiring a message to travel instantly all around the Universe to tell all other atoms that the photon has arrived 'here' and can't be seen anywhere else. But, even in the simplest, two slits, experiment, something has to tell each photon that it is part of a number of others which must, somehow sort themselves out into an interference pattern - which will always occur when there are 'enough of them'. It's a nightmare this way round; stick to the wave interpretation.

SC I read your thoughts with great interest, there are more than you sharing this view.

Still, what does that make the sun?
Isn't that a source of 'light' aka photons?

If there is no 'distance' involved,why do they need a source relative us measured as at a distance?
I'm sorry if I sound 'meta-physical' here, but if they are this in woven' in spacetime, why do 'they' (mostly) get created from 'sources' we measure as being 'distant' in space?

No disrespect meant SC, you are all interesting, I'm just trying to get a 'grip' of how you and others see it:)
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Offline ukmicky

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How can photons be localised if the universe is expanding?
« Reply #27 on: 24/12/2008 17:15:01 »
As has been explained elsewhere, for a photon travelling at c time has no meaning.
Your basic premise is flawed. Time has no meaning without the observable context of mass. Photons have mass(albeit infinitesimally small mass). This is the reason why black holes can capture light....if photons had no mass they would pass by black holes. Also effects like gravitational lensing would not be observed if photons had no mass.

"It therefore follows that a photon could be everywhere in the universe at the same time."

Time does exist for photons (because they have mass) which is why they cannot accelerate past the speed of light in a vacuum.

Gravitational lensing and the reason photons cant escape blackholes is due to space and the path that photons take through it being bent. Gravity has no direct affect on a photon. 

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Offline Mr. Scientist

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How can photons be localised if the universe is expanding?
« Reply #28 on: 24/12/2008 19:13:24 »
My little beaver brain is working overtime again. This is what its murky depths have churned out this time.

As has been explained elsewhere, for a photon travelling at c time has no meaning. In fact, time doesn't really exist for it. It therefore follows that a photon could be everywhere in the universe at the same time. But the universe is expanding, so there is now more "everywhere" for it to be in than there was at any time in the past. How can the photon be everywhere at once if everywhere is getting bigger?

 [???]

Localization is at a cost though. The Uncertainty inherent in matter, requires it's path be complimentary. Sure, you can localize a particle, if you are willing to give up your time to observe an infinite amount of paths simultaneously.

It would require impossible odds.
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Offline yor_on

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How can photons be localised if the universe is expanding?
« Reply #29 on: 09/01/2009 10:26:37 »
This is one of the many things making photons fascinating.

But we have sources for them.
We have interactions with them at different places in spacetime.
Even though they may change 'entity' in those interactions.
We can still construct a 'particle path' from them.
That will follow everything we know about light.

For us to have that 'shimmering weave' :) of 'light' hiding everywhere.
We don't seem to need any 'sources' at all.

And our ideas of how energy transforms seems childish if so.
As this potential is everywhere, not needing any 'source' at all to my eyes.
But it might be right.

A 'field' of light overlaying a 'field' of time overlaying a 'field' of space all seemingly centered around matter.
And no distance?

It is like we really have two different realities coexisting at all time.
In one there is three dimensions and time creating distance motion space light and matter.
All of them entities by themself.

And then we have ?
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lyner

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How can photons be localised if the universe is expanding?
« Reply #30 on: 09/01/2009 22:37:49 »
yor_on

You say that all those photons 'come from' the Sun. I would agree that photon interactions take place between atoms in the Sun and in your eyes. Between those places, the light behaves like a wave - it is refracted and diffracted on the way. Why can't that be enough?

Why is the idea of Photons being like little bullets such an attractive one, I wonder?

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How can photons be localised if the universe is expanding?
« Reply #31 on: 10/01/2009 12:45:01 »
Yes SC, I see some as coming from the Sun.
Most of them we see in fact:)

And I have no problem with accepting them to be waves, if traveling in spacetime.
What I have problem with is the idea that they only will exist as a 'interaction'.

To me that imply, if that idea is correct of course:) that they would exist independent of any source.
Accepting that view, all our ideas of spacetime seems to collapse.
Then what are what we call sources?

We have built spacetime around concepts as distance motion 'c' etc.
All of those seems questionable, to say the least, if we allow for photons to be at 'all paths'.

Our descriptions 'falters' if you see how I think:)

----------

Then again.
We can send coherent laser light in a very straight path, can't we?
And if we measure that specific wave length outside what we might call its 'path' it won't be there, right?
So light have a path, doesn't it?

Radiation by incoherent light should be able to be treated as the sum of all coherent 'wavelengths' there might be.
And if so, sun light also will have a 'path' in spacetime it seems to me.
Am I right?
« Last Edit: 10/01/2009 16:49:13 by yor_on »
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« Reply #32 on: 11/01/2009 13:09:46 »
Let us take the idea of superimposing photons upon each other.
Photons are bosons and can be superimposed as much as you like without taking up any space.

Treated as waves there are experiments proving that.
They can either cancel each other out, or build on each other.
This is called 'Constructive or Destructive Interference'.

If we can do it when they are treated as waves what hinders us from doing it when treating them as particles?
Why would it violate HUP (Heisenberg uncertainty principle) when treated as particles but not as waves?
Am I getting this wrong?

If I assumed that it was possible, as the HUP doesn't forbid it, (as I see it:)?
It only states that we as observers won't be able to prove all parameters, if observing.
That's not the same as stating that under no circumstances, observed or not observed, can all parameters for a given 'system/particle/object' be existing in spacetime at the same time, is it?

Is it possible to superimpose 'photons' on each other?
And will they then have more energy as measured from a point of impact?
« Last Edit: 11/01/2009 14:04:44 by yor_on »
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« Reply #33 on: 11/01/2009 19:19:08 »
Yes SC, I see some as coming from the Sun.
Most of them we see in fact:)

And I have no problem with accepting them to be waves, if traveling in spacetime.
What I have problem with is the idea that they only will exist as a 'interaction'.

To me that imply, if that idea is correct of course:) that they would exist independent of any source.
Accepting that view, all our ideas of spacetime seems to collapse.
Then what are what we call sources?
Sources of electromagnetic field.

Quote
We have built spacetime around concepts as distance motion 'c' etc.
All of those seems questionable, to say the least, if we allow for photons to be at 'all paths'.
Our descriptions 'falters' if you see how I think:)
Actually, we have built spacetime around tangible concepts as objects with mass.

Quote
Then again.
We can send coherent laser light in a very straight path, can't we?
And if we measure that specific wave length outside what we might call its 'path' it won't be there, right?
So light have a path, doesn't it?
Make this simple experiment: put a coin perpendicular to the light's beam, the coin's area greater than the beam's area. Will the coin stop photons from reaching a point after it? According to your view the answer should be yes, but actually it's not, because of diffraction.

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« Reply #34 on: 11/01/2009 20:05:54 »
Are you talking about coherent light or incoherent light here Lightarrow?

But my question wasn't about what would happen if you put matter in its path.
It was if one could prove that the lasers light had a certain path in space.
And from there ask if ordinary light also might have a defined path in spacetime.

As for building spacetime, didn't that start a long time ago:)
With Newton and Einstein, Feynman appearing relatively recently?
It's all a question of definitions of course.

I still have trouble seeing photons as something just appearing as 'interactions'.

---------

But yes, I can see what you mean here.
Still, to me that would be the next question:)
As we first have prove that there are no 'paths' as I see it.

So, do lasers have a 'specific' path in spacetime or not.
« Last Edit: 11/01/2009 20:59:18 by yor_on »
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« Reply #35 on: 11/01/2009 22:47:01 »
Quote
Are you talking about coherent light or incoherent light here Lightarrow?
No difference at all, in principle.
You get diffraction all the time with all em waves. It's just a matter of degree.

Quote
I still have trouble seeing photons as something just appearing as 'interactions'.
I think you ('one') must try to think through the true consequences of treating light as photons 'on the way'.
I realise that there is a huge photon culture because of the scale of things for visible light but any treatment must encompass all wavelengths of em energy. I can see why, because working out diffraction integrals (even just approximately) is a lot less friendly than drawing lines from a to b and saying that the energy 'goes that way' except when it occasionally gets diffracted.
Do / can you possibly think that a 1500m radio broadcast consists of a shower of little bullets - how big would they be? Would they be the same 'size' as gamma photons?

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« Reply #36 on: 12/01/2009 11:10:53 »
Good question SC.
I can give you one question with a twist:)

Do you think you and everything you use/meet today is made of light?
Explain that, no theories.
Just those experiments proving we are light.

What do you think:)

-------------

I haven't said that I don't believe in the result of the two slit experiments?
It's just that I do believe in them :)
And that matter and light, at least looking from where we are, is fundamentally differently expressed.
One of the reasons why I'm not happy with 'many paths' is that it seems to make us all 'probabilities' in a statistical universe.
And considering our self structuring capabilities, as well as entropy and the arrow of time we have?.
To me it seems that we are more than 'probabilities'.

« Last Edit: 12/01/2009 12:16:58 by yor_on »
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« Reply #37 on: 12/01/2009 12:38:52 »
Are you talking about coherent light or incoherent light here Lightarrow?
Both.

Quote
But my question wasn't about what would happen if you put matter in its path.
It was if one could prove that the lasers light had a certain path in space.
And from there ask if ordinary light also might have a defined path in spacetime.
Yes, but only statistically, in the sense that most of the field can be localized in space, in some cases as this one. If it wasn't so, optical geometry wouldn't have existed...The conditions which the fields must satisfy for the optical geometry approximation to be correct are:
1. Wavelenghts much smaller than all the other physical dimensions involved in the system.
2. Distance between stops/slits and detector screen not much greater than the stop's/slits' dimensions (or you will get a diffraction/interference pattern the same).

Quote
As for building spacetime, didn't that start a long time ago:)
With Newton and Einstein, Feynman appearing relatively recently?
It's all a question of definitions of course.
Remember that spacetime is not simply a mathematical object, but a physical one; to define it you need reference frames, physical objects, physical clocks.

Quote
I still have trouble seeing photons as something just appearing as 'interactions'.
A photon must be a physical object.
1.How would you define the existence of a physical object without ever using the word "measure"?
2.Can you measure a photon between source and detector?

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« Reply #38 on: 12/01/2009 14:06:20 »
Hhmmm :)

How about this then:)
If our Sun got quenched.

If now light do have a path, isn't there something called spontaneous particle creation?
That, it is said, the light enjoys itself 'playing' with, even though it goes back to being a wave very quickly?
If that is true, can't then light be seen as a particle having a geodesic path following spacetime.

And if that is true, as well as space containing 'in itself' a huge amount of energy.
And if Feynman is correct in his interpretation of possibilities innumerous for that 'waves/photons' path.
And if I'm right in wanting to allow that wave the properties of a particle?

Will then all be dark here as that sun goes out?
Why?

In my view it's quite simple.
The Sun went out, what do you expect?

From the other view it seems more of a question of probabilities, not discounting the one, wherein the 'light' still will shine with or without a 'source', even if it would be of extremly low probability.

Or am I thinking wrong here?
You could say that even without Feynman's 'many paths', spacetime still would have that possibility.
But to me that concept makes it so much more probable, as it invites us to a spacetime in where all paths are taken at all times, not caring for the 'geometry' we observe versus matter.

Ah the headache:)

"
A photon must be a physical object.
1.How would you define the existence of a physical object without ever using the word "measure"?
2.Can you measure a photon between source and detector? "

How do you mean by 'physical object'?
Only at its moment of 'interaction' or at all times?

1.Yep :)
Lovely question that one.
As well as difficult to answer.

Everything we do or experience comes from some kind of interaction with our surroundings.
So you are definitively right in that this (observing) is the first and last 'proof' of something existing outside ourselves.
Even though it is more of an archetype than a true 'objective evidence', it is still what we build upon.

But we also expect 'cause and effect' (times arrow) to work even without us observing.
For example you filling a bath tube, leaving it for a while and when coming back finding it overflowing.
That is also an archetype, but only at QM level can it be said to be 'broken'.

(Ah, times arrow I meant, not the bath tube:)

So going from those definitions I believe(?:) that this path reasonably could be seen to exist even without any observable interactions.

2. No.
(But see 1.)
(That is if you by measuring, mean observing it 'passively', as an object of its own (a ball)?)

But if you by 'measure' mean.
If it will interact with any 'obstacle' placed in, what I see as, its 'path'?

Then..
Yes, it will.




-----

Another problem I have is with dimensions:)
Take string theory.
Is it eleven dimensions in M theory?

When we start with one dimension.
Nothing special, just trying to see it here in 'spacetime' (in time).
Will we ever see it?
Nope.

Two dimensions then?
Yep, from some angles it will exist, from others it won't.
Have we ever observed anything like that here?
Nope.

What scientists define as 'two dimensional' today is just an 'approximation' of it.
Like a lattice wherein you hinder atoms from moving any other way than back and forth.
Is that two-dimensional?

Use my 'test' in space time and see for your self.
Will you at any angle observe this lattice as 'disappearing?'

And if your answer is no.
Well, then it can't be two-dimensional (as I define it).

What we have here is three dimensions and time.
In this spacetime we find 'matter' and 'time', 'space' and 'light'.
Most of the other 'things' we have defined, as gravity, motion and distance, seems to me to come from them.
Acceleration being a special cause.

We know it is so.
And that it 'works'.
Otherwise I wouldn't be able to write this.

I'll stop here for now:)

Btw: Anyone feeling that they do understand what a 'dimension' is?
You are very welcome to explain how you see it:)

Although DB might want that explanation in a different thread?

-----


(Maybe 'time' and 'space' also fall under matter and light?:)
Could 'time' exist without matter?

As without matter where would 'space' be?
That would be 'time' on its own, and time is a 'relation' right?

And yes, I'm just wondering, nothing more :)

-----------

« Last Edit: 12/01/2009 15:42:36 by yor_on »
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« Reply #39 on: 12/01/2009 15:38:28 »
Hhmmm :)

How about this then:)
If our Sun got quenched.

If now light do have a path, isn't there something called spontaneous particle creation?
That, it is said, the light enjoys itself 'playing' with, even though it goes back to being a wave very quickly?
If that is true, can't then light be seen as a particle having a geodesic path following spacetime.
Sorry, I don't understand what you want to say.

Quote
And if that is true, as well as space containing 'in itself' a huge amount of energy.
And if Feynman is correct in his interpretation of possibilities innumerous for that 'waves/photons' path.
And if I'm right in wanting to allow that wave the properties of a particle?

Will then all be dark here as that sun goes out?
See up. Could you explain what you want to say in a different way ?

Quote
Why?

In my view it's quite simple.
The Sun went out, what do you expect?

From the other view it seems more of a question of probabilities, not discounting the one, wherein the 'light' still will shine with or without a 'source', even if it would be of extremly low probability.

Or am I thinking wrong here?
You could say that even without Feynman's 'many paths', spacetime still would have that possibility.
But to me that concept makes it so much more probable, as it invites us to a spacetime in where all paths are taken at all times, not caring for the 'geometry' we observe versus matter.
See up.

Quote
Ah the headache:)

"
A photon must be a physical object.
1.How would you define the existence of a physical object without ever using the word "measure"?
2.Can you measure a photon between source and detector? "

How do you mean by 'physical object'?
Only at its moment of 'interaction' or at all times?
Let's make an example. I do the following statement: "everything you see is due to the interaction with your eyes or your camera, ecc. of little angels with blue wings and green faces. They are destroyed at the impact with your eyes or your detectors."
Do you think it's a scientific statement? Let's imagine that you say "No". Then I'll argue that my angels explains very well what you see and the properties of light (tell me a light's property and I'll explain you how the "theory of Angels" describes perfectly that property... [;)]).

Quote
But we also expect 'cause and effect' (times arrow) to work even without us observing.
For example you filling a bath tube, leaving it for a while and when coming back finding it overflowing.
Since this is a much more difficult question, for the moment I prefer to say that it's a different situation, because:
1. We are talking about macroscopic objects.
2. We are talking about objects with non-zero mass.
Remember that the fact photons don't have a position operator in QM (as, e.g., electrons, have) is essentially due to the fact they are massless. It is this absence of such an operator that makes it impossible to ascribe them a precise position in space when not detected.

About string theory, M theory and the rest, sorry but I don't know much about them...
« Last Edit: 12/01/2009 15:42:21 by lightarrow »

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« Reply #40 on: 12/01/2009 16:08:20 »
Well, :(At least it seemed logic to me:)

Lightarrow, as far as I understand we start everything by archetypes, or do you see it differently?
One of the first archetypes needed to be defined is if 'anything' exist at all outside ones mind.
If your answer is a yes to that one, the rest of what we call 'objectivity' 'observations' 'measurements' will follow and make sense as 'outside phenomena'.
Not hinging on us being here at all.

The second one I used was the arrow of time, and I called that one a archetype too :)
And that is as we without knowing why it does it, or how it does it, observes it as having an arrow.
And that we expect it to continue to do so, at least macroscopically.

And from those two 'postulates' I find it reasonable to expect photons to be able to have a 'path' in spacetime, even without either you nor me observing.

(And no, I don't see light as little angels, but I like the idea, who knows:)
Reminds me a little of that 'postulate' wherein the question was something like.
'How many angels can dance on a needles 'point'':)

As for the beginning of what I wrote, I agree.
It needs to be much clearer.

--------

Give me some 'time' on that one, please:)
« Last Edit: 12/01/2009 16:18:36 by yor_on »
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« Reply #41 on: 12/01/2009 16:27:34 »
Quote from: yor_on
Do you think you and everything you use/meet today is made of light?
Explain that, no theories.
Just those experiments proving we are light.
I've been lurking here following this thread with great interest. I've been compiling evidence FOR and AGAINST So far the evidence for that far outweighs the evidence against. It seems that since that is such a restrictive case it should be easy to dispose of.

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« Reply #42 on: 12/01/2009 18:19:47 »
Quote
Do you think you and everything you use/meet today is made of light?
Explain that, no theories.
Just those experiments proving we are light.

By 'light' I take it you mean electromagnetic waves(?).
The answer is No, in any case. The waves are only there due to interactions between charge systems, involving mass (thus excluding 'light' which is massless).

How can one explain without theory? "I feel that because it makes sense to me" is no use as an explanation.

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« Reply #43 on: 12/01/2009 18:30:36 »
Well, :(At least it seemed logic to me:)

Lightarrow, as far as I understand we start everything by archetypes, or do you see it differently?
Archetypes? Do you mean "basic concepts"?
Quote
One of the first archetypes needed to be defined is if 'anything' exist at all outside ones mind.
This is an interesting questions. Harry Palmer (creator of the Avatar course) says: "Let's start to take things away of the universe. Planets, then stars, then all the matter, dust and clouds and atoms or particles. Then even time and space,ecc. What remains? Our awarness. If we took away even our awarness, who could prove there is still something in the universe?"

Anyway this is more phylosophy than physics, at least now (maybe one day we will know something more about awarness).

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« Reply #44 on: 13/01/2009 15:53:28 »
As I understands it an 'archetype' is something so 'obvious' that we more or less take it as granted.
Like one and one makes two.
I read somewhere that most animals know the difference between one and two and 'many'.

Sometimes they can be wrong though.
The 'archetypes' I mean, well, the animals too:)

I mean?
Is one and one still two??
It can, as I see it, easily become three:)





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« Reply #45 on: 13/01/2009 22:57:35 »

Is one and one still two??

I think you will like this (hope to have said it well in english);
<<People are of 10 categories: those who know binary numbers and those who don't>>   [:)]

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« Reply #46 on: 14/01/2009 10:33:07 »
Yep:)
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« Reply #47 on: 14/01/2009 19:50:22 »
Apropos nothing at all:)
Considering my inclination for logic..

"If Logic is a systematic method for getting the wrong conclusion... with confidence.
Then surely statistics is a systematic method for getting the wrong conclusion... with 95% confidence."

Or something to that order?
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« Reply #48 on: 14/01/2009 20:52:24 »
My little beaver brain is working overtime again. This is what its murky depths have churned out this time.

As has been explained elsewhere, for a photon travelling at c time has no meaning. In fact, time doesn't really exist for it. It therefore follows that a photon could be everywhere in the universe at the same time. But the universe is expanding, so there is now more "everywhere" for it to be in than there was at any time in the past. How can the photon be everywhere at once if everywhere is getting bigger?

 [???]

I've been thinking about this and I think that something I added as a late post in another topic may have a bearing here too, because the premise that time has no meaning for a photon may not be correct.

From that earlier thread:

Quote
Although we can move through three spatial dimensions, at any point in time the movement vectors for all three spatial directions can be summed to a single vector.  Thus movement is essentially in a single direction and can be expressed by a single value, just as when we drive heading North-West we don't say we are driving West at x mph and North at y mph; we just use the summed vector.

With movement induced time dilation, the same thing is happening, except this time the two vectors being summed are the summed spatial movement vector and the temporal movement vector.  The reason we get time dilation is because it is the sum of these two vectors, spatial and temporal, which cannot exceed 'c', so as the spatial movement vector increases, the temporal vector must decrease.  With zero spatial movement then, we move temporally at 'c', which in turn implies we have zero length in that direction

Now, if we are moving at 'c' in the temporal dimension, have no length in that direction, and we are aware of time passing, then it would seem plausible that when we see a photon moving at 'c' though our spatial dimensions we are seeing a two-dimensional object moving along it's temporal dimension; this being our third spatial dimension, in which it has no length.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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« Reply #49 on: 05/02/2009 13:05:13 »
Ok another thought.
If we say that a photon if red shifted, that is, as seen from our frame of observation being of a lesser 'energy' content.
We also say that its wave is longer, right.
So in a BEC where we see photons as frozen/still that wave should be?
Infinite??

And if so then 'expansion' is no obstacle as that 'wave' then will cover 'everything' we can observe.

But if it are able to do this, our ideas of distance seems wrong to me.
They will only work at a macroscopic plane.
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