What Is Happening In The Smallest Part Of Space?

Discussion in 'Physics & Math' started by arthur brogard, Mar 14, 2018.

  1. arthur brogard Registered Member

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    I am a dunce. Okay? That's that settled. Have no maths and little intelligence. Perhaps I can ask a question, though? Just throw it out if you like, delete it all.

    This is it:

    I've read that when you get down near the Planck length then physics breaks down. Is that right?

    But I would like to know what is actually going on in ' points' of space. So make it a question about what is going on in the smallest part of space that you can comment on, know something about.

    What I mean by 'what is going on?' refers mainly to energy I guess. There's nothing much else there is there?

    And why is it a puzzle? Well any point can be considered as being at the centre of a sphere, can't it?

    Out in space there, the whole of the universe surrounding any point.

    And EM radiation coming from every point on the 'surface' of that sphere.

    An infinite numbers of photons wouldn't it be?

    All crossing at this one point.

    And this is the norm. This is what is happening at every 'point' of reality.


    What does physics have to say about what's happening at such a point? Pages of maths won't do anything for me, they'll be unintelligible. But a bookload of abstruse maths can be condensed or summarised with such as 'this means time and space are relative'. So perhaps something similar can be done here.

    Or perhaps it needs the moderator to delete the whole thing?
     
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  3. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    No, there would not be an infinite number of photons.
     
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  5. exchemist Valued Senior Member

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    Regarding Planck length, as far as I am aware there is no demonstrated physical significance to the Planck length: it was just part of a "natural" unit system developed by Max Planck. In some theories of quantum gravity (none of which works properly, yet) it has further significance. But all rather conjectural so far.

    But maybe others can elaborate further.
     
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  7. spidergoat Venued Serial Membership Valued Senior Member

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    Pick a random point, probably nothing is happening there.
     
  8. arthur brogard Registered Member

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    Yes, picked the wrong word. Point is a vast number all intersecting in the one place. Isn't it?

    True? I am referring to this kind of statement (from wiki, this one) : The Planck length is believed to be the shortest meaningful length, the limiting distance below which the very notions of space and length cease to exist.

    I'm not fussy. I just want to know what happens in the tiniest places and tried to obviate responders telling me I was asking a dumb question because at that scale.... etc... etc...

    That's the point: there can't be 'nothing' happening anywhere. Because everywhere feel EM radiation doesn't it? Isn't it so that EM radiation goes on forever? We see back 3 billion years I think, don't we, right there in the night sky.

    And the radiations have not 'spread out' like fingers with the growing area of the surface of the expanding sphere as they rush outwards from the source star.

    We don't have to hunt around to find a 'finger' of light ray to be able to see the star. There's no 'fingers'. There's a wavefront and it seems (to me, observing the above) to be indivisible (down to the Planck length?) and inexhaustible.

    Any 'point' in space, any particle in space if you prefer, feels, is influenced by that EM radiation from that star.

    And all others.

    So something is happening. Isn't it?
     
  9. DaveC426913 Valued Senior Member

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    9,219
    A point is defined by 3 spatial coordinates, regardless of how many photons happen to be passing through it.

    If you want to understand why there aren't an infinite number of photons from the rest of the universe passing through any given point, look up Olber's Paradox. (hint: it;s the same reason why, when we look out into space, it's dark).

    Yes they do. As the square of the distance.

    Yes we do. Sort of.

    Looking at the sky with the naked eye, you will only see about 6000 stars. The rest are too dim to be picked up by your tiny retina (no photons are intersecting it).

    Put a few lenses in front of your eye, (say a 6 inch one) and you are now collecting over about 400x the area of your eye. That will collect enough photons and direct them toward your eye for you to see them.
     
    Last edited: Mar 14, 2018
  10. spidergoat Venued Serial Membership Valued Senior Member

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    Light comes in photons, in most cases this is a good description. So even though it seems continuous, it's not. And they aren't infinitely small, like a point.
     
  11. arthur brogard Registered Member

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    Getting the 'points' mixed up I think. From my sloppy English when I said

    That should have read: "Yes, picked the wrong word. The point is a vast number all intersect in the one place."

    No, not really. As I've said I'm not attempting to stipulate there's an infinite number of photons intersecting. I've known about that night sky thing for a long time.

    But in fact your reference to Olber's paradox is a bit of a non sequitur or something. It seems to suggest that EM radiation effecting a point can only come from the stars and without them - nothing.

    No, of course not. EM radiation emanates from any particle, does it not? Certainly from any electron.

    Hence any particle or point in the universe is totally surrounded by sources of EM radiation.

    The Olber's thing relates to visible EM radiation. A tiny portion of the spectrum.

    If you see what I mean. No big deal. Just clarifying I'm not specifically talking about any particular frequency of EM radiation. Just saying it is coming in from all directions. What does it cause to happen? What's happening in the smallest volume we can say anything about?
     
    Last edited: Mar 14, 2018
  12. Confused2 Registered Senior Member

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    As far as I know Richard Feynman is still the go-to guy for photons. See either the book QED (by Feynman) or lectures here :- .
     
  13. arthur brogard Registered Member

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    Yes. I've read everything by Feynman that I could lay my hands on. Even attempted to read his maths, which I couldn't.

    And I've seen the lectures, have them downloaded and have QED and other publications of his.

    I don't know that he addressed this question. What happens in a tiny volume of space. I don't remember him dealing much with photons, either, though I feel I know that he's an expert on them. He deals to my mind mainly with particles. This particle does this and that... like talking about billiard balls...

    His Feynman diagrams look just like that.. diagrams of billiard balls interacting.

    What we have in a tiny volume of space is billiard balls from all directions occupying the same space.... don't we? Or what?
     
  14. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    Sorry, I don't know what you are talking about. If I pick a point in space you think there is going to be some huge amount of photons going
    through that point for some reason?
     
  15. arthur brogard Registered Member

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    Tiny volume. Yes.
     
  16. exchemist Valued Senior Member

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    Believed to be. But no demonstrated physical significance, as that Wiki article also states, in the previous line.

    This is one of those areas in which theory runs so far ahead of observation that it becomes more conjecture than anything else. There is nothing wrong with that of course, but in my opinion one should be careful not to let such esoteric and untested concepts run away with one's ideas. I think you just end up building castles in the air to no purpose.
     
  17. arthur brogard Registered Member

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    I'd agree with that. In my case it doesn't apply because I have no ideas. I'm not a physics or maths theorist or anything remotely like it.

    To me it is irrelevant whether or not the Planck length conjectures are correct. I just wanted to make it clear that I'm only asking about locations, volume, that can be asked about:

     
  18. exchemist Valued Senior Member

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    Fair enough. But then, why do you think there is anything special "going on" at points in space? You seem to be interested in the amount of radiation permeating space. Is that right?
     
  19. arthur brogard Registered Member

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    I don't think there's anything special going on. I'm referring to any point at all in all the vastness of everything - so by definition it'd be common not special, I think?

    What's special about it, to me, is the thought of all those photons coinciding in the same place. I can't imagine what's happening. The water wave analogy doesn't help me much.
     
  20. exchemist Valued Senior Member

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    But they don't "all coincide in the same place".

    If you stand on the end of a platform at Clapham Junction, the busiest railway station in Britain, you will see a lot of trains go by. But they don't crash into one another (though two once did). They come by at different times and pass through on different tracks.

    In the unlikely event that a pair of photons actually does arrive at the same point in space at the same time, the photons simply pass through one another, as waves do, emerge unaltered and continue on their way.

    Are you having difficulty with that particular idea- that waves pass through one another?
     
  21. RainbowSingularity Valued Senior Member

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    https://en.wikipedia.org/wiki/Planck_length#History
    http://www.particlecentral.com/strings_page.html

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    hope thats gives you a starter for 10
     
  22. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    I still cannot understand why you think all of the photons will coincide at the same point. Why would they? For that to be true all photons would have to be moving to the same point, which would be a remarkable coincidence.
     
  23. QuarkHead Remedial Math Student Valued Senior Member

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    What if that "one place" we're your retina? If it were not true, surely you would at best have a partial view of the environment?
     

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