?Speed of Reflection?

Discussion in 'General Science & Technology' started by Avatar, Dec 21, 2001.

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  1. Avatar smoking revolver Valued Senior Member

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    I have this question.

    If I put a really big mirror some 4 light minutes away from me and there would be nothing between us, would I see my reflection after 8 minutes?
    Or what I want to know exactly, what partciples carry my reflection. Is it photons?
    Or it isn't carried at all, which I don't beleive, because the information has to be sent by something. Just like for gravity there are gravitons.
    I would not see my reflection earlier than 8 min because nothing can go faster than light[for now], right?
    But if my reflection is carried by photons, why, because I don't emmit them.
     
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  3. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    Light is shootng about all over the place. Some hits you. Only some of that light that hits you bounces off your surface; the rest is absorbed, and you get a tiny bit warmer. Some of the light that bounces off goes toward the mirror. The speed could be just about anything, depending on what lies between you and the mirror. Assuming a void (which does not exist in nature) that's 300 million metres per second or something crazy like that, I can't remember off the top of my head. But you said four minutes, which still means the distance involved depends on the material between you and the mirror. But that doesn't matter, I'm wandering all over the place. The light that bounced off you hits the mirror, and a good deal of it bounces back off the mirror because that's the entire point of mirrors: they don't absorb much. Note that light is going off again all over the place, and only the bit that is modified by substances and bounces directly back through your iris is what you see; the rest goes to waste.

    Anyway, regardless of materials between ad such, if light must travel four minutes form you to the mirror, it must travel four minutes back. On the other hand, if the material is just our atmosphere or something, at a range of four minutes you won't see anything anyway; your reflection will be too damn small. Heck, the small amount of light heading from you toward the mirror (and that going back) is really small anyway, and will be so diffused and attenuated after a few minutes that there won't be any coherent signal anyway. That light would be a blur very shortly after leaving you. That's kinda why evolution gave us the eyes it did, and other animals. Our biology develops to fit what is around us. Thus we can see as far as one could expect normal daylight to carry a coherent signal of things of about our size.

    Photons: If anyone has proven conclusively that these are particles rather than just a measurement unit of EM waves, I'd love to see it. I'm still learning all this stuff, and I find this sort of thing very interesting.

    Gravitons: Never heard of these outside of purely speculative theories.
     
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  5. Avatar smoking revolver Valued Senior Member

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    speculative, yes?

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    OK maybe, but I like the idea.
    But I'd like to hear your idea, how gravititional force is carried about. It is true tht gravitons have not been proved do exist, but we have a lot to discover yet.[we slightly touched the theme in thread DarkMatter]. But even if they existed they decay very quickly[in universe distances]. My theory on this is tht, before they decay they hit other partciples met in empty space[which is not empty, there is a very low concentration of different partciples everywhere], by hitting them the graviton destroys and tht particle it hit continues the way with extra energ given by graviton. This is a very speculative theory though[K-12 student level

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    ], but it is how I immagine it. But because I find this to be very interesting I intend to think of a more believable theory.

    You could say tht light has dual properties. One of these is as for waves, other properties are like those of partciples. No-one knows for sure which is right, and it is highly possible tht they both are right.
     
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  7. odin Registered Senior Member

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    Light

    You would see nothing,it would be 44,640,000 miles away
     
  8. Avatar smoking revolver Valued Senior Member

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    the question was here not wheter I see or not, it is about delay and partciples. The distance could be 5 light seconds, I just took 4 minutes because it is easyer to pretend then
     
  9. odin Registered Senior Member

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    avatar

    5 light seconds that would be 930,000 miles.
    Just playing

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    Yes I think it would be 8 mins 4 mins there & 4 mins back.
     
  10. [f] Registered Senior Member

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    seems to make sense to me...

    interesting idea
     
  11. Dreamsa Dare to Dream! Registered Senior Member

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    Certainly 8 mins should be the answer.

    We're reflecting light around us.

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    Your comparison is a little bit weird. I would rather say gravity is just like light, light has photon and gravity has graviton.

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  12. Stryder Keeper of "good" ideas. Valued Senior Member

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    Heres a method to look at it:

    Get a golf ball and bounce it off a wall (not near windowsand remember to duck or move when it comes back)

    What velocity is applied when you throw it, is re-applied in the opposite direction when it collides with a brick wall, because the force has no other direction to disipate in.

    I would say that the speed that light takes on the way there, will be faster than that of the return and there would be a slight change in the position the light has in the spectrum. This is also noticable if you think of looking at stars on the other side of the universe in comparison to ones that are near us. Their spectral colour will be different depending on their overall size, light exersion and distance.
     
    Last edited: Dec 31, 2001
  13. Dreamsa Dare to Dream! Registered Senior Member

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    Hi!

    The golf ball will not bounce back with the same velocity. Energy is dissapated in the collision.

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    I don't understand what do you mean by this sentence, can you explain?

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  14. Avatar smoking revolver Valued Senior Member

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    I thinked tht the return should take longer, but had other assumption. When light reflects it is not the same light tht touched the surface. Surface takes its energy and generates new photons from it. It takes time. Of course those are only some million million parts of seconds.





    WHAT is other side of the universe? I first heard the frase in Stargate. Maybe in Latvian there is another definition for it. Would you please explain this term?
     
  15. Stryder Keeper of "good" ideas. Valued Senior Member

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    Sorry Dreamsa

    I've corrected the previous post with an update, sometimes my eyesight goes through stareing at a monitor for too long and I miss words.

    What Avatar mentioned is corrected, it's a rebound that also has a collaberative effect (a Photo-Electric Effect)

    *Thumbs up to Avatar for pointing out something I missed

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    *
     
  16. Boris2 Valued Senior Member

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    The speed of the photon from you to the mirror will be the same as the photon from the mirror back to you. Why would it be different?

    The photon from you is absorbed by an electron in the mirror, which boosts it into a higher orbital, the electron then drops back to the lower orbital and emits a photon of the same frequency. There is no time delay as this happens instantaneously, the electron does not traverse the "distance" between orbitals but disappears from one and reappears at the other in no time.

    It is a quantum weirdness thingy and it is no use applying macro perceptions to it.

    AFAIK.

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  17. Dreamsa Dare to Dream! Registered Senior Member

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    Hi!

    Won't the electron stay in the orbital with higher energy for a while?

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  18. Crisp Gone 4ever Registered Senior Member

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    Dreamsa,

    That's correct. Depending on the type of atom and orbital, this can take from a few picoseconds up to a few days. Mirrors as we know them have an almost instantaneous reflection

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    .

    Bye!

    Crisp
     
  19. Imahamster Registered Senior Member

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    Two phenomena

    Photoelectric effect or laser? Random delayed emission or immediate stimulated emission?
     
  20. SeekerOfTruth Unemployed, but Looking Registered Senior Member

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    This discussion brought up a question I have.

    Does it require an electron changing orbitals for a reflection to occur?

    If this is the case, then would a neutron star or a BEC reflect light?
     
  21. Dreamsa Dare to Dream! Registered Senior Member

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    Hi!

    Can the photons just bounce off instead of being absorbed then reemitted during reflection?

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    Photoelectric effect-immediate stimulated emission
    Laser-delayed emission

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  22. Crisp Gone 4ever Registered Senior Member

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    A bit more complicated...

    Hi all,

    I think reflection of a mirror is a bit more complicated than the absorption of a photon by electrons. The scenario of an electron going into a higher state and re-emitting a photon when it gets back to the ground state is only valid for gasses.

    The reflective part of a mirror is a solid, and for solids, the absorption and reflection of electromagnetic radiation (such as light) is mainly dependant on the atoms in the solid's lattice. One popular way to describe these atoms is as if they were connected with springs ( = harmonic oscillator approach ). In quantummechanics, a harmonic oscillator cannot just absorb any energy since its energy levels are quantized : the photon has to have almost the exact energy to get absorbed by the harmonic oscillator. In terms of the solid: the energy of the incoming photon has to exactly match the vibrational energy of the entire lattice it falls on. If this energy is not right, absorption is not allowed, and the photon bounces off.

    Sidenote: This is only an approximation (in real life the atoms are not connected in a spring-like mechanism - the situation is a lot more complicated) - but it works out for most solid metals.

    So Dreamsa: yes, photons can just bounce off instead of being reflected. But it's not a mechanical mechanism (eg. collisions or something) that is responsible for this.

    SeekerOfTruth: only for gasses an electron has to go to a higher state for reflection (or fluorescence). What concerns neutron stars and BEC's : I think reflection is possible, but the mechanism behind is without doubt not known yet.

    Bye!

    Crisp
     
  23. Dreamsa Dare to Dream! Registered Senior Member

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    Hi!

    If it is not mechanical then what is happening?

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    Also for reflection is it that those photons that cannot be absorbed results in the colour we see?

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