How fast is light?

Discussion in 'Bad Dog Cafe' started by Buckocaster51, Mar 30, 2019.

  1. MattyK-USA

    MattyK-USA Tele-Afflicted

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    Man, that guy is playing at the speed of... well, he's playing really quickly :)
     
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  2. DuckDodgers

    DuckDodgers Tele-Meister

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    Lightn
    Unless they’re travelling in an absolute vacuum, photons are constantly being absorbed and re-emitted, and so don’t actually travel at C. And even in a vacuum, a photon can decay into an electron-positron pair, and recombine, re-emitting a photon.
     
  3. MattyK-USA

    MattyK-USA Tele-Afflicted

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    Photons always travel at C (defined as maximum velocity of a particle or body through space-time). C itself changes depending on the medium, as I stated before. Space is enough of a vacuum that they can travel substantially unmolested. And of course if they impact another particle, they will be absorbed and (generally) re-emitted - once again traveling at C. Not sure why you made that statement in response to a post on electrical current, however off-topic it may be :)
     
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  4. Deaf Eddie

    Deaf Eddie Friend of Leo's

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    Uh... my friend used to describe speakers with a good frequency response as "going from DC to light..."
     
  5. JL_LI

    JL_LI Friend of Leo's

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    Yikes! Photons and their behavior are well described in quantum theory, the theory describing the probabilistic as opposed to the deterministic universe. Photons are not absorbed by contact with another particle. There is some probability of absorption when the photon traverses the dipole field of a potential absorber. Then there is another probability associated with what happens next; reflection, reemission of the photon, fluorescence, the emission of a photon of lower energy, resonance transfer, an interaction between the dipole field of the absorbing molecule with a neighboring and overlapping dipole field of another molecule, internal conversion, a reshuffling of orbital energies, and more. None of those things happen instantaneously. There is a lifetime associated with the excited state of the absorbing molecule. This is pretty simple stuff to me and pretty confusing to most people. I'd really like to understand how my amplifier takes the weak signal coming into it and turns it into the amazing tones I get on days when everything comes together just right. I'm really in awe of the glowing bottle folks.
     
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  6. DuckDodgers

    DuckDodgers Tele-Meister

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    The speed of light changes in different media, but c is always equal to 299,792,458 m/s. Interstellar space is not empty, but has an average hydrogen density of 1 atom/cc. It varies from 0.1 to 1000 hydrogen atoms/cc.
     
  7. MattyK-USA

    MattyK-USA Tele-Afflicted

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    O god, another superposition weenie! :p Good on you :)

    Who said anything happens instantaneously in the absorption scenario? I stated that (1) photons travel at C, which they do, and that (2) for the photon the trip is instantaneous, which it is.

    Yes, yes, there are many possibilities at the quantum level. Some if not all of those probabilities, as I understand it, are dependent on energy level - so maybe there's a little "deterministic" in there anyway. The only unknowns I'm aware of at the quantum level are spin/polarity and position (until one is measured). For instance "reshuffling of orbital energies" needs sufficient energy from the incoming photon for that Planck / quanta level leap. And really, for the layperson aren't you splitting the semantic hairs a bit fine with "traverses the dipole field of a potential absorber" as opposed to "impacting another particle"? It's all particles at the end of the day. I guess given that it's a field level interaction rather than a collision your point is made.
     
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  8. MattyK-USA

    MattyK-USA Tele-Afflicted

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    And yet, the propagation of light throughout the universe has managed just fine. If all those photons had been absorbed and re-emitted, we wouldn't be looking at quasars from 13 Billion LY away.
     
  9. 24 track

    24 track Doctor of Teleocity

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    I believe you are referring to tachyons and neutrinos read the link in post #34

    C referes to to universal constant
     
  10. 24 track

    24 track Doctor of Teleocity

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    Fun thread i love it,
    if this stuff was not confusing before we will kill it now!:lol::lol::lol::lol::lol:
     
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  11. String Tree

    String Tree Doctor of Teleocity

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    Dude, I have That Pedal!
     
  12. MattyK-USA

    MattyK-USA Tele-Afflicted

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    No, I am referring to photons. Tachyons are theoretical. Neutrinos do appear to have some mass.
     
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  13. P Thought

    P Thought Poster Extraordinaire Silver Supporter

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    I'd've guessed it was faster than that. What is a nanosecond?
     
  14. Buckocaster51

    Buckocaster51 Super Moderator Staff Member Ad Free Member

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    10^-9 s

    1/1,000,000,000 s

    One billionth off second (in the US)

    It’s a short period of time, but today shorter periods are routinely used

    During the Manhattan Project the term “shake” was used to denote 10 nanoseconds = 10 ns
     
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  15. eclecticsynergy

    eclecticsynergy Tele-Afflicted

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    3BC5F2D1-E844-443B-AEF4-261314A7D215.jpg

    74b66caeb8e4996d2e875a69e9cf598a--funny-science-jokes-lights.jpg
     
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  16. VWAmTele

    VWAmTele Friend of Leo's

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    Shortest unit of measurable time is Planck time. Nanosecond is 10^-9, Planck is 10^-44. The events immediately following the Big Bang are measured in Planck time. Impossible to conceptualize.
     
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  17. schmee

    schmee Poster Extraordinaire

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    .... and yet there is light just reaching us here that was sent our way at the formation of the universe! Billions of years ago... think that through for a minute........
     
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  18. Random1643

    Random1643 Tele-Afflicted

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    So, probably even faster than it takes me to avoid a request to perform a John Denver song...okay. I can't follow the science but there's always a life experience to provide context.
     
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  19. Buckocaster51

    Buckocaster51 Super Moderator Staff Member Ad Free Member

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    I think we are more than twenty orders of magnitude away from actually being to measure times on the scale of Planck time.

    It is certainly useful and interesting to talk about.
     
  20. 24 track

    24 track Doctor of Teleocity

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    Planc time had its application during the first second of the big bang to measure the expansion of the energy released at that point , time space and matter did not exsist at then , and as E= MC(2) matter can be created from energy by that same equasion appearently. or so the theory goes

    now its been etablished that through supernova events that heavier elements are created , how ever there was never a clear explanation for the creation of the heaviest elements we have on the periodic table until recently when 2 neutron stars collides ane the event was witnessed , and due to the intense denity of these stars reminents the energy was sufficient to create some of the heaviest elements we know ( fun Fact)



    https://www.iflscience.com/space/what-happens-when-neutron-stars-collide/

    https://www.cnbc.com/2017/10/16/sci...star-collisions-make-gold-other-elements.html
     
    Last edited: Apr 1, 2019
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