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i was reading and a question popped into my head and i could not find the answer anywhere

if photon destruction is instantaneous doesn't it mean that space-time is quantised?

here is my problem:

if space-time is continues and i can define the separate events of ""last point where a photon exists" and "the first point where said photon doesn't exist" there are infinitely many point in between all of witch have to be in some "in between" state and so the destruction of a photon is not instantaneous.

on the other hand:

if a photon is absorbed instantaneously then when an electron is absorbing a photon it "gets" the photons momentum and starts to move instantaneously witch means that if space-time is continues i can define the event of "last point that the electron had no velocity" and the event of "the first point that the electron had some velocity due to the absorption of the photon" and the same problem arises as before.

it all builds up on that "last point" "first point" argument is it valid?

i don't expect a simple answer but if someone can help me start to tackle the question that will be great

just to clarify i am not asking if space-time is quantised but if instantaneous events require a non continues function and there are instantaneous events like the the destruction of a photon how can space-time be continues (the electron does not experience a continues change in velocity?)

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  • $\begingroup$ Possible duplicates: physics.stackexchange.com/q/9720/2451 and links therein. $\endgroup$
    – Qmechanic ♦
    Commented Feb 7, 2018 at 21:04
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    $\begingroup$ These argument are essential the same ones made by Zeno in the fifth century BC. The fundamental issue is with language. The words and thought patterns suitable for day to day life are inadequate to address these issues, but you can develop a precise language for talking about them and the result is mathematical subject 'real analysis'. Space-time might or might not be quantized, but you have to move a bit forward in time to find a starting place. $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Feb 7, 2018 at 21:52
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    $\begingroup$ If the real number line is continuous, I can define the "largest number less than 4" and the "smallest number greater than 4" and then there have to be infinitely many points in between these --- all of which have to be in some in-between state, neither less than 4 nor greater than 4. Do you see any problem with this reasoning? $\endgroup$
    – WillO
    Commented Feb 7, 2018 at 21:56
  • $\begingroup$ Can you not apply pretty much the same reasoning to any quantum event, in that once an event occurs it must go to completion? This may just be the same question you are asking, e.g. a transition between two energy levels of an atom can't be stopped, once begun, AFAIK. $\endgroup$
    – user184116
    Commented Feb 7, 2018 at 22:16

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The possibility of quantized space-time is a topic of current research, but not for the reasons you mention. It is being studied because it furnishes a possible path to a model of quantum gravity. That model is called loop quantum gravity and the leading researcher in that field is Lee Smolin. See his book "Three Roads To Quantum Gravity" for more information about it.

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  • $\begingroup$ Smolin is certainly one of the better thinkers in physics today, though I'm more inclined myself to think that quantisation will eventually be abandoned in favour of an underlying reality. $\endgroup$
    – Steve
    Commented Feb 7, 2018 at 20:55
  • $\begingroup$ biggest problems to overcome are 1) coming up with a falsifiable model which makes testable low-energy predictions and 2) coming up with some method of directly testing the model at energies which we cannot yet access and may, in principle, never be able to access. $\endgroup$
    – niels nielsen
    Commented Feb 7, 2018 at 20:59
  • $\begingroup$ is the "event" thing nonsense? should i (can i) try to build upon it? $\endgroup$
    – Edo Mor
    Commented Feb 7, 2018 at 21:07
  • $\begingroup$ it is probably nonsense; but to demonstrate to the experts here that it might not be would require you to furnish a mathematical treatment of your idea which is complete enough to let them calculate predictions based on it. $\endgroup$
    – niels nielsen
    Commented Feb 7, 2018 at 21:22
  • $\begingroup$ @nielsnielsen please don't recommend users to post questions about their personal theories as that would clearly violate the non-mainstream policy. $\endgroup$
    – Kyle Kanos
    Commented Feb 8, 2018 at 12:54

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