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Not a physicist.

I am asking about causality here. If I look at matter as made of smaller chunks of matter, and there is a limited speed of information propagation, small can explain big, given a conventional time arrow.

But if matter is made of wave, the logic seems flawed. A smaller wavelength does not give birth to larger wavelength phenomena (unless other phenomena intervene).

So what do modern physics say about size, scale and causality? Is there a connection and how strong is it? Is the speed of light in the vacuum the only thing to know when asking about causality?

Winston
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    "But if matter is made of wave" - matter is not "made of wave", quantum mechanics in general simply works in a manner entirely unlike classical physics (both classical particle and classical wave mechanics). You cannot apply classical intuition to quantum mechanics and expect meaningful outcomes. – ACuriousMind Mar 09 '21 at 16:24
  • Do you mean like the Big Bang? – my2cts Mar 09 '21 at 18:58
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    "A smaller wavelength does not give birth to larger wavelength phenomena" Yes it does. Smaller wavelength implies higher energy, which can bring about lower energy phenomena. – my2cts Mar 09 '21 at 18:59
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    My intention was not to be sarcastic, but to point out that your question is based on a false premise (thinking about quantum causality in terms of classical wavelengths). Relativistic quantum mechanics/QFT is still a theory with a limited speed of information propagation, and we already have many questions about causality in QFT on this site. – ACuriousMind Mar 10 '21 at 10:00
  • @ACuriousMind I have clearly stated I am no physicist. I am talking about waves in general, not related to QM specifically for, I am no physicist and ACTUALLY ASKING WHAT MODERN PHYSICS SAY ABOUT THIS (emphasis intended). You are the one assuming I know what I am talking about. – Winston Mar 11 '21 at 09:55

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Waves in quantum mechanics are not like ordinary waves (e.g. waves in water), instead they are much better thought of as waves of probability - they are the likelihood that the particle of matter will be found at a particular point in space. In other words, the uncertainty of a particles position. Therefore, the particle of mass (be that an electron, quark, boson etc) is not a wave - its position is wave (of probability). The interaction of these particles follow ordinary intuition about causality. This is because as they interact, the uncertainty about their position collapses to a single point and their position in space is determined.

Furthermore, these uncertainties of position are on the scale of the Planck length (incredibly small), this is why matter doesn't exhibit probabilistic wavelike behaviour (e.g. a basketball will remain in the same place you put it, and not spontaneously change position every time you look away).

To answer your question, resulting (or bigger in terms of matter) phenomena will always be a consequence of their causal (or smaller in terms of matter) phenomena, as long as time keeps going in one direction.

ben13215
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  • Thank you for your answer. Although I feel it does not entirely answer my question. Dirac in his famous book says it would be ridiculous to keep asking about smaller parts in matter because that would never end. So unless he is wrong, it would seem there are parts of matter that have a size or a radius of influence or whatever that is not zero. My question is are these phenomena explained by smaller parts or not. – Winston Mar 11 '21 at 09:59