0
$\begingroup$

In introductory quantum physics, particles are described by the Schrodinger equation wave-function, which describes only an abstract probability wave.

But in quantum field theory, particles are vibrations in the fabric of their field. This would make them a literal wave in space (like sound in air)

Are particles both of these things somehow? EDIT Looking for dumbed-down popular science explanations in this posts's answers

$\endgroup$
5
  • $\begingroup$ possible duplicate? physics.stackexchange.com/q/16091 $\endgroup$
    – tbt
    Mar 4, 2021 at 10:58
  • 1
    $\begingroup$ @tbt Yeah, I just went through that. I'm looking for a dumbed-down popular science explanation in this post, as I haven't learned the theories yet $\endgroup$
    – Ryder Rude
    Mar 4, 2021 at 10:59
  • 1
    $\begingroup$ Physics is really good at inventing math to describe how things behave and, really good at predicting new behaviors. Physics is not so good at explaining what things "really" are. Every explanation that anybody has ever come up with for anything at all is always built on deeper assumptions. If the explanation stands--if it is accepted by the physics community--all that does is to push the question of what is "real" down to a deeper level. $\endgroup$ Mar 4, 2021 at 12:50
  • 1
    $\begingroup$ Keep in mind that the theories are models of behavior. We want to think of them as explanations of the nature of nature. This is likely (but not certainly) fruitless. A better question might be "What is it about nature that makes our model so good?" For example, can the theories be developed from a set of symmetries? It's possible that more than one model describes the behavior as was the case in the early days of QFT. But this begs the question: "What is it about nature that causes it to have these symmetries?" I think you can see where this leads you. $\endgroup$
    – garyp
    Mar 4, 2021 at 12:53
  • $\begingroup$ @SolomonSlow I wasn't expecting these two interpretations of "what a particle is" to be completely unrelated. As QFT is a model which builds on more fundamental QM ideas like probabilistic positions/momenta, I was expecting it to incorporate QM's probabilistic description of particles into its description of particles. But maybe their descriptions of particles are completely different $\endgroup$
    – Ryder Rude
    Mar 4, 2021 at 13:02

2 Answers 2

4
$\begingroup$

It's tempting to try to interpret the mathematics of QM or QFT too literally, however this can be a dangerous game to play. Quite often you will cause more problems for yourself than you will solve by asking what exactly particles are (are they points, are they waves, are they fields, are they strings etc.), not least because different theories will give you completely different answers.

Arguably (although I'm not sure this is in huge contention) the only meaningful physical information you can obtain in any theory is the prediction of physically measurable quantities. You can sink an endless amount of time into trying to visualise physics but usually you are just leaving yourself open to making mistakes because the real world often deviates from your "intuition". Especially when you start dealing with more abstract theories like quantum mechanics.

I hope this answer is somewhat useful, it might sound like I'm telling you to simply ignore the problem, but in my experience the question you're asking doesn't have a satisfying answer that isn't massively open to interpretation.

$\endgroup$
2
  • $\begingroup$ Oh. I was expecting both interpretations to unite somehow as QFT is just a model based on more fundamental Quantum mechanics ideas like uncertainty principle and probabilities. Does all of the probabilistic weirdness of the copenhagen interpretation go away in QFT? $\endgroup$
    – Ryder Rude
    Mar 4, 2021 at 12:31
  • 1
    $\begingroup$ QFT is entirely compatible with QM. Probabilities are still hard-wired into QFT just as they are in QM, the main difference is that in QFT the number of particles is no longer required to be constant, and the theory is consistent with special relativity. These two things are not trivial to include, QFT is considerably more messy than QM in practice (and in many cases not even well defined with current machinery). QFT does not provide a resolution to the measurement problem either. $\endgroup$
    – Charlie
    Mar 4, 2021 at 13:20
1
$\begingroup$

Here is another way to look at this which might be helpful.

For objects small enough that quantum mechanical effects cannot be ignored, material particles begin exhibiting wavelike properties. Whether we detect their material aspect or their wavelike aspect then starts to depend on the physical details of the detection apparatus we are using.

This is because to detect the location or momentum of one of these tiny things, we have to physically perturb it in some manner which unavoidably affects its behavior. It is as if trying to measure the location of a thrown baseball causes its velocity to change; similarly, if we try to measure the speed of that ball, its location is changed.

For objects the size of a baseball, those sort of effects are so small that it is impossible to detect them, but for objects like electrons, those effects are dominant.

In this connection, trying to measure the momentum of an electron alters its position and the more precisely we make that momentum measurement, the less certain we can be of its exact position. That "smeared-out" aspect of its position makes it seem as though the electron has stopped behaving like a point particle and is starting to act like a wave instead.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.