there is something associated with a physical quantity that describes a theory (principles and laws) which is already validated by the experiments. - Quora
What does “exist” mean in physics? In my thinking, the term “exist” in physics means there is something associated with a physical quantity that describes a theory (principles and laws) which is already validated by the experiments.
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Alan Cooper
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Some Guy on the Internet (1980–present)2y
The term “exist” doesn’t really exist in physics per se (though it may be popular among philosophers and “interpreters” of physics).
In the community of physicists, just as in the world at large, the claim that something exists is, I think, generally taken to imply that the thing in question is being identified with a phenomenon that is, in principle, apparent to any rational entity that is in a position to observe it. So, for example the existence of pain from my tooth cannot be denied by anyone other than either myself or someone with a way of detecting nerve impulses from that tooth to my brain; but the existence of the garden gnome that I (think I) see sitting on the couch in my living room can be denied (or confirmed) by any other (rational) person in the room.
The idea that “there is something associated with a physical quantity that describes a theory (principles and laws) which is already validated by the experiments” is too vague to be useful (and certainly is wrong because of the “already validated” condition, as several answers have already pointed out).
The claim of existence of photons, for example, is a popular way of expressing the fact that energy exchanges between the electromagnetic field and other entities appear to occur in discrete chunks or “quanta”. Since this is something that could in principle have been observed by anyone who performed the relevant experiment (including before the time when it was actually done), it is generally understood that photons “exist” (and have always existed), as units of such energy exchange, at the particular point in time and space where the exchange is (or could be) observed to happen. But it is a misunderstanding of the theory to infer that in between such events the photon “exists” as something that travels a well-defined trajectory between them.
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Anil Mitra
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I write on philosophy.2y
Originally Answered: What does “exist” means in physics?
In my thinking, the term “exist” in physics means something exists, which is associated with a physical quantity that describes a theory (principle and law) that is already validated by the experiments.
‘Particle’, ‘field’, ‘mass’, ‘momentum’, ‘space’, ‘time’… are some terms used in physical theories of the cosmos.
‘Exist’ is not a term used in the theories.
But in ordinary English to say something exists is to assert that there is such a thing. “I exist” means “I am”. If you get into philosophy, what ‘exists’ means, depends on one’s philosophical approach. Materialists think matter is the only ‘real’ kind of thing, so for materialists, something exists if it is material—which makes for a problem when a materialist asks whether ideas are real (I am not implying that the problem is insoluble).
Idealists think, roughly, that ideas, e.g., percepts, concepts, feelings, are the true reals. Existentialists may argue that existence itself is most fundamental—for them, something is real “if it is there” and is not to be measured in terms of—reduced to—matter or mind (they are not saying matter or mind are not real but that what they are is secondary to existence). I like that aspect of existentialism because it keeps things simple. However, the question remains—can we build up a true picture of the world based on existentialism? That is a project in philosophy (I hold that it can be done but to attempt to explain how to do so right here would not help answer the question).
So there are three approaches I suggest in explaining what exists means regarding the objects of the theories of physics.
Many physicists take for granted that the entities described in the most successful fundamental theories exist—i.e., they think of quantum and gravitational fields as examples of things that exist.
Other physicists, perhaps a little more philosophical, think, okay, we used to think Newtonian particles were ‘real’, but now our modern theories tell us that they were not really real, so maybe a future physics will tell us that quantum fields are not really real. Such physicists—and philosophers and thinking people generally—may think of the theories as models of reality, of what exists, and leave the question of the true nature of existence open.
Philosophical, for which refer to the third paragraph of this answer.
For a short term, practical answer I prefer #2 (#1 is fine for a practicing physicist, but is not an answer); for a long term ‘true’ answer, I prefer the approach from existentialism but would change my preference when and if a final true and complete physics is developed.
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Brent Meeker
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Studied Physical Sciences & Computer Science at The University of Texas at Austin (Graduated 1974)2y
That’s a good answer and it’s what W.V.O. Quine said. But I think of that as defining what it means to exist in a theory. Of course if the theory is true, then it also defines what exists in reality. But sadly we never know that our theories are true. I like the definition of my later friend Vic Stenger used: “If when you kick it, it kicks back.” That’s not strictly definitive since, as Vic knew, “kicking it” is always in part theory dependent. So from literally kicking a rock to “kicking” a rock with a gamma ray spectrometer is a little further from reality. But it means that mathematical structures like Hilbert space don’t exist; there are too many other mathematically equivalent formulations of quantum mechanics.
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Johann Holzel
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Originally Answered: What does “exist” means in physics? In my thinking, the term “exist” in physics means something exists, which is associated with a physical quantity that describes a theory (principle and law) that is already validated by the experiments.
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I think you’re mixing up ontology with theoretical support.
Before a certain point, nobody had any idea that quarks existed. Then, we knew there was some structure inside hadrons, but had no idea how it could work. A number of speculative theories were deployed, but of course none of them were actual theories validated by experiment. One of those, the quark model, turned out to work—but even then, it was hard to get any new predictions, rather than just retrodictions of known data, until quantum chromodynamics was developed.
So, are you suggesting that quarks did not exist in 1960, and suddenly came into existence (everywhere? only in our labs? in an expanding volume of spacetime about our labs?) once QCD passed enough tests?
Also, I’m not sure what the qualification “associated with a physical quantity” is supposed to mean. You can associate anything with a physical quantity; so what?
And a physical quantity certainly doesn’t describe a theory; it’s the other way around.
And a theory isn’t a principle and law; it’s more an explanation and model, where the explanation fits with neighboring theories and the model has been validated by experiment.
But, again, I don’t think any of this has anything to do with existence, either to a physicist or to a philosopher of science.
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Todd Smith
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Former Natural Born Metaphysician. 2y
Originally Answered: What does “exist” means in physics? In my thinking, the term “exist” in physics means something exists, which is associated with a physical quantity that describes a theory (principle and law) that is already validated by the experiments.
What “exist" means in today's physics is actually a metaphysical question, and the answer you will get from various physicists is dependent upon the metaphysical framework individual physicists choose to see through or look at the world from. Have you ever notice that physics has no ontology for physical matter? And the reason for this is because physical reality itself reduces to metaphysics. Planck was the Grandfather of quantum mechanics. QM is a million times more accurate than Newtonian physics at making predictions and is the best model science has ever produced. The problem is no one can explain it. All interpretations of QM are metaphysical theories that are never going to be proven in my opinion. What Planck discovered is that all matter reduces to a nonphysical form that can only be described in the language of mathematics. But at and around the Planck scale, the equations themselves disappear and this is why it makes no sense to peer below the Planck scale. Quantum physicists don't see any real solutions to the problem of what actually exists in reality. All physical matter has an non empirical component at the quantum level and there is no way to know what is actually going on at the quantum level. Heisenberg declared that we stand somewhere between an idea and an actual real object. Planck himself declared that consciousness was foundational to reality itself. At the Planck scale, the entire physical universe reduces to mathematical equations. But those equations themselves disappear and become undetectable at the quantum level. And this is precisely why physics has no ontology for physical matter. And, like it or not, I believe Planck nailed the actual Truth of things when he declared that consciousness was foundational to reality itself. All reasoning has no choice but to presuppose a Rational Universe by logical and metaphysical necessity of thought itself. And physicists speak of quantum particles as being omnipresent, omniscient and omnipotent which are the 3 main attributes of God according to Theology. I personally believe that the metaphysical math adds up to a universe that ultimately reduces to MIND. Planck, Schrodinger and Heisenberg among others held the same thing. And of course this is precisely what Heraclitus, Pythagoras and Plato told us some 2500 years ago.
I would add that you are correct that physics is justified or validated by experiments. And it is precisely because of what those experiments revealed that physics was forced into the theory of quantum physics. The theory of quantum mechanics is on solid ground via experimentation. But as Feynman asked, “What are the equations actually telling us”? In other words, what lay beneath the equations of a metaphysical Universe? Consciousness or Mind just as Planck declared.
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Danilo Angelo
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Graduate in Computer Engineering & Electrical Engineering, University of Campinas (UNICAMP) (Graduated 2000)
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Originally Answered: What does “exist” means in physics? In my thinking, the term “exist” in physics means something exists, which is associated with a physical quantity that describes a theory (principle and law) that is already validated by the experiments.
What about “be associated with one 4 dimension coordinate in space-time, or with a set of them”?
“Exists” in the simple present tense would mean “being associated with one 4 dimension coordinate in space-time, or with a set of them, being that the temporal coordinate is set to the present moment”.
Does that match you expexctations?
