# How do we know particles exist? Aren't they just waves?

In the book "A Briefer History of Time" Stephen Hawking wrote:

The unpredictable, random element comes in only when we try to interpret the wave in terms of the positions and velocities of particles. But maybe that is our mistake: maybe there are no particle positions and velocities, but only waves. It is just that we try to fit the waves to our preconceived ideas of positions and velocities. The resulting mismatch is the cause of the apparent unpredictability.

Are there evidences that disprove this hypothesis?

If true, would it eliminate most of the apparent quantum paradoxes, and necessity to "Shut up and calculate!" for those who attempt to interpret quantum physics with common sense?

Edit: I assume that S. Hawking is aware of Standard Model, and he considers this statement as a legitimate hypothesis. Are there evidences that prove that it's not? In other words, is it a philosophical or scientific question?

-
What is the definition of a particle? What is the definition of a wave? We can't answer your question until we know the definitions, because otherwise how do we know what a particle is? We're just arguing semantics. And if you don't write down the definitions carefully, you will find that the universe contains neither particles nor waves. – Peter Shor Nov 29 '14 at 21:59
If there are no distinguishing scientific definitions of waves and particles, then I assume it's more a philosophical question. Thank you for helping me to select the answer. – Serg Nov 30 '14 at 0:04
well ... I'm sure you can find definitions of waves and particles, but I don't think they're official agreed-on definitions, and I don't think they are that useful for solving this philosophical question. – Peter Shor Nov 30 '14 at 0:50
@PeterShor I think OP thought of classical particles and waves. A particle is a tiny point like object that have position and momentum. While wave is a disturbance spreading across some field described by a wave function eg. for surface waves on lake a function that describes height of the water at a position at a given moment. It's completely different. But I know in QM they are almost synonyms, and probably a source of lot of confusion. – Calmarius Dec 13 '14 at 16:38

It's not clear what sort of evidence could prove or disprove this idea. And that makes it philosophical, not scientific.

If someone were to develop an experiment by which we could distinguish between the two ideas, then the situation would change.

-

Hawking or not, the displayed statement is wrong. Wave theory was known two centuries ago and is very rigorous and predictive. It cannot explain the data for microscopic elementary particles.

What we call "elementary particles" at the microscopic level display properties of macroscopic type particles, as in this image of proton antiproton annihilation into pions:

and properties of wave type interference, of the kind we see with macroscopic waves, in innumerable different experiments, as this electron build up experiment with detectors at the slits.

The only consistent mathematical theory that encompasses both observations is that the quantum mechanical nature of "particles" is a probability function which displays spatial and timelike wave properties, mathematically as classical waves do, and particle properties under different experimental conditions.

Wave mechanics cannot do it, i.e. fit all the experimental data, otherwise it would have been done.

-
+1 for including images that clearly show both particle and wave properties :) – jabirali Nov 29 '14 at 19:49

read "What is a particle" by Rovelli and Colosi and also just any book about quantum fields on curved space. The truth is that our particle interpretation rests on an artifact of being in a flatish spacetime.

Sean Carroll's book on general relativity has a section at the end that is pretty accessible (albeit follows the book "Quantum Fields in Curved Space by Birrell and Davies rather closely") and outlines the notion that particle number is not conserved in a general spacetime. Thus it makes sense that Hawking would make a statement like this since his research prompted many of these ideas.

-
Particle numbers as such are not conserved if they are bosons. What is conserved are quantum numbers, like lepton number, baryon number, charge , etc and there are theories that may have the proton decay ( baryon number is lost) but they do keep B-L as conserved. – anna v Nov 2 '14 at 20:29

Contrary to what the cosmologist says, there are not waves [1], but just particles [2]. Everything around us has been found to be made of particles. The corresponding branch of physics is particle physics.

For a basic introduction to our current understanding of the structure of matter and the known particles

http://public.web.cern.ch/public/en/science/standardmodel-en.html

For a discussion of the wave-particle duality misconception and why there is no any real wave but particles

http://statintquant.net/siq/siqse3.html#x42-60003

[1] The wavefunction used in some formulations of quantum mechanics is not a physical wave, but an unobservable mathematical function.

[2] Quantum particles are not Newtonian particles. Quantum particles are not tiny balls and its motion is not described by classical mechanics.

-
Thank you. But this doesn't really answers the question. How do we know that particles in standard model aren't just our interpretation of waves measurements? What are the evidences for that? – Serg Dec 1 '12 at 0:03
I made an edit to my question in order to explain the comment above. – Serg Dec 1 '12 at 0:12
@Serg: As stated above there is no wave. No wave is detected/measured in the lab and there is not any wave in the theory; $\Psi(x,t)$ in quantum mechanics is not a wave but a function. It is not a question of interpretation. Everything what we measure are particles with well-defined properties such as energy, mass, spin, charge... – juanrga Dec 1 '12 at 18:39

## protected by Qmechanic♦Mar 15 at 7:01

Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.