# Particle Wave and time

So I'm not trained in physics. I'm self taught on most I know but this obviously gives me a huge handicap.

My question is: If a particle can also be a wave, is that wave spread out and frozen in a "time slice" a cross space time?

So... Would particle A, that's also a wave, exist in the same state since its origin?

I'm seeing a wave as if I dropped a rock in a pond. I have 3 measure points spread out from the first wave and then one every 4th wave (that's just for argument sake). So even though the wave has moved on in time, if I observe each measure points, they will all display the exact same particle?

• Possibly related; a particle is described by a finite wavepacket of probability, more than a wave. – Cosmas Zachos Jul 10 '18 at 19:56
• The mistake is trying to visualize "a particle as a wave" or vice versa. You don't really want to think about it as either. Rather, you want to think of the system being in some "state". That state, as time goes on (and depending on the initial state), is usually in a "superposition" of other states. It's this word "superposition" that we humans don't really have a good intuition for. But, I think of it as this quasi-purgatory of neither-being-here-nor-there-ness. English can't do it justice, math can do it better. The more you learn about it, the better your intuition will become. – InertialObserver Jul 11 '18 at 3:13

I'm not sure I understand everything in your original post (the last paragraph isn't clear to me). In it's simplest interpretation we can think of sufficiently low mass particles (think electrons) as having wave properties that are expansive in space and time. Generally the way this is taught (the proper interpretation of QM is an area of active debate) is that a particle has a probability wave spread through space and (possibly) varying with time. This probability wave (which, in extreme simplification, can be thought of as something like a radial sine wave which also decrease with distance, $sin(x)*e^{-x}$) which tells us how likely we are to "find" the given particle at a specific location when "measured", where you can think about measurement as some kind of interaction, such as a photon interacting with an electron.

So the wave associated with a given particle has a spatial extent but that doesn't mean the particle actually occupies many places simultaneously but rather it has a certain likelihood of occupying a give spot if the particle interacts with another particle.

• So does the double slit experiment not mean that some particles are in two (or more) places at the same time? Does that not mean they could be in different place still back in time to its origin? Essentially meaning that it has not past present or future but exists in all of them? – JohnFreethought Jul 10 '18 at 19:43
• @JohnFreethought the double slit experiment when performed one particle at a time, shows each particle as a dot. the sinusoidal pattern called interference is seen as one builds up one electron at a time the distribution, which is a probability distribution by construction ( sane as throwing dice which should give a flat line if the dice are unbiaced, by definition of probability curve) en.wikipedia.org/wiki/… – anna v Jul 11 '18 at 3:58
• Thank you so much for your time. This helps a lot and I understand better now – JohnFreethought Jul 11 '18 at 6:26

I'm a self study person also so good luck with it.

My question is: If a particle can also be a wave, is that wave spread out and frozen in a "time slice" a cross space time?

No, it's not frozen in time.

The reason we use wave particle duality is because we have mutually contradictory experimental results to reconcile.

I have a related answer here: The Shape of Waves

Treating the entity as a particle : we take electron photo emissions from metal as the usual example, andin this case we need to treat the entity as a particle, as treating it as a wave means we would be waiting a long time for an electron to be emitted. ( There are some theories that explain this using waves, but I would leave them for now)

Treating the entity as a wave: If the wave was frozen in time, we would not be able to explain the double slit experiment, we need a moving wave to explain interference effects.

I'm seeing a wave as if I dropped a rock in a pond. I have 3 measure points spread out from the first wave and then one every 4th wave (that's just for argument sake). So even though the wave has moved on in time, if I observe each measure points, they will all display the exact same particle?

No, particles of the same types are indistinguishable, so although an electron can be treated as if it was the same moving particle throughout the process, actually it's not. If you want to know why this is, you need to read Particles and Fields.

• Thank you so much for the link to particles and fields. Its exactly what I needed. – JohnFreethought Jul 11 '18 at 6:29

If a particle can also be a wave, is that wave spread out and frozen in a "time slice" a cross space time?

so, to handle your question one must leaf through the history of investigations in 'dual' nature of particles- are they waves or particles?

The de Broglie proposition that a particle of certain momentum can show a 'wavy' nature was confirmed by several experimenters looking at scattering of particles like 'electron', 'neutron' diffraction experiments.

the diffraction peaks were very much identical to X-ray diffraction peaks as if the the waves scattered were interfering and using Bragg's Law could explain the pattern.

So , that is history of looking at particles but getting a wavy nature.

The wavelength of those particles of momentum p came out to be exactly as

wavelength = h / momentum(p) ; where h is the Planck's constant.

So, all confusions could be set aside as physical world gives its 'signature' through different designed experiments and observations are to be taken in even if with a pinch of salt.

But your picture that the 'waves' may be 'frozen' in time slice did not come out as in the experiments in laboratories had never did a time slice measurement.the time was flowing as continuous river through out the observations.

I'm seeing a wave as if I dropped a rock in a pond. I have 3 measure points spread out from the first wave and .....

Your later observation of looking at a purely classical wave and trying to locate the particle nature is not in line with the dual picture observed in the described above diffraction experiments .

looking for a particle Einstein looked at the light waves of different frequencies falling on a metal plate and found some electrons coming out from it...the ejection of electrons from the metal surface followed an

energetics that came down to 'picturing' light waves as stream of balls/particles hitting the surface electrons and exchanging its energy such

that the incident frequency( energy =h.f) just matched the energy of electrons coming out added to the work function of individual metals (which represented a binding energy of surface electrons of metals).

the energetics of these 'photo electrons' told a story of light waves behaving like a bunch of balls called photons and the phenomena could be described as photons hitting the individual electrons and sharing energy such that

Photon Energy = work function + Kinetic energy of electron

these E.M. waves do not need medium to pass through, whereas your observation on ripples on water is actually water/medium particles oscillating up and down

and you perhaps tried to freeze it for looking at a particle representation of waves.

However , the people trying to reconcile the two observations (described above) of " particles diffracting like waves" and "waves moving like particles"

have tried their best to theoretically construct representation of particles by superposition of waves of varying momentum and getting a packet of waves whose

movements may represent a particle picture and this wave packet analogy fits the quantum picture.

and particles moving with a wavy pattern associated with it fits the other side...but it will depend on design of your experiment whether you wish the wave character to be expressed or a particle picture.

thereby one will have to look for "proper" measurements in the quantum world.

• Thank you so much for your time. This helps a lot. There was a lot I didn't consider before. Your explanation make so much sense. Thank you – JohnFreethought Jul 11 '18 at 6:27

It seems like the question is motivated by causality, or thoughts regarding causality, and the relativistic speed limit imposed on all signals and interactions. Since Schrodinger's equation is non-relativistic the the question doesn't really apply in this context. The wave function represents the probability amplitude to find the particle in a given state. For traveling wave there certainly is a velocity, or velocity related information, that is a measure of the particle's velocity (or it's possible observed velocities). But there is no medium like a fluid whose properties determine a wave velocity. There is a continuum of possible velocities that can be present in an arbitrary wave-function, and each is a potentially observed velocity of a particle.

• Most likely. I think I was trying to describe to much with to little understanding. Thank you for the time you took – JohnFreethought Jul 11 '18 at 6:28
• Quantum waves are not created by dropping a particle, or by a source (as in the example of the post). They carry information about likely observations but don't have a source like acoustic waves. – ggcg Jul 11 '18 at 10:46