Why do Photons Exhibit Quantum Behavior?

I don't know how many people here are familiar with quantum physics, so I'll focus on the basic double slit experiment. The experiment in question shows that certain particles behave both as a particle, and as a wave.
For example, an electron will provide a wave pattern (the same pattern as a wave) when fired through the double slits, while we know that they are particles (and if an instrument interferes to observe, they exhibit the same behavior as a particle).

It is also known that light does the same: it acts as a wave, but we also know that light is composed of particles called photons. My question is why: electrons, for example, possess a mass. It is very small, but they do possess it: the fact electrons may act as a particle is then not surprising.
How can a photon exist, then, if it does not have mass (which it must not to travel at the speed of light)? All known particles, however small, have some mass.

I first came upon this question while studying the concept of 'Solar Sails', which are propelled by the light from the Sun. This initially puzzled me, as how could a massless particle impart momentum, but it was quickly answered once the idea of a particle moving at light-speed and the relative formulae were used. (Momentum appears in another involved formula, for those interested, and can be calculated separately to find it would indeed have a value for a relativistic particle).

However, this doesn't seem to explain a non-mass exhibiting the behavior of a particle. What, for example, would compose a photon if it is not made of any substance involving mass?
I realize this question sounds bizarre, as fundamental particles like quarks and electrons and photons are not thought of to be made up of anything, but the fact remains that, as a particle, it occupies some position in space, and does so as an actual, tangible thing, and even if it can sometimes behave as a wave (as electrons, entities with mass, do) it still exists as some form of particle. If it can have a volume, however miniscule, which it must if it is a particle, how could it not also possess mass?

This is not to question the results of the experiments: simply to query. Why does a non-mass still behave enough like a particle to exhibit quantum behavior?

What exactally is the question?  I am a bit unclear on that.

What exactally is the question?  I am a bit unclear on that.

How is it photons possess some particle-like behavior when they cannot possess mass?
(That's the gist, the explanation is in the first post).

Quote from: mikeman7918 on September 02, 2015, 12:16:04 PM

What exactally is the question?  I am a bit unclear on that.

How is it photons possess some particle-like behavior when they cannot possess mass?
(That's the gist, the explanation is in the first post).

Because they are quantized. They are made of pure energy.

Because they are quantized. They are made of pure energy.

If that were so, how do they behave as particles?

Quote from: sokarul on September 02, 2015, 03:20:53 PM

Because they are quantized. They are made of pure energy.

If that were so, how do they behave as particles?

For starters, when you detect them. If you have a 5 Mev photon, you should be able to detect 5 MeV with a detector.  You can create a photon, have it propagate a distance as a wave, then hit a detector and have the detector detect one count. Two photons will give two counts. 

I'm really not sure how you can think we know nothing about physics, claim you can teach us how a photon has momentum as if we didn't know, but then not know such a simple idea and have to ask such a simple question.

For starters, when you detect them. If you have a 5 Mev photon, you should be able to detect 5 MeV with a detector.  You can create a photon, have it propagate a distance as a wave, then hit a detector and have the detector detect one count. Two photons will give two counts. 

I'm really not sure how you can think we know nothing about physics, claim you can teach us how a photon has momentum as if we didn't know, but then not know such a simple idea and have to ask such a simple question.

Are you being serious? I am trying to behave reasonably here, but I am not sure how you could intentionally misread me in that way.
I outlined the experiments which show light behaves as a wave and a particle in the original post. I am perfectly aware of what you're saying. My point is that there seems to be an inherent contradiction between the notions of a presence as a particle, and a presence with no mass. Perhaps you could do me the courtesy of reading my posts before dismissing them.
This is why I asked how it was possible for a massless photon to behave as a particle. Not why we know they do (which I clearly know as I have explained it), but how it is possible for something with no mass to function at all like a particle.

(The question of a photon having momentum is not so simple: momentum is mass times velocity, and they have no mass. Even so, I just mentioned that as an aside for any who wished to know, it's irrelevant).

Quote from: sokarul on September 02, 2015, 04:02:51 PM

For starters, when you detect them. If you have a 5 Mev photon, you should be able to detect 5 MeV with a detector.  You can create a photon, have it propagate a distance as a wave, then hit a detector and have the detector detect one count. Two photons will give two counts. 

I'm really not sure how you can think we know nothing about physics, claim you can teach us how a photon has momentum as if we didn't know, but then not know such a simple idea and have to ask such a simple question.

Are you being serious? I am trying to behave reasonably here, but I am not sure how you could intentionally misread me in that way.
I outlined the experiments which show light behaves as a wave and a particle in the original post. I am perfectly aware of what you're saying. My point is that there seems to be an inherent contradiction between the notions of a presence as a particle, and a presence with no mass. Perhaps you could do me the courtesy of reading my posts before dismissing them.
This is why I asked how it was possible for a massless photon to behave as a particle. Not why we know they do (which I clearly know as I have explained it), but how it is possible for something with no mass to function at all like a particle.

(The question of a photon having momentum is not so simple: momentum is mass times velocity, and they have no mass. Even so, I just mentioned that as an aside for any who wished to know, it's irrelevant).

We are already talking about the dual slit experiment in the Light=sound thread.

I did read your post. It's all over the place, probably why mikeman7918 wanted clarification. Here:

My question is why: electrons, for example, possess a mass. It is very small, but they do possess it: the fact electrons may act as a particle is then not surprising.
How can a photon exist, then, if it does not have mass (which it must not to travel at the speed of light)? All known particles, however small, have some mass.

Photons are just energy where as electrons are more than that. Energy cannot be created or destroyed, but it exists.

What, for example, would compose a photon if it is not made of any substance involving mass?

Nothing. It's energy.

If it can have a volume, however miniscule, which it must if it is a particle, how could it not also possess mass?

I don't think waves have volumes. Photons can occupy the same space as other photons where as electrons can't.

I did need to be 'all over the place' as you say, as there's a lot to cover. Even so, you could see the experiment you brought up directly mentioned.

Energy does exist, but it does not behave as a particle does. Waves do not have volumes, but particles do, and for photons to have any particle-like behavior so must they, in some fashion. Photons are not waves, though they exhibit some properties.
For something to exhibit the necessary traits of a particle, however, it seems (as far as current knowledge goes) that it would need to have some volume.

Electrons are just an analogy, but they make the point. Something with mass, that still functions as a wave: it shows that it's possible.

I did need to be 'all over the place' as you say, as there's a lot to cover. Even so, you could see the experiment you brought up directly mentioned.

Energy does exist, but it does not behave as a particle does. Waves do not have volumes, but particles do, and for photons to have any particle-like behavior so must they, in some fashion.

This is your opinion.

Photons are not waves, though they exhibit some properties.
For something to exhibit the necessary traits of a particle, however, it seems (as far as current knowledge goes) that it would need to have some volume.

Photons can act as particles and waves. They do not have to show all the properties of a particle.

Electrons are just an analogy, but they make the point. Something with mass, that still functions as a wave: it shows that it's possible.

Yes we know what De Broglie wavelengths are.

Photons can act as particles and waves. They do not have to show all the properties of a particle.

True: that is why I am only relying on the properties that have been observed.

It seems to be more than just my opinion that a volume is required for a particle to have any of its associated properties. Without that volume, it follows that no particle behavior is possible.

Quote from: sokarul on September 02, 2015, 05:33:06 PM

Photons can act as particles and waves. They do not have to show all the properties of a particle.

True: that is why I am only relying on the properties that have been observed.

It seems to be more than just my opinion that a volume is required for a particle to have any of its associated properties. Without that volume, it follows that no particle behavior is possible.

An answer that may satisfy you is that in order for a particle to have mass it is required that it has interactions with the higgs boson, a particle that photons do not interact with. It is not scientifically verified, but it would help answering your question.

An answer that may satisfy you is that in order for a particle to have mass it is required that it has interactions with the higgs boson, a particle that photons do not interact with. It is not scientifically verified, but it would help answering your question.

Thank you for the answer. That does explain it, partially: though as you say, with no scientific verification it seems we're at the edges of current science, so questions like how or why are quite tricky.
It is about what I suspected, though: there are aspects of light not completely understood. They're understood if a separate theory holds, but even then some details are not forthcoming (such as why there is no interaction between the Higgs-Boson and a photon).

Photons may act much like particles in many instances, but they don't have all properties commonly associated with particles.  For starters: they have no mass.  Since they have no mass a force of 0 can accelerate the particle infinitely fast but because of relativistic effects that infinite speed is perceived as being the infamous speed of light.  From a photon' perspective it is emitted and absorbed at the exact same instant because time dilation does some wierd things (but that's a topic for another day).

The main particle like property of light is that it's quantized.  It comes in packets that are indivisible and when a single photon is fired it is detected in a single location.  The properties of light are very well understood by science.

Photons may act much like particles in many instances, but they don't have all properties commonly associated with particles.  For starters: they have no mass.  Since they have no mass a force of 0 can accelerate the particle infinitely fast but because of relativistic effects that infinite speed is perceived as being the infamous speed of light.  From a photon' perspective it is emitted and absorbed at the exact same instant because time dilation does some wierd things (but that's a topic for another day).

The main particle like property of light is that it's quantized.  It comes in packets that are indivisible and when a single photon is fired it is detected in a single location.  The properties of light are very well understood by science.

The properties of anything can be fully understood: the problem is how they can be reconciled. This was my question: the only particle-like properties they possess would still indicate a volume of some description, which would normally imply mass. A lot of things are quanta, but photons are the only kind which have no mass.
The relationship with the Higgs-boson serves as a perfectly good answer to the question, and the only one I've seen.

It seems odd to call a photon indivisible, however: take the wave behavior in the double slit experiment. For quanta, 'indivisible' seems a misleading term to use: after all, it only makes sense when talking about something tangible like a particle.

The properties of anything can be fully understood: the problem is how they can be reconciled. This was my question: the only particle-like properties they possess would still indicate a volume of some description, which would normally imply mass. A lot of things are quanta, but photons are the only kind which have no mass.
The relationship with the Higgs-boson serves as a perfectly good answer to the question, and the only one I've seen.

It seems odd to call a photon indivisible, however: take the wave behavior in the double slit experiment. For quanta, 'indivisible' seems a misleading term to use: after all, it only makes sense when talking about something tangible like a particle.

In the standard model (the model that's generally accepted that does not include string theory) has every particle bring infinitely small points with no volume, not just photons.

The double slit experiment is not a photon dividing, it's in multiple places at once which does not imply any devision.  If you wanted to emit light you cannot emit 1/2 of a photon or 1/4 if a photon, you have to emit the whole photon.  An easier way to think of it is that a photon is a quantized "packet" of light.

In the standard model (the model that's generally accepted that does not include string theory) has every particle bring infinitely small points with no volume, not just photons.

Every particle would ultimately consist of those infinitely small points, but that's not really meaningful. The elementary particles that we're concerned with, (as infinitely small directly implies no volume: while photons are not infinitely small as they interact with matter) exist on a larger scale.

Quote from: mikeman7918 on September 03, 2015, 12:19:06 PM

In the standard model (the model that's generally accepted that does not include string theory) has every particle bring infinitely small points with no volume, not just photons.

Every particle would ultimately consist of those infinitely small points, but that's not really meaningful. The elementary particles that we're concerned with, (as infinitely small directly implies no volume: while photons are not infinitely small as they interact with matter) exist on a larger scale.

Actually photons do in fact have no volume.  Nothing ever really touches and the only way anything interacts with anything else is via the fundamental forces.  The reason you are not passing through the floor is because the electrons in your atoms are repelling the electrons in the floor because like charges repel.  The same goes everywhere else.  As far as we know, at a quantum scale everything is made up of infinitely small points.  String theory suggests that everything is made up of tiny vibrating strings, but that's yet to be proven and it's a topic for another day.

Actually photons do in fact have no volume.  Nothing ever really touches and the only way anything interacts with anything else is via the fundamental forces.  The reason you are not passing through the floor is because the electrons in your atoms are repelling the electrons in the floor because like charges repel.  The same goes everywhere else.  As far as we know, at a quantum scale everything is made up of infinitely small points.  String theory suggests that everything is made up of tiny vibrating strings, but that's yet to be proven and it's a topic for another day.

Everything will by default be made up of infinitely small points: you can zoom in an arbitrary amount, at least in theory. What matters is whether it's feasible to do so: electrons, for example, have mass. For a lack of volume to have mass seems, at best, counterintuitive.
Though admittedly much of quantum theory is that. Words aren't really meant to describe it: my understanding is that electrons do possess a volume, it simply isn't centred at a particular point: it's just a haze of probably locations.

This seems to be getting off-topic. Even so, I'm happy with the answer I've received.

Everything will by default be made up of infinitely small points: you can zoom in an arbitrary amount, at least in theory. What matters is whether it's feasible to do so: electrons, for example, have mass. For a lack of volume to have mass seems, at best, counterintuitive.
Though admittedly much of quantum theory is that. Words aren't really meant to describe it: my understanding is that electrons do possess a volume, it simply isn't centred at a particular point: it's just a haze of probably locations.

This seems to be getting off-topic. Even so, I'm happy with the answer I've received.

Having point particles is quite problematic and it's actually the reason for the contradiction between relativity and quantum mechanics.  That's why string theory is being developed: it solves this contradiction and the probekems you speak of but it's yet to be conclusively proven.

Having point particles is quite problematic and it's actually the reason for the contradiction between relativity and quantum mechanics.  That's why string theory is being developed: it solves this contradiction and the probekems you speak of but it's yet to be conclusively proven.

Thank you.
Do you see the reason for some of my wariness when it comes to science, however? All three of the theories you mention come from one source: interpreting reality. As with most things though, it is always going to be impossible to determine if you've examines every possibility: there might be one idea you've never thought of.
If string theory cannot be proven, what will that mean? It is of course possible that an alternative way to reconcile the two may be found: it's also possible that there is a completely different take on all the results we have for both relativity and quantum theory. If so, that could be the answer we needed: not to build on a foundation, but to reject it as flawed and to start anew.
Unfortunately, once a theory reaches a certain age, or a certain amount is based upon it, scientists become unwilling to do so.
It's the blind men and the elephant. Science is a very powerful tool, but it is still limited by what humans can hypothesize.

Thank you.
Do you see the reason for some of my wariness when it comes to science, however? All three of the theories you mention come from one source: interpreting reality. As with most things though, it is always going to be impossible to determine if you've examines every possibility: there might be one idea you've never thought of.
If string theory cannot be proven, what will that mean? It is of course possible that an alternative way to reconcile the two may be found: it's also possible that there is a completely different take on all the results we have for both relativity and quantum theory. If so, that could be the answer we needed: not to build on a foundation, but to reject it as flawed and to start anew.
Unfortunately, once a theory reaches a certain age, or a certain amount is based upon it, scientists become unwilling to do so.
It's the blind men and the elephant. Science is a very powerful tool, but it is still limited by what humans can hypothesize.

String theory is being approached with a lot of skepticism and one of the top priorities of string theorists is to find a way to conclusively prove or disprove string theory.  There are some predictions made by string theory that could possibly be verified by a large enough particle collier but no such things have been observed yet and it is unknown weather that means our collides are not big enough or that string theory is false.  String theory is certainly not widely accepted as there are many people who oppose it, mostly because opposition is the fastest way to figure out if a theory is true.  Without evidence it will not be widely accepted until it's proven,

Science is specifically designed to get around issues like bias, and there have been many times where drastic modifications to preconceptions and previous models were made that are now widely accepted.  The two most notable are special relativity and quantum mechanics.  Relativity shows that gravity was not quite as Newton thought it was and that although Newton's laws predicted gravity nicely in every day situations they didn't work in more extreme scenarios which is why it was revised, and relativity also showed us that the Newtonian notion of time and space being constant, separate, and unchanging are false as space and time are a single entity that can move and flow.  Quantum mechanics showed everyone that the universe is uncertain at a fundamental level which challenged the Newtonian notion of the universe being fully predictable.  There have even been things like the heliocentric model that challenged the long held belief that Earth was the center of the universe and now Earth orbiting the Sun is widely accepted.  The point is: you don't really have to worry about a theory not being accepted just because it challenges long held notions.

String theory is being approached with a lot of skepticism and one of the top priorities of string theorists is to find a way to conclusively prove or disprove string theory.  There are some predictions made by string theory that could possibly be verified by a large enough particle collier but no such things have been observed yet and it is unknown weather that means our collides are not big enough or that string theory is false.  String theory is certainly not widely accepted as there are many people who oppose it, mostly because opposition is the fastest way to figure out if a theory is true.  Without evidence it will not be widely accepted until it's proven,

I am aware of the scientific method. it should be pointed out, however, that string theory will never be proven: science is not about proof. Go to pure maths if you want proof, in applied maths and science it's only about probability. String theory has made certain predictions; we will then see whether those predictions are accurate. This would not preclude an alternative theory being able to cause the exact same observations.
In addition, just because the scientific method instructs behavior a certain way, this doesn't mean scientists will automatically behave that way.

Science is specifically designed to get around issues like bias, and there have been many times where drastic modifications to preconceptions and previous models were made that are now widely accepted.  The two most notable are special relativity and quantum mechanics.  Relativity shows that gravity was not quite as Newton thought it was and that although Newton's laws predicted gravity nicely in every day situations they didn't work in more extreme scenarios which is why it was revised, and relativity also showed us that the Newtonian notion of time and space being constant, separate, and unchanging are false as space and time are a single entity that can move and flow.  Quantum mechanics showed everyone that the universe is uncertain at a fundamental level which challenged the Newtonian notion of the universe being fully predictable.  There have even been things like the heliocentric model that challenged the long held belief that Earth was the center of the universe and now Earth orbiting the Sun is widely accepted.  The point is: you don't really have to worry about a theory not being accepted just because it challenges long held notions.

The heliocentric case is far from representative: and you can't deny that the community at large didn't exactly welcome the replacement of part of the theory.
Even when it comes to Newton, the core of Newton remains completely respected: special cases have simply been added. There's a difference between adding an asterisk, and striking out a paragraph: I doubt many, if any, have considered that, rather than unifying three disparate models, they should be rejected as a flawed framework and a new one developed from scratch.

All the technology we have certainly shows that our understanding of the universe, while not perfect, is quite good.  There is no reason to start from scratch if we have come so far already.  If you can come up with a new working verifiable model then I am sure that scientists will be all ears but until then everyone will just stick with the current model, which has successfully put men on the Moon and sent proves all over the Solar System.

All the technology we have certainly shows that our understanding of the universe, while not perfect, is quite good.  There is no reason to start from scratch if we have come so far already.  If you can come up with a new working verifiable model then I am sure that scientists will be all ears but until then everyone will just stick with the current model, which has successfully put men on the Moon and sent proves all over the Solar System.

Beyond talks of conspiracy, it should be acknowledged that only partial understanding is required for technology to work; the moon landing, if genuine, is certainly an impressive feat that would need a lot of technical knowledge. Even so, it was far from automated: there was plenty of room for human correction. All there needs to be is a similar enough system: and said system was based on observation, not pure maths.

What's arguably even more impressive then the Moon landings and something that is not debated is the invention of the computer.  Computers use quantom mechanics and chemistry to exploit the properties of impure silicon crystals and the behavior of electrons according to quantum mechanics to do logic.  They are very impressive and they do show that things like quantom mechanics, chemistry, and information theory are real.

What's arguably even more impressive then the Moon landings and something that is not debated is the invention of the computer.  Computers use quantom mechanics and chemistry to exploit the properties of impure silicon crystals and the behavior of electrons according to quantum mechanics to do logic.  They are very impressive and they do show that things like quantom mechanics, chemistry, and information theory are real.

Computing is impressive, though I'm not sure how relevant quantum theory is. Quantum computers are still strictly theoretical.

Quantum mechanics are at the basis of many semiconductive effects, and so, are the basis of current electronics.
Photons may be massless, but its not void of momentum. The equation E^2 = (m₀ * c^2) + (p^2 * c^2) , which is the actual general equation for energy in relativity (from which it can be simplified in many cases to the E=mc^2 equation) gives us a little hint at why. That is how light sails can propel themselves.

What's arguably even more impressive then the Moon landings and something that is not debated is the invention of the computer.  Computers use quantom mechanics and chemistry to exploit the properties of impure silicon crystals and the behavior of electrons according to quantum mechanics to do logic.  They are very impressive and they do show that things like quantom mechanics, chemistry, and information theory are real.

Not to mention frying pans!  Frying pans are known for their use of quantum mechanics.  If it was not for QM, frying pans would not exist!  Just think about how much QM theory and chemistry is in something that all of us take for granted everyday!  Do you not want to have frying pans?  Well, then, you had better study up on QM or mikeman will make another dumb post!

Please explain this then, other than an ad hominum.