# Infinite mass and energy.

If a photon is traveling at the speed of light, wouldn't infinite mass and energy be a condition?

It has no mass therefore zero mass times infinite mass still equals zero mass. However you would be correct in the case of an electron even though its mass is very tiny, when it is accelerated in a particle accelerator then it also would require infinite energy and acquire infinite mass if it travelled at the speed of light, so it can be accelerated to 99.9999% the speed of light and it takes more an more energy to keep getting it closer and closer, but as it's mass increased it requires more and more energy for smaller and smaller increases approaching but never attaining c.

Makes you wonder what light really is.

russ_watters
Mentor
Light is light. As with anything, it is the compilation of all of its properties.

This is precisely what I was investigating in this thread which has now been locked because someone put a very strange connotation on my "prove me wrong", which merely expressed a hope rather than a challenge. I have asked that the thread be reopened.

russ_watters
Mentor
Sorry, but those questions really don't have anything to do with science.

Dale
Mentor
2021 Award
This is precisely what I was investigating in this thread which has now been locked because someone put a very strange connotation on my "prove me wrong", which merely expressed a hope rather than a challenge. I have asked that the thread be reopened.
The thread was pretty useless, the lock was reasonable and re-opening it would surprise me greatly. Any time you have to use a "really" or "actually" in your question it is probably a non-scientific question, especially if you feel that you have to italicize or otherwise emphasize the word in order to properly ask the question.

In my experience threads with titles of the form "What is X?", where X is a single word basic physics concept, generally wind up being locked with one or more of the participants being banned. I am glad that the moderators locked it before it got to that point.

Dale
Mentor
2021 Award
Makes you wonder what light really is.
We know exactly what light is. Quantum electrodynamics completely describes every aspect of light.

In my experience threads with titles of the form "What is X?", where X is a single word basic physics concept, generally wind up being locked with one or more of the participants being banned. I am glad that the moderators locked it before it got to that point.

better to get it nutted out once and for all in one thread otherwise this forum will have endlessly questions like

Makes you wonder what light really is.

ceaselessly posted by lay persons.

We know exactly what light is. Quantum electrodynamics completely describes every aspect of light.

QED explains interactions, not photons.

I guess you subscribe to the idea of; "shut up and calculate." Or "light is light", or "gravity is gravity."

Keep on calculating, have fun.

ceaselessly posted by lay persons.

How would you know that?

In my experience threads with titles of the form "What is X?", where X is a single word basic physics concept, generally wind up being locked with one or more of the participants being banned. I am glad that the moderators locked it before it got to that point.

When an investigation into 'what is matter', which had some good replies and to which I was about to offer a considered response, is deemed unsuitable for a physics forum as it is beyond the abilities of the moderators to stop such a contentious question collapsing into peace shattering conflagration, then one may wonder what the point is of allowing the general public to participate at all. This is most disappointing.

Matterwave
Gold Member
QED explains interactions, not photons.

I guess you subscribe to the idea of; "shut up and calculate." Or "light is light", or "gravity is gravity."

Keep on calculating, have fun.

Since observations are interactions, and all of physics is about interactions, I'm not sure what kind of an explanation you want if the one offered by QED is not acceptable.

"Makes you wonder what light really is."

I think scientists are those who dare ask such questions.

How this forum can inspire young people to go into science is in my opinion not by putting down those who ask such questions even if they are laymen.

Dale
Mentor
2021 Award
QED explains interactions, not photons.
QED explains everything about light. There is not one single behavior or experimental observation about light which is not accurately predicted by QED.

If you can predict in detail what a given thing will do in every possible situation or interaction or relationship then you know what that thing is in the fullest sense of the word. Hence, we know exactly what light is.

Light is light. As with anything, it is the compilation of all of its properties.

But this is an answer to a classical question but a photon is a quantum object. This in essence is the problem is it not.

So in answer to 'what is a photon' the answer is that it is an electomagnetic wave, that may set off detectors that see it as a wave or as a particle depending on what type of detectors are used.

Which brings us right back to the real problem, which is comparing a quantum object to a classical object. To ask what a classical object is, is a perfectly acceptable question. What is a baseball, or what is a mountain. Most people will be satisfied with the answer. However the scientist is willing to answer the question, 'what is a baseball REALLY', by saying that REALLY, it is in fact a collection of up and down quarks and electrons, plus a couple of forces that hold them all together.

There is no problem with the word 'really' in this case.

It only gets the mentors all hot and bothered if one asks, but what is a quark 'really', this 'really' is really a pain and causes all sorts of huffing an puffing.

Ironically, because one of the foundations that all science is built on it the principle of relativity. What is relative and what is absolute needs to be considered when using the word 'reality'.

This is why it is preposterous for a science advisor on these boards to complain about being asked 'what is matter, or what is a photon, really (even if the 'really' is not italicised).

You see the concepts of 'relative' and 'absolute' are also applicable to terms like 'reality' or 'real'. Is a photon 'real'. No one seems to consider the question is really about what is meant by 'real'. I think what we mean by real in this context is, what is 'absolutely' real.

That is for example if I use a photon. Is a photon absolutely real. Asked like this it is a perfectly acceptable question. I suppose the next question is what does it mean to be absolutely real. And that would be as the speed of light is absolutely real because it's speed is not dependent on anything else, then for something to BE absolutely real, then 'be' means 'exists', so the question is, does a photon exist absolutely, or does it's existence depend on the existence of something else.

That's what we really want to know, when we ask 'what is matter'. Science reduces atoms to protons and protons to quarks, so atoms depend on the existence of protons and protons depend on the existence of quarks, and I suppose electromagnetic radiation may or may not depend on the existence of something else in order for itself to exist.

No I'm trying my best to keep this out of the realm of metaphysics because then I'll get a slap. However, the scientists started it all by reducing objects to things that are dipping their toes into the pool of metaphysical notions in fact maybe even wading in to the deep end.

Is there anything that is absolutely 'real', meaning that exists independently of anything else. Surely that's an OK question here. Otherwise why don't you put up a big disclaimer that says... "look we really don't have the faintest clue what any of this stuff that we study is, we can predict how it behaves and that enables us to build this big a55 five story high detectors and it's pretty much a lot of fun but in the end we are just amusing ourselves with the amazingness of it all, and you people out there should be content with your cars and computers and digital painting programs and microwave background plotting, that enrich your lives and which are the final products of our investigations.

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Dale
Mentor
2021 Award
better to get it nutted out once and for all in one thread otherwise this forum will have endlessly questions like ...
If one good thread were enough to end a topic "once and for all" then we wouldn't continue to see the daily thread on a photons rest frame, the weekly thread on the twin paradox, the monthly thread on FTL communication with a rigid rod, or the quarterly thread on something fast turning into a black hole.

Dale
Mentor
2021 Award
Any time you have to use a "really" or "actually" in your question it is probably a non-scientific question, especially if you feel that you have to italicize or otherwise emphasize the word in order to properly ask the question.

Which brings us right back to the real problem, which is comparing a quantum object to a classical object. To ask what a classical object is, is a perfectly acceptable question. What is a baseball, or what is a mountain. Most people will be satisfied with the answer. However the scientist is willing to answer the question, 'what is a baseball REALLY', by saying that REALLY, it is in fact a collection of up and down quarks and electrons, plus a couple of forces that hold them all together.

There is no problem with the word 'really' in this case.

It only gets the mentors all hot and bothered if one asks, but what is a quark 'really', this 'really' is really a pain and causes all sorts of huffing an puffing.

Ironically, because one of the foundations that all science is built on it the principle of relativity. What is relative and what is absolute needs to be considered when using the word 'reality'.

This is why it is preposterous for a science advisor on these boards to complain about being asked 'what is matter, or what is a photon, really (even if the 'really' is not italicised).

You see the concepts of 'relative' and 'absolute' are also applicable to terms like 'reality' or 'real'. Is a photon 'real'. No one seems to consider the question is really about what is meant by 'real'. I think what we mean by real in this context is, what is 'absolutely' real.

That is for example if I use a photon. Is a photon absolutely real. Asked like this it is a perfectly acceptable question. I suppose the next question is what does it mean to be absolutely real. And that would be as the speed of light is absolutely real because it's speed is not dependent on anything else, then for something to BE absolutely real, then 'be' means 'exists', so the question is, does a photon exist absolutely, or does it's existence depend on the existence of something else.

That's what we really want to know, when we ask 'what is matter'. Science reduces atoms to protons and protons to quarks, so atoms depend on the existence of protons and protons depend on the existence of quarks, and I suppose electromagnetic radiation may or may not depend on the existence of something else in order for itself to exist.

No I'm trying my best to keep this out of the realm of metaphysics because then I'll get a slap. However, the scientists started it all by reducing objects to things that are dipping their toes into the pool of metaphysical notions in fact maybe even wading in to the deep end.

Is there anything that is absolutely 'real', meaning that exists independently of anything else. Surely that's an OK question here. Otherwise why don't you put up a big disclaimer that says... "look we really don't have the faintest clue what any of this stuff that we study is, we can predict how it behaves and that enables us to build this big a55 five story high detectors and it's pretty much a lot of fun but in the end we are just amusing ourselves with the amazingness of it all, and you people out there should be content with your cars and computers and digital painting programs and microwave background plotting, that enrich your lives and which are the final products of our investigations.
Thank you for illustrating my point so completely.

QED explains everything about light. There is not one single behavior or experimental observation about light which is not accurately predicted by QED.

If you can predict in detail what a given thing will do in every possible situation or interaction or relationship then you know what that thing is in the fullest sense of the word. Hence, we know exactly what light is.

If we know what light is then surely it's OK to ask, 'what is light made of'. QED predicts how it interacts and behaves, but what is it made of. That's what the general public wishes to know. Are you going to tell people. "you can't ask what's it made of, it's a stupid question". To which one could postulate that there are no stupid questions, only stupid people.

Thank you for illustrating my point so completely.

Ok Dale, draw a line in the sand for me. Where does science end and metaphysics begin. Are virtual particles metaphysics or science. Is 11 dimensional space, simply mathematics, metaphysics or science. Is asking what is a gluon made of allowed or not allowed.

Dale
Mentor
2021 Award
Photons.

Dale
Mentor
2021 Award
Ok Dale, draw a line in the sand for me. Where does science end and metaphysics begin.
Science ends where experiments end. If a question cannot be answered through experimental observation then it is not a scientific question.

Try phrasing any of your "really" questions in terms of a possible experiment that could answer the question. If you can do so then the question is scientific.

Photons.

OK what about the virtual photons that swarm around a travelling electron. 1. Is there an experiment of any kind that can detect them. 2. Can they be considered a part of an electron, or a different thing than a electron. Or are they just a mathematical abstraction that nevertheless gives the right answers. 3. Is 'virtual' a part of their name, or is it somehow meant to convey they have a degree of 'reality' but not to the extent of non virtual photons.

Dale
Mentor
2021 Award
OK what about the virtual photons that swarm around a travelling electron.
Light is made up of ordinary photons, not virtual photons.

1. Is there an experiment of any kind that can detect them.
Virtual photons have experimentally testable consequences, although by definition they are not themselves directly observed. I will post some references in the morning.

2. Can they be considered a part of an electron, or a different thing than a electron. Or are they just a mathematical abstraction that nevertheless gives the right answers.
All correct physics theories are mathematical abstractions that give right answers. But electrons are fermions and photons are bosons, they are not the same thing and each is fundamental.

3. Is 'virtual' a part of their name, or is it somehow meant to convey they have a degree of 'reality' but not to the extent of non virtual photons.
How would you propose to experimentally test the "degree of reality" of something?

Ok, thanks for that, but I think there's been a slight misunderstanding. I was under the impression that a free travelling electron has a sort of a swarm of virtual photons around it. What I wanted to know is that is the term 'virtual photon' a noun. Or is 'virtual' in the context of 'virtual photon' an adjective that distinguishes it from a normal photon. If 'virtual' is an adjective describing a particle other than a photon, then why is it not called something else.

If 'virtual photon' is a noun, then isn't that just unnecessarily confusing. Or is 'virtual', as it suggests to me meant to suggest a degree of reality compared to a normal photon.

Also when we talk about virtual particle pairs where one gets sucked into a black hole and the other become a standard or garden variety particle, is 'virtual' used in the same sense as 'virtual' in 'virtual photon'. ie is there some way even as a thought experiment that could turn a virtual photon that surrounds a bare electron, into a normal particle of light.

Then, if a bare electron cannot exist without it's swarm of virtual photons, then can the electron ever be said to be 'fundamental' if it must have it's swarm. Therefore does that mean a bare electron has 'parts'.

Hope that's not too convoluted.

Drakkith
Staff Emeritus
Seeing as how all virtual particles keep the same name as their real versions I don't see how it matters if its a noun or an adjective. And since virtual particles are either just a mathematical construct or they actually do pop in and out of existence extremely fast I would say that an electron is not considered to have parts.

It matters to me if I get a slap for straddling the line between metaphysics and science too closely. basically I'm wishing to know if any question about what is it about a particle like a photon or electron that can be said to exist independently.

For example a proton cannot be said to exist independently because it depends on the existence of quarks.

Are physicists satisfied with describing the behaviour of quantum objects and measurements of characteristics of quantum objects without saying exactly if there is anything material that exists fundamentally. ie that cannot be reduced further.

Or are you guys saying, these sorts of questions are where science ends. Which means you must say to the lay person that "yes we can describe a particle's characteristic pattern of measurements but we cannot say what it is actually made of." What is it's substance. What is it's very stuff.

Or is it that there is no material substance at all, matter really is just energy. Concentrated energy. But energy is just a capacity to do work. Which seems kind of odd. So is 'capacity' the fundamental stuff of stuff.

Drakkith
Staff Emeritus
When asking what X is, all science can do is give you the properties of X and describe how it interacts. This may include smaller particles and their interactions that make up X. Anything beyond the known properties and interactions of X is not science. If in the future a new property of X is discovered or believed to be able to be discovered then that property becomes science. More or less at least. If you have to ask what something is really made up of or what it really is then it doesnt belong here on PF.

Dale
Mentor
2021 Award
Ok, thanks for that, but I think there's been a slight misunderstanding. I was under the impression that a free travelling electron has a sort of a swarm of virtual photons around it. What I wanted to know is that is the term 'virtual photon' a noun. Or is 'virtual' in the context of 'virtual photon' an adjective that distinguishes it from a normal photon. If 'virtual' is an adjective describing a particle other than a photon, then why is it not called something else.
I don't know how an english major would parse the term "virtual photon" in a sentence diagram, but I also don't think it is important. What is important are the experimental predictions that the term leads to.

If 'virtual photon' is a noun, then isn't that just unnecessarily confusing. Or is 'virtual', as it suggests to me meant to suggest a degree of reality compared to a normal photon.
Again, how do you experimentally measure "degree of reality"?

Then, if a bare electron cannot exist without it's swarm of virtual photons, then can the electron ever be said to be 'fundamental' if it must have it's swarm. Therefore does that mean a bare electron has 'parts'.
Since photons mediate an exchange of energy and momentum between two electrons it would be very difficult to say which of the two electrons a given virtual photon belongs to. If you can come up with a way to experimentally determine that then I think it would be a reasonable thing to claim.

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Dale
Mentor
2021 Award
It matters to me if I get a slap for straddling the line between metaphysics and science too closely.
I have already told you how to avoid that. Stick with mainstream scientific definitions of terms and with topics that are amenable to the scientific method, i.e. things which can be tested, and you will not get a slap. Don't stick with science and you deserve the slaps you will get. You have agreed to the rules when you signed up.