They seem to be woven into the very fabric of the universe, but what do they manifest as?Not sure what you mean by that. For instance the conservation of energy is manifested as energy being conserved.
Did they always exist, or did the big bang create them?Physical laws came into existence as a result of the big bang.
Let me put it in a way that's easy to understand. Some people on Earth have a genetic disability called Autism, which manifests in the brain (which is different from a neurotypical's brain) and brings about said people's difficulty in social engagement, enhanced sensitivity to bright lights and loud sounds, increased difficulty in focusing on others, etc. If the laws of physics are the effects of Autism, what is the thing it manifests as and brings those effects about (does this analogy make any sense? let me know if it doesn't)?That analogy doesn't help, it complicates and muddies the water.
Ok, so remember that time I asked about what energy is? Do you also remember the time I asked about why Conservation of Energy can't be violated? Well consider this question a fusion between those two.
The laws of physics, as everyone already knows, are statements made about the way the universe works based on carefully-calculated observations. They define the line between what's possible and impossible in our lives, and as far as we're currently concerned, cannot be broken in any way whatsoever.
But like, what are they exactly?
The laws of physics aren't like societal laws that are made by those in power and, if broken, result in you going to prison. They seem to be woven into the very fabric of the universe, but what do they manifest as?
Did they always exist, or did the big bang create them?
Let me put it in a way that's easy to understand. Some people on Earth have a genetic disability called Autism...
Just What Exactly are the Laws of Physics?Well, we can't exactly tell you, because we haven't worked them all out, yet.
How can something with no mass, carry momentum and more importantly, where does the momentum even come from?The momentum comes from the energy of the photon.
Photons are capable of transferring light (electromagnetic energy) as radiationNo, photons are light.
but why is light the only form of energy that has the ability to move as a particle?Photons are not a form of energy.
There's no air or stone to steal the particles energy away, so do they hold onto that energy foreverIf you are talking about the solar wind, the yes they go on forever if they never interact with anything.
How feasible on a scale of 1 to 10 (1 being not at all feasible and 10 being very feasible) is the idea of a Photon blaster/cannon? Think of something like Star Trek's particle cannons, but with Photons instead of electrons/protons. Could we realistically weaponize Photons like this?10. We call it a laser.
How can something with no mass, carry momentum and more importantly, where does the momentum even come from?It might be worth turning this question around a little. Don't be so certain that a photon has 0 mass in any real sense . All we know is that in any inertial reference frame a photon has momentum and energy.
First of all, deleting your OP and writing another OP is an absurd thing to do!!! All the original answers make no sense now. Start another thread next time. ::)
I admit in retrospect, it was a poorly thought out idea. I just didn't wanna a question that made no sense when spoken out loud (I'll admit, even I wasn't 100% certain what it was I was originally asking) to sit here and collect dust. That... and the website physically would not allow me to delete the question for some weird reason. I'll keep this in mind for next time though, don't you worry.
Quote The momentum comes from the energy of the photon.
That doesn't make an atom of sense. Are you saying there's some kind of energy to matter conversion happening during a photon's journey from one location to another? Is energy being converted directly into momentum (how the actual duck would THAT even work?)? What does this answer mean exactly?
Quote No, photons are light.
Quote Photons are not a form of energy.
This feels like a contradiction. You say Photons themselves are light, but then you immediately say shortly afterwards that they aren't a form of energy. Now, you could argue that light itself isn't a form of energy, but, like, there's absolutely no reason at all to think that, or did you just forget about the existence of solar panels? Eternal Student has also stated that Photons aren't made out of light energy, but are rather carriers of it so... which is the correct answer then? Are photons made out of energy, or do they merely carry it? Is light itself a form of energy, or is it something distinct from energy and matter entirely?
Quote We call it a laser.
Ok, yeah. I deserve this for not being descriptive enough. I know that real-life laser beams are capable of inducing blindness and can even defect/ignite matter through a conversion of light energy to thermal energy. Those weren't the kind of light-based weapons I had in mind though. I was referring to something akin to the blaster from the Star Wars franchise. You know, blasts of concussive light capable of imparting the same level of force onto their victims as a bullet, melting through metallic matter in an instant and levelling entire cities/planets. Is something like THAT possible?
Hi.
You might be worrying about your posts too much, Aeris.
Realistically, hardly anyone is likely to ever look at the thread again after it gets old. You've gone back and edited your Original post (OP) for very little reason. When I started on this forum, I thought posts might be quite important and people might read them for a long time after they were finished - but it's not like that.
The number of regular members using this forum is about one dozen people per day. Most of the rest of the views that are reported in the statistics are likely to be people who were curious about the forum but not really about your particular post and there's always plenty of people who were keen to see if they could just drop some advertising into something you've written.
I'm inclined to support the spirit of what @Origin has said. Starting a new thread is going to work better rather than completely re-writing the OP. Some of the people who have already replied may not even realise that the OP has shifted it's nature and so they won't even know there are new questions.
Really? I wasn't under that impression at all. Tons of people have come to give their answers to my past questions (my question about the true nature of energy is like 3 pages long with over 40 replies). I've also never seen a single person drop even a little bit of advertisement into their answer once, but maybe I didn't look hard enough for it at the time.
I agree with your second paragraph though. Changing the question from the ground-up instead of asking a new one was very silly of me and I promise never to do it again. You have my word on that (like, seriously the words telling you I will never do this again are right there on your screen and not going away anytime soon).
Quote It might be worth turning this question around a little. Don't be so certain that a photon has 0 mass in any real sense . All we know is that in any inertial reference frame a photon has momentum and energy.
Just consider what the rest mass of a photon might actually be. We say that it is 0 (zero) but we have no way of measuring it directly. To measure the rest mass of a particle we need to be in a frame of reference where the particle is at rest. There isn't a rest frame for a photon. There is no inertial reference frame where a photon would be at rest, it must always have velocity c in any inertial reference frame. Whatever the qunatity we call the "rest mass" of a photon might be it is a bit abstract, it isn't telling us anything about the mass of a photon when it's at rest.
We have equations like this from Special relativity:
E2 = m02.c4 + p2.c2 and from this we can infer that the quantity m0 must be 0 for a photon. We call this the rest mass but in the case of a photon, it's just a quantity, an abstract quantity.
So, we could answer your question by saying there is a fault in the question: You are attempting to use a simple expression for momentum like mv but the mass you need to know, m, is not 0, it is undetermined. The rest mass of a photon is 0 but this is an abstract quantity and not a description of the mass of a photon when it's at rest (despite the name "rest mass").
Best Wishes.
The only thing (I think) I understood was that the question was inherently flawedI need to explain what I meant.
So... Photons lack mass (you know, the thing that gives an object its weight and the ability to impart a force onto another object), yet they carry momentum capable of... moving solid objects? What? How on Earth does this work exactly? How can something with no mass, carry momentum and more importantly, where does the momentum even come from?1. Photons have 0 invariant mass but this is just an abstract thing. We could never directly measure the mass of the photon when it's at rest. So the mass of a photon is actually undetermined, all we know is it's "invariant mass" and, if we wish to calculate it and use it, "the relativistic mass".
IIRC Einstein's argument was a lot simpler.
Imagine a box full of electromagnetic energy - i.e. photons bouncing off the walls.
Allow one side of the box to move.
Common sense (and a few very clever observations) says that it will move outwards, reducing the energy density inside the box.
So we have imparted some momentum to the wall - or the solar sail
Conservation of momentum says that if we have added mv to the wall, we must have added -mv to the contents of the box
Thus photons can impart momentum, so they must have momentum.
Well yes. I have chemical energy in me, and I can convert that to momentum by moving. This is probably not direct since several chemical reactions are involved, but the light example isn't direct either. Light has energy (and momentum), but light isn't energy (or momentum) itself.Conservation of momentum says that if we have added mv to the wall, we must have added -mv to the contents of the boxSo... energy is being converted directly into momentum? Is that what you're saying basically?
Thus photons can impart momentum, so they must have momentum.
Tons of people have come to give their answers to my past questions (my question about the true nature of energy is like 3 pages long with over 40 replies). I've also never seen a single person drop even a little bit of advertisement into their answer once, but maybe I didn't look hard enough for it at the time.This thread, I think is the one you refer to: https://www.thenakedscientists.com/forum/index.php?topic=83150.0
.....Then came the realisation that internet advertising was good, coupled with the development of bots and we started getting 200 spams a day - more than legitimate posts. Even now the main site can get over 500 a day and recently one of our mods took down 64.....
Hi again.
I was also going to address this point:Tons of people have come to give their answers to my past questions (my question about the true nature of energy is like 3 pages long with over 40 replies). I've also never seen a single person drop even a little bit of advertisement into their answer once, but maybe I didn't look hard enough for it at the time.This thread, I think is the one you refer to: https://www.thenakedscientists.com/forum/index.php?topic=83150.0
It didn't have as many responses as you might have thought. It's showing as two pages and if I counted correctly, only 8 people (plus yourself) commented on it. Half of these people were moderators, so there were almost obliged to engage with people who post.
I often look at the statistics on the main page when I first log on. Quite often I'll be the only one loged on.
As regards advertising. Here's some info from a moderator on another thread:.....Then came the realisation that internet advertising was good, coupled with the development of bots and we started getting 200 spams a day - more than legitimate posts. Even now the main site can get over 500 a day and recently one of our mods took down 64.....
Don't get me wrong. I quite like this forum but it's worth recognising that it is actually a really small forum in comparison to many others.
Best Wishes.
Ok, so if light isn't energy or matter (I'm at least 99% confident in saying that light most definitely is not matter), what the hell is it then?At school level (let's say under 16 years of age). Light is one form of energy. That's it, full stop. ....Well, almost, for some UK examination syllabuses energy is NOT considered to have forms, there are just some stores of energy - but let's not worry too much about that for the moment. If you said light was one form of energy you'd get that marked right most of the time.
Hi.Ok, so if light isn't energy or matter (I'm at least 99% confident in saying that light most definitely is not matter), what the hell is it then?At school level (let's say under 16 years of age). Light is one form of energy. That's it, full stop. ....Well, almost, for some UK examination syllabuses energy is NOT considered to have forms, there are just some stores of energy - but let's not worry too much about that for the moment. If you said light was one form of energy you'd get that marked right most of the time.
At University level, it's much harder to define what energy is. I think you (Aeris) have started other threads about this. Energy becomes a much more abstract quantity - just some number you can calculate and it stops being considered as any sort of substance or physical thing in it's own right. With this idea, light isn't made of energy because energy just isn't any kind of physical substance. Instead, light just carries some energy or has some energy value associated with it.
So what is light at University level? Well, it's interesting and I'm sure I don't have the definitive answer.
We want both of these things:
1. It's something that exhibits both wave-like and particle-like properties.
2. On macroscopic scales, classical Electric and Magnetic fields seem to permeate all of space and light is a special type of oscillation or excitation in those fields.
There is a model describing light as a classical electro-magnetic wave, which is true enough or good enough for most purposes at University. It doesn't describe the particle-like behaviour all that well, we need some sort of qunatum model for that.
And we often end-up with this conclusion:
3. A quantum field theory seems the best model to explain what light is and how it behaves. There is a fundamental field (which permeates all of space) for every particle in the standard model of particle physics. So a photon is a quantised excitation of the underlying electromagnetic (or photon) field.
I'm sorry, that probably doesn't help much. It just says that fields may be the most (or the most so far) fundamental things in the universe and all particles are just excitiations in these fields. This is unlikely to be the final story, it's just one of the best and most up-to-date that I'm aware of. String theorists probably have their own opinions (which I know incredibly little about).
Best Wishes.
2. What exactly are Photonic Molecules?Sorry, I have very little idea. There's some reference on Wikipedia: https://en.wikipedia.org/wiki/Photonic_molecule
You know, it's funny. I LITERALLY just had an online chat with a cosmologist yesterday evening and one of the things he said to me was that matter, as we currently know it, may not actually exist at all. Fields exist, and particles such as Protons, Neutrons and Electrons are merely excitations of those fieldsClassic things often tend not to exist in the quantum realm, so 'matter' is just a classical thing that defies close analysis, just as a rock (or the moon) might have a classic location in space even when nobody is looking, but that location defies close analysis. Fundamental things don't have a size and thus no density, but that doesn't mean that a rock doesn't have a density.
You know, it's funny. I LITERALLY just had an online chat with a cosmologist yesterday evening and one of the things he said to me was that matter, as we currently know it, may not actually exist at all. Fields exist, and particles such as Protons, Neutrons and Electrons are merely excitations of those fieldsI agree with @Halc on this, but I think you need to sit down and think what you mean by the word exists.
At any rate though, I do understand most of what you're saying. Mostly that we have very little idea what light actually is.Actually we we know a great deal about what light is, how it works etc. It is another of those “merely” excitations of a field, and that means we can understand it in ways we couldn’t before.
The next important thing is that you have probably read or been taught that momentum = mass x velocity. This is probably why you are concerned about the photon having 0 mass but still having a non-zero momentum.I may be misreading what you say, but it implies that relativistic mass was ‘developed’ in response to the ‘rest mass’ of the photon being zero, and hence to maintain the concept of momentum for the photon.
There are at least two ways we can address this issue. The first is to say that many physicists were also troubled about this. It's a very good question to ask and something that does seem quite puzzling.
Physicist's were sufficiently determined to maintain this simple concept of momentum that they developed a quantity called "relativistic mass". They accepted that the invariant mass of a photon wasn't anything you could ever really measure, it certainly wasn't going to be measured as the mass of the particle when it was at rest in some inertial frame. So they determined that the invariant mass wasn't something that should be used in that formula momentum = mv.
Physicist's were sufficiently determined to maintain this simple concept of momentum that theyFor certain, Relativistic mass was developed as a concept for several reasons and not specifically because there was an issue with photons having momentum.developedhad a good reason to cling on to a quantity called "relativistic mass".
3. Photons are capable of transferring light (electromagnetic energy) as radiation, but why is light the only form of energy that has the ability to move as a particle? Why don't other forms of kinetic energy like heat and sound have their own particles to move as?Well, there is some interest in things called Phonons (note the spelling).
4. When the Sun radiates its energy as a storm of particles, many of them travel throughout space, all the way to the planets around it such as Earth, Mars, Venus and the Moon. Once the energy reaches those planets, they radiate an equal amount of energy away back into space in the form of infrared photons and useless radiation. What about the particles that don't reach anything though, and bolt of into the unobservable universe? There's no air or stone to steal the particles energy away, so do they hold onto that energy forever, or do they eventually loose it through a radiation-like process?
5. How feasible on a scale of 1 to 10 (1 being not at all feasible and 10 being very feasible) is the idea of a Photon blaster/cannon? Think of something like Star Trek's particle cannons, but with Photons instead of electrons/protons. Could we realistically weaponize Photons like this? Just for the record, I know I'm more or less describing a laser, but I was thinking more along the lines of Star War's blasters, or Iron Man's Repulsors. Would something like THAT be possible?I don't really know and a detailed discussion is probably more suited to the Just Chat section. I would have thought those TV shows and stories show blasters and all sorts of other energy weapons as transferring some momentum to their target just because that is what we would expect from a weapon. It's also much easier to film and more dramatic when someone is pushed backward rather than just having a small hole put in them. Such a hole would tend to be really neat and tidy and automatically cauterized by the heat of the laser anyway. Probably not a very effective weapon to be honest with you and certainly not dramatic enough for TV.
5. How feasible on a scale of 1 to 10 (1 being not at all feasible and 10 being very feasible) is the idea of a Photon blaster/cannon? Think of something like Star Trek's particle cannons, but with Photons instead of electrons/protons. Could we realistically weaponize Photons like this?Weaponized photons is just a laser, and yes, they've already got prototypes of stuff like that. The intent is to heat/vaporize the target, at least enough to render it (typically something in orbit) non-functional. There isn't significant momentum transfer there, but plenty of energy. Very hard to hit an accelerating target at any distance with any ballistic weapon like that, so it makes for a poor choice of weapon between space ships. Sorry star wars/trek.
Such a hole would tend to be really neat and tidy and automatically cauterized by the heat of the laser anyway.I'd think it would boil any body fluids, and the steam explosion would blow the immediate area to bits.
it's a shot of some other energetic stuff with the outer layers of it giving off photons as it travels.Definitely so since it doesn't move at light speed and you can't see light from the side, only if it is aimed straight at your eyes.