[Bored chemist]

Quote from: Bored chemist on 29/06/2021 12:17:51
Quote from: Bored chemist on 28/06/2021 21:57:19
Just keep reading this
"so photons, which are slowing down the mirror are giving up their own energy"
until you realise it is nonsense.

But they ARE giving up their energy...

OK, so the bat slows down- which means it has less energy.
And (according to you) the photons are losing energy- so they have less energy.

So there is less energy overall- in total.
Which is a breach of the conservation of energy.

[Bored chemist]

But in order to create a "Kugelblitz" you need to have a constant amplification of the emitted light

Not really.
The model I'm using says you simply keep adding light to a cavity from outside or you add light to the cavity and then make the cavity smaller.

[Bored chemist]

Sure, there are limitations of our current technology

You really refuse to understand this, don't you?

Strictly, what it does is tell you that a perfect measurement is meaningless.
It's not an issue of measuring things.
The diameter of the sphere does not exist to a greater precision than that permitted by the uncertainty principle.

Again, you have not got to grips with early 20th C science.

[Bored chemist]

Screen will always appear to get darker in the sunlight...

"appear to".
Because the eye / brain system which perceives the brightness is a non linear detector.
That's nothing to do with physics.
You may have noticed that scientists doing measurements don't typically gauge things "by eye" because it's very unreliable.

Were you not aware of that?

[Bored chemist]

EM fields with similar bandwidth can SHARE the probability distribution in one volume of space. If they would overlap each other, their amplitudes would be added. Thing is, that when 2 (or more) EM waves at similar wavelenghts pass through the same space, probability of detecting a photon at one of those wavelenghts is being shared between interfering waves, according to their intensities of that probability

In empty space, at anything like normal intensities, the interaction between EM fields is very simple; they add.
So waves pass through one another without being perturbed.

If you have phase coherence between two sources of (at least very nearly) the same frequency, you will get interference patterns.
Those were documented centuries ago, and haven't changed since.

The interference patters don't stop photons existing, they move their probable location in space.

All of which misses the point.
Imagine that you magically do away with the uncertainty principle which you so steadfastly refuse to consider anyway.

I have a perfect mirror sphere with an internal diameter of 1 metre.
In spite of needing magic to do this, we assume it's exactly 1 metre.
I can set up a standing wave with a length of 1 metre.
And also 1/2 metres and 1/3 metres and so on.
There is, in principle, no reason why I can't keep adding photons with shorter and shorter wavelengths.

(as an aside, I can add one going left to right, and one going up and down for each frequency too and, as in a laser cavity, I can have many photons bouncing back and to along any axis).

And, as I go to higher and higher energies,the photons get more and more massive.

So the sum of the masses of all the photons tends to infinity, but the diameter of the sphere stays the same.
So, eventually, there's enough mass inside the 1M sphere to collapse into a BH.


So, even if you were not full of misunderstandings about the uncertainty principle, and the existence  of signal splitters, you should still understand how, in principle, one can build a black hole from photons.

So why won't you grasp this idea?

[CrazyScientist (OP)]

Quote from: Bored chemist on 29/06/2021 12:17:51
Quote from: Bored chemist on 28/06/2021 21:57:19
Just keep reading this
"so photons, which are slowing down the mirror are giving up their own energy"
until you realise it is nonsense.

But they ARE giving up their energy...

OK, so the bat slows down- which means it has less energy.
And (according to you) the photons are losing energy- so they have less energy.

So there is less energy overall- in total.
Which is a breach of the conservation of energy.

Photons will have less energy in the rest frame of mirror (bat). They CAN have more energy in the frame of a laboratory (batsman), if the mirror is moving fast enough, so that Doppler effect can compensate the energy which photons are loosing due to momentum transfer. And no one knows, what will be observed by photons, since according to mainstream science, rest frame of photons doesn't even exist...

Energy conservation would be violated, if photons wouldn't loose energy, when they are being reflected

https://physics.stackexchange.com/questions/539983/energy-conservation-in-reflection-of-light-from-a-perfect-mirror

"Differently phrased: One shouldn't interpret the term "perfectly reflecting" as preserving the energy of the light, as this is dependent on the frame. It just means that there is no absorption going on."

"There is no contradiction. You should interpret "perfectly reflecting mirror" to mean that every photon incident upon the mirror is reflected. It is indeed the case that this requires the reflected photons to have longer wavelength than the incident photons. You aren't given the reflected wavelength, but imposing energy-momentum conservation (two relations) allows you to solve for both the reflected wavelength and the value of N (two unknowns).

If you ask "what if we imagined a perfectly reflecting mirror" in the sense of a mirror that would always reflect each incident photon without changing its wavelength, then you are effectively asking "what if energy or momentum was not conserved?" Well, then you'd have to propose some new laws of physics that would make this possible, and would hopefully answer your question."

[Bored chemist]

, if the mirror is moving fast enough

And, if they are not, where does the energy go?
In the experimenter's frame of reference, both bat and ball suddenly slow down, but the energy has no place to go?
And, since absorbtion isn't allowed...

But... whatever.
I will just move the mirror quickly.

As I said, the point's moot.

I have a perfect mirror sphere with an internal diameter of 1 metre.
In spite of needing magic to do this, we assume it's exactly 1 metre.
I can set up a standing wave with a length of 1 metre.
And also 1/2 metres and 1/3 metres and so on.
There is, in principle, no reason why I can't keep adding photons with shorter and shorter wavelengths.

(as an aside, I can add one going left to right, and one going up and down for each frequency too and, as in a laser cavity, I can have many photons bouncing back and to along any axis).

And, as I go to higher and higher energies,the photons get more and more massive.

So the sum of the masses of all the photons tends to infinity, but the diameter of the sphere stays the same.
So, eventually, there's enough mass inside the 1M sphere to collapse into a BH.

[CrazyScientist (OP)]

But in order to create a "Kugelblitz" you need to have a constant amplification of the emitted light

Not really.
The model I'm using says you simply keep adding light to a cavity from outside or you add light to the cavity and then make the cavity smaller.

Only both actions will lead to different results - "adding light" is not the same, as "making the cavity smaller". First action leads to the increase of intensity, while second action might actually lead to a shorter wavelenght of trapped EM waves (if you properly synchronize the speed at which cavity is changing it's size with the frequency of trapped radiation)

[Bored chemist]

Only both actions will lead to different results

So you keep saying.
But you have yet to explain why the result isn't a BH in both cases.

[CrazyScientist (OP)]

, if the mirror is moving fast enough

And, if they are not, where does the energy go?
In the experimenter's frame of reference, both bat and ball suddenly slow down, but the energy has no place to go?
And, since absorbtion isn't allowed...

1. Photons DON'T change their velocity.
2. If the mirror doesn't move fast enough, then reflected photons will have higher frequency than those reflected from a stationary mirror, but it still will be lower, than before the reflection
3. Transfer of momentum doesn't require absorbtion of photons

But... whatever.
I will just move the mirror quickly.

Actually you need to apply a constant force to it, to counter the radiation pressure

I have a perfect mirror sphere with an internal diameter of 1 metre.
In spite of needing magic to do this, we assume it's exactly 1 metre.
I can set up a standing wave with a length of 1 metre.
And also 1/2 metres and 1/3 metres and so on.
There is, in principle, no reason why I can't keep adding photons with shorter and shorter wavelengths.

(as an aside, I can add one going left to right, and one going up and down for each frequency too and, as in a laser cavity, I can have many photons bouncing back and to along any axis).

And, as I go to higher and higher energies,the photons get more and more massive.

So the sum of the masses of all the photons tends to infinity, but the diameter of the sphere stays the same.
So, eventually, there's enough mass inside the 1M sphere to collapse into a BH.

Of course you can increase the frequncy of trapped radiation - I never claimed otherwise. BUT my scenario involves a source of constant radiation. In order to get a EM waves at a different frequencies, you'll need to use a different source, than the one, which emits waves at 1m wavelenght

OF COURSE you can always go in the opposite direction by having a constant source of radiation and increasing the size of cavity x2, x3, x4, x5 and so on...

Other thing is, that when you'll trap EM radiation with the wavelenghts of 1/2m and 1/3m in a cavity with 1m of diameter, you won't get a normal addition of their amplitudes. This is what you'll observe:

[CrazyScientist (OP)]

Only both actions will lead to different results

So you keep saying.
But you have yet to explain why the result isn't a BH in both cases.

Because in the case of EM radiation, intensity ≠ frequency.
If the creation of a Kugelblitz is somehow possible, then it can be achieved ONLY by the increase of frequency of trapped radiation and not it's intensity

[Bored chemist]

1. Photons DON'T change their velocity.

Careless of me; it doesn't lose speed, but it does lose energy.

If the mirror doesn't move fast enough, then reflected photons will have higher frequency than those reflected from a stationary mirror, but it still will be lower, than before the reflection

So, if the mirror has a high enough, mass the momentum transfer will be small.
And if it's moving fast then ...

Because in the case of EM radiation, intensity ≠ frequency.

Nobody said they were.
But a given number of photons where the photon energy is higher (i.e. the wavelength is shorter) will have more mass
and
A larger intensity (strictly, a larger number of photons) at a given wavelength will have more mass.

And if I want a BH , all I need is lots of mass in a small space.

If the creation of a Kugelblitz is somehow possible, then it can be achieved ONLY by the increase of frequency of trapped radiation and not it's intensity

That seems to be proof by loud assertion, and your record on that (FM radio etc) isn't good.

[Bored chemist]

Actually you need to apply a constant force to it, to counter the radiation pressure

As you point out, the intensity (w/m^2) will increase and so the pressure will increase.
The area falls.
Which effect wins is left as an exercise for the interested reader.

[Bored chemist]

. This is what you'll observe:

I won't observe anything- I won't be in there.
Nor will anything else.

[Bored chemist]

If the mirror doesn't move fast enough, then reflected photons will have higher frequency than those reflected from a stationary mirror, but it still will be lower, than before the reflection

We really need to sort out what a perfect mirror does.
There are two things I pointed out ages ago.
If the mirror has a large enough  mass the transfer of momentum to it is small.

But there's the more interesting effect.

Imagine you have a sphere with some photons- all of the same wavelength, bouncing back and to across the middle of it, horizontally.
The photons are in a bunch.
So they all hit the left hand side of the sphere and they impart some momentum to it. They bounce off to the right, with slightly reduced energy
The sphere starts to move to the left.
The photons carry on to the right.
So the photons now hit the right hand side of the sphere, but it's moving towards them.
And, as a consequence, they bounce off with a slightly shorter wavelength than they had.

The symmetry is such that the photons are back as they were and the sphere is (in the lab frame) stationary again.
The sphere bounces back and to, very slightly and the photons bounce around inside it.

Now imagine that there was a photon bouncing up and down, slightly out of phase with the horizontal photon bunches.
It now hits the top of the sphere at a point when the sphere is moving slightly to the left or the right (depending on the phase).
And so it gets reflected slightly out of line with the vertical.And that , of course means that next time it hits the wall, it is even further from the flat bits of the mirror (the top + bottom) so it gets knocked even further away from vertical.


You can also consider a photon that's bouncing back and to "nearly horizontally".
As the photon hits the moving wall s of the mirror it will gain or lose energy.

And, of course, the original photons are not perfectly bunched. The early ones hit a mirror that is (initially) stationary and lose momentum to it.
The later ones hit a mirror which is moving (very slightly) away from them, so they lose slightly less momentum to it.
So, even if they start off bunched, their momenta get scrambled a bit with each reflection.

So there's a way by which the energy and momentum of all the photons in the sphere will get shared out.

My best guess is that (as I said ages ago) they photons will end up looking like a black body distribution.

However, there's another way to do it.
You can imagine a nearly massless mirror.
When a photon hits it, it will move and take some energy from the photon. But that means that, when another photon hits it on the other side, it will add energy to that photon.
Overall, the sum of the energies will be conserved The wavelengths of the photons will be "scrambled" and will settle down to a black-body distribution.

It's going to get horribly complicated but, here's the clever bit.
Imagine that I add a lot of photons randomly to the sphere.
They all get "scrambled" in this way into a BBR distribution.

As I keep adding more and more photons, I increase the total energy in the sphere.
So I increase the temperature of the distribution.
And that raises the (average) energy and thus shortens the average wavelength.
So, even if I add  monochromatic photons, I do end up with my sequence of increasing energies - with increasing masses and , eventually, I get a black hole.

[CrazyScientist (OP)]

Screen will always appear to get darker in the sunlight...

"appear to".
Because the eye / brain system which perceives the brightness is a non linear detector.
That's nothing to do with physics.
You may have noticed that scientists doing measurements don't typically gauge things "by eye" because it's very unreliable.

Were you not aware of that?

Yes. However the same principle can be applied in the case of digital camera. What matters in both cases, is the difference of intensity - and intensity of light is defined by the probability of detecting a photon at a given frequency. This means, that there's a specific limit of light intensity, as probability of detecting a photon can't get higher, than each time when a measurement is made.

If due to constructive interference of 2 EM waves with the same wavelenght, probability of detecting a photon at the given frequency will get amplified to a specific level, then the total number of photons detected in a given period of time, will be divided between those 2 waves, according to their intensities.

So, if the mirror has a high enough, mass the momentum transfer will be small.
And if it's moving fast then ...

Momentum transfer will be exactly the same, no matter what's the rest mass of the mirror - mirror with less mass will just accelerate faster than one with higher mass  due to smaller inertia (resistance of rest mass to acceleration).

And if in the laboratory frame, mirror will move fast enough, then due to Doppler shift, reflected radiation will have higher frequency (shorter wavelenght) than before the reflection...

Nobody said they were.
But a given number of photons where the photon energy is higher (i.e. the wavelength is shorter) will have more mass
and
A larger intensity (strictly, a larger number of photons) at a given wavelength will have more mass.

And if I want a BH , all I need is lots of mass in a small space.

Intensity of EM radiation describes the probability/number of detected photons, but energy of those photons is defined by their frequency - in such case, it's possible that EM radiation at low frequency and high intensity, will have the same energy level as radiation at high frequency and low intensity. However for the same level of intensity, radiation with higher frequency, will always have higher energy.

Besides in the case of radiation trapped in a cavity, wavelenghts are limited to those, which can form a standing waves in the given volume of space. Those wavelenghts are associated with so called eigenstates, where the energy and number of photons can reach only a certain level for each of those states

That seems to be proof by loud assertion, and your record on that (FM radio etc) isn't good.

It's been proven experimentally, that matter creation due to p-p scattering is possible only with EM radiation at very high frequencies (gamma radiation)

https://en.wikipedia.org/wiki/Matter_creation

"The law of conservation of energy sets a minimum photon energy required for the creation of a pair of fermions: this threshold energy must be greater than the total rest energy of the fermions created. To create an electron-positron pair, the total energy of the photons, in the rest frame, must be at least 2mec2 = 2 × 0.511 MeV = 1.022 MeV (me is the mass of one electron and c is the speed of light in vacuum), an energy value that corresponds to soft gamma ray photons. The creation of a much more massive pair, like a proton and antiproton, requires photons with energy of more than 1.88 GeV (hard gamma ray photons)."

TBC

[Bored chemist]

It's been proven experimentally, that matter creation due to p-p scattering is possible only with EM radiation at very high frequencies (gamma radiation)

Nobody ever said otherwise, so that can't be relevant.

(Though you are, of course, technically wrong.
You can't experimentally prove that something is impossible.
maybe your experiment didn't use the right conditions)

[Bored chemist]

If due to constructive interference of 2 EM waves with the same wavelenght, probability of detecting a photon at the given frequency will get amplified to a specific level, then the total number of photons detected in a given period of time, will be divided between those 2 waves, according to their intensities.

You are just repeating what I said earlier.

t's quite an interesting question- bright schoolkids usually ask a related one.
When you show them interference fringes on a screen, the clever pupils ask where the energy from the dark stripes has gone to.
And the answer is that it goes into the bright stripes.

That's clearly pointless.

Momentum transfer will be exactly the same, no matter what's the rest mass of the mirror - mirror with less mass will just accelerate faster than one with higher mass  due to smaller inertia (resistance of rest mass to acceleration).

That's just wrong.

Imagine bouncing a snooker ball off a bowling ball- it bounces back.
But if you try to bounce a snooker ball of another snooker ball the first ball stops and the second one moves off at the same speed as the ball that hit it was travelling.

[Bored chemist]

And if in the laboratory frame, mirror will move fast enough, then due to Doppler shift, reflected radiation will have higher frequency (shorter wavelenght) than before the reflection...

And, finally, you work out what a bat is for.

That's what I have been saying all along.

[CrazyScientist (OP)]

Actually you need to apply a constant force to it, to counter the radiation pressure

As you point out, the intensity (w/m^2) will increase and so the pressure will increase.
The area falls.
Which effect wins is left as an exercise for the interested reader.

Thing is, that intensity of radiation trapped in a cavity can reach only a certain level and the radiation pressure will then become constant.

I won't observe anything- I won't be in there.
Nor will anything else.

So, the wavefunction will become similar to the one presented on that image

We really need to sort out what a perfect mirror does.
There are two things I pointed out ages ago.
If the mirror has a large enough  mass the transfer of momentum to it is small.

Mass of the mirror doesn't change anything, except the rate of it's acceleration due to radiation pressure - momentum of that mirror will be the same for higher mass/lower velocity and for lower mass/higher velocity

Imagine you have a sphere with some photons- all of the same wavelength, bouncing back and to across the middle of it, horizontally.
The photons are in a bunch.
So they all hit the left hand side of the sphere and they impart some momentum to it. They bounce off to the right, with slightly reduced energy
The sphere starts to move to the left.
The photons carry on to the right.
So the photons now hit the right hand side of the sphere, but it's moving towards them.
And, as a consequence, they bounce off with a slightly shorter wavelength than they had.

The symmetry is such that the photons are back as they were and the sphere is (in the lab frame) stationary again.
The sphere bounces back and to, very slightly and the photons bounce around inside it.

For a constant motion, you would need to solve this scenario using the Doppler shift - e.g. photons reflected to the right by a mirror which moves to the left, will have lower frequency, than those reflected by a stationary mirror. Then their frequency will get higher after reflection from the second mirror, which also moves to the left - but in the end, their energy will still be decreasing in a realistic scenario or remain constant in an idealised version

I think however, that energy level of trapped radiation could be increased with a vibrational motion of the cavity at a proper frequency and velocity

Now imagine that there was a photon bouncing up and down, slightly out of phase with the horizontal photon bunches.
It now hits the top of the sphere at a point when the sphere is moving slightly to the left or the right (depending on the phase).
And so it gets reflected slightly out of line with the vertical.And that , of course means that next time it hits the wall, it is even further from the flat bits of the mirror (the top + bottom) so it gets knocked even further away from vertical.

Only here we'd have to include the aberration of light. Also different results will be observed for light propagating stright up in the laboratory frame (diagonally in the rest frame of moving cavity) and stright up in the rest frame of moving cavity (diagonally in the lab. frame).

You can also consider a photon that's bouncing back and to "nearly horizontally".
As the photon hits the moving wall s of the mirror it will gain or lose energy.

And, of course, the original photons are not perfectly bunched. The early ones hit a mirror that is (initially) stationary and lose momentum to it.
The later ones hit a mirror which is moving (very slightly) away from them, so they lose slightly less momentum to it.
So, even if they start off bunched, their momenta get scrambled a bit with each reflection.

So there's a way by which the energy and momentum of all the photons in the sphere will get shared out.

My best guess is that (as I said ages ago) they photons will end up looking like a black body distribution.

Woow! It's the first time, when I agree with  your predictions

It's going to get horribly complicated but, here's the clever bit.
Imagine that I add a lot of photons randomly to the sphere.
They all get "scrambled" in this way into a BBR distribution.

As I keep adding more and more photons, I increase the total energy in the sphere.
So I increase the temperature of the distribution.
And that raises the (average) energy and thus shortens the average wavelength.
So, even if I add  monochromatic photons, I do end up with my sequence of increasing energies - with increasing masses and , eventually, I get a black hole.

But to increase the temperature beyond some level, you would have to start increasing the frequency of emitted radiation - or maybe "shake" the cavity around at such rate and velocity, that the trapped EM waves would actually start to gain frequency. I'm not sure, but maybe you also would have so to keep gradually increasing the intensity of scavity vibration...