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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 24/01/2024 12:50:02 »Does the unit of the radiation frequency have no effect on the numeric value of their quantum of energy?The number of joules of energy which a photon carries doesn't know or care if you measure frequency in 1/seconds or 1/weeks
The value of Planck's constant (h) would change.
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Physics, Astronomy & Cosmology / Re: How many stars in the most dark sky without {The_Sun-0001} naked eye with 20/20!
« on: 24/01/2024 11:40:36 »I need an answer from NASA and the European Space Agency (ESA) to this question:Then why are you asking us?
Why not just ask google or wiki?
https://en.wikipedia.org/wiki/List_of_brightest_natural_objects_in_the_sky
There are thousands of visible stars.
You can find a list here.
http://tdc-www.harvard.edu/catalogs/bsc5.html
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 23/01/2024 00:21:55 »So let's have a 1 tesla bar magnet spinning at 1000Hz in a vacuum. Can anyone please describe its electromagnetic emission spectrum? I just can't visualise it!Can you visualise the emission if you had an electric dipole rotating at that rate?
(Say I have an insulating horizontal disk with two metal balls on the perimeter on either end of a diameter and one is positively charged and the other negatively.) I rotate the disk at 1000 Hz.
Failing that, what about a (horizontal) dipole antenna being fed with 1000 Hz at the centre?
From the side, the disk looks like the dipole.
There's a slight complexity from the movement towards and away from you.
But if you consider two dipoles at right angles fed with two signals (both at 1KHz) and pi/2 radians out of phase, the emission will look like the pair of charges on a turntable (or a rotating dipole).
I'm pretty sure that the emission pattern from a magnetic dipole would be the same (give or take a phase/ polarisation change)
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 22/01/2024 20:33:14 »And had anyone said it should?Pushing electrons to and fro in an antenna is cyclical (Particularly if the antenna is resonant.)but doesn't involve any rotation.
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 22/01/2024 15:38:59 »
Does that mean that shaking a magnetic monopole about (if it existed) would emit radiation like shaking an electric charge does?
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 22/01/2024 14:18:08 »I also am fairly sure a rotating magnet would radiate em. It would have to rotate at quite a high speed to generate easily detectable radiation. I have been trying for several hours to mentally model the maths involved but I have failed so far. We normally look at charge acceleration to produce em as it is the most convenient method but one has to remember that the magnetic field is simply the electric field as seen from a different frame of reference.I never could do the maths, but I don't care.
I can get a toy magnet and put it on the turntable of a record player.
I can put a compass near it.
And I can watch the compass needle move.
If I'm lucky it will even rotate in synchrony with the turntable.
The force acting on the needle is electromagnetic.
The carrier of the EM force is the photon.
So, in this case, I know that a rotating magnet emits EM radiation. That force is periodic and thus there must be a component of the EM radiation with the same period.So it must have photons with energies corresponding to the frequency of rotation of the record player.
Re. "but a magnet in an infinite vacuum won't. "
If the magnet falls over in a non-existent forest with no observers, does it matter?
I contend that it will still emit EM radiation.
Imagine that we somehow have a magnet in an infinite empty universe.
We set it spinning (We know it is spinning, because an ant who happens to be standing on it notices the centrifugal effect).
After a while, and at some distance from the magnet, we magically call a compass needle into being.
Does the needle have to "wait" for EM radiation from the magnet to reach it, or is that changing field already there?
I can't see how it would so I think the magnet must have been emitting EM radiation all along.
But... if there's EM radiation, then there are photons.
And, if there are photons, the universe isn't empty.
So the solution may be that you can't have a rotating magnet in an empty universe.
All seems a bit esoteric..
But let's ignore nearly the whole of the universe and consider some hydrogen atoms.
Some of them have the magnetic dipoles of the electron and the proton aligned parallel, and in others it's antiparallel.
And if one happens to flip from the first state to the second, it emits a photon of about 21 cm wavelength.
That photon crosses space and is picked up many years later by a detector here on earth.
But we have only been constructing such detectors for about 100 years.
So, for a source more than 100 light years away, the detector had not been built when the photon was emitted.
I think that's close enough to " we magically call a compass needle into being." for the analogy to work.
An electron- with a magnetic diploe moment- was flipped and sent out EM radiation. It did so in a universe in which the detector did not exist.
You may say that, without the proton of the hydrogen atom, the energy of the photon would be undefined. Which is a fair point
But, at that point, I think you need to be able to do Laplace transforms and, as I said, I can't do the maths.
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 22/01/2024 13:51:50 »You seem to have invented a requirement for an orbit.He's not talking about a betatron.
He's talking about the angular speed of an electron. What else would you call a device that makes electrons orbit at a constant 109radians per second?
Pushing electrons to and fro in an antenna is cyclical (Particularly if the antenna is resonant.)
Possible answers to your question would include
https://en.wikipedia.org/wiki/Halo_antenna
and
https://en.wikipedia.org/wiki/Cavity_magnetron
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 22/01/2024 13:44:59 »Necromancy?, BC. I always thought necromancy was the divination of future events by dissecting a dead creature and examining it's entrails. This method has not as yet been ascertained to be effective!And someone tried to divine the future from the entrails of a long-dead thread.
It's not clear why.
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The Environment / Re: The link between global warming and world population expansion.
« on: 21/01/2024 22:39:49 »UNHCR and other charities who are surely encouraging the problem of overpopulation rather than solving itSolving population problems is not the job of refugee camps.
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General Science / Re: What Is Gray?
« on: 20/01/2024 12:44:57 »
The immediate effect of teh introduction of Davy's safety lamp was an increase in mine explosions.
Previously, people didn't even try to work in "gassy" mines.
With the lamp, they could do so.
And when a pickaxe struck a spark...
Previously, people didn't even try to work in "gassy" mines.
With the lamp, they could do so.
And when a pickaxe struck a spark...
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General Science / Re: What Is Gray?
« on: 20/01/2024 00:19:08 »Nonsense, most people drive in a way to prevent damage to their car, seat belt or no, the idea of imminent demise is not really a thought. Seatbelts save lives.OK imagine that one day you are asked to drive to a meeting across town. They give you an armoured truck to make the trip.
Then, the next day, for the same trip, they give you a rickety old schoolbus which has a bottle of nitro-glycerine on the next seat and dodgy suspension.
Do you drive the same way in both cases, or do you adjust your driving according to the apparent risk?
Anyway, here's some data. from
https://en.wikipedia.org/wiki/Reported_Road_Casualties_Great_Britain
Seat belt death.png (118.79 kB . 1024x650 - viewed 183 times)
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 19/01/2024 15:05:01 »Earth calling Alan.Photonic interpretation for Planck's law states that hf is the energy of one photon. Thus radius of theBut it does affect the energy of the electron that generates the photon. It all gets a bit complicated as it's quite easy to get an electron up to 0.9c in a betatron, at which point the relativistic corrections become very significant.
torus or antenna doesn't affect photon energy, as long as the frequency can be kept the same.
He's not talking about a betatron.
On one hand, that's a pity because it's more interesting.
On the other hand, it may be just as well because I think he'd make a mess of it.
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 19/01/2024 15:02:30 »The question is the same, what is the photon energy radiated by the rotating magnet?Small.
3000 RPM is 50Hz so the photon energy is 50 times Planck's constant.
That's high school maths. Why have you reopened a long-dead thread to ask about it?
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New Theories / Re: New theories
« on: 19/01/2024 13:09:35 »spray with unsaturated Olea europea lipidsHow do you remove the saturated ones?
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Physics, Astronomy & Cosmology / Re: Can Planck's law curve be matched to Rayleigh-Jean's law curve like this?
« on: 18/01/2024 16:29:16 »109 rad/sec is a rate of rotation,Not necessarily.
https://en.wikipedia.org/wiki/Angular_frequency
In which case the answer isn't hard to calculate.
But I don't see any point.
Certainly not any point that justifies the thread necromancy.
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General Science / Re: What Is Gray?
« on: 17/01/2024 10:41:38 »
What Is Gray?
An American elephant.
Or, given the spelling.
https://en.wikipedia.org/wiki/Louis_Harold_Gray
An American elephant.
Or, given the spelling.
https://en.wikipedia.org/wiki/Louis_Harold_Gray
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The Environment / Re: The link between global warming and world population expansion.
« on: 14/01/2024 16:44:07 »refugee camps need to become self sufficient.How many towns are self- sufficient?
How many countries?
Or households?
Yet you somehow think that a group of displaced people- in shock and devastated- are somehow going to "have to" do it.
Did you think that through?
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General Science / Re: What Is Gray?
« on: 13/01/2024 22:53:56 »Cars kill ~1500 Brits a year, I don't think that many are killed by planes, what's in operation is the Availability Heuristic: people perceive probability according to how easily something springs to mind.I know more people who have been in car crashes than have been in plane crashes.
So the "availability" argument isn't convincing.
If anything, it's the other way round. The newspapers etc publish stories about 10 people dying in a plane crash but not about the 25 killed on the road each month precisely because people are more interested in rare events involving a moderately large number than in the thing which kills a lot more people, but by a steady drip feed of corpses.
I'm told most drivers think they are "better than average" so they aren't so concerned about risks from their own driving.
(If I really wanted to cause an argument, I'd make the point that gun owners think that "their gun" keeps them safe, but "everybody else's gun" is a threat).
The big reason are less scared of car travel than plane travel is related to the perception of control.
People don't think they will crash their own car. Every year about 1500 find out (briefly) that they are wrong.