"Illegal" Colors

I'm uncertain about a lot of things...

jpanhalt said:

I assumed he meant a very large number, not infinite in the mathematical sense.

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Actually, I meant "infinite" in the sense that the changes can be so minute as to fall within the uncertainty principle and since (unless we come up with the next decimal point of accuracy beyond that somehow) can be considered infinite since we have no way of knowing how fine the increments may be beyond that threshold.

jpanhalt said:

Is temperature continuous?
...

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I believe that temperature is continouous. Quantum Mechanics applies at very small scales in bound systems. Unbound particles do not have quantized energies.

On the subject of infinity there is a distinction between a countable infinity represented by the rational numbers, and an uncountable infinity represented by the real numbers. It may seem paradoxical but there are more real numbers between 0 and 1 then there are rational numbers. Any quantity which is continuous like voltage, current, or temperature represents an uncountable infinity between any two values.

Maybe I'd better plead the 5th...

Papabravo said:

Dag-nab-it yourself young feller-- Here is the relevant quote from the article.

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I can't say that I understand all that I read but, there is no reason to believe that electrons (either valence or in deeper orbits) when knocked clear out of atoms can't have energies unrelated to the "quantum" energies. I can't say that for sure, however since I don't know.

I have read that when a photon and electron don't have the same energies, they simply ignore each other (which I suppose is the principle behind optical filters for example).

One could say that stepping on the brakes in a car brings it smoothly to a stop but, I don't think anyone here would argue that it's not actually a series of grab-and-releases as the brake lining and disk or drum interact and bits are torn off of each. In the subatomic world is "continuous" really continuous or is it incrmental.

There's also the issue of what constitutes "radiation". When a radioactive material pops out a neutron it's certainly radiation but, is it a photon? Is it "light"?

The bottom line is that I'm much to ignorant to be able to do much beyond pondering and posing the questions. The good part is that even though I'm still pig-ignorant I feel like I'm at least a little smarter for having asked.

Papabravo said:

Mechanics applies at very small scales in bound systems. Unbound particles do not have quantized energies.

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On that, I would have to disagree.

For example, macro quantum effects have been shown in liquid helium, as I recall. One of the physicists in the link I provided in my edit (immediately above) suggests that the red-shift of entire galaxies is quantitized. And finally, Hawking radiation from black holes is a quantum thermodynamic effect.

What we are really talking here are quantum effects that are so tiny on the macro scale of everyday experience as to have insignificant effects on the observed properties we see around us.

Over lunch, I did a calculation of how short 10E-44 seconds is (i.e., a hypothetical quantum of time). One might gain a little perspective by considering that 1 microsecond is approximately 1.6X10E-23 of the age of the universe. John

Here's the article on radiation.

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

We have been primarily talking about non-ionizing electro-magnetic radiation. We have not talked about ionizing and particle radiation. It is worth noting that since visible light and radio waves are fundamentally the same thing, what is true for one should be true for another. It is also woth noting that both light and radio waves are characterized by Maxwell's equations which were developed a good half century before Qunatum Mechanics.

So I'm sticking with the idea radio waves and light occupy a continuum in frequency and wave length and do not need Quantum Mechanics for their description and understanding.

The idea of quantum time is interesting, but I'm not sure of what predictions would follow from that hypotheses. The most immediate one I can think of would be a disconnect between mathematics and physics in the processes of taking limits and derivatives. Since we cannot properly take the limit as dt approaches zero if time is quantized, we might conclude that an exact derivative does not exist. I find this prospect highly suspect.

Edit: So I read the article. It is the quantization of 3-D time that leads to quantized redshifts. Our local time remains 1-D and continuous. Frankly I have trouble wrapping my arms around 3-D time. That and string theory might just be the biggest bust in physics of last several decades.

Papabravo said:

Since we cannot properly take the limit as dt approaches zero if time is quantized, we might conclude that an exact derivative does not exist. I find this prospect highly suspect.

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You know, being off by a factor of 1 part in 10E-44 or so is probably good enough for government work.

It is always a good discussion to compare quantum with non-quantum approaches. Maxwell worked before quantum theories were developed, as you noted. So did Newton, Gauss, etc., and to some extent Einstein. Frankly, the difference between predictions by the two theories is trivial in most of our every day lives. One place where quantum considerations make it easy to explain what we see and do impact our lives is in spectroscopy, including NMR, ESR, etc. And of course, there is always the duality argument regarding any EM radiation.

The dialog is always good and enjoyable. When the really smart people finally get it figured out, will physicists still have jobs? John

There are no illegal colours, or wavelengths of electromagnetic radiation. A free electron laser can produce radiation from microwave frequencies all the way up to soft X-rays. This is a largest dynamic range of any oscillator.

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

Hero999 said:

There are no illegal colours, or wavelengths of electromagnetic radiation. A free electron laser can produce radiation from microwave frequencies all the way up to soft X-rays. This is a largest dynamic range of any oscillator.

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

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Interesting information, but how does that relate to whether the wavelengths of light emission are continuous or restricted to allowed quantum levels?

One article I looked at, for example, gave a typical calculation of allowed energy levels for the emission and referred specifically to allowed quantum levels. John

Two words --> "BOUND STATES"

Free electrons are unbound that is why I mentioned two other types of radiation which are possible with unbound particles. Since unbound particles are not restricted in their energy levels there are no "illegal" colors.

But if it makes you happy to believe that there are illegal colors, then please be my guest.

The Trouble With Science...

Papabravo said:

Since unbound particles are not restricted in their energy levels there are no "illegal" colors.

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That's the trouble with science. Every answer leads to two more questions (relates to my logarithm post in another area?).

If a photon of a certain wavelength is produced (or absorbed) when an electron changes quantum states in an atom, what is the mechanism by which photon and electrons exchange energy when the electron is "free" and thus has no particular proclivity to "change states" at all (are there even states for it to change to)?

We can complicate that question somewhat. If, within atoms, electrons and photons essentially ignore each other unless they are of the same energy levels (related to the jumps from orbit to orbit), What changes in energy levels are involved in the interaction between photons and electrons when there's not even an "other state" for the electrons to go to.

I suppose one could argue that the elctron itself absorbs and then re-radiates the energy as a photon but, that brings up a whole series of really nasty questions.

Alright let's grossly simplify things.

Light is just electromagnetic radiation and is no different than say RF radiation.

Does anyone know of any illegal radio frequencies?

Of course there is a limit to the maximum frequency electronics will work at but they're no gaps in the radio spectrum and I don't see why it should be any different at optical frequencies. The idea that there are certain frequencies of light that just can't be generated sounds pretty silly to me. At least in theory it should be possible to build an oscillator that can generate any frequency from 1Hz up to gamma rays.

The only thing that does interest me is if there is an upper limit to the electromagnetic spectrum. Surely there becomes a point where it's not possible for energies to get beyond a certain magnitude.

I suppose another question is is there a maximum possible temperature in the universe?

I imagine that there might not be defined limits but higher energies, frequencies and temperatures might become less common past a certain point.

How'd we end up in this madcap universe, anyway?

Hero999 said:

Light is just electromagnetic radiation and is no different than say RF radiation.

Does anyone know of any illegal radio frequencies?

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By your own definition, that's the question that was asked. I had only limited the original post to the visible spectrum so I could use the term "colors" without having the nit pickers pick nits. And, to be able to zoom in on a smaller, perhaps more manageable, chunk of the overall EM spectrum.

I suppose another question is is there a maximum possible temperature in the universe?

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I have considered this and it does seem as if higher temperature is represented by faster moving atoms, there would be a temperature at which the atoms would have to move fater than light speed to attain and thus there would indee be an upper temperature limit. But, I have been wrong before (once, back in 1987 I thoguht I'd made a misteak but, it turns out I was misteaken).