Is Planck's constant the key to understanding a quantum?

[trogan]

Is there a standard, agreed on definition of a Quantum in physics ?

Also, I have picked up this information about a quantum on the internet (http://www.peterrussell.com/SG/Ch5.php" ). Does this correctly describe Plank's constant and its relation to a quantum ?

"Although the amount of energy in a photon varies enormously, there is one aspect of the quantum that is fixed. Each and every quantum has a constant amount of action.

Mathematicians define action as an object’s momentum multiplied by the distance it travels; or the object’s energy multiplied by the time it is traveling–the two are equivalent. The amount of "action" in a ball thrown across a football field, for example, would be greater than the same ball thrown half the distance. Double the ball’s mass, and you double the action. Or imagine yourself running at a constant rate of energy output. If you run for twice as long, there will be twice the action–which makes intuitive sense.

The actual amount of action in a quantum is exceedingly small, about 0.00000000000000000000000000662618 erg.secs (or 6.62618x10-27 erg.secs in mathematical shorthand)–but it is always exactly the same amount.

This is called Planck’s constant (after its discoverer). It is the second universal constant to emerge from modern physics. Like the first–the speed of light–it is a constant of light. Light always comes in identical units of action.
"

 

[Vanadium 50]

Quantum is an adjective, not a noun. So you won't find a universal definition of "a quantum" any more than you will find a universal definition of "a blue" or "a slow".

 

[trogan]

Quantum is an adjective, not a noun. So you won't find a universal definition of "a quantum" any more than you will find a universal definition of "a blue" or "a slow".

Not according to the dictionaries I have visited.

For example, from the Free Dictionary:

quan·tum (kwntm)
n. pl. quan·ta (-t)
1. A quantity or amount.
2. A specified portion.
3. Something that can be counted or measured.
4. Physics
a. The smallest amount of a physical quantity that can exist independently, especially a discrete quantity of electromagnetic radiation.
b. This amount of energy regarded as a unit.
adj.
Relating to or based upon quantum mechanics.

 

[DaveC426913]

So don't use the Free Dictionary...


Quantum means, generally: discrete. A quantum leap is a discrete leap.

 

[SimonA]

For what it's worth, my definition of quantum would include the word "step". It's all about a step change, it's about being on this step and not the other. When we understand quantum properly, I reckon step will be a usefull word to use.

 

[trogan]

So don't use the Free Dictionary...


Quantum means, generally: discrete. A quantum leap is a discrete leap.

Then there is "quantum of light" or "light quantum" where it is definitely used as a noun. It is the definition of the noun that interests me. I have books on physics where neither it nor Planck's constant are defined and I thought to myself I wonder why and whether physicists work with standard definitions of these two entities at all ?

 

[SimonA]

Excellent point. I would contend that a photon is the result of an atoms energy level reaching the top step(ie no longer on the steps and free to travel elsewhere)

 

[Born2bwire]

Excellent point. I would contend that a photon is the result of an atoms energy level reaching the top step(ie no longer on the steps and free to travel elsewhere)

The "top step" as you put it of an atom would be the ionization energy, when the bounded electron is freed from the atom's orbitals. Photon emission does not require any such phenomenon, photons are emitted from atoms when an electron drops down from a given excited state to a lower state.

I would also throw my hat into the "quantum = discrete" ring. In general, one of the defining properties of quantum mechanics is the quantization of modes as opposed to the continuous spectrum of modes that exist for classical physics. This meaning can also be applied to the specific examples where we use quantum/quanta as well. For example, photons are the quanta of the electromagnetic wave. Thus, when physicists talk about the light quanta, they are talking about the discrete packets of light, the photons.

 

[Vanadium 50]

If you are trying to learn physics from a dictionary, you have a difficult - probably impossible - job ahead of you.

If you are trying to learn anything at all without discarding your preconceptions, you have an even more difficult job ahead of you.

 

[Vanadium 50]

Excellent point. I would contend that a photon is the result of an atoms energy level reaching the top step(ie no longer on the steps and free to travel elsewhere)

There is no top step. The inverse square law has an infinite number of bound states.

 

[trogan]

Quantum is an adjective, not a noun. So you won't find a universal definition of "a quantum" any more than you will find a universal definition of "a blue" or "a slow".

I will settle for a definition of the adjective. Does Physics have a standards body that oversees that sort of thing ?

It is weird. The description of Quantum Mechanics on Wiki does not say what "Quantum" means. And it seems wherever I look the Quantum seems to rate little or no mention when dealing with Quantum Theory. Has it been misnamed ?

 

[Mentz114]

Excellent point. I would contend that a photon is the result of an atoms energy level reaching the top step(ie no longer on the steps and free to travel elsewhere)

Not so. A photon is emitted when the electron drops to a lower energy level. This can happen spontaneously even if the electron is only 1 step above its ground state.

See any elementary text on quantum mechanics.

 

[trogan]

Actually, there IS a very satisfying definition of a quantum on WIKI:

"In physics, a quantum (plural: quanta) is the minimum unit of any physical entity involved in an interaction. An example of an entity that is quantized is the energy transfer of elementary particles of matter (called fermions) and of photons and other bosons. The word comes from the Latin "quantus", for "how much." Behind this, one finds the fundamental notion that a physical property may be "quantized", referred to as "quantization". This means that the magnitude can take on only certain discrete numerical values, rather than any value, at least within a range. There is a related term of quantum number.

A photon, for example, is a single quantum of light, and may thus be referred to as a "light quantum". The energy of an electron bound to an atom (at rest) is said to be quantized, which results in the stability of atoms, and of matter in general.

As incorporated into the theory of quantum mechanics, this is regarded by physicists as part of the fundamental framework for understanding and describing nature at the infinitesimal level, for the very practical reason that it works. It is "in the nature of things", not a more or less arbitrary human preference.
"

 

[Feldoh]

I have a question for the OP. Now that you have a supposed definition of "quantum" do you feel any smarter?

Have you learned anything that has built up your physical intuition?

Probably not. My point is is that learning definitions is not what you should be focused on it you want to understand physics. A rose by any other name would still smell as sweet, and all that...

 

[trogan]

I have a question for the OP. Now that you have a supposed definition of "quantum" do you feel any smarter?

Have you learned anything that has built up your physical intuition?

Probably not. My point is is that learning definitions is not what you should be focused on it you want to understand physics. A rose by any other name would still smell as sweet, and all that...

Define "smarter" !

Seriously, I am quite satisfied with what I have achieved here and thank you for your advice.

 

[trogan]

It seems then that a quantum is a discrete amount of energy. Can someone tell me then how Quantum Physics came to be mainly about waves in various forms ? Would Wave Physics better describe the reality ?

 

[trogan]

It seems then that a quantum is a discrete amount of energy. Can someone tell me then how Quantum Physics came to be mainly about waves in various forms ? Would Wave Physics better describe the reality ?

Also, it would seem that (for example) a photon and an electron are the same deal in one respect in that they both have the same "action" potential (as given by Planck's constant). The big difference between the two (as far as the quantum of energy each contains) seems to be the rate at which they vibrate. This is my extremely hard-won understanding. Is it correct ?

This seems to me to strongly point to elementary particles at least being composed of photons with some attributes changed.

 

[Vanadium 50]

This seems to me to strongly point to elementary particles at least being composed of photons with some attributes changed.

Trojan, you are flying towards crackpottery at a million miles an hour. I suggest you slow down and change direction. Yesterday you didn't know if the word "quantum" meant. Today you are saying that people who have studied quantum mechanics for decades have their models all wrong.

 

[DrChinese]

Would Wave Physics better describe the reality ?

The name is fine as is. As Vanadium 50 says, you might want to spend a additional time learning about some of the quantum concepts, reasoning and experimental support before trying to come up with improved names. Everyone starts out with lots of questions and hunchs, and these are mostly addressed in introductions to the subject. So you will learn about things like wave/particle duality. There have probably been 250,000+ papers/experiments published on QM since inception, so please be cognizant that the premises have been studied and examined in great detail by a lot of people.

 

[trogan]

The name is fine as is. As Vanadium 50 says, you might want to spend a additional time learning about some of the quantum concepts, reasoning and experimental support before trying to come up with improved names. Everyone starts out with lots of questions and hunchs, and these are mostly addressed in introductions to the subject. So you will learn about things like wave/particle duality. There have probably been 250,000+ papers/experiments published on QM since inception, so please be cognizant that the premises have been studied and examined in great detail by a lot of people.

I am a long way from being a novice. I have many books on the subject (for example Quantum Reality by Nick Herbet and The Emporer's New Mind by Roger Penrose). I understand the concepts reasonably well. The maths I only seek to understand if I really need to. I am totally aware that some of the things I talk about will be naive. I try and limit my questions on Physics Forum to those I cannot find answers to in my books and searches.

My deeper understanding of the quantum as expounded here only came in recent days, yet I have studied Quantum Mechanics for years. Ditto for Planck's Constant. I hope other novices like myself will benefit from it as it is as rare as hen's teeth elsewhere.

I wonder why no one gave me a definition of a quantum. I am guessing the question seemed trivial.

 

[trogan]

Trojan, you are flying towards crackpottery at a million miles an hour. I suggest you slow down and change direction. Yesterday you didn't know if the word "quantum" meant. Today you are saying that people who have studied quantum mechanics for decades have their models all wrong.

I had a fairly good idea what quantum meant. I was after a definition that would verify what I thought. I am not saying quantum mechanical models are all wrong. Heck I am not THAT naive.

What I would really like from you and other experts like yourself is answers to my questions. I thought I gave a good account of why an electron and a photon are similar quantum-wise. So what is wrong with my statement that: "This seems to me to strongly point to elementary particles at least being composed of photons with some attributes changed" ?

 

[DaveC426913]

What I would really like from you and other experts like yourself is answers to my questions...


So what is wrong with my statement that..."This seems to me to strongly point to elementary particles at least being composed of photons with some attributes changed" ?

Because your statement is not a question?

 

[trogan]

Because your statement is not a question?

Hokay, I will rephrase it:

"Given that what I have just said is true, does this point to elementary particles (at least) being composed of photons with some attributes changed"

I don't like to seem ungrateful but this thread has been pretty tortuous form my point of view and none of my questions to date have been answered. Are you trying to discourage me (don't blame you ... being a software developer I can be annoyingly pedantic) ?

 

[DaveC426913]

"Given that what I have just said is true, does this point to elementary particles (at least) being composed of photons with some attributes changed"

Two things sharing a property does not mean they are the same thing.

"Java and JavaScript share a similar name, it seems to me therefore that they are probably the same language with some syntactical differences."

I don't like to seem ungrateful but this thread has been pretty tortuous form my point of view and none of my questions to date have been answered. Are you trying to discourage me (don't blame you ... being a software developer I can be annoyingly pedantic) ?

I am a software developer as well. There is nothing wrong with being pedantic. The resistance you're encountering is due to the fact that you are putting forth unfounded hypotheses and then asking for validation of them. You will get nowhere fast.

If you want to get answers about how the world works, then ask questions about how the world works.

 

[trogan]

Two things sharing a property does not mean they are the same thing.

An apple and a firetruck are both red but that does not mean they are the same thing.

It is the fact that both an electron and a photon have the same action potential that intrigues me. This seems to me to indicate an extraordinarily strong connection between the two.

And you should know from software development that you can have two objects of type X with different attributes yet each is still behaves as a type X object.

 

[Born2bwire]

What action potential?

 

[trogan]

What action potential?

See my first post: "Each and every quantum has a constant amount of action".

I have shortened it to action potential. It seems like a good description and there no others around that I can ascertain.

 

[DaveC426913]

And you should know from software development that you can have two objects of type X with different attributes yet each is still behaves as a type X object.

Yes you can. But does that mean ALL things behave that way such that it would make a good general principle to imagine how any old thing works?

 

[Born2bwire]

See my first post: "Each and every quantum has a constant amount of action".

I have shortened it to action potential. It seems like a good description and there no others around that I can ascertain.

What action potential?

 

[trogan]

What action potential?

alrighttt, ditch Action Potential ! ... pity I thought it quite evocative (although potential action would have been better - in line with potential energy). Instead replace it with Quantum Unit of Action (i.e Planck's Constant h). This seems to be the generally agreed on expression.

Therefore is my understanding of this unit correct ? Namely that all energy quanta have the same unit of action and this is related to the energy via the equation E = hf.

 

[Feldoh]

I don't know what you're saying but...

Planck's constant is simply a proportionality constant between the energy and frequency of a photon in the way you're trying to use it.

It's a number that is always equal to E/f for a photon.

 

[trogan]

I don't know what you're saying but...

Planck's constant is simply a proportionality constant between the energy and frequency of a photon in the way you're trying to use it.

It's a number that is always equal to E/f for a photon.

See my first post.

My understanding is that it is the Unit of Action of a Quantum of Energy. Maybe it could be called "oomph" ! It is applicable not only to photons but to ANY particle containing energy (all of them ?). It stands by itself as a unit.

It is the very basis of Quantum Mechanics and I am guessing if you (like I used to) think of it as E/f then your understanding of Quantum Physics is not as deep as it could be (I am willing to be shot down in flames on this statement !).

 

[SimonA]

Sorry - I agree "top step" was not the best description. Maybe "top of the step" is ? The discreet entity is like integers, the remainder exists in a different form, hence photon emmision ?

 

[SimonA]

Sorry that's even worse...

What do you people think orbital shells represent ? Explain them to me in a way that's based on reasoned thought, rather than assumption based on results...

 

[Vanadium 50]

then your understanding of Quantum Physics is not as deep as it could be (I am willing to be shot down in flames on this statement !).

I repeat my recent comment - you are headed towards crackpottery at a million miles an hour. You're a QM novice. Nothing wrong with that; we all were at one time. But now you're now telling other people that they are doing it wrong and/or don't understand it. You really need to base this kinds of judgments on expertise, and you haven't put the effort into developing this expertise.

I highly recommend Steve Dutch's essay on http://www.uwgb.edu/dutchs/PSEUDOSC/SelfApptdExp.htm"

The resistance you're encountering is due to the fact that you are putting forth unfounded hypotheses and then asking for validation of them. You will get nowhere fast.

If you want to get answers about how the world works, then ask questions about how the world works.

Exactly.

Explain them to me in a way that's based on reasoned thought, rather than assumption based on results...

"Sit! Beg! Roll Over! Play Dead!"

You might think about using a little friendlier language than barking orders at the rest of the membership. It might put people in a better mood for replying.

I'm trying not to close this thread - but thus far, it's virtually entirely about unfounded hypotheses (and I have had to remove a number of messages). Please everyone, take a look at the PF Rules on overly speculative posts.