B Can a Wave Exist Without a Medium?

[Gary Smith]

An atom of oxygen can be suspended in air, yes? Can a wave be suspended independently? Or does it need to be generated?

 

[DrChinese]

Can a wave be suspended independently? Or does it need to be generated?

What kind of wave are you referring to? Is this about quantum physics or classical?

 

[fresh_42]

I moved it to General Physics, as I think there are some fundamental questions to be addressed before we talk about Schrödinger equations.

A wave is a form of energy transmission. This can be interrupted, absorbed, created and so on. So the question is indeed, what kind of wave are you thinking of?

 

[sophiecentaur]

Can a wave be suspended independently?

Independently of what? You can have a hypothetical wave that exists purely in Maths but any Physical wave has to be in the form of some variations of a quantity and that quantity needs to be measurable and 'there'. If you can't measure or detect it then it doesn't exist.
Gravitational Waves have only recently been shown to exist. Before some valid detection was achieved, they only 'existed' in our theories.

 

[fresh_42]

Gravitational Waves have only recently been shown to exist. Before some valid detection was achieved, they only 'existed' in our theories.

This is mined territory! I want to remind participants (in advance) that we don't debate philosophical questions, the more as we already have plenty of threads, in which the question about the connection between "existence" and "measurement", resp. "observation" is discussed. Our search engine will be of help to all who are interested in following this path.

The distinction is easy: measurement / observation = physics ; existence / real = philosophy.

 

[Gary Smith]

fresh_42,

'The distinction is easy: measurement / observation = physics ; existence / real = philosophy.'

That is very helpful. 8th grade Earth science was as far as I got with science education, so this is all new territory to me.

I will keep this distinction very much in mind before posting further questions or comments.

Thank you.

 

[Gary Smith]

I am referring to the often posted references to waves such as in wave/particle duality. One was in a quote by a physicist:

'If I have to express quantum physics only in one phrase, it will be: wave particle duality of nature. Rest is the detail.'

 

[weirdoguy]

Too bad "wave-particle duality" is an outdated concept since like 1925-26... You won't find it in quantum mechanics, nor in QFT.

 

[nasu]

The question is confused from the beginning. What is the meaning of an atom of oxygen being suspended in air? How do you know which oxygen is part of the air itself and which is "suspended"? If you mean to have an atom completely at rest in the surrounding air, by what method do you think it was done?

"Suspended" refers to something which will have the tendency to fall to the ground and which can be at rest if we somehow counteract the gravity. A wave is not an object to which we can apply these concepts. Will a "suspended" wave still propagate? Will the particles of the medium still move? You can attach "suspended" to "wave" but then you may have to redefine the word.

We can link words to each other but they results does not always make sense, even though the grammar may be correct.

 

[Gary Smith]

nasu,

As my science education ended 50 years ago, I have some catching up to do.

Admittedly, many of my questions will be based on my personal concepts -- though I am working very hard to keep them within PF guidelines. Many, maybe most, may prove to be confused. That is why I am participating in PF. To become 'un-confused.'

I would like to pursue the discussion with you, but am being very careful about what I write, as it is challenging to frame my thoughts within observation and measurement.

But, perhaps you can tell me, what it is to be an atom of oxygen in air, or water, or wherever else it appears. What can physics say for certainty about its properties besides what I have read, that it has mass, charge and spin? The atom is 'somewhere' in the air I breathe. Can it be isolated from other atoms in air?

A wave has to travel, yes? From one point to another? In its travelling, say a radio wave through the atmosphere, is it wrong to think of the wave as suspended?

I don't know, that is why I ask.

 

[berkeman]

A wave has to travel, yes? From one point to another?

You can have a stationary wave, or "Standing Wave", like the waves on a guitar string that generate traveling sound waves...

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

 

[anorlunda]

A wave has to travel, yes? From one point to another? In its travelling, say a radio wave through the atmosphere, is it wrong to think of the wave as suspended?

Why do you ask only about the radio wave in the atmosphere? Why not in space? What do you thing the answer is for a radio wave in space?

 

[Gary Smith]

You can have a stationary wave, or "Standing Wave", like the waves on a guitar string that generate traveling sound waves...

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

That is fascinating. I will check it out. Thank you.

 

[Gary Smith]

Why do you ask only about the radio wave in the atmosphere? Why not in space? What do you think the answer is for a radio wave in space?

I did not have a reason for framing the question as I did. It was an example only. My understanding of waves and space is elementary. Perhaps you can fill me in. What are all the places where waves (quantum waves?) occur?

 

[nasu]

nasu,

But, perhaps you can tell me, what it is to be an atom of oxygen in air, or water, or wherever else it appears. What can physics say for certainty about its properties besides what I have read, that it has mass, charge and spin? The atom is 'somewhere' in the air I breathe. Can it be isolated from other atoms in air?

A wave has to travel, yes? From one point to another? In its travelling, say a radio wave through the atmosphere, is it wrong to think of the wave as suspended?

I don't know, that is why I ask.

Regarding the atom part, I am now confused about what are you asking. Atoms can be manipulated and isolated. Initially I thought you read about these atom traps where atoms are slowed down or even at rest for some time. But these experiments are done in high vacuum so if the atom can be considered suspended, it is not in air. Unless you man the "in air" as a figurative way of saying "in space".

For the wave part, it looks more like a matter of words. I don't see how insisting on being or not "suspended" bring anything useful. The dictionary definition of "suspended", the one that would apply to a an atom, is
" to keep from falling or sinking by some invisible support (such as buoyancy)".
Do you think this will apply to a propagating (or standing) wave? Or even to a bullet flying through the air. Would you say that the bullet is suspended while is approaching the target?

 

[Gary Smith]

Too bad "wave-particle duality" is an outdated concept since like 1925-26... You won't find it in quantum mechanics, nor in QFT.

Huh! What concept has replaced it?

 

[sophiecentaur]

is it wrong to think of the wave as suspended?

What would it be suspended in? One thing about all waves is that energy is being transported. Even in a standing wave, energy can be thought of as moving leftwards and rightwards, to produce stationary peaks and nulls in the energy distribution.
The ancient idea of particle wave duality still has some legs because it is possible to treat matter and EM waves in either of the two ways, depending on what you are actually observing. The basic lesson about EM waves is to avoid ever ever ever treating them as if the photons are like little bullets. The Particles that are Photons are only visualised for the purposes of discussing the interaction of EM waves with matter.

 

[DennisN]

Huh! What concept has replaced it?

See e.g. this page: https://www.physicsforums.com/threads/is-light-a-wave-or-a-particle.511178/

 

[sophiecentaur]

Huh! What concept has replaced it?

Do not expect an easy ride on the way to getting this sorted.
It has long been admitted that people who think they understand QM, don't. Your brain will hurt.

 

[Gary Smith]

S. - 'What would it be suspended in?'

G. - My thought is that there are atoms of oxygen surrounding me, suspended in the air. They are also in my veins, suspended in the blood. And so on. If suspended is the wrong word, can you give me the correct one? Or, tell me, where all of those atoms of oxygen, if they are not suspended?

S. - 'One thing about all waves is that energy is being transported.'

G. - Excellent! That is what I need to understand.

S. - 'Even in a standing wave, energy can be thought of as moving leftwards and rightwards, to produce stationary peaks and nulls in the energy distribution.'

G. - Is there a specific name for the type of energy being transported by the wave?

S. - 'The ancient idea of particle wave duality still has some legs because it is possible to treat matter and EM waves in either of the two ways, depending on what you are actually observing.'

G. - I had to look up the definition of EM waves. Of course, ElectroMagnetic. Would you say that all waves of quantum physics are EM waves? I imagine so, as what other type of wave could there be... except maybe sound waves... but are those EM waves also?

S. - The basic lesson about EM waves is to avoid ever ever ever treating them as if the photons are like little bullets. The Particles that are Photons are only visualised for the purposes of discussing the interaction of EM waves with matter.

G. - Photons, it seems, are in a class by themselves. A physicist told me a few years ago that super-string theory had been replaced by 'wavicles.' Is it true that photons behave sometimes like waves and sometimes like particles? I also read that photons are particles without mass. Oi. So many new questions come to mind...

 

[Gary Smith]

N. - 'Initially I thought you read about these atom traps where atoms are slowed down or even at rest for some time.'

G. - No, I had not heard of atom traps.

N. - Unless you mean the "in air" as a figurative way of saying "in space".

G. - Yes, that is true. I meant it as the air we breathe, which in the space around us.

N. - I don't see how insisting on being or not "suspended" brings anything useful.

G. - It is not my intention to insist anything on PF. If I sound like I insist, it is probably because I am groping (though only in context) for a way to convey my concept.

N. - Do you think this will apply to a propagating (or standing) wave?

G. - I have to look up propagating wave and read up on standing wave.

N. - Would you say that the bullet is suspended while is approaching the target?

G. - No, I guess not. Suspended would imply it is stationary or not moving by its own force. Are atoms always in motion, like a bullet? As I understood, they have spin, mass and charge. But motion?

Thank you for your patience with me.

 

[DennisN]

Is it true that photons behave sometimes like waves and sometimes like particles?

Please see my post #18 above .

I also read that photons are particles without mass.

That is correct. But also note that when talking about particles on this level (e.g. elementary particles), "particle" does not mean a classical object with a specified size (like let's say a small ball, a grain of sand or a dust particle), it means an object behaving according to the Rules of Quantum Mechanics.

EDIT: Here is an overview of the elementary particles:
http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/parcon.html

 

[davenn]

N. - 'Initially I thought you read about these atom traps where atoms are slowed down or even at rest for some time.'

G. - No, I had not heard of atom traps.

N. - Unless you mean the "in air" as a figurative way of saying "in space".

G. - Yes, that is true. I meant it as the air we breathe, which in the space around us.

N. - I don't see how insisting on being or not "suspended" brings anything useful.

Hi Gary
it would be really nice if you got the text quoting sorted out

hilite the line of text in some one's post you wish to quote and click the reply button

results in this

G. - No, I guess not. Suspended would imply it is stationary or not moving by its own force. Are atoms always in motion, like a bullet? As I understood, they have spin, mass and charge. But motion?

this has 2 awesome functions
1) makes it really easy to see who is being quoted
2) makes it really easy to separate quoted text from the responses by you (or whoever) Dave

 

[nasu]

N. - 'Initially I thought you read about these atom traps where atoms are slowed down or even at rest for some time.'
G. - No, I guess not. Suspended would imply it is stationary or not moving by its own force. Are atoms always in motion, like a bullet? As I understood, they have spin, mass and charge. But motion?

The molecules of the air around us (most of them are oxygen and nitrogen molecules) have speeds around 500 m/s (average). This is higher than the speed of sound in the air. The atoms in a solid vibrate about their equilibrium positions. Some of them may do this billions of time per second. It is very difficult indeed to find an atom that does not move (in respect to other surrounding atoms).

 

[Gary Smith]

Do not expect an easy ride on the way to getting this sorted.
It has long been admitted that people who think they understand QM, don't. Your brain will hurt.

To be honest, I do not expect to understand QM or to have an easy ride. I see that I confused myself in this thread by introducing the example of an atom in air when the question is about waves. I lost track of whether I was talking about atoms or waves, and apologize to participants for this.

Ideally I would have freedom to express my specific thoughts in a forum where scientists also have interest to discuss those ideas, which would include consciousness. But I do not have that freedom here. I do understand and respect that discussions outside the standards of physics could dilute the mission of PF. What I don't understand is why consciousness is such a controversial subject. A search on the word in PF brings up numerous examples of where it has been discussed. And a mentor gave me a link to a Wikipedia article on the unsolved problems of physics, the first of which is about the arrow of time and consciousness. The PF guidelines are still confusing to me, but becoming clearer as I recognize the distinction of accepted journals to quote and so on. So I will continue to express what is on my mind as fully as possible, constrained by staying within the guidelines.

 

[Gary Smith]

Hi Gary
it would be really nice if you got the text quoting sorted out

hilite the line of text in some one's post you wish to quote and click the reply button

View attachment 206133

results in this
this has 2 awesome functions
1) makes it really easy to see who is being quoted
2) makes it really easy to separate quoted text from the responses by you (or whoever) Dave

Thank you, Dave. I will follow that suggestion.

 

[Gary Smith]

See e.g. this page: https://www.physicsforums.com/threads/is-light-a-wave-or-a-particle.511178/

Read it. Thanks.

 

[Gary Smith]

What kind of wave are you referring to? Is this about quantum physics or classical?

I think I am talking about a quantum wave. Is there such a thing?

 

[Gary Smith]

That is fascinating. I will check it out. Thank you.

The article has animated GIFs which I can relate to.

Under one animation, it says, 'Standing wave in stationary medium...'

What all is included in a stationary medium? Can a standing wave be in a rock? Are standing waves within atoms?

Under another animation, it says, 'Standing waves in a string...'

Is this referring to the string of super string theory?

Are strings, superstrings or wavicles, whatever is the current understanding of a quantum wave, within atoms?

 

[sophiecentaur]

I think I am talking about a quantum wave.

This could be word salad, I think.
You would probably benefit from reading a few Popular Science books. They would at least direct your path through the subject in an ordered way and show the way thinking has progressed over the centuries. You could try "Forces of Nature" by Brian Cox. It has a lot of good reader revues.
Q and A is all good fun but it tends to lead you along a 'random walk', which will not take you very far very fast. Questions are only of use if they can give you answers that you can understand - hence my idea of 'structured learning'.

 

[Gary Smith]

The molecules of the air around us (most of them are oxygen and nitrogen molecules) have speeds around 500 m/s (average). This is higher than the speed of sound in the air. The atoms in a solid vibrate about their equilibrium positions. Some of them may do this billions of time per second. It is very difficult indeed to find an atom that does not move (in respect to other surrounding atoms).

Thank you. I see that my understanding of physics will never be fully informed. But gaining this piece of understanding helps me grow closer to the actual picture. Finding specific information like this with a general search would be like looking for a needle in a haystack. I appreciate the time of all who respond.

 

[sophiecentaur]

Thank you. I see that my understanding of physics will never be fully informed.

That is true for all of us. But I can say that most PF members would not aspire ever to 'know it all'. We can all learn as we go and most of us do a fair amount of reading round on a regular basis.

 

[nasu]

Thank you. I see that my understanding of physics will never be fully informed. But gaining this piece of understanding helps me grow closer to the actual picture. Finding specific information like this with a general search would be like looking for a needle in a haystack. I appreciate the time of all who respond.

Actually is not so hard to find information nowadays.
"Speed air molecules" in Google provides the answer right on top, in bold characters.

 

[Gary Smith]

Actually is not so hard to find information nowadays.
"Speed air molecules" in Google provides the answer right on top, in bold characters.

Okay, I can drop my mental barrier then to finding such answers with a Google search. Normally I am quite adept at searching in this way, but for some reason had the pre-conceived idea such specific information would not be found. My solution to the frustration of having posts blocked is to make inquiries first of Mentors, to have an okay before posting new questions.

 

[nasu]

I am not advocating Google as the main source of learning. I still think that books are the best source for systematic learning. But for finding quickly a specific fact, the web is a great advance over the times when you had to go through several books just to find a simple fact.

 

[Gary Smith]

I am not advocating Google as the main source of learning. I still think that books are the best source for systematic learning. But for finding quickly a specific fact, the web is a great advance over the times when you had to go through several books just to find a simple fact.

Yes, the problem of only doing Google searching, or even reading from what seems to be reputable sources, is that someone like me has some difficulty piecing it together without getting lost in a maze of wishful thinking. That is why I come to PF. I have just posted a bio on my profile in case anyone is interested in knowing 'where I am coming from.'

 

[zbikraw]

Atom of oxygen was used as non-bonded idea, I suppose. In reality oxygen exists mainly in diatomic molecules, sometimes triatomic (ozone). Monotomic one exist in high temperatures and "dimerizes" spontaneously and strongly exothermally. Tchnically this is used in a Langmuir torch.

 

[Gary Smith]

Atom of oxygen was used as non-bonded idea, I suppose. In reality oxygen exists mainly in diatomic molecules, sometimes triatomic (ozone). Monotomic one exist in high temperatures and "dimerizes" spontaneously and strongly exothermally. Tchnically this is used in a Langmuir torch.

Does 'diatomic molecule' mean a pair of bonded atoms of oxygen?

 

[nasu]

Yes, this is how oxygen is found in the air. The single atom of oxygen is not stable in normal conditions. Not in the sense that it decays but that it will find another atom to bind to.

 

[Gary Smith]

Yes, this is how oxygen is found in the air. The single atom of oxygen is not stable in normal conditions. Not in the sense that it decays but that it will find another atom to bind to.

That type of answer makes it worthwhile to ask. Thank you.

 

[Gary Smith]

Please see my post #18 above .

That is correct. But also note that when talking about particles on this level (e.g. elementary particles), "particle" does not mean a classical object with a specified size (like let's say a small ball, a grain of sand or a dust particle), it means an object behaving according to the Rules of Quantum Mechanics.

EDIT: Here is an overview of the elementary particles:
http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/parcon.html

What a great diagram! Clearly I am a visual person.

May I ask, when is it right to say Quantum Physics and when Quantum Mechanics?

 

[nasu]

Why not ask? Others did before you. :)
https://physics.stackexchange.com/q...-mechanics-and-quantum-physics-the-same-field

 

[Gary Smith]

This could be word salad, I think.
You would probably benefit from reading a few Popular Science books. They would at least direct your path through the subject in an ordered way and show the way thinking has progressed over the centuries. You could try "Forces of Nature" by Brian Cox. It has a lot of good reader revues.
Q and A is all good fun but it tends to lead you along a 'random walk', which will not take you very far very fast. Questions are only of use if they can give you answers that you can understand - hence my idea of 'structured learning'.

I understand your idea of 'structured learning' but in my case it works far better to ask specific questions. Briefly, I am 64 and though semi-retired have daily responsibilities and a lifestyle which make prolonged periods of reading next to impossible. Also, I have little interest in physics outside my specific questions. Though once an avid reader, that was before 2000. Since then, I have rarely made it through even a book which started out to be quite compelling. It just is not my way of learning. I have enough of whatever it takes to sort things out eventually, with some solid pieces of information which answer my specific questions. There have been some real gems in this thread for me.

 

[Gary Smith]

Why not ask? Others did before you. :)
https://physics.stackexchange.com/q...-mechanics-and-quantum-physics-the-same-field

From that article,

'So one could say that all the three terms are synonyma. Physicists would almost always pick "quantum mechanics" as the preferred label for any theory that follows the postulates of quantum mechanics or for the postulates themselves. On the other hand, "quantum physics" and "quantum theory" is more likely to be used by the outsiders or in the non-expert context.'

If it won't offend anyone, I will continue to use 'quantum physics,' as mine is in the non-expert context. Thanks.

 

[sophiecentaur]

but in my case it works far better to ask specific questions.

It may be less trouble but are you really in a position to judge that it is better? And you have not been asking a specific question, which is why this thread has had so many facets and so few answers for you. A grumpy response, perhaps but you are actually undervaluing the subject by imagining that there is much mileage in the scattergun approach that you advocate. If you have found it hard to make it to the end of the books you have been reading you could perhaps start with less advanced texts. I know how turgid a book can be when you find something new and difficult on each new page. I have launched out on several books and been relieved to put them down, unfinished.

 

[Gary Smith]

sophiecentaur, I really appreciate your input. Yes, I would say that with a lifetime of experience -- of observing and measuring what works and what doesn't for me -- I am in a position of saying what works better -- more effectively, efficiently and productively. I am quite happy with the answers in this thread, which I inadvertently confused by mentioning atoms as an example, when the question was about waves. Everyone who responds does so voluntarily, and I appreciate each response, even grumpy ones.

 

[rootone]

An atom of oxygen can be suspended in air, yes? Can a wave be suspended independently? Or does it need to be generated?

Oxygen in air is largely O2 molecules, and it exists in the air with other gases, mostly N2, but there are significant other components of air, water vapor being one.
The atmosphere does have waves in it, like the sea does, we call it weather systems,
The air on Earth is for now though a fairly predictable mix.
H20 content being of most interest for practical stuff like agriculture.

 

[Gary Smith]

Oxygen in air is largely O2 molecules, and it exists in the air with other gases, mostly N2, but there are significant other components of air, water vapor being one.
The atmosphere does have waves in it, like the sea does, we call it weather systems,
The air on Earth is for now though a fairly predictable mix.
H20 content being of most interest for practical stuff like agriculture.

Thank you.

 

[Khashishi]

G. - I had to look up the definition of EM waves. Of course, ElectroMagnetic. Would you say that all waves of quantum physics are EM waves?

No. EM waves are one type of wave. Water waves, sound waves, and matter waves are different kinds of waves.

G. - Photons, it seems, are in a class by themselves. A physicist told me a few years ago that super-string theory had been replaced by 'wavicles.' Is it true that photons behave sometimes like waves and sometimes like particles? I also read that photons are particles without mass. Oi. So many new questions come to mind...

No. It's possible something got lost in translation. According to https://en.wikipedia.org/wiki/Wave–particle_duality, Eddington coined the term wavicle for a particle that has wavelike characteristics in 1928. It has not entered standard parlance, and today we don't ever use the term. We just call particles "particles", where our modern definition of particle includes all of the wavelike behavior. So, it doesn't make sense to say a particle "sometimes acts like a wave and sometimes like a particle" since a particle always acts like a particle by definition. But yes, it has wavelike properties.

 

[Gary Smith]

No. EM waves are one type of wave. Water waves, sound waves, and matter waves are different kinds of waves.No. It's possible something got lost in translation. According to https://en.wikipedia.org/wiki/Wave–particle_duality, Eddington coined the term wavicle for a particle that has wavelike characteristics in 1928. It has not entered standard parlance, and today we don't ever use the term. We just call particles "particles", where our modern definition of particle includes all of the wavelike behavior. So, it doesn't make sense to say a particle "sometimes acts like a wave and sometimes like a particle" since a particle always acts like a particle by definition. But yes, it has wavelike properties.

Thank you.