Gravity...wave or particle?

[Garrettguy457]

If i am correct we don't know if gravity is a wave or a particle or what it is. I was just wondering if gravity could be like light and it be a graviton riding on a "gravity wave". Is that possible?

[Klaynos]

The graviton is supposed to be similar to a photon.

 

But neither is a partcle riding on a gravity wave.

 

A photon is both a wave and a particle. As would a graviton be.

[Obelix]

It is reasonable to expect that gravitational waves and particles (gravitons) will display a wave - particle duality.

 

Unfortunately, as yet, gravitational waves have not been detected (let alone studied experimentally) and there is no complete theory regarding gravitons. Hence, no definite conclusions can be drawn, so far.

[ajb]

Morally, "the graviton to a gravitational wave is what the photon is to an electromagnetic wave".

[Pete]

A photon is both a wave and a particle. As would a graviton be.

I disagree. Something like a photon (or electron etc) displays both particle properties and wave properties, but never at the same time. In this sense one can't say that it is both a particle and a wave since stating it implies it displays both properties simultaneously, which it does not.

 

Pete

Edited July 22, 2008 by Pete

[Klaynos]

This is not precisely correct. Something like a photon (or electron etc) displays both particle properties and wave properties, but never at the same time. In this sense one can't say that it is both a particle and a wave since stating it implies it displays both properties simultaneously, which it does not.

 

Pete

 

True, that is a better answer but *shrug* in reality our language is just not good enough.

[Pete]

True, that is a better answer but *shrug* in reality our language is just not good enough.

 

Note: I changed This is not precisely correct. to I disagree. The later seems more conversational and less judgemental.

 

Pete

[Klaynos]

Well in that case...

 

displays both particle properties and wave properties

 

I disagree, it displays particle like and wave like properties. The problem still steams from our language just not being able to deal with something as odd as QM. Don't be so pedantic when answering questions like this.

Edited July 22, 2008 by Klaynos
multiple post merged

[Daecon]

What about if gravity is similar in nature to time, whereas instead of being comprised of particles, gravity is made out of the curve of space itself?

[Pete]

I disagree, it displays particle like and wave like properties.

Please clarify. To me that is indistinguishable from displays both particle properties and wave properties.

Don't be so pedantic when answering questions like this.

I'm not being pedantic. I'm being precise.

 

Pete

[Kyrisch]

I disagree. Something like a photon (or electron etc) displays both particle properties and wave properties, but never at the same time. In this sense one can't say that it is both a particle and a wave since stating it implies it displays both properties simultaneously, which it does not.

Pete

 

Recent experiments have cast doubt upon the Copenhagen interpretation regarding complementarity. An experiment was done that allowed a neutron interferometer to be subject to gravitation, and the neutrons created the interference pattern while simultaneously being affected by the gravitational field, something that should only affect particles.

[Pete]

Recent experiments have cast doubt upon the Copenhagen interpretation regarding complementarity. An experiment was done that allowed a neutron interferometer to be subject to gravitation, and the neutrons created the interference pattern while simultaneously being affected by the gravitational field, something that should only affect particles.

A photon is often referred to as a particle of light. When that is said it is referring to the particle property of a photon. Since light waves are affected by gravity then I don't see why you find this surprising or why you said it cases done on complementarity. Also, I never heard of the phrase Copenhagen interpretation regarding complementarity. The Copenhagen interpretation refers to the interpretation of the wave function whereas complementarity refers to the uncertainty principle. They are not the same thing.

 

Pete

[Mr Skeptic]

There's no such things as waves or particles anyhow. They're all wavicles.

[Pete]

They're all wavicles.

 

It was Sir Arthur Eddington who coined that term. Since an electron has wave properties and particle properties it is different than something which has either of them. For this reason a new name was sought and Eddington coined the term wavicle for that reason. I personally don't like that term because it can tend to give the wrong idea of the wave-particle duality. E.g. an electron is a pointlike object and is thus localized, quite unlike a wave. Statistically there is a wave pattern associated with the behaviour of the electron which can't be understood in classical terms and thus can'tbe understood if one thinks of an electron as being a classical particle. Hence the term waveicle. However people tend to take that to mean that an electron is both a particle and a wave simultaneously (i.e. displays both properties at the same time), which is not true.

 

Please note that this is my personal opinion and am not sure how wide spread it is. To be fair I should point out that Feynman wrote the following on page 85 of his book QED. After discussing electrons Feynman writes

It's rather interesting to note that electrons looked like particles at first, then their wavish character was later discovered. On the other hand, apart from Newton making a mistake and thinking that light was "corpuscular," light looked like waves at first, and its characteristics as a particle were discovered later. In fact, both objects behave somewhat like waves and somewhat like particles. In order to save oursleves from inventing new words such as "wavicles", we have chosen to call these objects "particles," but we all know that they obey these rules for drawing and combining arrows that I have explaining. It appears that all the "particles" in Nature - quarks, gluons, neutrinos, and so forth (which will be discussed in the next lecture) - behave in this quantum mechanical way.

However this is not the whole story of course since on page 37 Feynman writes

Quantum electrodynamics "resolves" this wave-particle duality by saying that light is made of particles (as Newton originally thought), but the price of this great achievement of science is a retreat by physics to the position of being able to calculate only the probability that a photon will hit a detector, without offering a good model of how it actually happens.

Well ... nobody ever said that quantum mechanics was easy to understand, right?

 

Pete

Edited July 24, 2008 by Pete

[Anu-Ki Ptah]

I have an Idea about this that may or may not at all be applicable.

 

I was noticing that gravity is still something of a mystery and wanted to attempt in joining the march in the discovery of what it may be.

Let's fo rthe sake of this instance place space as water. just for the moment. Now a whirlpool begins thus making a suction and a force to downward motion and thusly you have a sinking effect and cause of cyclical motion. Is it at all conceivable that gravity is a mere result of Material existence? (Remember limited model here or we would need a manuscript again between us all for comparison value)

Like the water itself being still no effect is present until we have the formation of a whirlpool and thusly the result is the force of motion toward the central axis of the pool due to the whirling of the water itself water equals+space in this instance.

 

and matter (it has been said) bends space. in that effect causing a bit of a whirl effect if you will.

 

Resulting in gravity,(which is now more of an effect rather than a tangible thing. much like falling on your face after drinking too much alcohol.)

 

The alcohol is not the fall in itself and the result is not at all the alcohol but the former has caused the latter.

[Kyrisch]

A photon is often referred to as a particle of light. When that is said it is referring to the particle property of a photon. Since light waves are affected by gravity then I don't see why you find this surprising or why you said it cases done on complementarity....

 

Pete

 

Well, complementarity is the notion that particles must either exhibit particle properties or wave properties, but never simulataneously. The observation that waves can be affected by gravity while still maintaining wave properties (since gravitational force only exists between two objects with mass, a particle property) violates that notion.

[Pete]

Well, complementarity is the notion that particles must either exhibit particle properties or wave properties, but never simulataneously. The observation that waves can be affected by gravity while still maintaining wave properties (since gravitational force only exists between two objects with mass, a particle property) violates that notion.

Recall "The Feynman Lectures on Physics," by Feynman, Sands and Leighton, Vol -I page 7-11 - Section entitled Gravitation and Relativity

One feature of this new law is quite easy to understand is this: In Einstein relativity theory, anything which has energy has mass -- mass in the sense that it is attracted gravitationaly. Even light, which has energy, has a "mass". When a light beam, which has energy in it, comes past the sun there is attraction on it by the sun.

Light has (passive) gravitational mass and therefore gravity exerts a gravitational force in light. Nothing is violated here.

 

Pete

[Royston]

With regards to wave-particle duality...plus I'm still quite new to QM i.e beyond anything you'd read in pop sci (so correct me with this). But I'm surprised nobody has mentioned Fourier synthesis (wave packets) and HUP, because these are really the first melding of the two, i.e waves and particles.

 

When you view the wave particle duality from just these principles and math, the distinction does blur somewhat.

 

My course, and a QM module I took several years ago, describes the wave-particle duality (wpd) with photons as 'light propogates as a wave, and interacts as a particle'...but I'm not too happy with this definition.

 

Another way I tried to reconcile wpd, is that a particle could be just described as a discrete unit of a wave, but I'm not too happy with that description either. As it appears to me, and sorry if I've missed something in this thread, but as Klaynos said, it's a phenomena that is almost impossible to describe with words...and hence we try to categorize as one or the other, or just simply can't understand it at all.

 

Please let me know if I'm missing something here.

[Pete]

With regards to wave-particle duality...plus I'm still quite new to QM i.e beyond anything you'd read in pop sci (so correct me with this). But I'm surprised nobody has mentioned Fourier synthesis (wave packets) and HUP, because these are really the first melding of the two, i.e waves and particles.

Good point. However it has been mentioned in other threads about the uncertainty principle. However the wave particle duality is the physical phenomena for which Fourier describes. The purpose of this thread seemed to me to be about the basic concept of wave particle duality and not the math which is constructed to describe it, which follows from the physical notion.

When you view the wave particle duality from just these principles and math, the distinction does blur somewhat.

I highly disagree. The wave function embeds the wave aspect of the wave-particle duality in that it provides statistical predictions. The particle aspect is embedded in what it predicts, i.e. the distributions of discrete events, e.g. the distribution of precisely localized positions of particles.

 

Pete

[Royston]

I highly disagree. The wave function embeds the wave aspect of the wave-particle duality in that it provides statistical predictions. The particle aspect is embedded in what it predicts, i.e. the distributions of discrete events, e.g. the distribution of precisely localized positions of particles.

 

Pete

 

Thanks Pete, I've quite literally studied this over the last couple of days, and knew I was missing something. What you stated is covered, but I didn't put all the aspects together, so my understanding was a tad vague, or slightly misled as it were. I guess I just needed a succinct overview of what's going on.

[Pete]

Thanks Pete.

You're most welcome. Its my pleasure. When I take the time to respond to someone's question I am actually helping myself in the process. In all cases I learn how to provide better responses and in some cases I actually learn something new. This is a result of being forced to look at something from a different perspective.

 

Keep asking these great questions!

 

Pete