Fictitious Forces

Nobody is saying that quarks don't exist.

Raist says that he's not sure if quarks exist or not.

Quote from: markjo on March 21, 2009, 07:25:48 AM

Quote from: Tom Bishop on March 21, 2009, 03:00:33 AM

Quote from: svenanders on March 21, 2009, 02:46:28 AM

Can you see your fingers if you hide them under a table? No.
Does this mean that they will cease to exist just because you can't see them? No.

Fingers have been observed, and the existence of fingers are easily peer reviewed.

The existence of "gravitons" have never been observed, detected, peer reviewed, or suggested by anything beyond idle hypothesis. That puts them squarely in the realm of the paranormal and pseudo-science.

At least some people claim to see ghosts. No one claims to see gravitons.

Tom, please learn the difference between "see" and "observe".  It's subtle, but significant.  Sub-atomic particles are generally indirectly observed as opposed to directly seen.  No one has ever seen an up quark, but through careful observation physicists know that they exist.

And no one has "observed" a graviton. Did you manage to think up a point other than to derail?

Ahh, but can you see the wind? You can see the effects of the Wind, but you can not directly see the wind can you.

There are certain behaviours that wind exhibits, and this allows us to learn about what wind is and that it really does exist. This is exactly the same with subatomic particles. We can not directly see them, but we can see effects caused by them, and upon close examination of these effects we can learn something about what they really are.

Accepting that your kite is held up by wind, and accepting that forces are exchanged by particles is no different in principal. We can not directly see either, but we can see the effects and upon close examination of these effects we can tell certain things about them.

Even if Gravitons don't exist it doesn't prove gravity doesn't exist. It just prove string theory is wrong.

I doubt they will ever find the graviton, nevermind the superforce or the sparticles. The LHC will probably be powerful enough to generate something they never seen before, thereby rewriting most, if not all, laws of physics.

I tend to agree. I don't think gravitons are a good explanation for how gravity works. I think just plain space-time is being warped works better then gravitons.

Hmmmm gravitons are not entirely dependent on super symmetry. General relativity cannot be the final word in gravity as it is fundamentally not reconcilable with quantum mechanics. While there is a very good theoretical reason for supersymmetry, namely explaining why the weak interaction scale so so much smaller than that of gravity, I agree with Jack and as a theory I find it aesthetically not very pleasing.

Personally, I think that one of the biggest fallacies of science is that scientists feel the need to make their theories aesthetically pleasing.

Hmmmm gravitons are not entirely dependent on super symmetry. General relativity cannot be the final word in gravity as it is fundamentally not reconcilable with quantum mechanics. While there is a very good theoretical reason for supersymmetry, namely explaining why the weak interaction scale so so much smaller than that of gravity, I agree with Jack and as a theory I find it aesthetically not very pleasing.

True, but they still introduces the gravitino (a superpartner of the graviton) anyway, in an attempt to combine supersymmetry with general relativity. Sometimes I question myself that maybe gravitation is not one of the four interactions at all; gravitation is a completely different thing and is not carried by a particle. Maybe gravitation is just the curvature of space-time after all.

Personally, I think that one of the biggest fallacies of science is that scientists feel the need to make their theories aesthetically pleasing.

Personally, I think that one of biggest fallacies of posting here is that some of the posters feel the need to make their post overly general.

Quote from: bowler on March 25, 2009, 12:50:25 PM

Hmmmm gravitons are not entirely dependent on super symmetry. General relativity cannot be the final word in gravity as it is fundamentally not reconcilable with quantum mechanics. While there is a very good theoretical reason for supersymmetry, namely explaining why the weak interaction scale so so much smaller than that of gravity, I agree with Jack and as a theory I find it aesthetically not very pleasing.

True, but they still introduces the gravitino (a superpartner of the graviton) anyway, in an attempt to combine supersymmetry with general relativity. Sometimes I question myself that maybe gravitation is not one of the four interactions at all; gravitation is a completely different thing and is not carried by a particle. Maybe gravitation is just the curvature of space-time after all.

But what particle mediates the message for space-time to curve at a distance?

Quote from: Jack on March 25, 2009, 07:23:22 PM

Quote from: bowler on March 25, 2009, 12:50:25 PM

Hmmmm gravitons are not entirely dependent on super symmetry. General relativity cannot be the final word in gravity as it is fundamentally not reconcilable with quantum mechanics. While there is a very good theoretical reason for supersymmetry, namely explaining why the weak interaction scale so so much smaller than that of gravity, I agree with Jack and as a theory I find it aesthetically not very pleasing.

True, but they still introduces the gravitino (a superpartner of the graviton) anyway, in an attempt to combine supersymmetry with general relativity. Sometimes I question myself that maybe gravitation is not one of the four interactions at all; gravitation is a completely different thing and is not carried by a particle. Maybe gravitation is just the curvature of space-time after all.

But what particle mediates the message for space-time to curve at a distance?

Why is a particle needed?

But what particle mediates the message for space-time to curve at a distance?

That's an attempt to unify QM with GR, and I could care less about that. General Relativity doesn't need a particle to propagate information between mass and space-time.

Quote from: MayTheBetterModelWin on March 25, 2009, 07:52:11 PM

Quote from: Jack on March 25, 2009, 07:23:22 PM

Quote from: bowler on March 25, 2009, 12:50:25 PM

Hmmmm gravitons are not entirely dependent on super symmetry. General relativity cannot be the final word in gravity as it is fundamentally not reconcilable with quantum mechanics. While there is a very good theoretical reason for supersymmetry, namely explaining why the weak interaction scale so so much smaller than that of gravity, I agree with Jack and as a theory I find it aesthetically not very pleasing.

True, but they still introduces the gravitino (a superpartner of the graviton) anyway, in an attempt to combine supersymmetry with general relativity. Sometimes I question myself that maybe gravitation is not one of the four interactions at all; gravitation is a completely different thing and is not carried by a particle. Maybe gravitation is just the curvature of space-time after all.

But what particle mediates the message for space-time to curve at a distance?

Why is a particle needed?

The basic idea is that information must be carried by either medium (Sound through the air) or particle (a photon exciting an atom). Since we know based on the M&M results that there is no medium involved, then it seems the only choice known to Science is a particle. Jack's idea only moves the problem.

(Oh and the correct phrase, Jack, is "I couldn't care less".)

Why can't space be a medium?

Why can't space be a medium?

Well, it's probably best that you look up http://en.wikipedia.org/wiki/Michelson-Morley_experiment rather than rely on my explanation.

Here's the jest... Imagine that the Earth moves around the Sun as M&M did. (Yes, I know that begs the question about the shape of the Earth. Realize though the the M&M result leads directly to SR that FET relies upon. Without M&M, SR is not validated (or needed) and FET fails quickly.) If space-time is a medium than the Earth must at more than one time be moving relative to the medium. Imagine now sending two swimmers (photon streams actually) in perpendicular directions on a linear equidistant circuit (with one reflection, a mirror for the photons). The swimmer who wins the "luck" of the draw who gets to swim upstream then downstream would travel the circuit faster than the less lucky swimmer who must swim cross-stream. (You'll need to understand vectors and the energy the cross-stream swimmer must loose to fighting the current while the up/down-stream swimmer gets to "bank" and "reclaim" his energy.)

(There was an attempt to explain the result that the Earth dragged along the surrounding medium. This quickly fails for several reasons including the absence of aberrations caused by the Earth's bow waves.)

What M&M found was the speed of light was constant for all observers regardless of the time of year or orientation of the photon streams. Hence we know that there can't be a medium. (and Einstein had his start on SR).

Quote from: optimisticcynic on March 25, 2009, 08:49:42 PM

Why can't space be a medium?

Well, it's probably best that you look up http://en.wikipedia.org/wiki/Michelson-Morley_experiment rather than rely on my explanation.

Here's the jest... Imagine that the Earth moves around the Sun as M&M did. (Yes, I know that begs the question about the shape of the Earth. Realize though the the M&M result leads directly to SR that FET relies upon. Without M&M, SR is not validated (or needed) and FET fails quickly.) If space-time is a medium than the Earth must at more than one time be moving relative to the medium. Imagine now sending two swimmers (photon streams actually) in perpendicular directions on a linear equidistant circuit (with one reflection, a mirror for the photons). The swimmer who wins the "luck" of the draw who gets to swim upstream then downstream would travel the circuit faster than the less lucky swimmer who must swim cross-stream. (You'll need to understand vectors and the energy the cross-stream swimmer must loose to fighting the current while the up/down-stream swimmer gets to "bank" and "reclaim" his energy.)

(There was an attempt to explain the result that the Earth dragged along the surrounding medium. This quickly fails for several reasons including the absence of aberrations caused by the Earth's bow waves.)

What M&M found was the speed of light was constant for all observers regardless of the time of year or orientation of the photon streams. Hence we know that there can't be a medium. (and Einstein had his start on SR).

Yes, we all know how the MM experiment showed there is no "ether" for the propagation of light.  But gravitational waves can propagate information through empty spacetime in GR.  Why is a particle needed?

Wouldn't the velocity of space have no affect on the object. It should be the acceleration of space that would affect something velocity. that is the thing that is making other galaxy get farther from us, the acceleration of the universe expansion or the expansion of space time. otherwise the all that matters with relativity's is objects relation to each other not there relationship to space. I thought relativity did this without ignoring space as a medium.

Quote from: MayTheBetterModelWin on March 25, 2009, 09:15:24 PM

Quote from: optimisticcynic on March 25, 2009, 08:49:42 PM

Why can't space be a medium?

Well, it's probably best that you look up http://en.wikipedia.org/wiki/Michelson-Morley_experiment rather than rely on my explanation.

Here's the jest... Imagine that the Earth moves around the Sun as M&M did. (Yes, I know that begs the question about the shape of the Earth. Realize though the the M&M result leads directly to SR that FET relies upon. Without M&M, SR is not validated (or needed) and FET fails quickly.) If space-time is a medium than the Earth must at more than one time be moving relative to the medium. Imagine now sending two swimmers (photon streams actually) in perpendicular directions on a linear equidistant circuit (with one reflection, a mirror for the photons). The swimmer who wins the "luck" of the draw who gets to swim upstream then downstream would travel the circuit faster than the less lucky swimmer who must swim cross-stream. (You'll need to understand vectors and the energy the cross-stream swimmer must loose to fighting the current while the up/down-stream swimmer gets to "bank" and "reclaim" his energy.)

(There was an attempt to explain the result that the Earth dragged along the surrounding medium. This quickly fails for several reasons including the absence of aberrations caused by the Earth's bow waves.)

What M&M found was the speed of light was constant for all observers regardless of the time of year or orientation of the photon streams. Hence we know that there can't be a medium. (and Einstein had his start on SR).

Yes, we all know how the MM experiment showed there is no "ether" for the propagation of light.  But gravitational waves can propagate information through empty spacetime in GR.  Why is a particle needed?

First, I think you may well be able to help most of us understand more. Second, I think this post needed more review before you posted it.
1) No, we all don't know that hence the answer to poster's question (Geesh!)
2) "But gravitational waves can propagate information through empty spacetime in GR." So? Light can propagate information through empty spacetime in SR. Does that mean there aren't any photons, after all?
3) Asked and answered.

Wouldn't the velocity of space have no affect on the object. It should be the acceleration of space that would affect something velocity. that is the thing that is making other galaxy get farther from us, the acceleration of the universe expansion or the expansion of space time. otherwise the all that matters with relativity's is objects relation to each other not there relationship to space. I thought relativity did this without ignoring space as a medium.

If conventional physics ruled, the velocity of space would sweep along everything in it. We know from M&M that it doesn't. The only viable answer is the space isn't a medium. Even if spacetime isn't a medium, it can still have metrics, like distance and time. (That's its definition after all.)

Quote from: Euclid on March 25, 2009, 09:25:42 PM

Quote from: MayTheBetterModelWin on March 25, 2009, 09:15:24 PM

Quote from: optimisticcynic on March 25, 2009, 08:49:42 PM

Why can't space be a medium?

Well, it's probably best that you look up http://en.wikipedia.org/wiki/Michelson-Morley_experiment rather than rely on my explanation.

Here's the jest... Imagine that the Earth moves around the Sun as M&M did. (Yes, I know that begs the question about the shape of the Earth. Realize though the the M&M result leads directly to SR that FET relies upon. Without M&M, SR is not validated (or needed) and FET fails quickly.) If space-time is a medium than the Earth must at more than one time be moving relative to the medium. Imagine now sending two swimmers (photon streams actually) in perpendicular directions on a linear equidistant circuit (with one reflection, a mirror for the photons). The swimmer who wins the "luck" of the draw who gets to swim upstream then downstream would travel the circuit faster than the less lucky swimmer who must swim cross-stream. (You'll need to understand vectors and the energy the cross-stream swimmer must loose to fighting the current while the up/down-stream swimmer gets to "bank" and "reclaim" his energy.)

(There was an attempt to explain the result that the Earth dragged along the surrounding medium. This quickly fails for several reasons including the absence of aberrations caused by the Earth's bow waves.)

What M&M found was the speed of light was constant for all observers regardless of the time of year or orientation of the photon streams. Hence we know that there can't be a medium. (and Einstein had his start on SR).

Yes, we all know how the MM experiment showed there is no "ether" for the propagation of light.  But gravitational waves can propagate information through empty spacetime in GR.  Why is a particle needed?

First, I think you may well be able to help most of us understand more. Second, I think this post needed more review before you posted it.
1) No, we all don't know that hence the answer to poster's question (Geesh!)
2) "But gravitational waves can propagate information through empty spacetime in GR." So? Light can propagate information through empty spacetime in SR. Does that mean there aren't any photons, after all?
3) Asked and answered.

1) He wasn't asking you why space can't be a medium for light, he was asking why it couldn't be a medium for gravitational propagation.
2) Light is a completely different phenomenon from gravitational waves.  Gravitational waves propagate via the bending of spacetime itself.  Light is only a phenomenon occurring on spacetime.  It doesn't follow that they both require/do not require a particle for propagation.  Is the explanation of gravitational waves via spacetime bending somehow insufficient such that a particle is required?  That is what I am asking you.

Second, I think this post needed more review before you posted it.

What's that supposed to mean?

...

1) He wasn't asking you why space can't be a medium for light, he was asking why it couldn't be a medium for gravitational propagation.
2) Light is a completely different phenomenon from gravitational waves.  Gravitational waves propagate via the bending of spacetime itself.  Light is only a phenomenon occurring on spacetime.  It doesn't follow that they both require/do not require a particle for propagation.  Is the explanation of gravitational waves via spacetime bending somehow insufficient such that a particle is required?  That is what I am asking you.

Quote

Second, I think this post needed more review before you posted it.

What's that supposed to mean?

1) False. His question does not mention any particular data.
2)
 a) Do you have any evidence to support your claim that "Light is a completely different phenomenon from gravitational waves."?
 b) You attack a strawman. I never argued that the need of a particle to mediate the EM force meant that a particle was required for  the curving of spacetime at a distance.
 c) You, however, have argued without substantiation that GWs propagate without medium or particle. And that this characteristic, by unsupported extrapolation, must also apply to G.

I must admit when I was an undergraduate I had this debate so often with myself in my head. I had this rather nice idea of the fundamental nature of force is my head. If one starts with the basic definition of force as something which causes an inertial mass to change velocity. It used to make perfect sense in my head that gravity was the way that space/time, the stage as it were, interacted with the actors. The other quantum fields represented the way that the actors interacted with each other. I have no idea where the theater analogy comes from thats just how it appeared in my head. Though as time has gone on this has become less acceptable to me.

My first argument comes from very high energy physics above the GUT scale. Right now general relativity and quantum mechanics cannot explain this regime. It doesn't prove anything but it does show that we don't know how they truly relate to each other. While this does not disprove my stage analogy it does show that its not based on a massive piece of relevant information. My second concern is the nature of mass. It seems likely that in the next few years the origin of inertial mass will be uncovered in the form of interactions with the Higgs field or something similar. This is still hypothetical but electroweak theory has been so massively successful and indicates that a field responsible for inertial mass should be on the weak mass scale. So then we are left trying to explain gravitational mass and why it appears to be equal to inertial mass. Which is really the crux of this entire debate.

In short we cannot tell whether the gravitational field is quantized or not and I have not yet come across a reason to suggest one explanation over another. As we have descended into philosophy I would like to make a point about interpretation. This is like describing blue to a blind man. By this I mean we can describe very accurately what is going on in GR and QFT with some rather funky maths. In QFT we picture a particle as a series of vibrations in some field. Do I honestly believe that if I had a powerful microscope there is physically this thing wibbling, not really, no. However that is the form that the equations take so thats how we picture things mentally. Is an electron a particle or a wave, I don't honestly think it's either i'm sure what it really is I can't comprehend but as I need to comprehend it, I picture it in different situations as something thats appropriate sometimes thats a particle other times its a wave. We argue about whether gravity is the bending of space-time or the exchange of a virtual particle, in truth I imagine its neither but we'll continue to use whatever we deem appropriate for a given situation. 

I must admit when I was an undergraduate I had this debate so often with myself in my head. I had this rather nice idea of the fundamental nature of force is my head. If one starts with the basic definition of force as something which causes an inertial mass to change velocity. It used to make perfect sense in my head that gravity was the way that space/time, the stage as it were, interacted with the actors. The other quantum fields represented the way that the actors interacted with each other. I have no idea where the theater analogy comes from thats just how it appeared in my head. Though as time has gone on this has become less acceptable to me.

My first argument comes from very high energy physics above the GUT scale. Right now general relativity and quantum mechanics cannot explain this regime. It doesn't prove anything but it does show that we don't know how they truly relate to each other. While this does not disprove my stage analogy it does show that its not based on a massive piece of relevant information. My second concern is the nature of mass. It seems likely that in the next few years the origin of inertial mass will be uncovered in the form of interactions with the Higgs field or something similar. This is still hypothetical but electroweak theory has been so massively successful and indicates that a field responsible for inertial mass should be on the weak mass scale. So then we are left trying to explain gravitational mass and why it appears to be equal to inertial mass. Which is really the crux of this entire debate.

In short we cannot tell whether the gravitational field is quantized or not and I have not yet come across a reason to suggest one explanation over another. As we have descended into philosophy I would like to make a point about interpretation. This is like describing blue to a blind man. By this I mean we can describe very accurately what is going on in GR and QFT with some rather funky maths. In QFT we picture a particle as a series of vibrations in some field. Do I honestly believe that if I had a powerful microscope there is physically this thing wibbling, not really, no. However that is the form that the equations take so thats how we picture things mentally. Is an electron a particle or a wave, I don't honestly think it's either i'm sure what it really is I can't comprehend but as I need to comprehend it, I picture it in different situations as something thats appropriate sometimes thats a particle other times its a wave. We argue about whether gravity is the bending of space-time or the exchange of a virtual particle, in truth I imagine its neither but we'll continue to use whatever we deem appropriate for a given situation. 

I find your conclusion rational and well presented.

Quote from: optimisticcynic on March 25, 2009, 09:28:45 PM

Wouldn't the velocity of space have no affect on the object. It should be the acceleration of space that would affect something velocity. that is the thing that is making other galaxy get farther from us, the acceleration of the universe expansion or the expansion of space time. otherwise the all that matters with relativity's is objects relation to each other not there relationship to space. I thought relativity did this without ignoring space as a medium.

If conventional physics ruled, the velocity of space would sweep along everything in it. We know from M&M that it doesn't. The only viable answer is the space isn't a medium. Even if spacetime isn't a medium, it can still have metrics, like distance and time. (That's its definition after all.)

Not exactly. in conventional physics acceleration of space should be the only thing that changes something velocity. Otherwise I believe relativity makes everything work fine.
That is the way I understood it.   this  is the reason you can only get energy from spinning black holes. I could be wrong but that is how it was explained to me.

I must admit when I was an undergraduate I had this debate so often with myself in my head. I had this rather nice idea of the fundamental nature of force is my head. If one starts with the basic definition of force as something which causes an inertial mass to change velocity. It used to make perfect sense in my head that gravity was the way that space/time, the stage as it were, interacted with the actors. The other quantum fields represented the way that the actors interacted with each other. I have no idea where the theater analogy comes from thats just how it appeared in my head. Though as time has gone on this has become less acceptable to me.

My first argument comes from very high energy physics above the GUT scale. Right now general relativity and quantum mechanics cannot explain this regime. It doesn't prove anything but it does show that we don't know how they truly relate to each other. While this does not disprove my stage analogy it does show that its not based on a massive piece of relevant information. My second concern is the nature of mass. It seems likely that in the next few years the origin of inertial mass will be uncovered in the form of interactions with the Higgs field or something similar. This is still hypothetical but electroweak theory has been so massively successful and indicates that a field responsible for inertial mass should be on the weak mass scale. So then we are left trying to explain gravitational mass and why it appears to be equal to inertial mass. Which is really the crux of this entire debate.

In short we cannot tell whether the gravitational field is quantized or not and I have not yet come across a reason to suggest one explanation over another. As we have descended into philosophy I would like to make a point about interpretation. This is like describing blue to a blind man. By this I mean we can describe very accurately what is going on in GR and QFT with some rather funky maths. In QFT we picture a particle as a series of vibrations in some field. Do I honestly believe that if I had a powerful microscope there is physically this thing wibbling, not really, no. However that is the form that the equations take so thats how we picture things mentally. Is an electron a particle or a wave, I don't honestly think it's either i'm sure what it really is I can't comprehend but as I need to comprehend it, I picture it in different situations as something thats appropriate sometimes thats a particle other times its a wave. We argue about whether gravity is the bending of space-time or the exchange of a virtual particle, in truth I imagine its neither but we'll continue to use whatever we deem appropriate for a given situation. 

Interesting point made there, I like it.

Quote from: Euclid on March 25, 2009, 11:28:28 PM

...

1) He wasn't asking you why space can't be a medium for light, he was asking why it couldn't be a medium for gravitational propagation.
2) Light is a completely different phenomenon from gravitational waves.  Gravitational waves propagate via the bending of spacetime itself.  Light is only a phenomenon occurring on spacetime.  It doesn't follow that they both require/do not require a particle for propagation.  Is the explanation of gravitational waves via spacetime bending somehow insufficient such that a particle is required?  That is what I am asking you.

Quote

Second, I think this post needed more review before you posted it.

What's that supposed to mean?

1) False. His question does not mention any particular data.
2)
 a) Do you have any evidence to support your claim that "Light is a completely different phenomenon from gravitational waves."?
 b) You attack a strawman. I never argued that the need of a particle to mediate the EM force meant that a particle was required for  the curving of spacetime at a distance.
 c) You, however, have argued without substantiation that GWs propagate without medium or particle. And that this characteristic, by unsupported extrapolation, must also apply to G.

a)  Bending spacetime vs. electromagnetic field.  Real force vs. fictitious force. Sounds completely different to me. 
c)  Gravitational waves are predicted by GR in its present form via the bending of spacetime only.  As far as I know, spacetime is the medium, as it is spacetime itself that is expanding and contracting.  My knowledge is incomplete, and I am wondering why some sort of messenger particle is required.  I am not claiming that a particle is not required.  I am wondering what are the theoretical justifications for a graviton.  And they are not the same justifications for the existence of a photon, since light and gravitation are completely different phenomena.

Well showing that gravity is quantized is impractical in any plausible experiment, a fact I guess most of the physicists here will have shown in their first year. Still though personally I think that gravitational waves would not do the idea of the graviton any harm. Though unless the hierarchy problem has an unexpected solution such as my favorite ADD theory then its likely to be one of the last questions to be answered.

the original post seems to be slightly confused. it says centrifugal force does not exist. it does, obviously. the car-tape animation is simply inertia, the tape is not attached tothe car and as such will attempt to follow its original path, which is outwards. which is what centrifugal force is, an obviously nonfictitious force.

centrifugal force is simply inertia of an object moving in a circle, trying to find a straight path, hence pushing itself outwards


if you say "then why arent people thrown off the earth because of earths spin", that is due to gravity another nonfictituos force which can be observed by monitoring every single galactic body; stars, planets, moons, blackholes, pulsars etc. the gravity is easily noticible. espeically here, on earth. the acceleration bullshit has nothing to back it up, yet gravity has countrless reports, expereriments and observations to back it up

which is what centrifugal force is, an obviously nonfictitious force.

No, it is a fictitious force. It is said that it does not exist because it arises purely through the observer's choice of a non-inertial frame of reference, just as gravity does.

Quote from: lupey on April 16, 2009, 02:35:08 AM

which is what centrifugal force is, an obviously nonfictitious force.

No, it is a fictitious force. It is said that it does not exist because it arises purely through the observer's choice of a non-inertial frame of reference, just as gravity does.

centrifugal force, regardless of the observers frame of reference, pushes things outwars, due to inertia. centrifugal force is simply inertia in a circle. what dont you get about that?