Galileo

[mich2]

In Galilean and Newtonian mechanics, the laws of physics are identical in any non-accelerating frame. That is an equivalence claim. Newton held an absolute space - ie one which was completely describable by Euclidean geometry and unaffected by external bodies. He also acknowledged that there was no way that we can determine the absolute rest frame or whether a body is static or moving with respect to that frame.He might have been a metaphysical absolutist, but he was a pragmatic relativist.

I agree; in a way; However, we know that such an absolute rest frame was sought by others.I believe Bradley’s aberration of light was once believed to be a proof for a stationary’ aether. There was also the Michelson and Morley experiment, of course. Maybe Newton was skeptical with detecting such an aether.

(This is with regard to the aberration of starlight). Is there anything else I can do to clarify this?

Thank you for your assistance. I did mention that I believe you clarified some things. For example, the aberration we observe is the movement of the stars in a circular motion due to the revolution of the earth around the sun. From this, I would see that if a galaxie would be moving simply in with a transverse velocity, no aberration would be detected,because the star does not “change it’s direction of movement” although I believe an aberration ought still to exist; I can’t see it otherwise. For example, if the earth was simply moving at 30 km / sec in a transverse direction, we would not detect any aberration at all. My problem with this view, however, is that we ought to observe an different aberration index for a rotating double star system, and I don’t think we do…so, I’m still stuck.

It is certainly the case that stellar aberration does NOT show anything about the motion of the source, and only about the motion of the observer with respect to the line joining the source and observer. That is why stellar aberration is uniformly the same across all sources (depending only on ecliptic latitude), regardless of their velocity with respect to other objects in the Universe.

I’m still unsure of the reason why this is the case.

Andre

 

[mich2]

Spacetime curvature does not impose roatation on bodies. All I can do is repeat what I wrote before:

Rotation is a parameter that is free to adopt whatever value (vector) the physical history of the body dictates, such as collisions, close encounters, initial rotation and other contingent causes. It has nothing to do with being in a spacetime curvature.

Alec
evolutionpages.com

I don’t disagree with what you wrote, Alec; I simply suspect that there is more to it.

Andre

 

[bobzills]

I am coming into this discussion late, and perhaps this has already been answered, but I would be interested to know how geocentrism can explain:

1. Stellar aberration.
2. Variations in the length of the day caused by earthquakes or atmospheric conditions? Why would the millions of galaxies change their rotation about a fixed earth, when there is an earthquake? Is there some physical principle or mathematical formula that would explain or model the slowing down of the rotation of the galaxies about the earth when there was an earthquake?
3. Retrograde motion of Mars. How does Mach’s principle support the motion of Mars and other planets in epicycles, but the earth is fixed? What are the mathematical formulas and physical principles which lead to the description of such orbits?

 

[buffalo]

I am coming into this discussion late, and perhaps this has already been answered, but I would be interested to know how geocentrism can explain:

1. Stellar aberration.
2. Variations in the length of the day caused by earthquakes or atmospheric conditions? Why would the millions of galaxies change their rotation about a fixed earth, when there is an earthquake? Is there some physical principle or mathematical formula that would explain or model the slowing down of the rotation of the galaxies about the earth when there was an earthquake?
3. Retrograde motion of Mars. How does Mach’s principle support the motion of Mars and other planets in epicycles, but the earth is fixed? What are the mathematical formulas and physical principles which lead to the description of such orbits?

You can check here:

Galileo Was Wrong:
The Church Was Right

 

[bobzills]

You can check here:

Galileo Was Wrong:
The Church Was Right

This book advocates the Tycho Brahe model which really doesn’t make any sense from a physics point of view since it is a hybrid geocentric – heliocentric model. Why do all the planets except the earth revolve about the sun? In the Tycho Brahe model, is it not true that Newton’s laws and Kepler’s laws are all nicely in place for all of the planets and the sun except for the earth, where they are suspended because of a literal interpretation of a phrase from the Bible?

 

[buffalo]

This book advocates the Tycho Brahe model which really doesn’t make any sense from a physics point of view since it is a hybrid geocentric – heliocentric model. Why do all the planets except the earth revolve about the sun? In the Tycho Brahe model, is it not true that Newton’s laws and Kepler’s laws are all nicely in place for all of the planets and the sun except for the earth, where they are suspended because of a literal interpretation of a phrase from the Bible?

Somewhere there was a forum that discussed all this after the book came out. Try searching on the book title, sungenis, forums. It has pretty much all been discussed.

 

[hecd2]

Somewhere there was a forum that discussed all this after the book came out. Try searching on the book title, sungenis, forums. It has pretty much all been discussed.

The first Galileo book by Sungenis (the one ostensibly about the science) is absolute garbage. It is both scientific and logical blancmange. It is filled with multiple elementary scientific errors. It has had the reception it deserves, being completely ignored by the scientific community. It is useless to advance it as a potential answer to objections to geocentrism.

Alec
evolutionpages.com/pink_unicorn.htm

 

[hecd2]

ok; However, I would personally view the farthest galaxies as being closer to some sort of centre. The image of the sphere used as an analagy of an expanding universe is fine; however, the surface of the sphere itself, in my opinion, would represent only one dimention of time, whereas, in order to fully represent our spacetime universe, it would seem that we ought to include the whole volume of the sphere, and not simply it’s surface.

Your interpretation is incorrect. The surface of the sphere is a two dimensional analogy of 3-D space. In the analogy we observe all objects on the surface, however far away they are and however long ago they emitted the photons that we observe. Objects that are a long way away are closer to us than they are at the moment of observation. No matter how far away they are, the photons come to us in a straight line, even through curved space. The same situation pertains in our real 3-D universe.

if the influence of matter is the cause of inertia, it is an effect neither quantified nor part of either Newtonian or Einsteinian mechanics.

I don’t know; if he meant the inertia of a body is determined in relation to all other bodies in the universe , I think that both the Newtonian (gravitational force) and especially the spacetime of GR (since Einstein was interested in Mach’s principle), can fit this description.

It has not been quantitatively fitted. Don’t forget that Einstein changed his mind about the Newton bucket experiment - when he found that solutions to the field equations could not explain the phenomenon of inertia, he accepted that the effects of rotation would be felt in an empty universe.

It seems that Mach was simply against the notion of an absolute stationnary space frame.

Mach was against all absolute measures. But it seems that rotation, even under GR, is meaningful, even in an empty universe.

I fully agree; this was indeed his understanding. If you don’t mind, I would like to share my thoughts to this particular point.
In my opinion, a single body in space could indeed rotate and feel the centrifugal forces eventhough no other mass would be present.

And that is the conclusion that Einstein eventually came to, even though this conclusion contradicts strict Machian ideas.

If I think of a single body of mass, let it be someone in a spaceship, who starts the engine and then releases a great deal of energy from the engine ( steps on the gas pedal), a non-inertial system would exist, being a force of acceleration being experienced within the frame of reference. The way I view a non-inertail frame is simply a situation where a part of the frame accelerates (changes velocity) and part of the frame resists the acceleration.

No this is not a good way to think of non-inertial frames - there is no such thing as part of a frame experiencing acceleration and another part resisting the acceleration. It’s simpler than that - any test particle at rest in a non-inertial frame experiences a force.

Therefore, in the case of a body in rotation, since the center of the body turns more slowly than the surface, it would resist the surface velocity, creating a centrifugal force.

I don’t think this is right. In the case of a rotating frame, forces are experienced by particles at rest in the frame because rotation entails changes of the vector of velocity - ie accelerations. It has nothing to do with the centre turning more slowly than the surface.

Secondly, Mach was not saying that the rotation of the earth is due to matter elsewhere - he was saying that the arrow of inertia and the effects of rotation with respect to an inertial frame depend on matter elsewhere.

While I agree, I think his answer to the question; what truly can be called the cause and effect, would be somewhat relative in nature…I maybe wrong in my assertion, here.

Yes, I think you wrong. It is clear that Mach was not claiming that the rotation of the earth is caused by nor causes the presence of matter elsewhere (any more the rotation of a top or the wheels of a car are caused by or are a cause of the motion of matter in the rest of the universe.)

I am sorry that in almost every paragraph of your post I say that you are wrong, but in this case, that is the way I see it.

Alec
evolutionpages.com

 

[hecd2]

continued…

hecd2:

No - the rotation of the earth is caused by its history, like the rotation of a top is caused by its history - it is not caused by spacetime curvature - in fact I can’t see how the rotation of any body can be caused by spacetime curvature.

I do agree that the history of the body in question has a great deal to do with this, as space alone does not exist. I’m not implying that a body can cause immediate inertia to a distant body, since gravity also has a finite velocity. However, I am implying that whatever caused the earth to start to rotate in the first place, let it the Milky Way’s rotating galactic system, or whatever, the direct cause remains gravity, that is, spacetime.

Or the direct impact of a body, or a tidal effect?

It is with this particular frame of argument that I ask, what are the causes and what are the effects? Is spacetime created by matter or does space time create matter? It is in this respect that I ask whether it is the earth that might be creating a spacetime vortex due to it’s rotation, or is it the vortex that makes the earth rotate? My personal opinion for now, would be that such is a relative question, which makes part of the equivalence principle.

This is not at all relative in the way you describe it. Have you any idea how tiny an effect the rotation of the earth has on spacetime in the vicinity of the earth? Frame dragging in the vicinity of the earth’s surface has a magnitude of about 80 milli-arc-seconds per year - ie the inertial frame is dragged round with respect to the stars by this absolutely minute angle every year while the earth rotates through over 131,000 degrees. In other words, the rotation of the earth is about 5 billion times faster than the dragging of spacetime in its vicinity. It is quite clear that the earth’s rotation results from its mechanical history and has nothing to do with any so-called space-time vortex.

it seems that even in such a point of view, the light from the galaxie close to the time of the big bang carries information of a universe having a much greater spacetime curvature than the one we experience at this moment ,which, to my knowledge, ought to carry a telescopic type of imaged information.

Well, the earliest light in the universe is the CMB, arising at z=~1000. What effect do you think that would have on light? I have no idea what you mean by “a telescopic type of imaged information” - what does that mean?

Alec
evolutionpages.com

 

[hecd2]

Thank you for your assistance. I did mention that I believe you clarified some things. For example, the aberration we observe is the movement of the stars in a circular motion due to the revolution of the earth around the sun.

No, this isn’t quite so. The aberration is a straight line for stars in the ecliptic plane - to and fro in a period of one year; an apparent circle for a star on the ecliptic pole with a period of one year; and an ellipse, increasing in eccentricity with decreasing ecliptic latitude also with a period of one year.

From this, I would see that if a galaxie would be moving simply in with a transverse velocity, no aberration would be detected,because the star does not “change it’s direction of movement” although I believe an aberration ought still to exist; I can’t see it otherwise.

I’m afraid that it doesn’t matter how you see it or don’t see it - stellar aberration carries no information about the transverse velocity of the star and is identical for all stars in the same location at the point of light emission, regardless of their velocities. Stars emit light in all directions, and only photons which travel in a straight line between the location of the star at the time of emission and the location of the observer at the time of observation can be detected, and this is independent of the transverse velocity of the star.

For example, if the earth was simply moving at 30 km / sec in a transverse direction, we would not detect any aberration at all.

That is correct, because although the aberration would be present, we can only detect changes in velocity such as the rotation of the earth around the sun.

My problem with this view, however, is that we ought to observe an different aberration index for a rotating double star system, and I don’t think we do…so, I’m still stuck.

Since the aberration carries no information about the transverse velocity of the source, we do not observe a different aberration for a binary or for any other stellar source. (We can, of course, detect the longitudinal component of velocity by red shift). You are still misunderstanding the nature of stellar aberration and I don’t know what else I can say to help you. Let me ask you a analogous question about someone shooting at you - what can you tell about the transverse velocity of the gunman by the bullets thudding into the armour just in front of you? Think about it. I’m sure that, like the relationship between the sun’s mass and its surface gravity, you can figure out the answer if you think about it.

Alec
evolutionpages.com

 

[mich2]

Your interpretation is incorrect. The surface of the sphere is a two dimensional analogy of 3-D space.

I believe that I understand this aspect; however, the surface, if shown to be static, represents only the distances between galaxies in real time. If we allow a dynamic surface (allow the sphere to expand), then we have a full image of the universal spacetime, however, here, it seems that we must allow the whole volume of the sphere, in order to represent the whole timeline of the universe, in which the big bang event would indeed represent some type of center

In the analogy we observe all objects on the surface, however far away they are and however long ago they emitted the photons that we observe.

But here, the way I see it, if we can indeed observe all objects,then, the upper model is invalid.
If we are able to observe every body on the sphere, we are then speaking only of the observable universe, which, in this case, the farthest object lying close to the bigbang event exists on the opposite side of the sphere, relative to the observer.

Objects that are a long way away are closer to us than they are at the moment of observation.

I don’t understand…don’t you mean they now exist to be farther away than the time the body exists during when we observe them?

No matter how far away they are, the photons come to us in a straight line, even through curved space. The same situation pertains in our real 3-D universe.

ok.

It has not been quantitatively fitted. Don’t forget that Einstein changed his mind about the Newton bucket experiment - when he found that solutions to the field equations could not explain the phenomenon of inertia, he accepted that the effects of rotation would be felt in an empty universe.

ok…I didn’t know this;

Mach was against all absolute measures. But it seems that rotation, even under GR, is meaningful, even in an empty universe.
And that is the conclusion that Einstein eventually came to, even though this conclusion contradicts strict Machian ideas.

ok.

No this is not a good way to think of non-inertial frames - there is no such thing as part of a frame experiencing acceleration and another part resisting the acceleration. It’s simpler than that - any test particle at rest in a non-inertial frame experiences a force.

ok; thanks; How about this… a single body, alone in the universe will produce a spacetime curvature, in which the mass will rest in the center.
When a force is apllied to the body(jet engines), the force will move the mass off-center and therefore, there will be a counter force applied by the spacetime which will try to return the mass back to the center?

I don’t think this is right. In the case of a rotating frame, forces are experienced by particles at rest in the frame because rotation entails changes of the vector of velocity - ie accelerations. It has nothing to do with the centre turning more slowly than the surface.

ok.

Yes, I think you wrong. It is clear that Mach was not claiming that the rotation of the earth is caused by nor causes the presence of matter elsewhere (any more the rotation of a top or the wheels of a car are caused by or are a cause of the motion of matter in the rest of the universe.)

ok.

I am sorry that in almost every paragraph of your post I say that you are wrong, but in this case, that is the way I see it.

Alec
evolutionpages.com

Don’t be sorry, Alec; I consider myself lucky in being able to speak to a scientist regarding these matters.

Andre

 

[mich2]

Or the direct impact of a body, or a tidal effect?

ok; however, if we observe the planets as revolving around the sun in the same direction, and rotating in the same direction (except for Unranus and Venus),it would seem that those two planets might have been hit, while the earth, as well as the rest of the planets seem to follow some type of physical law instead.

This is not at all relative in the way you describe it. Have you any idea how tiny an effect the rotation of the earth has on spacetime in the vicinity of the earth? Frame dragging in the vicinity of the earth’s surface has a magnitude of about 80 milli-arc-seconds per year - ie the inertial frame is dragged round with respect to the stars by this absolutely minute angle every year while the earth rotates through over 131,000 degrees. In other words, the rotation of the earth is about 5 billion times faster than the dragging of spacetime in its vicinity. It is quite clear that the earth’s rotation results from its mechanical history and has nothing to do with any so-called space-time vortex.

I’m not refering to observed vortex (if we do observe one).I was mearly speaking of the vortex we are accustom of seeing on GR models of spacecurvatures where marbels rotate around the curved spacetime surface. However; what if such a model was used identifying the spacetime as not mearly funnel shaped, but as spinning around the mass? The image of a whirlpool?

Well, the earliest light in the universe is the CMB, arising at z=~1000. What effect do you think that would have on light? I have no idea what you mean by “a telescopic type of imaged information” - what does that mean?

Well, I;m not actually sure as to what I meant. I thought that the light of the farthest galaxies are giving us an imaged information…a galaxie. The image of the galaxie, however, comes from a time when the spacetime universe curvature was much more pronounced than the curvature of spacetime that we observe around us today. I therefore thought that the image of the far galaxies would be different ( double image or whatever) than those near to our galaxie.

Andre

 

[mich2]

No, this isn’t quite so. The aberration is a straight line for stars in the ecliptic plane - to and fro in a period of one year; an apparent circle for a star on the ecliptic pole with a period of one year; and an ellipse, increasing in eccentricity with decreasing ecliptic latitude also with a period of one year.

ok; thanks.

I’m afraid that it doesn’t matter how you see it or don’t see it - stellar aberration carries no information about the transverse velocity of the star and is identical for all stars in the same location at the point of light emission, regardless of their velocities. Stars emit light in all directions, and only photons which travel in a straight line between the location of the star at the time of emission and the location of the observer at the time of observation can be detected, and this is independent of the transverse velocity of the star.

That is correct, because although the aberration would be present, we can only detect changes in velocity such as the rotation of the earth around the sun.

This was the reason why I believed most star didn’t show any aberration, eventhough the aberration would still be present.But with this line of reasoning, we ought to observe an aberration ondouble star system…and we don’t. So I know that you’re correct, I’m just not grasping why

Since the aberration carries no information about the transverse velocity of the source, we do not observe a different aberration for a binary or for any other stellar source. (We can, of course, detect the longitudinal component of velocity by red shift). You are still misunderstanding the nature of stellar aberration and I don’t know what else I can say to help you.

Thanks for trying, though. It may come to me eventually.

Let me ask you a analogous question about someone shooting at you - what can you tell about the transverse velocity of the gunman by the bullets thudding into the armour just in front of you? Think about it. I’m sure that, like the relationship between the sun’s mass and its surface gravity, you can figure out the answer if you think about it.

Alec
evolutionpages.com

My problem with the upper example is that before the bullets hit the target , they need to pass through a tube…the telescope. Now, in order for the bullet to pass through and hit the tartget, a perfect alignment is needed. If the gunman moves, I would need to consider the transverse velocity of the bullet as well, it seems.

Andre

 

[hecd2]

I believe that I understand this aspect; however, the surface, if shown to be static, represents only the distances between galaxies in real time. If we allow a dynamic surface (allow the sphere to expand), then we have a full image of the universal spacetime, however, here, it seems that we must allow the whole volume of the sphere, in order to represent the whole timeline of the universe, in which the big bang event would indeed represent some type of center

But in the analogy, the third dimension is meaningless to observers on the sphere - it doesn’t represent time, it doesn’t represent anything. It is as inaccesssible to 2-D people living on the surface of sphere, as a fourth spatial dimension is to us, living on a 3-solid (eg a hypersphere) in 4-D space.

But here, the way I see it, if we can indeed observe all objects,then, the upper model is invalid.
If we are able to observe every body on the sphere, we are then speaking only of the observable universe, which, in this case, the farthest object lying close to the bigbang event exists on the opposite side of the sphere, relative to the observer.

I wasn’t clear. What I meant was that whatever objects we can observe (and we might only be able to observe a tiny fraction of the total sphere if it is very big), we observe on the surface of the sphere, not in its volume - the extra dimension is inaccessible to us.

I don’t understand…don’t you mean they now exist to be farther away than the time the body exists during when we observe them?

I think what I meant was that objects that are currently a long way away are closer to us than they will be when we observe them.

ok; thanks; How about this… a single body, alone in the universe will produce a spacetime curvature, in which the mass will rest in the center.
When a force is apllied to the body(jet engines), the force will move the mass off-center and therefore, there will be a counter force applied by the spacetime which will try to return the mass back to the center?

I don’t think so. The cause of the spacetime curvature is the mass of the body. If the body moves, then the curvature follows it. In your scenario, the gravity of a massive body would attract other bodies to where it used to be, not where it is. We don’t observe that. In an empty universe, if we accelerate an object, then there is no force trying to “return the mass back to the center”

Alec
evolutionpages.com

 

[hecd2]

ok; however, if we observe the planets as revolving around the sun in the same direction, and rotating in the same direction (except for Unranus and Venus),it would seem that those two planets might have been hit, while the earth, as well as the rest of the planets seem to follow some type of physical law instead.

Well, planets revolving round the sun in the same direction are completely understandable since the sun and planets condensed out of the same pre-stellar gas and preserve its angular momentum.

I’m not refering to observed vortex (if we do observe one).I was mearly speaking of the vortex we are accustom of seeing on GR models of spacecurvatures where marbels rotate around the curved spacetime surface. However; what if such a model was used identifying the spacetime as not mearly funnel shaped, but as spinning around the mass? The image of a whirlpool?

The marbles spinning round the spacetime surface represent orbits, such as the earth around the sun. The surface itself is dragged near to rotating objects in the way that I described - it is a tiny effect compared with the actual rotation of the object causing it. Let’s summarise - in the absence of masses spacetime is flat. In the presence of a mass, spacetime is distorted (that gives rise to gravitational attraction) and in the vicinity of a rotating mass, spacetime is dragged so that the arrow of inertia acually rotates - but at a minute rate compared to the rate of the physical rotation of the mass causing it. This local dragging of inertia has been recently measured by tiny perturbations in the orbits of earth satellites.

Well, I;m not actually sure as to what I meant. I thought that the light of the farthest galaxies are giving us an imaged information…a galaxie. The image of the galaxie, however, comes from a time when the spacetime universe curvature was much more pronounced than the curvature of spacetime that we observe around us today. I therefore thought that the image of the far galaxies would be different ( double image or whatever) than those near to our galaxie.

No, we get double images when light from a distant object passes close by and either side of a very massive galaxy - that is gravitational lensing. The oldest galaxies are at z=20ish - ie the universe would have been about 20 times more dense. That would not cause any general imaging effects

Alec
evolutionpages.com

 

[hecd2]

This was the reason why I believed most star didn’t show any aberration, eventhough the aberration would still be present.But with this line of reasoning, we ought to observe an aberration ondouble star system…and we don’t. So I know that you’re correct, I’m just not grasping why

Because the aberration is not caused by any transverse velocity of the source.See below.

My problem with the upper example is that before the bullets hit the target , they need to pass through a tube…the telescope. Now, in order for the bullet to pass through and hit the tartget, a perfect alignment is needed. If the gunman moves, I would need to consider the transverse velocity of the bullet as well, it seems.

So, you need to point the tube so that bullets pass down its centre. If you are moving with a component at right angles to the line of the incoming bullets, you need to adjust the angle of the tube (that is stellar aberration).

The gunman can move however he likes, and that does not affect the trajectory of the bullet which is a straight line between the position of the gunman when he fired and you. Note that it is only the position of the gunman that matters and not his transverse velocity. You cannot tell anything about the transverse velocity of the gunman from the trajectory of the bullets. Think about it. If I asked you to determine the transverse velocity of the gunman, what parameter of the bullets would you measure?

Alec
evolutionpages.com

 

[mich2]

But in the analogy, the third dimension is meaningless to observers on the sphere - it doesn’t represent time, it doesn’t represent anything. It is as inaccesssible to 2-D people living on the surface of sphere, as a fourth spatial dimension is to us, living on a 3-solid (eg a hypersphere) in 4-D space.

I wasn’t clear. What I meant was that whatever objects we can observe (and we might only be able to observe a tiny fraction of the total sphere if it is very big), we observe on the surface of the sphere, not in its volume - the extra dimension is inaccessible to us.

My perception may not be very good, because I still don’t get it.

Let the surface on the sphere represent the universe in real time.
If the light from the moon takes a couple of seconds to arrive at the earth, then I cannot observe even the moon in real time, which would be a point on the surface of the sphere. So, where or what (on the sphere)are we looking at, when we see the galaxies far away, if such observation cannot be located on the surface sphere, since the surface sphere represents the universe in real time?. Certainly what we observe is the light which has come from the galaxies and has arrived at our observation point, represented as mearly a point on the sphere, but that wouldn’t explain much as to what we observe.
However,I totally agree with you that I should not speak of the volume of the sphere since this would represent a higher space dimention, so I do agree that we need to continue to speak of a surface, but which surface? What about an option given in one of the last posts? What about a surface which represents simply the observable universe? Would this not mean that the farthest galaxies close to the big bang would be located on the opposite side of the sphere relative to us?

I don’t think so. The cause of the spacetime curvature is the mass of the body. If the body moves, then the curvature follows it. In your scenario, the gravity of a massive body would attract other bodies to where it used to be, not where it is. We don’t observe that. In an empty universe, if we accelerate an object, then there is no force trying to “return the mass back to the center”

I agree that my thought is too simplistic. I like to try to imagine what a force or what gravity might “look like”. However, I might not have been specific enough, so if you don;t mind, I’ll continue my thought on this. When I was saying that the force is moving the mass off center, this was relative to the spacetime frame itself, this being the spacetime surounding the mass. We know that when a force is exerted upon a mass, an acceleration will be produced… Therefore, the acceleration would be that of the whole spacetime frame trying to catch up with the mass. The force trying to return the mass back to it’s center would be what I would see as Newton’s 3rd law of motion.

Andre .

 

[mich2]

Well, planets revolving round the sun in the same direction are completely understandable since the sun and planets condensed out of the same pre-stellar gas and preserve its angular momentum.

Now, this angular momentum has everything to do with inertia of mass and gravity, right? It’s somewhat the direction I’m focussing on. It sort of agrees, in my opinion, with Mach’s principle, it would seem.

The marbles spinning round the spacetime surface represent orbits, such as the earth around the sun. The surface itself is dragged near to rotating objects in the way that I described - it is a tiny effect compared with the actual rotation of the object causing it. Let’s summarise - in the absence of masses spacetime is flat. In the presence of a mass, spacetime is distorted (that gives rise to gravitational attraction) and in the vicinity of a rotating mass, spacetime is dragged so that the arrow of inertia acually rotates - but at a minute rate compared to the rate of the physical rotation of the mass causing it. This local dragging of inertia has been recently measured by tiny perturbations in the orbits of earth satellites.

ok; but it’s not quite what I was getting at, though.
What if the spacetime curvature surrounding the earth, the funnel shape we see in science museum, is actually spinning around the earth (assuming it’s something still not yet detected). The
farther away from the body (earth), the less curvature there is, the less rotational velocity it would experience, just like in a whirlpool. Would this not bring into effect a centrifugal force which it’s direction would be towards the earth, being what we experience as gravity? A mass far away from such a body would not experience a great deal of centrifugal force, so, will simply revolve around the massive body instead.

No, we get double images when light from a distant object passes close by and either side of a very massive galaxy - that is gravitational lensing. The oldest galaxies are at z=20ish - ie the universe would have been about 20 times more dense. That would not cause any general imaging effects

ok.

Andre

 

[mich2]

So, you need to point the tube so that bullets pass down its centre. If you are moving with a component at right angles to the line of the incoming bullets, you need to adjust the angle of the tube (that is stellar aberration).

ok

The gunman can move however he likes, and that does not affect the trajectory of the bullet which is a straight line between the position of the gunman when he fired and you.

I would understand this in the image of a wave traveling in a medium. However, as I see it, the bullet does not make a straight line between the position where the gunman is when he shoots, and me, but would be following the gunman instead. The gunman, who is travelling, would observe the bullet as travelling in a straight line.

Note that it is only the position of the gunman that matters and not his transverse velocity. You cannot tell anything about the transverse velocity of the gunman from the trajectory of the bullets. Think about it. If I asked you to determine the transverse velocity of the gunman, what parameter of the bullets would you measure?

I am certainly not saying that you are wrong, Alec, I just still can’t see it.

Andre

 

[hecd2]

My perception may not be very good, because I still don’t get it.

Let the surface on the sphere represent the universe in real time.
If the light from the moon takes a couple of seconds to arrive at the earth, then I cannot observe even the moon in real time, which would be a point on the surface of the sphere.

I think that’s correct.

So, where or what (on the sphere)are we looking at, when we see the galaxies far away, if such observation cannot be located on the surface sphere, since the surface sphere represents the universe in real time?.

In the analogy, light always propagates through the surface of the sphere, since the third dimension is inaccessible. When it arrives, it appears to arrive from a point on the surface of the sphere closer to us than the object which emitted it actually is the time of observation.

However,I totally agree with you that I should not speak of the volume of the sphere since this would represent a higher space dimention, so I do agree that we need to continue to speak of a surface, but which surface? What about an option given in one of the last posts? What about a surface which represents simply the observable universe?

The problem is that if the universe is bigger than the observable universe then by representing only the observable universe with a sphere we are arbitrarily creating a model where the most distant observable galaxies are on the other side of the sphere. In fact, for a universe much larger than the observable universe, then the galaxies on the edge of observation (at the time they emitted the light) would form a circle centred on us about 13 billion light years away. (In the real 3-D universe we see the furthest observable galaxies on a sphere centred on us with a radius of about 13 billion light years.

Would this not mean that the farthest galaxies close to the big bang would be located on the opposite side of the sphere relative to us?

No galaxies are closer to the Big Bang than any others. The Big Bang pervades the whole universe and is present everywhere.

I like to try to imagine what a force or what gravity might “look like”. However, I might not have been specific enough, so if you don;t mind, I’ll continue my thought on this. When I was saying that the force is moving the mass off center, this was relative to the spacetime frame itself, this being the spacetime surounding the mass. We know that when a force is exerted upon a mass, an acceleration will be produced… Therefore, the acceleration would be that of the whole spacetime frame trying to catch up with the mass. The force trying to return the mass back to it’s center would be what I would see as Newton’s 3rd law of motion.

The space time is curved as a consequence of the presence of the mass. If the mass is moved then the curvature moves with it. In order to move the mass we need to exert a force, sure, but having exerted that force, the acceleration of the mass returns to zero, but its velocity is different from before and will remain at the new value until another force is exerted.

Are you trying to explain inertia by suggesting that space time has some sort of viscosity? I don’t think anyone knows for sure at the moment, but one theoretical possibility is the influence of the Higgs field, which is a bit like adding viscosity to spacetime (although I don’t think that the curvature of spacetime in the Higgs model lags the position of the mass as you suggested), so I think your idea is quite insightful.

Alec
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