Can we measure absolute motion of Earth and Sun?

[zasvitim]

TL;DR Summary

What if we can measure absolute motion of Earth and Sun?

Slow particles (solar wind) should come from a direction that is different than the direction photons come from: it takes slow particles more time to reach the Earth, therefore slow particles should be emitted earlier.

Some calculations:
- Sun diameter is about 1400000 km
- solar wind speed is 300-1000 km per second - at least 300 times slower than light.
- it takes light about 500 seconds to reach Earth. So it should take about 500*300 = 150000 seconds.

If we assume that the absolute speed of the Sun is 100 km per second, the distance it passes within 150000 seconds is at least: 150000 * 100 = 15000000 km - more than 10 Sun diameters.
For particles with speed 300 km per second it's 30 sun diameters

Should be measurable..

 

[zasvitim]

Animation:

 

[PeroK]

TL;DR Summary: What if we can measure absolute motion of Earth and Sun?

There is no concept of absolute space and time against which an absolute velocity (or absolute motion) could be calculated.

 

[Ibix]

TL;DR Summary: What if we can measure absolute motion of Earth and Sun?

Should be measurable.

And the fact that we don't see any such difference in angle tells you what about the existence of an absolute frame?

 

[zasvitim]

There is no concept of absolute space and time against which an absolute velocity (or absolute motion) could be calculated.

In classical physics? But can't we just measure where it comes from?

 

[zasvitim]

And the fact that we don't see any such difference in angle tells you what about the existence of an absolute frame?

Are there any papers / studies?

 

[Ibix]

In classical physics?

In all physics since Galileo.

 

[Ibix]

Are there any papers / studies?

Of what? The solar wind? It's constantly monitored - have a look at the Space Weather thread in the Astronomy and Astrophysics forum where there are regular links to the NOAA forecasts.

 

[zasvitim]

In all physics since Galileo.

But it works for light only, no? Slow motion's different? For example sound comes not from where jet is at this exact moment but from where it was?
Otherwise sonic booms would not exist?

 

[zasvitim]

If you throw a stone and make a step, stone will not come from the place you are now, it will come from where you were when you threw it..

 

[PeroK]

If you throw a stone and make a step, stone will not come from the place you are now, it will come from where you were when you threw it..

That is irrelevant.

Are there any papers / studies?

The introduction to Einstein's famous paper of 1905 deals with the issue of the lack of an absolute rest frame for electromagnetic phenomena. That was another way of saying there is no concept of absolute motion.

The laws of physics have no cencept of asbolute motion. For example, Newton's second law is
$$F = ma$$If absolute motion were relevant, that equation would have to include a term for the absolute velocity of the particle. In Newtonian physics, it's acceleration that is absolute. You can measure forces and acceleration independent of your inertial reference frame. But, there is no experiment that would determine your absolute velocity. Einstein, in 1905, took this idea a step further and applied it to electromanetic phenomena as well.

 

[zasvitim]

That is irrelevant.


The introduction to Einstein's famous paper of 1905 deals with the issue of the lack of an absolute rest frame for electromagnetic phenomena. That was another way of saying there is no concept of absolute motion.

The laws of physics have no cencept of asbolute motion. For example, Newton's second law is
$$F = ma$$If absolute motion were relevant, that equation would have to include a term for the absolute velocity of the particle. In Newtonian physics, it's acceleration that is absolute. You can measure forces and acceleration independent of your inertial reference frame. But, there is no experiment that would determine your absolute velocity. Einstin, in 1905, took this idea a step further and applied it the electromanetic phenomena as well.

Electromagnetic force comes from current position, but light comes from retarded position

 

[PeroK]

Electromagnetic force comes from current position, but light comes from retarded position

That's not correct. The EM field at a point depends on the retarded position. Maxwell's equations and all the laws of physics are explicitly independent of any absolute velocity.

There is no concept of absolute velocity in modern physics.

 

[zasvitim]

We are attracted to the point where the moon is "now" if it moves straight, not to the point where moon light comes from

 

[zasvitim]

I'm not speaking about absolute velocity now, I'm speaking about absolute direction in space. Direction is absolute, right?

 

[PeroK]

I'm not speaking about absolute velocity now, I'm speaking about absolute direction in space. Direction is absolute, right?

You'd need to define what you mean by "absolute direction". There's no experimental evidence that the universe has an up direction and a down direction, for example.

 

[berkeman]

Thread closed for Moderation.

 

[berkeman]

Thread is reopened provisionally.

 

[Ibix]

There is no such thing as an absolute direction or velocity, and direction measurements do not work the way the OP appears to think. I'll draw a diagram to explain later - on my phone at the moment and I don't have appropriate tools here.

 

[DaveC426913]

We are attracted to the point where the moon is "now" if it moves straight,

No.

For all intents and purposes, "now" is not instant; it moves at the speed of light.

 

[Ibix]

Here's a diagram that shows what's going on. It's effectively the same as the animation in #2, but with two important additions.

The first addition is that there are two frames of reference shown here. At the bottom, we see the frame where the Earth (blue circle) and Sun (yellow circle) are at rest, and above it we see a frame where they are moving up the page. The second addition is an angle-measuring device on the Earth - in this case it's an absurdly long telescope pointing at the Sun - that's the narrow black tube extending to the right of the Earth.

At the start of the animation the Sun emits a red particle which flies on a trajectory intercepting Earth at the end of the animation and leaving a red trail. Half way through the animation a faster green particle is emitted, also leaving a trail, and arrives at the Earth at the same time as the red one. In the bottom frame (where Earth and Sun are stationary) it's obvious that the Earth sees the particles coming straight down.

Where the OP has gone wrong is in the analysis of the other frame where the Earth and Sun are moving. Yes, the particles have lateral motion in this frame - but so does the angle detector. This is the key point that you missed, OP. It has exactly the correct motion to catch both particles, so it detects both particle as incoming straight from the Sun - as it must, because that's what happened in the rest frame.

The OP's analysis failed to take into account what the lateral motion does to the function of the angle detector. Angle detectors at rest in the moving frame would see a different impact angle for the two particles, but not angle detectors at rest on the Earth. So they couldn't detect absolute motion even if there were any such thing to detect.

 

[zasvitim]

Here's a diagram that shows what's going on. It's effectively the same as the animation in #2, but with two important additions.
View attachment 355868
The first addition is that there are two frames of reference shown here. At the bottom, we see the frame where the Earth (blue circle) and Sun (yellow circle) are at rest, and above it we see a frame where they are moving up the page. The second addition is an angle-measuring device on the Earth - in this case it's an absurdly long telescope pointing at the Sun - that's the narrow black tube extending to the right of the Earth.

At the start of the animation the Sun emits a red particle which flies on a trajectory intercepting Earth at the end of the animation and leaving a red trail. Half way through the animation a faster green particle is emitted, also leaving a trail, and arrives at the Earth at the same time as the red one. In the bottom frame (where Earth and Sun are stationary) it's obvious that the Earth sees the particles coming straight down.

Where the OP has gone wrong is in the analysis of the other frame where the Earth and Sun are moving. Yes, the particles have lateral motion in this frame - but so does the angle detector. This is the key point that you missed, OP. It has exactly the correct motion to catch both particles, so it detects both particle as incoming straight from the Sun - as it must, because that's what happened in the rest frame.

The OP's analysis failed to take into account what the lateral motion does to the function of the angle detector. Angle detectors at rest in the moving frame would see a different impact angle for the two particles, but not angle detectors at rest on the Earth. So they couldn't detect absolute motion even if there were any such thing to detect.

There still should be a difference on where particle can get. That should be measurable. I mean particle cannot get to a "shadow" area. Or to "opposite side" of Earth.
"Shadow" areas are different for red and green particles.

 

[zasvitim]

By the way. Very cool animation.
Thanks.

 

[jbriggs444]

There still should be a difference on where particle can get. That should be measurable. I mean particle cannot get to a "shadow" area. Or to "opposite side" of Earth.
"Shadow" areas are different for red and green particles.

The shadow areas are the same for red and green particles. This is clearly seen in the rest frame shown on the bottom. It will remain true in the moving frame.

It is tempting to think of the target just sitting there in its final location with the green particle sneaking up from underneath. But the target is moving upward. It can block a shot prior to the time when the target reaches its final position. You can't sneak a shot underneath because the target was right there already, blocking the shot with its right hand side.

 

[zasvitim]

Are

The shadow areas are the same for red and green particles. This is clearly seen in the rest frame shown on the bottom. It will remain true in the moving frame.

It is tempting to think of the target just sitting there in its final location with the green particle sneaking up from underneath. But the target is moving upward. It can block a shot prior to the time when the target reaches its final position. You can't sneak a shot underneath because the target was right there already, blocking the shot with its right hand side.

Are you saying that the "southern hemisphere" of the planet is as reachable as the "northern hemisphere" for red particles? Because it seems like red particles have more possibilities in southern hemisphere.

 

[zasvitim]

I mean.. Reachable areas are definitely different.. And that would show the direction of absolute motion..

 

[Dale]

Electromagnetic force comes from current position, but light comes from retarded position

This is not true. The electromagnetic force also depends only on the retarded position of any source charges. See Jefimenko’s equations the fields are exclusively from the retarded time.

However, the direction of the field is not the same as the direction from the point to the source charge at the retarded time. That direction is the direction that the source charge would be if it continued to move inertially after the retarded time. However, since the charge may move non-inertially, it is clear that this is not the position that it is now, but rather an extrapolation from the retarded time and retarded velocity.

 

[Ibix]

I mean.. Reachable areas are definitely different.. And that would show the direction of absolute motion..
View attachment 355879

You forgot the motion of the planet again. Add my telescope to the diagram in the post I quoted and your reasoning will show that no particles can enter the telescope because it's all in the "shadow" of the lower edge - yet the animation shows that they can enter. What has happened is that you drew the Earth where it is at the end of the particles' motion, and assumed that this is the only time and place where it blocks the particle trajectories. You treated it as transparent at all other times.

@jbriggs444 has already noted the simplest way to see that the shadow area is the same - do the analysis in the test frame. Then you note that the moving frame animation would be identical whether the Earth and Sun are moving, or the "camera" is moving in the opposite direction. Obviously the camera can make no difference to the result, and hence neither can the Earth and Sun moving. In fact, there is literally no difference between the two cases, an observation known as the principle of relativity. No experiment has ever detected a violation of this principle, and there have been some very sensitive efforts.

 

[A.T.]

I mean.. Reachable areas are definitely different.. And that would show the direction of absolute motion..
View attachment 355879

What is your diagram supposed to show? You have to consider multiple timepoints from two frames, like Ibix' animation does. Can you modify the animation to add the two points you are worried about? Free Software like GIMP should be able to edit the GIF file.

 

[Ibix]

Free Software like GIMP should be able to edit the GIF file.

It created it, so definitely!

 

[zasvitim]

You forgot the motion of the planet again. Add my telescope to the diagram in the post I quoted and your reasoning will show that no particles can enter the telescope because it's all in the "shadow" of the lower edge - yet the animation shows that they can enter. What has happened is that you drew the Earth where it is at the end of the particles' motion, and assumed that this is the only time and place where it blocks the particle trajectories. You treated it as transparent at all other times.

@jbriggs444 has already noted the simplest way to see that the shadow area is the same - do the analysis in the test frame. Then you note that the moving frame animation would be identical whether the Earth and Sun are moving, or the "camera" is moving in the opposite direction. Obviously the camera can make no difference to the result, and hence neither can the Earth and Sun moving. In fact, there is literally no difference between the two cases, an observation known as the principle of relativity. No experiment has ever detected a violation of this principle, and there have been some very sensitive efforts.

In some situations we will still get green particles yet don't get red particles because they bump into planet.
On the other side we should get red particles when sun is not visible already.

 

[zasvitim]

What is your diagram supposed to show? You have to consider multiple timepoints from two frames, like Ibix' animation does. Can you modify the animation to add the two points you are worried about? Free Software like GIMP should be able to edit the GIF file.

Some of timepoints will be within the planet.

 

[Ibix]

In some situations we will still get green particles yet don't get red particles because they bump into planet.

No we won't. You still aren't factoring in the motion of the Earth in this frame.

Again, by your reasoning, there cannot possibly be particles arriving at the left of the telescope - yet I've demonstrated how it works. The maths to prove it doesn't need anything more complex than vectors.

 

[PeroK]

View attachment 355885
In some situations we will still get green particles yet don't get red particles because they bump into planet.
On the other side we should get red particles when sun is not visible already.

You seem to be trying to prove that relative motion between the Sun and Earth is detectable. This has nothing to do with absolute motion.

 

[Ibix]

You seem to be trying to prove that relative motion between the Sun and Earth is detectable.

I don't think that's what he's trying to do, but agree that it is one interpretation of what he is doing