Are laws of nature really the same in all reference frames?

[Dale]

Perhaps it would help to talk a little about the curved geometry of this situation.

If we consider a spherical coordinate system centered on the sun then we can fix r to be the Earth orbital radius and we can fix the azimuthal angle to be in the orbital plane. That leaves only the orbital angle and time. So we have reduced the problem from 4 dimensions down to 2 dimensions and we can consider curved 2D surfaces embedded in a non-physical flat 3D embedding space which would accurately represent the geometry of the situation.

So, our space is essentially a cylinder, and if there were no spacetime curvature then the cylinder would be flat, meaning that you could cut it and lay it out on a table smoothly without any bumps. However, there is spacetime curvature, specifically, there is a little "dent" on the cylinder which goes around the cylinder in a helical pattern.

Now, suppose we draw a vertical line along the cylinder and we measure the length of the path around the cylinder down in the bottom of the helical dent and the length of the path up on the top edge of the helical dent from one intersection with the line to the next.

We will find that those lengths are slightly different. This is not because our measuring device is different from the top to the bottom of the dent, nor that the laws of physics are different, but simply because we are measuring the length of a different path. Due to the curvature of the space the lengths are different even though in the original 4D space the paths have the same radius.

This is why understanding the concept of curved spacetime is essential to understanding gravity and how it can be represented in a self-consistent, non-contradictory manner. It becomes very difficult to describe verbally, and that is why the math is important.

 

[Bjarne]

Let’s now (again) say that the time dilation is 50% at the ISS.
Again the ISS and the Earth is in the same orbit. Only gravity is different.

The mission is now a gravity experiment. Acceleration due to gravity (ADG) must be measured on board. On board is a ruler completely identical to one on Earth.

A stone is dropped from 1 meters altitude and reach the bottom.
From Earth we can observe the same event, - we will now say that ADG was exactly as we beforehand have calculated, it was 1 m/s. – But on board they do not agree, because it took the stone 2 second to reach the bottom.

So is the gravity constant “G” not the same.
Is it something wrong with the ruler, I mean is a 1 meter ruler no longer 1 meter ?
Is something wrong with the universal definition of one second?
And finally, how can we be sure what the problem is?

 

[Dale]

Before we change topics, do you understand and agree with the above? I.e. do you understand and agree that simply measuring a different time for one orbit does not imply any of the universe-is-changing or laws-of-physics-are-changing conclusions? Do you understand the curved geometry presented?

 

[Bjarne]

Before we change topics, do you understand and agree with the above? I.e. do you understand and agree that simply measuring a different time for one orbit does not imply any of the universe-is-changing or laws-of-physics-are-changing conclusions? Do you understand the curved geometry presented?

Before we change topics, do you understand and agree with the above? I.e. do you understand and agree that simply measuring a different time for one orbit does not imply any of the universe-is-changing or laws-of-physics-are-changing conclusions? Do you understand the curved geometry presented?

I don’t understand how comparable space-time distances both can be the same and not the same at the same time.
As I understand it you say that the orbit path would be comparable different for the ISS compared to the Earth, - (even though the Earth would follow the exact same orbit).
This must mean that you also must agree that the radius to the Sun is comparable different too.
If there is a long train beside the "radius path" or "orbit-path" - this too must off course be comparable different, and hence also the rest of the Universe.
I mean before complicating it all, try to answer the very simple questions asked in post 122. Try to keep it so simple as possible, and let’s then start from there.

Let me show what I mean...

Question;
So is the gravity constant “G” not the same?
Supposed answer;
I guess it must be Yes.

Question;
Is it something wrong with the ruler, I mean is a 1 meter ruler no longer 1 meter?
Supposed answer….
I don’t know how you would answer.
But it is pretty logical that when the calculation-result of Acceleration Due to Gravity (ADG) at the ISS must be correct both seen from the Earth’s perspective and seen from the ISS perspective, - then the ruler on board must be 1 meter seen from the Earth perspective and 2 meter seen from the IIS perspective, so that the result of ADG in both cases is the same = 1m/s.

Take a look at the equation
MG/r^2 – We both agree that M and G is the same values both places, so the only factor we can adjust is now “r” ( the ruler) as I just did. – But this could be wrong, because we can also just say that the definition of one second is not the same. We do ONLY have these 2 option – so long GM is nailed.

When the laws of nature (e.g the equation MG/r^2) is universal, - for me it seems that (at least) one of these factors must be flexible.

You said (above) distances is not comparable the same, - so what do you mean?.
I have no idea how you can limit that to only be valid for the “path”
A falling stone follows its own path
A light beam also, and these are also affected, so how can you say comparable differences are limited to a certain path?

An third observer (let say on the Sun) would not see any difference to the paths, he would see both objects orbiting the same orbit/path.
So it makes no sense to say that the “path” is the key to any truth understanding.

At least try to answer this question; - What would be the comparable difference between the ruler on board the ISS and the one still on the Earth?

Question;
Is something wrong with the universal definition of one second?
Supposed answer;
I understand it is not, but I am not convinced.
How can we know which factor(s) is/are comparable different.
Yes a clock would be ticking different, but is it the definition of 1 second really universal ?

Shortly Spoken
I am not convinced about anything so long it seems to be so complicated, - in a simple way - to explain what must be comparable space-time differences .

 

[Agerhell]

I don’t understand how comparable space-time distances both can be the same and not the same at the same time.
As I understand it you say that the orbit path would be comparable different for the ISS compared to the Earth, - (even though the Earth would follow the exact same orbit).
This must mean that you also must agree that the radius to the Sun is comparable different too.
If there is a long train beside the "radius path" or "orbit-path" - this too must off course be comparable different, and hence also the rest of the Universe.
I mean before complicating it all, try to answer the very simple questions asked in post 122. Try to keep it so simple as possible, and let’s then start from there.

Let me show what I mean...

Question;
So is the gravity constant “G” not the same?
Supposed answer;
I guess it must be Yes.

Question;
Is it something wrong with the ruler, I mean is a 1 meter ruler no longer 1 meter?
Supposed answer….
I don’t know how you would answer.
But it is pretty logical that when the calculation-result of Acceleration Due to Gravity (ADG) at the ISS must be correct both seen from the Earth’s perspective and seen from the ISS perspective, - then the ruler on board must be 1 meter seen from the Earth perspective and 2 meter seen from the IIS perspective, so that the result of ADG in both cases is the same = 1m/s.

Take a look at the equation
MG/r^2 – We both agree that M and G is the same values both places, so the only factor we can adjust is now “r” ( the ruler) as I just did. – But this could be wrong, because we can also just say that the definition of one second is not the same. We do ONLY have these 2 option – so long GM is nailed.

When the laws of nature (e.g the equation MG/r^2) is universal, - for me it seems that (at least) one of these factors must be flexible.

You said (above) distances is not comparable the same, - so what do you mean?.
I have no idea how you can limit that to only be valid for the “path”
A falling stone follows its own path
A light beam also, and these are also affected, so how can you say comparable differences are limited to a certain path?

An third observer (let say on the Sun) would not see any difference to the paths, he would see both objects orbiting the same orbit/path.
So it makes no sense to say that the “path” is the key to any truth understanding.

At least try to answer this question; - What would be the comparable difference between the ruler on board the ISS and the one still on the Earth?

Question;
Is something wrong with the universal definition of one second?
Supposed answer;
I understand it is not, but I am not convinced.
How can we know which factor(s) is/are comparable different.
Yes a clock would be ticking different, but is it the definition of 1 second really universal ?

Shortly Spoken
I am not convinced about anything so long it seems to be so complicated, - in a simple way - to explain what must be comparable space-time differences .

I really do not get where you want to go with this discussion. Basically in a gravitational field of a planet or some other objects there are two effects:

1. Light slows down with a certain factor, sometimes named as "the Shapiro effect".
2. Time as measured with a local clock slows down with exactly the same factor, often called "gravitational time dilation".

This means that the locally measured velocity of light as "Distance traveled per time unit" will always be the same and equal to "c".

The fact that light and time slows down in a gravitational field has no "magical effects" as you seem to believe...

Assuming the guys on the Earth, Mercury, the ISS or whatever example you have made are decent physicisists they can do the math. These effects basically complicates things, especially for an instituion such as Nasa that has spacecraft s moving around that they are trying to communicate with using frequencies that may appear different and trying to get the spacecraft s to start their engines at exactly the right time although there are several factors that have influence on the clock of the spacecraft and relativity is also a factor when trying to decide how long time it will take a signal to get from the Earth to the space-craft...

So there is no magic, only the fact that light and time slows down in a gravitational field that complicates the computations. Of course for Nasa you also have gravitational redshift to put up with which might have to be described as a third effect...

 

[Dale]

I don’t understand how comparable space-time distances both can be the same and not the same at the same time..

Of course, they cannot be both the same and not the same, that is nonsense and nobody is claiming that except you. They are simply not the same.

As I understand it you say that the orbit path would be comparable different for the ISS compared to the Earth, - (even though the Earth would follow the exact same orbit).

Yes, they are two different paths with different lengths.

This must mean that you also must agree that the radius to the Sun is comparable different too.

If there is a long train beside the "radius path" or "orbit-path" - this too must off course be comparable different, and hence also the rest of the Universe

No, the radius and the azimuthal angle coordinates are the same for both paths, as discussed above in post 121. Because the geometry is curved, the fact that the lengths of the two paths are different does not imply that the radius of the two paths are different.

We have a situation with curved geometry and you are making conclusions based on reasoning from flat geometry. Such conclusions will generally be wrong.

One other subtelty that you may not be aware of which may be important: there is a difference between a radial coordinate and the length of some spacelike path along the radial direction. I have been referring to the former, which is what I have assumed you meant by "radius".

 

[Bjarne]

Ok
I understand much better now, thank’s...
But still I wonder that when calculation based on GM/r^2 would show a stone will fall let say 1m/s^2 a certain place (due to gravity) different space-time observer would say that they have seen the stone was falling ½ , - or - 2 m/s^2, - (because time ticks different).
So who is all right, and wrong, - and why?
GM is the same, - "r" should also be, so how is it possible that the results are different?
Yes, because of time is different, - but do that not mean that when we compare distances these cannot be the same?
Or that the GM/r^2 not is universal.
This is really what mostly confuses me.

 

[A.T.]

1. Light slows down with a certain factor, sometimes named as "the Shapiro effect".
2. Time as measured with a local clock slows down with exactly the same factor, often called "gravitational time dilation".
...
Of course for Nasa you also have gravitational redshift to put up with which might have to be described as a third effect...

Is the gravitational redshift are third effect, or just a manifestation of 2?

 

[Dale]

Or that the GM/r^2 not is universal.

This is essentially the correct one. Newtons law of gravitation is not, in fact, a law of nature. The law of nature (as far as we can tell) is the Einstein Field Equations. Newtons law is a reasonable approximation for certain situations.

The laws of nature are the same for the ISS and on the surface of the Earth, but GM/r^2 is not one.

 

[Bjarne]

This is essentially the correct one. Newtons law of gravitation is not, in fact, a law of nature. The law of nature (as far as we can tell) is the Einstein Field Equations. Newtons law is a reasonable approximation for certain situations.

The laws of nature are the same for the ISS and on the surface of the Earth, but GM/r^2 is not one.

Each time the radius of a circle doubles, the area quadruples.
Since, in this case, the circles share a common centre, the space the larger circle occupies, that the smaller circle does not, accounts for 75% of the larger circle’s area.
At the same time the force of acceleration due to gravity (ADG) always decreases by 75%.
Is this a coincidence, or rather expresses a relation between matter, space and gravity that we haven’t understood?

So, - when the acceleration due to gravity decreases by 75 %, the distance square increment will increase inversely proportional by 75 %.
As we can see there is equal proportionality between space (square) increase, and gravity decrease and hence the proportional 1:1
Hence the equation GM/r^2 in fact seems to reflect a law of nature, also even though we can’t say we have understood why this seems to be so.

I am therefore not convienced that we in this case can conclude that : "The Newtons law (only) is a reasonable approximation for certain situations".
Rather it seems that the equation GM/r^2 is universal, and only can be understood so, - so long the proportional’s 1:1 is respected.

This mean that result of the equation only is valid in the particular space-time where the calculation apply.

Let us now say that ADG (acceleration due to gravity) must be calculated on a white dwarf.
Based on the known mass of the star all observers that would calculate the expected ADG of the star (at the surface), would (off course) come to the same result, - let’s say 1000m/s^2.

Let's say time is ticking 50% slower at the surface of the star compared to Earth.
How far would a stone accelerate the first 1 second?
Will a stone now fall 1000 meter the first second or for example 2000 meter, due to the slower time rate at the star? - or how far?

The answer must be; - because the definition of the second and the meter both are universal and of course also MG too (in the equation GM/r^2), - we are dealing with a mathematical equation with only 1 variant, - and this is time.

Purely mathematical we are then forced to conclude that when a Earth based observer is watching the stone that falls to the ground on the star, he must observe that the stone falls 1000 meter the first second, - but because time is ticking comparable slower locally on the star, locally observed it must fall 2000 meter the first second. (As you can see this puts the Earth in some kind of relativistic center).

Both observer are observing the same event in the same period of time (although time ticks different), - and the result is obvious different.
Off course this is a contradiction, both results cannot be true. The equation only allows one result and this is 1000 meter the first second.

Hence it is off course easy to conclude that the Newtonian equation only is an approximation.
But remember there is equal proportionality between space (square) increase and gravity decrease and hence the proportional 1:1 , - shown above. This proportionality doesn’t sounds like an insignificant coincidence.
The fact that the cause of this not is understood, and hence also not whether this is a reflection of a law of nature, or not, - should that not mean that we must be more carefully to violate what could be a law of nature?

Does that not mean that the equation instead maybe should be treated like was it a law of nature?
If so the consequences would be that the result of the equation GM/r^2 =(for example ADG = 1000 m/s^2) only is valid in the particular space-time where the calculation (the time rate) is connected to, - and that that distance always must stretch and shrink proportional with time dilation.

This is the only possibility (as I see it) that not would violate the nice equal proportionality between square and magnitude of ADG .

Would that be possible?

 

[Dale]

Each time the radius of a circle doubles, the area quadruples.

If and only if the space is flat.

At the same time the force of acceleration due to gravity (ADG) always decreases by 75%.
...
Hence the equation GM/r^2 in fact seems to reflect a law of nature, also even though we can’t say we have understood why this seems to be so.

You are assuming your conclusion, this is called circular reasoning.

If it were true that the force of the acceleration due to gravity (weight) always decreased by 75% then GM/r^2 would be a law of nature. However, the fact is that if you make sensitive measurements you find that your assumption does not reflect reality.

 

[Bjarne]

If and only if the space is flat.

No, ADG is always equal proportional with the square increase, and yes, only when you equal square with "space" – space must be flat. .
I am not saying we understand what the proportionality is reflecting, only that it is remarkable and deserves attention.

If it were true that the force of the acceleration due to gravity (weight) always decreased by 75% then GM/r^2 would be a law of nature. However, the fact is that if you make sensitive measurements you find that your assumption does not reflect reality.

What happens when the ADG equation only is valid as a "flowing equation" , only valid at a local point in space time, - as I wrote above?
Furthermore what happens when distances is proportional stretching / shrinking with time dilation ?
Anyway maybe there is more to discover, also not relativity always seems to give us the expected results.
http://www.nature.com/news/2011/111005/full/news.2011.575.html

 

[Dale]

No, ADG is always equal proportional with the square increase

This is not true. It is approximately true in many cases, but it fails for others.

You need to stop assuming your conclusion, it is circular logic. And it is particularly bad when your assumption has been falsified experimentally.

 

[Bjarne]

This is not true. It is approximately true in many cases, but it fails for others.

You need to stop assuming your conclusion, it is circular logic. And it is particularly bad when your assumption has been falsified experimentally.

The equation is true, and the ADG/Square proportionality result of that is also true.
That the equation "fails for others" etc... - to reflect measurement is a different story.

 

[DrGreg]

The equation is true, and the ADG/Square proportionality result of that is also true.

No matter how many times you say it is true doesn't make it true. Einstein and Schwarzschild proved it to be false.

The nearest equation general relativity can provide is<br /> g = \frac{GM}{r^2\sqrt{1 - \frac{2GM}{rc^2}}}<br />That is only true in certain circumstances -- a non-rotating uncharged spherically-symmetric mass and an observer at rest relative to the mass and whose own mass is insignificant -- and even then, r isn't quite what you thought it was -- the circumference of a circle around the mass divided by 2π.

 

[Agerhell]

If and only if the space is flat.

You are assuming your conclusion, this is called circular reasoning.

If it were true that the force of the acceleration due to gravity (weight) always decreased by 75% then GM/r^2 would be a law of nature. However, the fact is that if you make sensitive measurements you find that your assumption does not reflect reality.

Now, that was interesting Dalespam. Have you conducted any experiment and come to the conclusion that the gravitational force between two spherically symmetric objects is anything ells than F=GMm/r^2? Or at least maybe you can provide some more information regarding that experiment that you are referring to.

If the two spheres are moving with respect to each other in your experiment I may agree with your findings.

 

[Bjarne]

No matter how many times you say it is true doesn't make it true. Einstein and Schwarzschild proved it to be false.

The nearest equation general relativity can provide is<br /> g = \frac{GM}{r^2\sqrt{1 - \frac{2GM}{rc^2}}}<br />That is only true in certain circumstances -- a non-rotating uncharged spherically-symmetric mass and an observer at rest relative to the mass and whose own mass is insignificant -- and even then, r isn't quite what you thought it was -- the circumference of a circle around the mass divided by 2π.

You misunderstood what I wrote above.
I am not saying that relativity is wrong, but only that the proportionately between ADG and Square increase 1:1 , as a result of the equation itself, - is true ( in a classic sense).
That things are different in relativity is a different history.

I agree that the equation gives contradictory result when compared to relativity; at least we must expect the result of it to be limit to local space-time.

The point is only that I wonder whether the equation when put right together with other facts, for example Schwarzschild , and relativity , - could it maybe be so that the proportionality 1:1 reveals a aspect of a law of nature that we have overlooked, and that maybe not is in conflict with relativity, but instead forms a synthesis?

I don’t know, I am not an expert in this field, but I think the proportionality is remarkable, and maybe could be a clue to discover something that maybe could have been overlooked .

One thing is that time ticks different, and that space is really strange, but another question is; - are there more to discover in this field? Or have we fully understood the nature of space?
I mean we know matter is deforming space.
From a classical perspective we see that ADG and square increase is connected proportionally 1:1 , - this could at least be a clue to better understanding. So long we don’t know what this really reflect, if anything, it could be stupid to ignore it.

And it is particularly bad when your assumption has been falsified experimentally.

Which experiment do you have in mind ?

“The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.” Niels Bohr

 

[Dale]

The equation is true, and the ADG/Square proportionality result of that is also true.

Have you conducted any experiment and come to the conclusion that the gravitational force between two spherically symmetric objects is anything ells than F=GMm/r^2? Or at least maybe you can provide some more information regarding that experiment that you are referring to.

Which experiment do you have in mind ?

The equation a=GM/r² is the fundamental equation of Newtonian gravity, so any observation which falsifies Newtonian gravity falsifies that equation. Those observations include:

The anomalous precession of Mercury
The orbital decay of PSR1913+16
Geodetic precession (Gravity Probe B)
Gravitational lensing/deflection
Shapiro delay experiments

All of these experiments falsify Newtonian gravity. It is no use repeating the claim that a=GM/r² is a law of nature when nature disagrees.

 

[Bjarne]

The equation a=GM/r² is the fundamental equation of Newtonian gravity, so any observation which falsifies Newtonian gravity falsifies that equation. Those observations include:

The anomalous precession of Mercury
The orbital decay of PSR1913+16
Geodetic precession (Gravity Probe B)
Gravitational lensing/deflection
Shapiro delay experiments

All of these experiments falsify Newtonian gravity. It is no use repeating the claim that a=GM/r² is a law of nature when nature disagrees.

I agree that the "problem" to the Newtonian equation is that because of space-time disturbing "r" in the equation is twisted by space-time, whereby the classic understanding not can be completely correct.
But after modifying from that influence I am not sure the equation is so bad (?).

Before digging deeper into this let us first finish what the Shapiro delay really must mean.

1 second at the ISS is still 1 second, but comparable to 1 second at the Earth it is "stretching" at the ISS.
Hence 1 second at the ISS is comparable longer.

Speed on board the ISS (e.g. the speed of light) is comparable slower as speed on the Earth

I am often walking round a lake near my hometown.
If we would copy that lake and paste it into a low gravity planet, - it will still (locally) take me the 'same' amount of local time, - to walk around it.
My speed would also locally be the same, - but time (1 second and speed) would comparable to the same tour on Earth both be ‘stretching’ factors (comparable slower).

Anyway I assume I would not have any feeling of moving in slow motion, everything would be the 'same' both places.
So is it not true to say that also distances (the ruler) at the ISS, - is a relative proportional comparable stretching factor too, - so like both time and speed also are ?

Let say the size of the kitchen on board the ISS is identical to one in my house, but on board the ISS it is stretching proportional with time and speed.
But locally everything seems exactly the same as on Earth.

(Sizes is off course exaggerated)
It would still take the ‘same’ time to walk (with the ‘same’ speed) from A to B, - doesn’t matter in which space-time that kitchen would be.

Do we know whether distance is a streching factor too?

Or its it only possible that also distances are comparable different in different space-time, - (without violating any laws of nature)?

I mean why is time really ticking comparable different?

Is it “because” also distances are comparable different?

If not also distances are affected it is hard even to imagine how my tour round the lake on a low gravity planet would be?

At least I would discover something is wrong, - due to 'slow motion'.
If distance also is stretching proportional factor together with time and speed, - everything would be “normal”.

Many experiments have been done when it comes to speed and time, - but what about local distances, why should they be comparable the same everywhere, (if that really should be so) ?

So what can we say for sure here ?

 

[Dale]

I agree that the "problem" to the Newtonian equation is that because of space-time disturbing "r" in the equation is twisted by space-time, whereby the classic understanding not can be completely correct.
But after modifying from that influence I am not sure the equation is so bad (?).

I never said it was bad. In fact, I have repeatedly said that it is a close approximation in many circumstances.

Nevertheless, it is not a law of nature.

1 second at the ISS is still 1 second, but comparable to 1 second at the Earth it is "stretching" at the ISS.
Hence 1 second at the ISS is comparable longer.

How exactly do you plan on making the comparison?

 

[zonde]

The equation a=GM/r² is the fundamental equation of Newtonian gravity, so any observation which falsifies Newtonian gravity falsifies that equation. Those observations include:

The anomalous precession of Mercury
The orbital decay of PSR1913+16
Geodetic precession (Gravity Probe B)
Gravitational lensing/deflection
Shapiro delay experiments

All of these experiments falsify Newtonian gravity. It is no use repeating the claim that a=GM/r² is a law of nature when nature disagrees.

When it is clear that there is significant domain where assumptions of the theory hold good you do not say that theory is falsified but instead you say that experiments have established it's domain of applicability.

So no, these experiments do not falsify Newtonian gravity. And because Newtonian gravity talk only about massive objects optical observations (Gravitational lensing, Shapiro delay) have nothing to do with it's predictions.

 

[Bjarne]

I never said it was bad. In fact, I have repeatedly said that it is a close approximation in many circumstances.
Nevertheless, it is not a law of nature.

Maybe, maybe not, - I am not convinced, but I have also not taken any decision.
Have we understood the full range of relativity?
Never say never.

Bjarne
1 second at the ISS is still 1 second, but comparable to 1 second at the Earth it is "stretching" at the ISS.
Hence 1 second at the ISS is comparable longer.
Dalespam
How exactly do you plan on making the comparison?

Sorry, - I mean the opposite
1 second at the ISS is still 1 second, (the definition is correct) but comparable to 1 second at the Earth, time (1 second) is "stretching" at the Earth.

Hence 1 second at the ISS is comparable shorter at the ISS.
When time (1 second) compared to time at a different space-time is "stretching" and speed can be said to doi the same (since speed of light always is the "same") - what prevent us from assuming that also distances are doing exactly and proportional the same,- so that also the 1 meter ruler still is one meter, but comparable stretching, exactly the same rate as speed and time. ?

So the question is, - is the "big kitchen" and "big lake" etc... (together and proportional with strech of time and speed) also "stretching" on the Earth, and comparable "shrinking" in lower gravity space time, as for example on board the ISS or on a low gravity planet etc…?

At least this would make sense, when I would imagine how it would be to jump to an (extreme) different time space reality and walk around. I would expect everything to be the same, - but not comparable the same. (except the magnitude of gravity).

 

[Dale]

When it is clear that there is significant domain where assumptions of the theory hold good you do not say that theory is falsified but instead you say that experiments have established it's domain of applicability.

I am fine with this phrasing. Nevertheless, Bjarne's scenario dealing with gravitational time dilation is outside the domain of applicability of Newtonian gravity.

And because Newtonian gravity talk only about massive objects optical observations (Gravitational lensing, Shapiro delay) have nothing to do with it's predictions.

I disagree here. While the gravitational force between a massive object and a massless object is 0 according to Newton's laws it doesn't take force to accelerate a massless object. So the acceleration of massless objects in Newtonian gravity is still given by a=GM/r².

 

[Dale]

I am not convinced

That is not an indication of a failure in physics or relativity.

1 second at the ISS is still 1 second, (the definition is correct) but comparable to 1 second at the Earth, time (1 second) is "stretching" at the Earth.

Again, how exactly do you plan on making the comparison?

 

[Bjarne]

Again, how exactly do you plan on making the comparison?

I don't understand the question..
Time, and hence 1 second is not comparable the same in different space time, - do you not agree to that?

 

[Dale]

I don't understand the question.

I am asking for a detailed description of what experiment you are planning on doing in order to compare a 1 s on the ISS to 1 s on the earth, and how are you going to interpret different possible results of that experiment in terms of comparing the seconds?

 

[Bjarne]

I am asking for a detailed description of what experiment you are planning on doing in order to compare a 1 s on the ISS to 1 s on the earth, and how are you going to interpret different possible results of that experiment in terms of comparing the seconds?

I cannot see the problem.
Clocks ticks different in different space time.
Let us say you were living in a relative very strong gravitionel field, compared to me.
Let’s say it will take 2 second on my atomic clock, - to observer one second ticking on yours atomic clock.

Opposite it will take you ½ second to observe 1 second ticking on my atomic clock.

The definition of 1 second is for both of us 9,192,631,770 cesium frequency cycles per second.

But it will take a comparable long second (relative double period “of time”) for your clock to reach this number, and only a relative comparable short (½) period, and hence a short second for me to count the same numbers of frequencies.

So the comparable second is not the same. I cannot understand how you seem not to agree to that.

 

[Dale]

Clocks ticks different in different space time.

You are going in circles. I ask you how you are making the comparison and you simply assert that they are "different". Since "different" is a comparison where you find that they are not equal that still leaves the question of exactly how you are making the comparison.

Please answer the question. How are you comparing clock rates at different points in spacetime?

Let us say you were living in a relative very strong gravitionel field, compared to me.
Let’s say it will take 2 second on my atomic clock, - to observer one second ticking on yours atomic clock.

What is the experiment you are proposing here? How do you "observer" the time ticking on your clock and mine?

 

[Bjarne]

You are going in circles. I ask you how you are making the comparison and you simply assert that they are "different". Since "different" is a comparison where you find that they are not equal that still leaves the question of exactly how you are making the comparison.

Please answer the question. How are you comparing clock rates at different points in spacetime?

Satellites proves this every day

What is the experiment you are proposing here? How do you "observer" the time ticking on your clock and mine?

The same answer as above.
I cannot see any other option, - can you ?

 

[Mentz114]

Bjarne, your answers are getting more and more feeble. I think you misunderstand what is meant by "the laws of physics are the same in all inertial frames" so I'll spell it out.

If an experiment is done in lab A to test the law f=ma using billiard ball type experiments and of course measuring with local clocks and rulers, then the result will be the same as in any other lab frame, where of course, they use their local clocks and rulers.

It matters not a jot if the local clocks and rulers are 'different', both frames will verify that f=ma is true, up to a small experimental error.

Going on about seconds or centimeters being different in different frames is irrelevant.