Terra revolving round Sol question

[H'ethetheth]

Originally Posted by ynot

It's even simpler than that.

Stationary cannot be said to exist. Therefore only motion can be said to exist . . . Your turn . . .

Now you're moving into weird territory.
This "simple" argument only works if you equivocate 'stationary' and 'absolutely stationary'. The premise is only true for 'absolutely stationary' and the conclusion only follows if the premise would have been about both kinds of stationary. So no, it's not that simple.

[ynot]

Originally Posted by H'ethetheth

Now you're moving into weird territory.
This "simple" argument only works if you equivocate 'stationary' and 'absolutely stationary'. The premise is only true for 'absolutely stationary' and the conclusion only follows if the premise would have been about both kinds of stationary. So no, it's not that simple.

Stationary is no more or less stationary with or without the word “absolute”. Relative stationary is an abstract construct that isn't actually stationary.

[Roboramma]

Originally Posted by ynot

When I stop laughing I might be able to reply.

Stationary is a value for NO motion.

ETA - All that laughter makes me want to be more agreeable so I will agree - “Stationary is just a particular value for motion”. That value is none, nil, zero, 0, nada, non-existent, completely lacking motion, without motion, still, motionless, no motion . . .

That's right, and zero is just another number.

[ynot]

Originally Posted by Roboramma

That's right, and zero is just another number.

Are you claiming that nothing is the same as something?

[Roboramma]

Originally Posted by ynot

Are you claiming that nothing is the same as something?

Here's what I'm saying:

According to relativity we can say that something is stationary. In fact, we can choose anything and call it stationary. In that reference frame other objects will have particular values to their motion.
If we choose a different object and say that it is stationary, other objects will have different values for the motion than in that first frame, but if we know the relative motion between object 1 and object 2 we can conveniently transform between frames.

Thus your claim that we can't say anything is stationary is identical to a claim saying that we can't say anything has any particular value for it's motion. There's nothing special about "stationary", as should be obvious from the above.

[Farsight]

This thread has descended into farce. If you come across an object in space that's spinning, you don't start thinking that the whole universe is spinning around it. Because hey look, there's another spinning object over there, and another, and another. What kind of logic starts postulating distant masses rotating at some hyperlight speed and magical mysterious forces? It isn't physics, it isn't cosmology, it's posturing geocentric quackery, peddled by people who ignore the CMBR dipole anisotropy, and who don't have a clue about gravitomagnetism or inertia. They try to pass off the nonsense they're pushing as relativity, and then the next breath say it doesn't matter what Einstein said. Talk about Emperor's New Clothes.

[H'ethetheth]

Originally Posted by ynot

Stationary is no more or less stationary with or without the word “absolute”.

It is if you conflate the two, yes.
To me, not so much. One of them does not exist in any meaningful way, the other one is useful. That is, in my head, stationary always means "declared stationary".

Originally Posted by ynot

Relative stationary is an abstract construct that isn't actually stationary.

Perhaps, but absolutely stationary is an even more abstract concept that doesn't actually refer to anything in the physical world.
The same thing goes for its "opposite", which you call universal motion, which can take any real value except zero, and cannot be quantified for any given object.

Most importantly, this whole conundrum goes away when you just ignore absolute stationarity, because it does not meaningfully exist. Then forget about the opposite of this non-existent thing, and accept that velocity is a quantity that can exclusively be described relative to something declared to be stationary.

[Farsight]

You're forgetting about light.

ETA: and absolutely stationary is meaningful when an object has no motion relative to the CMBR. It is stationary with respect to the universe, and that's as absolute as it gets.

[Humanzee]

sorry to ask but...how can you tell the difference between a universe that is spinning around an object verses a stationary universe where the object is spinning? If you can't then does it matter which one you choose?

[H'ethetheth]

Originally Posted by Farsight

This thread has descended into farce. If you come across an object in space that's spinning, you don't start thinking that the whole universe is spinning around it. Because hey look, there's another spinning object over there, and another, and another. What kind of logic starts postulating distant masses rotating at some hyperlight speed and magical mysterious forces?

It's not postulating. It's just a coordinate transformation. The fact that you think the resulting picture is strange is because your ancestors did not evolve to deal with a world that is significantly rotating.
Yet they did evolve to deal with significantly curved spacetime, so that nobody bats an eye when an object thrown does not continue on a straight path. See how that works? It's just a question of what perspective makes most intuitive sense to you. To ask which perspective describes reality more truly is meaningless. They are perfectly equivalent descriptions.

[H'ethetheth]

Originally Posted by Farsight

You're forgetting about light.

What about light?

Originally Posted by Farsight

ETA: and absolutely stationary is meaningful when an object has no motion relative to the CMBR. It is stationary with respect to the universe, and that's as absolute as it gets.

Yes, and as it turns out, it doesn't actually get all that absolute. For instance, I read that the CMB is constant to within 1 part in 100,000 or so. What would be the corresponding error margin on velocities?

ETA: Also, Humanzee makes a good point.

[edd]

The way you get a rest frame from the CMB is to work out how you'd have to move relative to our position in order to get its dipole to zero. The primordial anisotropies that are about one part in 100,000 are after the much larger dipole we see due to our motion has been subtracted.
That dipole is off the top of my head equivalent to about 600-700km/s towards Leo, roughly.
There's actually probably a very small primordial dipole not due to our motion relative to the average of the rest of the universe - but it can't be disentangled and is likely to be a couple of orders of magnitude smaller - equivalent to probably no more than 10km/s error.

[H'ethetheth]

Originally Posted by edd

The way you get a rest frame from the CMB is to work out how you'd have to move relative to our position in order to get its dipole to zero. The primordial anisotropies that are about one part in 100,000 are after the much larger dipole we see due to our motion has been subtracted.
That dipole is off the top of my head equivalent to about 600-700km/s towards Leo, roughly.
There's actually probably a very small primordial dipole not due to our motion relative to the average of the rest of the universe - but it can't be disentangled and is likely to be a couple of orders of magnitude smaller - equivalent to probably no more than 10km/s error.

Cool, thanks. So if I understand you correctly, declaring something "absolutely stationary" the way Farsight wants would imply saying that its stationary to within 10 km/s?

And this is due to anisotropy, not measurement errors, correct?

[edd]

Yes. We would have the same error even if we made perfect measurements of the CMB. It's a kind of cosmic variance (googleable term there) - we are limited by only being able to see the one CMB and so can't use it alone to narrow things down further.

This doesn't change the theoretical existence of the ideal frame in discussion either.

[nvidiot]

If we could measure a cosmic neutrino background would that make a difference in the error or identification of such an "ideal" reference frame?

[edd]

The neutrinos would come from a different surface to the CMB and so would in principle provide an extra measurement you could use to reduce the effect of cosmic variance, yes.

Aside from the practical difficulties I'm a bit worried there's something I've not thought of about that, but I think it's alright in principle.

[Kwalish Kid]

Originally Posted by ynot

ETA - All that laughter makes me want to be more agreeable so I will agree - “Stationary is just a particular value for motion”. That value is none, nil, zero, 0, nada, non-existent, completely lacking motion, without motion, still, motionless, no motion . . .

Yes, and it is something that has no application outside of a particular choice of what is stationary. As Maxwell said, if you take the time to think about the issue, you will find no reason to try to find absolute motion.

[sol invictus]

Originally Posted by ynot

I will try to explain once again - I’m simply saying that because we can’t say anything is ever actually stationary we can conclude that everything is actually continuously moving.

No we can't - not using logic, at least.

A murder was committed last night. We don't have any evidence so we can't conclude that ynot didn't do it. Therefore, we can conclude that ynot committed the murder, and so did everyone else.

Originally Posted by ynot

Originally Posted by Roboramma

"Stationary" is just a particular value for motion. By ruling out "stationary", as I said, your argument rules out all values of motion, thus, by your argument, motion does not exist.

When I stop laughing I might be able to reply.

Stationary is a value for NO motion.

ETA - All that laughter makes me want to be more agreeable so I will agree - “Stationary is just a particular value for motion”. That value is none, nil, zero, 0, nada, non-existent, completely lacking motion, without motion, still, motionless, no motion . . .

You are aware that zero is a number and "stationary" means "velocity=0" - right?

[Kwalish Kid]

Originally Posted by Farsight

You're forgetting about light.

ETA: and absolutely stationary is meaningful when an object has no motion relative to the CMBR. It is stationary with respect to the universe, and that's as absolute as it gets.

The CMB is made up of photons. There is no meaningful reference frame for photons.

The photons that make up the CMB clearly did not originate from a completely homogenous collection. How do you pick out the particles that were at rest when the CMB was emitted?

[sol invictus]

Originally Posted by Kwalish Kid

The CMB is made up of photons. There is no meaningful reference frame for photons.

The photons that make up the CMB clearly did not originate from a completely homogenous collection. How do you pick out the particles that were at rest when the CMB was emitted?

An individual CMB photon of course doesn't define a frame. But the collection of them does (approximately) - it's the frame in which the temperature (CMB photons have a black body spectrum) looks uniform in all directions, or rather uniform up to fluctuations of about 1 part in 100,000. An observer moving with respect to that frame will see a higher temperature in front of her and a lower temperature behind, due to Doppler shift.

[Kwalish Kid]

Originally Posted by sol invictus

An individual CMB photon of course doesn't define a frame. But the collection of them does (approximately) - it's the frame in which the temperature (CMB photons have a black body spectrum) looks uniform in all directions, or rather uniform up to fluctuations of about 1 part in 100,000. An observer moving with respect to that frame will see a higher temperature in front of her and a lower temperature behind, due to Doppler shift.

I know how there is a reference frame associated with the CMB. However, I want to know how Farsight identifies a particular reference frame with absolute rest.

[Farsight]

Originally Posted by Humanzee

sorry to ask but...how can you tell the difference between a universe that is spinning around an object verses a stationary universe where the object is spinning?

You line up your rocket to point at some nearby planet and fire the engines for a couple of seconds. If after a few hours you find you missed the planet by a mile, the universe is spinning. Or you string a weight radially out from the object, then shorten the string and watch the weight's rotation rate increase by virtue of conservation of angular momentum. The point to note here is that inertia is local - an object resists some change to its state of motion because of the energy-momentum of the object, not because of something else.

Originally Posted by Humanzee

If you can't then does it matter which one you choose?

You could pick a reference frame in which the universe is said to be spinning instead of the object, but that's only like choosing a map. The map is not the territory. You don't think of the earth as being flat and square just because that's what your map's like. So don't get suckered into thinking the universe might be rotating at 1000rpm just because somebody is banging on about a rotating reference frame and then dreaming up magic forces to try to justify it. A reference frame is "an artefact of measurement". You can't point up to the clear night sky and say "Wow! Look at that reference frame!" It doesn't actually exist, and it's important not to let things that don't actually exist get in the way of your understanding of the things that do.

[H'ethetheth]

Originally Posted by Farsight

So don't get suckered into thinking the universe might be rotating at 1000rpm just because somebody is banging on about a rotating reference frame and then dreaming up magic forces to try to justify it.

I'll stop banging on about it when you start understanding that these "magic" forces are simply a result of the transformation.

Let me put this another way. If our ancestors would have evolved in a world that rotated very quickly, they would be as intuitively familiar with coriolis forces and centrifugal forces as we are with gravity.
The fact that you don't like them does not change the fact that they are part of a consistent description of physics in a rotating reference frame.

[ynot]

Originally Posted by sol invictus

No we can't - not using logic, at least.

A murder was committed last night. We don't have any evidence so we can't conclude that ynot didn't do it. Therefore, we can conclude that ynot committed the murder, and so did everyone else.

Silly analogy.

Originally Posted by sol invictus

You are aware that zero is a number and "stationary" means "velocity=0" - right?

Within the niceties of your language perhaps, but I don’t speak Matheist.

[ynot]

Originally Posted by Humanzee

sorry to ask but...how can you tell the difference between a universe that is spinning around an object verses a stationary universe where the object is spinning? If you can't then does it matter which one you choose?

A spinning object displays properties of spinning. Some people apparently believe that a very distant, unseen and otherwise undetected shell of spinning mass can make a top on a desk appear as if it’s spinning when it isn’t I’m not one of those people.

[sol invictus]

Originally Posted by ynot

Silly analogy.

As far as I can tell, it's formally identical to your "logic". We can't ever say anything is stationary, "therefore" we can conclude everything is moving. We can't say any particular person is innocent, therefore everyone is guilty.

Originally Posted by ynot

A spinning object displays properties of spinning. Some people apparently believe that a very distant, unseen and otherwise undetected shell of spinning mass can make a top on a desk appear as if it’s spinning when it isn’t I’m not one of those people.

It's not a question of belief. There's a quantitative, precise theory - general relativity - that makes certain predictions. So far, all the predictions that have been tested have been consistent with experiment, and there are no other theories of gravity that can say the same. So at least for now, it's the best thing we have to go on.

[ben m]

Originally Posted by ynot

A spinning object displays properties of spinning. Some people apparently believe that a very distant, unseen and otherwise undetected shell of spinning mass can make a top on a desk appear as if it’s spinning when it isn’t I’m not one of those people.

Then you think that General Relativity is wrong. Simple as that. Why didn't you say so in the first place? Instead of listening to 100 time-consuming explanations of what the known laws of physics say about rotation and coordinates, you could have said "Here is what I think about coordinates, and I'm going to keep thinking that no matter what laws of physics I have to disagree with."

Unfortunately you picked a particularly bad way to disagree with a law of physics, because experiments explicitly contradict you.

Remember, ynot, the Gravity Probe B experiment was exactly this: a spinning object that didn't feel like it was spinning. They sent a satellite up into space with a gyroscope aboard. Using actual, physics-based measurements of the "properties of spinning", the GPB spacecraft was sitting perfectly still. However, GPB had a telescope on board, and this telescope---which, remember, has none of the "properties of spinning", sa measured very carefully using on-board measurements---saw the stars sweeping past it at 30 milliarcseconds per year.

In other words, Gravity Probe B "saw"---literally saw, through a telescope--- the Andromeda Galaxy zipping across the sky at 15 times the speed of light. And it did so while its onboard gyroscopes measured its own measurable-spin-effects to be zero (or at least below 4 mas/y).

[Michael C]

Originally Posted by Roboramma

What you are saying amounts to saying that because we can't assign any particular absolute value to the motion of anything, we can thus rule out one particular absolute value for the motion of everything (that is, zero).

Your argument works for any value: 0 m/s (stationary), 10 m/s, whatever value you choose. Thus, not only is nothing stationary (and thus everything is moving), nothing is moving at exactly 10 m/s.
But this argument works for 11 m/s as well. And 12. And 13...

Therefore nothing has any particular absolute motion.

Spot on. The fallacy is to think that "at rest" and "in motion" are two essentially different states. It's like saying that the place with coordinates (0,0) on a map is essentially different from all other locations on the map.

We can choose any place we like and create a map with a coordinate system in which this place has the coordinates (0,0). In the same way we can choose any object we like and define a reference frame in space-time which this object is at rest.

In the case of the map, if we have not defined a coordinate system, the phrases "location A is at (0,0)" or "location B is not at (0,0)" simply have no meaning.

In the case of space-time, if we have not defined a reference frame, the phrases "object A is at rest" or "object B is moving" simply have no meaning.

[ynot]

Originally Posted by ben m

Then you think that General Relativity is wrong. Simple as that. Why didn't you say so in the first place? Instead of listening to 100 time-consuming explanations of what the known laws of physics say about rotation and coordinates, you could have said "Here is what I think about coordinates, and I'm going to keep thinking that no matter what laws of physics I have to disagree with."

Unfortunately you picked a particularly bad way to disagree with a law of physics, because experiments explicitly contradict you.

Remember, ynot, the Gravity Probe B experiment was exactly this: a spinning object that didn't feel like it was spinning. They sent a satellite up into space with a gyroscope aboard. Using actual, physics-based measurements of the "properties of spinning", the GPB spacecraft was sitting perfectly still. However, GPB had a telescope on board, and this telescope---which, remember, has none of the "properties of spinning", sa measured very carefully using on-board measurements---saw the stars sweeping past it at 30 milliarcseconds per year.

In other words, Gravity Probe B "saw"---literally saw, through a telescope--- the Andromeda Galaxy zipping across the sky at 15 times the speed of light. And it did so while its onboard gyroscopes measured its own measurable-spin-effects to be zero (or at least below 4 mas/y).

Spoken like a true Matheist - “If you’re not with us you’re against us”. Not accepting is not saying “wrong”.

[edd]

Originally Posted by ben m

Remember, ynot, the Gravity Probe B experiment was exactly this: a spinning object that didn't feel like it was spinning. They sent a satellite up into space with a gyroscope aboard. Using actual, physics-based measurements of the "properties of spinning", the GPB spacecraft was sitting perfectly still. However, GPB had a telescope on board, and this telescope---which, remember, has none of the "properties of spinning", sa measured very carefully using on-board measurements---saw the stars sweeping past it at 30 milliarcseconds per year.

In other words, Gravity Probe B "saw"---literally saw, through a telescope--- the Andromeda Galaxy zipping across the sky at 15 times the speed of light. And it did so while its onboard gyroscopes measured its own measurable-spin-effects to be zero (or at least below 4 mas/y).

It's a minor nitpick as those sorts of numbers certainly would apply to more distant galaxies, but I'm not sure you've got it right for Andromeda if it was seen going at 30mas/year? It'd need to be going about 5 times that rate from what I just worked out (but I may have gone wrong somewhere).

[sol invictus]

Originally Posted by ynot

Spoken like a true Matheist - “If you’re not with us you’re against us”. Not accepting is not saying “wrong”.

Could you answer these questions, ynot?

(1) Do you understand the results of gravity probe B, at the level of ben's explanation of them just above?

(2) Do you think those results were in error?

(3) If not, how do you account for them?

[ben m]

Originally Posted by edd

It's a minor nitpick as those sorts of numbers certainly would apply to more distant galaxies, but I'm not sure you've got it right for Andromeda if it was seen going at 30mas/year? It'd need to be going about 5 times that rate from what I just worked out (but I may have gone wrong somewhere).

Aha, you're right, I got distracted by the arcseconds-to-radians conversion and I dropped the "30e-3" entirely.

[ynot]

Originally Posted by sol invictus

Could you answer these questions, ynot?

(1) Do you understand the results of gravity probe B, at the level of ben's explanation of them just above?

(2) Do you think those results were in error?

(3) If not, how do you account for them?

I only know about gravity probe B what I’ve read on this forum. If I get time I might read further about it to see if I can understand it enough to answer your questions.

I’m very busy with other things at present so may leave you to deal with other Relativity denial nutters for a while.

[theprestige]

Originally Posted by ynot

A spinning object displays properties of spinning. Some people apparently believe that a very distant, unseen and otherwise undetected shell of spinning mass can make a top on a desk appear as if it’s spinning when it isn’t I’m not one of those people.

Let's consider a top in our universe, then. So it's spinning. Relative to what?

The top is spinning relative to the table. That is, it's spinning relative to a frame in which the table is stationary.

But as you pointed out earlier, "saying something is stationary doesn't make it stationary." And we know that of course the table isn't really stationary. It's stuck to the surface of the Earth, and the Earth is spinning relative to, say, the Moon. So the table is moving pretty fast. And so is the top. What does the top look like from the Moon's reference frame? Spinning, or doing something else?

Of course, the Earth isn't just spinning relative to the Moon; it's also moving around the Sun, relative to the other planets in the Solar System. What about from Mars's reference frame? What does the top's motion look like from there? Spinning? Or doing something else?

Of course the Earth (and the table, and the top) isn't just moving around the Sun: It's being dragged around the center of the Milky Way galaxy. What does the top's motion look like from the frame of the Galactic core? All that motion! Spinning in the table's frame, whirling through space in the Moon's frame, flying through the Solar System in Mars's frame, hurtling around the Galactic core in the Milky Way's frame! Does the Milky Way see the top as spinning, or doing something much more elaborate and fantastical?

And of course the Milky Way itself is in motion, relative to, say, the Andromeda galaxy. What does the top's motion look like from Andromeda?

And of course the entire Local Cluster is in motion, relative to, say, the CMBR. What does the top's motion look like from the frame of the CMBR?

There are an infinite number of frames in which we can look at the top. Only one frame--the frame of the stationary table--actually sees the top spinning in place around a stationary axis. But as you pointed out, "saying a thing is stationary doesn't make it stationary". So what's the motion of the top?

Are you still going to insist that the top can be in "universal" motion, not relative to something else, and that that motion is "spinning"?

[xtifr]

Originally Posted by ynot

Nothing can ever be said to be actually stationary. All things are constantly moving relative to other things. All things are therefore constantly moving.

If you're saying that no two things can ever be at rest relative to each other, I can disprove that with some common household glue. If you're saying that for any given object, there exist an infinite number of frames of reference where that object is not at rest, then that's true, but those frames of reference are no more special than the single frame of reference where the object is at rest. In fact, you seem to be suggesting that all those frames of reference where no objects are at rest somehow constitute a single, special frame of reference on their own. They don't--they're a set of frames of reference. And none is any more special on its own than any other.

I actually think you're really close to understanding this. You realize that a frame of reference where an object is motionless is not special. You just seem to think that the set of other frames of reference collectively constitutes some sort of special frame of reference. But it's not--it's not a frame of reference at all. At best, it's a notion.