Frame of Reference as Subject in Subjective Idealism

[md65536]

Just as the pancake does not actually change its reality, neither does earth. Simply the three dimensional piece that we consider to be 'now'.

All of our interactions are based on a 3d slice of the 4d object, so this is what we perceive at any given time.

This is what I've been saying throughout this whole thread. Where does that leave the "length contracted" earth of 1000 mile diameter, as seen from a near lightspeed fly-by FOR, as posited by Cap 'n R?

I think I understand now. Just as the 3d shape of a pancake doesn't change depending on its 2d representation (which can change as you turn it), the 4d shape of the Earth doesn't change when its 3d shape is affected by length contraction. I didn't realize that's what you were saying throughout the thread.

 

 

 

 

You missed the point that realism supports the general (non specific) proposition that "the world" in general is real, as it is, regardless of how we observe or measurement.

If you say that some of "the world's" properties are intrinsic, again, "good for you." You are a realist regarding those properties.

If you say some properties of "the world" are not intrinsic, then you are an idealist regarding those properties, because they will depend, for their pseudo-reality on the FOR from which they are measured.

Clear enough?

owl, I dare say you've won this discussion, using a technique that I've found very useful over the last few years called "proof by redefinition".

I still think that there are some contradictions and inconsistencies to work out, but basically I accept that your own definition of realism and your own definition of distance deny the reality (as you define it) of your definition of relativity.

Edited September 21, 2011 by md65536

[tar]

All,

 

Many things in science are defined by their definitions, and then of course live up to them.

 

The number of carbon 12 atoms in 12 grams of carbon is such and such and this number of anything we will call a mole of anything.

Fine, if you have less than this number of something you have less than a mole of it. If you have more than this number you have more than a mole of it, and if you have exactly this number of something you exactly a mole of it. If then a mole of it wheighs a gram, then two moles will wheigh 2 grams. No argument. But it is a contrived, agreed upon convention, to make figuring the amount of stuff you need to complete chemical reactions and such, easy and predictable. The number itself doesn't really tell you anything special about the universe.

 

Speed of light however tells us something. Not sure what, but if a second is not always a second, and a meter is not always a meter, then it can't tell us much, because it would not be an invariant speed. If a second was shorter than a second and light traveled 300,000,000 meters in that time, then it would be going faster than our invariant speed. Or if light covered the distance between here and a spot 300,000,000 meters away, but it took more or less than a second to make the trip, then again, our invariant speed would be not be invariant.

 

The consequences of relativity seem to be saying to me that light can take half a second to make a 300,000,000 meter trip, as long as the distance it traveled was actually shortened to 150,000,000 meters. Huh?

 

If in a thought experiment, an object is traveling at some exact percentage of the speed of light, then it covers that percentage of 300,000,000 meters in a second. If meters shortened or seconds lengthened then the object would no longer be traveling the stated percentage, and the premises would lose their meaning.

 

If two supernovae appeared at the exact same moment, similtaneously, in the same area of the sky, and one was larger and brighter than the other, and the one was figured to be 200,000 lightyears distant and the other 400,000 lightyears distant, one could put themselves in the shoes of an inhabitant of a planet that orbited the 200,000 ly away star just prior its explosion who was just witnessing the explosion of a star 200,000 lightyears distant from him/her in roughly the opposite direction than that of our Sun, when their star exploded. Simultaneous for us, simultaneous for the unlucky observer, but the two explosions were 200,000 years apart, and the first observation of the two explosions made 200,000 years ago. (except for the unlucky observer on the 400,000 ly away explosion, that observed their own star's demise 400,000 years ago, and was not around 400,000 years later(now) to see the demise of the 200,000 ly away "second" explosion.

 

Seems even simultaneity is relative, except for the imaginary universal now which we can continually extend to include the entire universe, seen from a Godlike, hypothetical position that is NOT constrained by the speed of light.

 

Regards, TAR2

Edited September 21, 2011 by tar

[Iggy]

Speed of light however tells us something. Not sure what, but if a second is not always a second, and a meter is not always a meter, then it can't tell us much, because it would not be an invariant speed. If a second was shorter than a second and light traveled 300,000,000 meters in that time, then it would be going faster than our invariant speed. Or if light covered the distance between here and a spot 300,000,000 meters away, but it took more or less than a second to make the trip, then again, our invariant speed would be not be invariant.

That's not right.

 

In our frame the distance from earth to sun is 150 million km. The time it takes light to move the distance is 500 seconds. Dividing 150 million km by 500 seconds gives the speed of light (0.3 million km/s).

 

In another frame moving .6c relative to us the sun-earth distance is 120 million km. The time it takes light to move the distance in that frame is 400 seconds. Dividing 120 million km by 400 seconds again gives the speed of light -- .3 million km/s.

 

The distance and time is variable, but the speed is invariant.

[Schrödinger's hat]

Speed of light however tells us something. Not sure what, but if a second is not always a second, and a meter is not always a meter, then it can't tell us much, because it would not be an invariant speed. If a second was shorter than a second and light traveled 300,000,000 meters in that time, then it would be going faster than our invariant speed. Or if light covered the distance between here and a spot 300,000,000 meters away, but it took more or less than a second to make the trip, then again, our invariant speed would be not be invariant.

 

The consequences of relativity seem to be saying to me that light can take half a second to make a 300,000,000 meter trip, as long as the distance it traveled was actually shortened to 150,000,000 meters. Huh?

Yup! Spot on.

If in a thought experiment, an object is traveling at some exact percentage of the speed of light, then it covers that percentage of 300,000,000 meters in a second. If meters shortened or seconds lengthened then the object would no longer be traveling the stated percentage, and the premises would lose their meaning.

You forgot to take into account that the only way for the metres and seconds to change size is by changing to a different frame of reference. Ie. by changing your velocity.

If something has a certain velocity in your frame (for example a train moving at 90km/h) then when you change velocity it'll have a different velocity (in our example, you might get on the train, then it'd be moving at 0km/h).

 

There are some invariant parameters though.

If our object was travelling at some exact percentage of the speed of light between two planets, then no matter which frame you use:

The clock on the object will show the same time when it is a set percentage of the way there,

The clocks on the planets will show the same time when it arrives or leaves

and a few other things, basically they will all agree on any events that happened.

 

If two supernovae appeared at the exact same moment, similtaneously, in the same area of the sky, and one was larger and brighter than the other, and the one was figured to be 200,000 lightyears distant and the other 400,000 lightyears distant, one could put themselves in the shoes of an inhabitant of a planet that orbited the 200,000 ly away star just prior its explosion who was just witnessing the explosion of a star 200,000 lightyears distant from him/her in roughly the opposite direction than that of our Sun, when their star exploded. Simultaneous for us, simultaneous for the unlucky observer, but the two explosions were 200,000 years apart, and the first observation of the two explosions made 200,000 years ago. (except for the unlucky observer on the 400,000 ly away explosion, that observed their own star's demise 400,000 years ago, and was not around 400,000 years later(now) to see the demise of the 200,000 ly away "second" explosion.

We observe these at the same time, so the observations are simultaneous.

This does not mean that the events were simultaneous.

As I said (tried to say?) earlier, you get time something happened in your frame only once you account for light delay.

Also these events are exactly too close together in space and too far apart in time to happen at the same time in any frame, as one is in the light cone of the other.

Seems even simultaneity is relative, except for the imaginary universal now which we can continually extend to include the entire universe, seen from a Godlike, hypothetical position that is NOT constrained by the speed of light.

Nearly. The point is that simultaneity is relative. We can define an imaginary universal now seen from a godlike position, but this imaginary now changes with our reference frame.

[Iggy]

Speed of light however tells us something. Not sure what, but if a second is not always a second, and a meter is not always a meter, then it can't tell us much, because it would not be an invariant speed. If a second was shorter than a second and light traveled 300,000,000 meters in that time, then it would be going faster than our invariant speed. Or if light covered the distance between here and a spot 300,000,000 meters away, but it took more or less than a second to make the trip, then again, our invariant speed would be not be invariant.

 

The consequences of relativity seem to be saying to me that light can take half a second to make a 300,000,000 meter trip, as long as the distance it traveled was actually shortened to 150,000,000 meters. Huh?

Yup! Spot on.

Jesus! I must have been more than half asleep last night Spot on, Tar

[md65536]

Speed of light however tells us something. Not sure what, but if a second is not always a second, and a meter is not always a meter, then it can't tell us much, because it would not be an invariant speed. If a second was shorter than a second and light traveled 300,000,000 meters in that time, then it would be going faster than our invariant speed. Or if light covered the distance between here and a spot 300,000,000 meters away, but it took more or less than a second to make the trip, then again, our invariant speed would be not be invariant.

 

The consequences of relativity seem to be saying to me that light can take half a second to make a 300,000,000 meter trip, as long as the distance it traveled was actually shortened to 150,000,000 meters. Huh?

Jesus! I must have been more than half asleep last night Spot on, Tar

Iggy, I think you were fully awake when you wrote the previous "That's not right."

 

tar, the second paragraph that you wrote is... fine... but the first paragraph is more confusing than good. Whether a statement like "a meter is not always a meter" is right or wrong depends on how you interpret it, and whether the two "meters" refer to separate things. Wrong: A meter is by definition a meter. Right: One's measure of a meter's distance is not always the same as another's measure of the space. I don't think I can explain what I mean in a helpful way without explaining relativity and I don't think I'd be any good at that. I think that understanding relativity first, and then understanding the meaning of length contraction, is better than trying to grasp relativity by first figuring out the meaning of length contraction.

 

But this is all "learn SR... trust us it makes sense in the end... mostly" which can only be experienced for yourself.

 

Philosophically, I think that what this all says is this: If you think about how you know and understand the concept of distance, what is it ultimately based on? Is it the length of a stick or the diameter of the Earth? If so then is it because there are a certain number of molecules lined up side-by-side in those lengths, and each molecule has a certain size and spacing? How do you intuitively know that what you consider the definition of a meter will not vary? I would argue that our intuitive understanding of distance comes from the speed of light. Since anything we've ever observed or measured in history was done with an invariant speed of light, we intuitively have a very consistent perception of distance.

 

The caveat is that distance must adhere to the rules of light, rather than the number of molecules in a stick etc.

 

 

Edit: Okay so I can't read. tar actually your first paragraph is a good example of how treating distance and time inconsistently leads to contradictions, which leads to the correct conclusion in the second paragraph.

Edited September 21, 2011 by md65536

[Iggy]

I think that understanding relativity first, and then understanding the meaning of length contraction, is better than trying to grasp relativity by first figuring out the meaning of length contraction.

 

I think you just perfectly summarized this whole thread.

 

Edit: Okay so I can't read. tar actually your first paragraph is a good example of how treating distance and time inconsistently leads to contradictions, which leads to the correct conclusion in the second paragraph.

 

I feel better not being the only one who needed a double take

[Schrödinger's hat]

I think that understanding relativity first, and then understanding the meaning of length contraction, is better than trying to grasp relativity by first figuring out the meaning of length contraction.

I think you just perfectly summarized this whole thread.

Hear hear.

It's best to start by completely ignoring all the weird effects, and just focus on what a constant speed of light means.

 

But this is all "learn SR... trust us it makes sense in the end... mostly" which can only be experienced for yourself.

Yes, it's hard enough to wrap one's head around it when you trust those who are explaining it to you. I can't imagine the level of dissonance involved when one believes that all scientists are crazy kooks and/or conspiring to teach a warped version of reality.

 

Addendum: At times I feel like I've travelled back a century. This debate seems more appropriate to the early 20th than 21st.

Edited September 21, 2011 by Schrödinger's hat

[owl]

md65536:

I think I understand now. Just as the 3d shape of a pancake doesn't change depending on its 2d representation (which can change as you turn it), the 4d shape of the Earth doesn't change when its 3d shape is affected by length contraction. I didn't realize that's what you were saying throughout the thread.

 

No, that's not what I'm saying. Objects with volume are 3-D objects. Time is often considered a 4th "dimension", but I just see it as event duration, how long it takes physical processes to happen. A pancake is a 3-D disk with thickness/volume. It will look like a disk of whatever thickness on your plate and like a line of that thickness when turned on edge. It stays the same shape, regardless of how you look at it.

Earth is a nearly spherical 3-D object. It doesn't change shape either as you look at it from different frames of reference. Length contraction claims that either it does change with FOR or that we can not know its true shape because of the "no preferred FOR" dictum of relativity. We know its true shape, but length contraction advocates are in denial of this well established knowledge.

 

owl, I dare say you've won this discussion, using a technique that I've found very useful over the last few years called "proof by redefinition".

I still think that there are some contradictions and inconsistencies to work out, but basically I accept that your own definition of realism and your own definition of distance deny the reality (as you define it) of your definition of relativity.

 

It is not about definitions. Realism says that the distance between Sun and Earth (and the shapes of both) do not depend on measurement. Cosmos and all its parts exist, with all their intrinsic properties independent of measurement.

The task of science is to measure things as accurately as possible. At rest with those objects is best, not flying by at high speed. As for distances between objects, either at an end point ( at one of the objects) or midway between them are the "preferred frames of reference" from which to measure them.

 

I am not denying relativity per se. I deny that "curved spacetime" in GR is essential to how gravity works. We observe curved trajectories of objects (and light... perhaps with a non-zero mass?) being pulled by gravity. The "spacetime fabric" is like "the Emporer's New Clothes" for me and for many critics in the International Society for the Advanced Study of Spacetime.

I agree that the speed of light is constant, as per SR. I do not agree that simultaneity is relative, as explained over and over above. Now IS now everywhere. And I obviously do not accept the validity of length contraction or time dilation.

The world/cosmos does not change to accommodate measurements from different FORs. Clocks tick slower at higher velocities and in higher gravity fields. Time does not "dilate" or slow down. Clocking time is an artifact of measure, but physical processes "proceed" (earth turns and orbits) whether measured or not.

I hope this clarifies my position.

Ps, (edit):

I could have used the other "reply" button to timestamp this and give the quote notification, but I forgot. Just a bad habit. Sorry.

Edited September 21, 2011 by owl

[Schrödinger's hat]

No, that's not what I'm saying. Objects with volume are 3-D objects. Time is often considered a 4th "dimension", but I just see it as event duration, how long it takes physical processes to happen. A pancake is a 3-D disk with thickness/volume. It will look like a disk of whatever thickness on your plate and like a line of that thickness when turned on edge. It stays the same shape, regardless of how you look at it.

Earth is a nearly spherical 3-D object. It doesn't change shape either as you look at it from different frames of reference. Length contraction claims that either it does change with FOR or that we can not know its true shape because of the "no preferred FOR" dictum of relativity. We know its true shape, but length contraction advocates are in denial of this well established knowledge.

The events on earth that are viewed as synchronous in the moving frame are not the events that are viewed as synchronous on earth.

If the events at different times did were not real outside of this present then we would not see earth at all in the moving frame.

The reason the earth we measure becomes contracted is because we are not seeing the different parts of it at the same time any more, (if you wish to consider the positions of the events that the earthlings consider synchronous then you will have to consider different times).

 

It is not about definitions. Realism says that the distance between Sun and Earth (and the shapes of both) do not depend on measurement. Cosmos and all its parts exist, with all their intrinsic properties independent of measurement.

We are not saying that anything is subjective. Merely that one of the inputs required to define a distance is a frame of reference.

Just like one of the inputs required to define an angular size is a position.

The task of science is to measure things as accurately as possible. At rest with those objects, and at an end point of distances between objects are the "preferred frames of reference" from which to measure them.

What if I'm measuring something that involves two or three different objects with different velocities?

 

I agree that the speed of light is constant, as per SR. I do not agree that simultaneity is relative, as explained over and over above. Now IS now everywhere. And I obviously do not accept the validity of length contraction or time dilation.

Then any discussion over length contractions is completely irrelevant.

Resolve the simultaneity issue first.

The world/cosmos does not change to accommodate measurements from different FORs. Clocks tick slower at higher velocities and in higher gravity fields. Time does not "dilate" or slow down. Clocking time is an artifact of measure, but physical process "proceed" (earth turns and orbits) whether measured or not.

I hope this clarifies my position.

No it does not.

Are you saying moving clocks tick slower, or are you saying that they don't?

How do we define not moving?

A clock is just a physical process. If a clock (as in the abstraction of clock -- ie. any physical process) slows down, then all physical processes slow down.

 

@Owl, capn's a bit busy to continue his train of reasoning and I'd like to continue before everyone forgets what he said.

Are you willing to proceed with some more thought experiments on the following assumptions:

1) The speed of light appears to be constant when measured on the assumption that one's laboratory is stationary. No matter the velocity of the laboritory.

2) Either:

There is no absolute rest frame or;

There is no way to know (or physicists are as still not smart enough to know) whether or not we are in the stationary frame, or what speed we are moving.

Edited September 21, 2011 by Schrödinger's hat

[Iggy]

Addendum: At times I feel like I've travelled back a century. This debate seems more appropriate to the early 20th than 21st.

 

That makes me think -- in 1916 Einstein wrote "Relativity: The Special and General Theory" that I think could not be better or more recommended for Owl and Tar. It is available online. Einstein writes in the preface:

 

The present book is intended, as far as possible, to give an exact insight into the theory of

Relativity to those readers who, from a general scientific and philosophical point of view,

are interested in the theory, but who are not conversant with the mathematical apparatus of

theoretical physics...

 

...I have purposely treated the empirical physical foundations of the theory

in a "step-motherly" fashion, so that readers unfamiliar with physics may not feel like the

wanderer who was unable to see the forest for the trees. May the book bring some one a few

happy hours of suggestive thought!

 

I just skimmed the first three chapters and I see that the seventh chapter is titled "The Apparent Incompatability of the Law of Propagation of Light with the Principle of Relativity"... exactly what we're talking about now. This, I believe strongly, would be a huge help to read.

[owl]

The events on earth that are viewed as synchronous in the moving frame are not the events that are viewed as synchronous on earth.

If the events at different times did were not real outside of this present then we would not see earth at all in the moving frame.

The reason the earth we measure becomes contracted is because we are not seeing the different parts of it at the same time any more, (if you wish to consider the positions of the events that the earthlings consider synchronous then you will have to consider different times).

Earth does not become contracted. Reality is not ALL about frames of reference. I have likened FOR to "subject" in subjective idealism with the difference that no person or subject need occupy whatever abstract FOR. Yet when a length contraction advocate says that "for a muon, earth's atmosphere is way less than 200 miles"... he claims that that is just as accurate as the well established "length" or thickness of the atmosphere. Wrong.

We are not saying that anything is subjective. Merely that one of the inputs required to define a distance is a frame of reference.

Just like one of the inputs required to define an angular size is a position.

Hopefully I just addressed the "subjective" issue. If one believes that reality depends on the FOR from which it was measured, that is a form of idealism in denial of an objective "world" independent of how it is observed. And the moon doesn't change shape with the variable "angular size" as seen from different positions.

 

What if I'm measuring something that involves two or three different objects with different velocities?

 

Get "up close and personal" with each moving object to get the most accurate measure of each. For the overall relationship between them, look at the overview, not from the individual FOR of each. See my "jousting lasers" thought experiment as an illustration of two moving objects. (They were both going at 1/2 lightspeed while firing lasers at each other, just to make it simpler, but if they were going different speeds, the math would be more complex without changing the principle... which was 'no length contraction.')

Then any discussion over length contractions is completely irrelevant.

Resolve the simultaneity issue first.

 

So you say. Are you the arbiter here for what is and is not relevant?

The claim of length contraction is totally relevant to this thread's topic. Does earth change shapes or not? Does the distance between earth and sun vary with FOR or not. Realism says "not," and the FOR version of idealism says "yes."

 

No it does not.

Are you saying moving clocks tick slower, or are you saying that they don't?

How do we define not moving?

A clock is just a physical process. If a clock (as in the abstraction of clock -- ie. any physical process) slows down, then all physical processes slow down.

 

Yes, clocks in orbit have a higher velocity relative to clocks on the surface, and tick more slowly. The trade off seems to be that they are also in a lower gravity field than clocks on the surface, so relativity does a good job of figuring them both out and keeping, for instance, GPS guidance very accurate. Yes, I think astronauts at higher velocities than surface dwellers also have a slower physical aging process while going faster.

To: "How do we define not moving?"...

At rest with the object or distance measured.

@Owl, capn's a bit busy to continue his train of reasoning and I'd like to continue before everyone forgets what he said.

Are you willing to proceed with some more thought experiments on the following assumptions:

1) The speed of light appears to be constant when measured on the assumption that one's laboratory is stationary. No matter the velocity of the laboritory.

2) Either:

There is no absolute rest frame or;

There is no way to know (or physicists are as still not smart enough to know) whether or not we are in the stationary frame, or what speed we are moving.

 

No. I have re-posed several unanswered questions, repeated in my last few posts, and I think they deserve answers before you go ahead assuming that all of reality depends on frames of reference.

Of course velocity of objects is defined "relative to what?" I went into great detail on that, and it need not be repeated. (Car rel. to road; road rel. to earth's center; earth rel. to sun; sun rel. to galactic center, etc.)

 

I have re-studied the summary of the Michelson/Moreley experiment and more contemporary experiments (abstracts) verifying the constant speed of light, so I know how it is derived.

[swansont]

I think you just perfectly summarized this whole thread.

 

Other than the struggle of whether philosophy (or religion) can tell nature how it behaves.

[Cap'n Refsmmat]

So you say. Are you the arbiter here for what is and is not relevant?

Yes, because he understands the physics, and the physics depends on relativity of simultaneity.

[Schrödinger's hat]

Earth does not become contracted. Reality is not ALL about frames of reference. I have likened FOR to "subject" in subjective idealism with the difference that no person or subject need occupy whatever abstract FOR. Yet when a length contraction advocate says that "for a muon, earth's atmosphere is way less than 200 miles"... he claims that that is just as accurate as the well established "length" or thickness of the atmosphere. Wrong.

 

Hopefully I just addressed the "subjective" issue. If one believes that reality depends on the FOR from which it was measured, that is a form of idealism in denial of an objective "world" independent of how it is observed. And the moon doesn't change shape with the variable "angular size" as seen from different positions.

And the (4d) earth as modelled by relativity doesn't change shape with the variable "width" as seen from different frames of reference.

I have mentioned on several occasions that the quantity proper length or proper distance (distance measured when at rest w/ respect to an object) exists in the literature.

It is also invariant where it is defined.

But this quantity is not sufficient to explain all phenomena. Two that come to mind are rapidly rotating objects, and systems of non co-moving objects.

 

Get "up close and personal" with each moving object to get the most accurate measure of each. For the overall relationship between them, look at the overview, not from the individual FOR of each. See my "jousting lasers" thought experiment as an illustration of two moving objects. (They were both going at 1/2 lightspeed while firing lasers at each other, just to make it simpler, but if they were going different speeds, the math would be more complex without changing the principle... which was 'no length contraction.')

If you were to follow your jousting lasers experiment through to its conclusion you'd find that it implied a non-constant speed of light. I would cover this in a series of thought experiments, but I need a common base of assumptions to work from.

 

So you say. Are you the arbiter here for what is and is not relevant?

The claim of length contraction is totally relevant to this thread's topic. Does earth change shapes or not? Does the distance between earth and sun vary with FOR or not. Realism says "not," and the FOR version of idealism says "yes."

 

Yet again, you present a false dichotomy.

Noone here is advocating a three dimensional universe in which length contraction works.

Noone here is advocating a universe with a universal well defined now in which length contraction works.

Both the three dimensional universe and the well universal now are assumptions you have made. They are inconsistent with a constant speed of light.

 

 

We have tried to explain over and over again that the following are inconsistent:

Speed of light which appears constant in any non-accelerating frame

Universal now

No Ether theory*

 

But the chain of reasoning is quite long and you have an uncanny ability to derail any train of logic heading in that direction.

I'm willing to draw up some diagrams and try and explain why this is so, but I will not bother if it will just fall on deaf ears.

 

Yes, clocks in orbit have a higher velocity relative to clocks on the surface, and tick more slowly. The trade off seems to be that they are also in a lower gravity field than clocks on the surface, so relativity does a good job of figuring them both out and keeping, for instance, GPS guidance very accurate. Yes, I think astronauts at higher velocities than surface dwellers also have a slower physical aging process while going faster.

To: "How do we define not moving?"...

At rest with the object or distance measured.

 

But you just said moving clocks tick slower, Clocks moving relative to WHAT tick slower?

 

No. I have re-posed several unanswered questions, repeated in my last few posts, and I think they deserve answers before you go ahead assuming that all of reality depends on frames of reference.

 

Any explanation I give to any questions about length contraction is contingent on assumptions about the relativity of simultaneity. You are asking me to answer questions without accepting the premise on which I base the answers. Any response I give will be useless.

 

In addition I very carefully worded my statement to avoid assuming that anything depended on frame of reference, this is intended to be my conclusion. Here are the assumptions with a bit more explanation, seeing as I failed to communicate my point.

1) The speed of light appears to be constant when measured on the assumption that one's laboratory is stationary. No matter the velocity of the laboritory.

I mean that, no matter what experiment you perform, or what velocity your laboritory is moving at (relative to, for example: Earth), so long as you assume you are stationary any experiment you do to determine the speed of light will come up with the value 299 792 458 m/s.

 

The second assumption was:

2) Either:

There is no absolute rest frame or;

There is no way to know (or physicists are as still not smart enough to know) whether or not we are in the stationary frame, or what speed we are moving.

I can weaken this further if you like to "The frame of reference we are using for our thought-experiments has an unknown velocity relative to some object (say, Earth)." if you like.

 

Note carefully that I am assuming nothing about length contraction, time dilation, simultaneity, or which variables depend on frame of reference.

 

 

*Ether theories are ones in which there is a universal 'still' frame and a speed of light which appears to be constant in all frames, but actually is not. They also share a result in that objects moving relative to this frame do physically contract, as opposed to relativity which posits that length contraction is a phenomenon caused by measuring things without taking the time coordinate into account.

 

I think you just perfectly summarized this whole thread.

Other than the struggle of whether philosophy (or religion) can tell nature how it behaves.

 

But surely there were philosophers around in the 1910s as well?

Edited September 21, 2011 by Schrödinger's hat

[owl]

This is just starting in order of replies. Called away soon but back to finish when I can. (Sorry, the timestamp requires too much editing for now.)

Schrodinger’s hat:

No it does not. ( Ed:clarify my position)

Are you saying moving clocks tick slower, or are you saying that they don't?

How do we define not moving?

A clock is just a physical process. If a clock (as in the abstraction of clock --

ie. any physical process) slows down, then all physical processes slow down.

 

I just clearly said that clocks in orbit tick slower than clocks on the surface. I also clearly said that everything is moving. This is frustrating when you don’t seem to hear what I just clearly (I thought) said.

Yes, clocks in orbit and astronauts in orbit (I think) both “experience” a slowing down of physical processes, “ticking” in the clock and “aging process” in the astronauts. (Again, I thought that this was clearly stated in my last post. There is a very real communication problem here.)

 

Another example of you simply not listening:

Me:

Yes, clocks in orbit have a higher velocity relative to clocks on the surface, and tick more slowly.

You:

But you just said moving clocks tick slower, Clocks moving relative to WHAT tick slower?

 

Ummm... relative to clocks on the ground.

I just said that in-orbit clocks tick slower and have a higher velocity relative to clocks on the surface.

Gotta go. Back soon, I hope.

[swansont]

But surely there were philosophers around in the 1910s as well?

 

Sure there were. Even before that, too. But they were generally wrong when they tried to dictate reality.

[Schrödinger's hat]

I just clearly said that clocks in orbit tick slower than clocks on the surface. I also clearly said that everything is moving. This is frustrating when you don't seem to hear what I just clearly (I thought) said.

Yes, clocks in orbit and astronauts in orbit (I think) both "experience" a slowing down of physical processes, "ticking" in the clock and "aging process" in the astronauts. (Again, I thought that this was clearly stated in my last post. There is a very real communication problem here.)

 

Ummm... relative to clocks on the ground.

I just said that in-orbit clocks tick slower and have a higher velocity relative to clocks on the surface.

I apologise, this was just so unexpected that I was not sure I had read your post correctly.

 

According to your model, would the clocks in the Sol system tick faster or slower when measured from a lab orbiting Barnard's star (which is moving at about 140km/s relative to Sol)?

Would a clock orbiting Barnard's star tick faster or slower when measured from Earth?

 

Edit: Changed observed to measured for clarity. Note that measured means the measurement you get after taking into account the effects of the doppler effect and light delay.

Edited September 22, 2011 by Schrödinger's hat

[Iggy]

We have tried to explain over and over again that the following are inconsistent:

Speed of light which appears constant in any non-accelerating frame

Universal now

No Ether theory*

 

But the chain of reasoning is quite long and you have an uncanny ability to derail any train of logic heading in that direction.

I'm willing to draw up some diagrams and try and explain why this is so, but I will not bother if it will just fall on deaf ears.

 

It seems like it should be easy because Owl has already said...

 

Sunlight traveling from sun to earth has the well known constant velocity relative to both sun and earth. From Alpha Centauri to earth, its velocity is relative, again, to both source and destination of the light.

If the two planets in that scenario are approaching each other at half the speed of light (to make the calculation easy) and they are 10 lightyears apart then here's the first frame where the red triangle (the light) moves relative to the green planet...

 

 

It is easy to calculate, Owl, that the speed of the red triangle is 1 light-year per year. In 10 years it goes 10 light-years. 10 / 10 = 1.

 

Then assuming distance and duration are invariant and there is a universal now the blue planet's frame is...

 

 

Everything that happened in the first frame happens at the same time in this frame (a universal now). All of the distances in the green planet's frame are the same in this frame (no length contraction). With those assumptions it should be easy to see that the speed of light in this frame (relative to the blue planet) is not the same as the other frame (relative to the green planet). In this frame light moves 5 light-years in 10 years. Its speed is .5c

 

This is where I see the conversation keep breaking down... or getting derailed as Schrodinger's Hat put it. In March, the first time I tried to prove that the speed of light couldn't be invariant with your other assertions (I used stick figures rather than planets) your solution was:

 

He is a confused stick figure guy in a confused thought experiment.

 

But, without addressing this logical inconsistency your version of reality (your description of realism) can't make logical sense -- if not addressing my animations then addressing the Captain's diagrams or Schrodinger's Hat could, like he says, make a representation showing the contradiction.

 

How can the red thing go the same speed relative to the green thing and the blue thing when your other assumptions clearly and directly contradict that assertion? It remains unanswered.

[tar]

if I was spot on, it was accidental or misinterpreted.

 

I think the double takes were inappropriate and the first takes were probably better.

 

My "Huh?" was not intended to be "that's the way it is. Right?" It was "this makes no sense to me, I am bewildered, and questioning an unbelievable, impossible thing, that does not add up."

 

I wish the double takes were appropriate, and an indication that yes indeed TAR is finally getting it.

 

This is not the case. I sometimes understand what is meant, but still very easily lose track of what it is that we are holding invariant, and when we are talking about the map, and when we are talking about the territory.

 

There is a "point of view" I can take, where the "reality" of the Earth includes all the states and positions all its contituent matter was in since the big bang till now, and from this godlike, "stand back and consider" perspective, imagine some giant blur where everything "exists" on equal footing. The past, the present, the future, here, there and everywhere, being "one" thing, that "exists", currently, here and now, in my minds eye. And then "pick out" my actual experiencial "here and now" existence as being just one positon in this 4D manifold, that has no particular important differenciation from any other "point", and any other point could be considered "just as real".

 

But that denies my actual experience of it as having any special value. And it presumes that I have the ability to stand back and consider all time at once, and all space as here.

 

As it turns out, it is exactly my nature, of being a limited being, that "exists" at only one place, and at only one time, that "allows" me to experience reality at all. If I did not have my frame of reference, reality would be an infinite blur with no distinctions.

 

I am thinking that we have to get a little selfish here, and consider our own frame of reference as the "preferred" one.

 

Regards, TAR2

[md65536]

if I was spot on, it was accidental or misinterpreted.

 

I think the double takes were inappropriate and the first takes were probably better.

 

My "Huh?" was not intended to be "that's the way it is. Right?" It was "this makes no sense to me, I am bewildered, and questioning an unbelievable, impossible thing, that does not add up."

 

I wish the double takes were appropriate, and an indication that yes indeed TAR is finally getting it.

You took some intuitive assumptions based on observations, and you logically deduced some conclusions that were not intuitive.

Yes, it felt like you were arguing that this doesn't make immediate intuitive sense... but -- refreshingly for this thread -- you didn't actually say "Therefore it must not be true." This is probably the reason for the double-takes.

 

Einstein and many others probably went through the same thing, accidentally deducing something puzzling, and then figuring it out instead of denying it. To figure out the puzzle often requires trusting the logical deductions, over preconceived intuitive ideas or beliefs. If the solution to every puzzle was intuitive and something you already knew, you wouldn't learn anything new from it.

Edited September 22, 2011 by md65536

[Schrödinger's hat]

As it turns out, it is exactly my nature, of being a limited being, that "exists" at only one place, and at only one time, that "allows" me to experience reality at all. If I did not have my frame of reference, reality would be an infinite blur with no distinctions.

 

Yes, this is why we select a FOR, and do calculations/experiments and such in it.

It's also a metaphysical/philosophical question which is somewhat outside the realm of SR. Why time appears to go one way rather than another, whether or not things are deterministic (in SR, just like Newtonian mechanics, there is no concept of choice or non-determinism. This is a limitation of the theory rather than something it asserts), issues like free will etc. are all open philosophical questions which should be informed and guided by thermodynamics and quantum physics, not just SR in isolation.

 

As to this "me" business, I look at it this way.

If there was a deterministic machine operating by a set of highly complicated rules in order to mimic me, but it didn't perceive this 'here and now'ness (or have any perception about reality), noone would notice.

It would act exactly the same and be perceived exactly the same by everyone else's me.

If it can trick the whole rest of the world, why couldn't it trick this entity I think of as me -- whatever that is?

It was this lovely little piece of cognitive dissonance which lead to my sig.

I see no objective evidence that free will is not just an illusion, but it makes me happier to have it. So I'll choose to pretend it exists.

 

I am thinking that we have to get a little selfish here, and consider our own frame of reference as the "preferred" one.

 

Sure, you do everything in a FOR based on your here and now.

I'll do everything in mine, but I won't pretend mine is any more or less significant than yours.

 

When we talk about a preferred frame, we mean one that is special, and should be singled out no matter who, where,or when you are. We've never been able to detect one of these, so Occam's razor says we should prefer a theory which doesn't have one over a compatable theory which does.

 

(Assuming for a moment we accept all this special relativistic nonsense)

The reason we need to consider the four dimensional picture, rather than just our own now goes something along these lines:

Let's say we have a universe with you, me, and Jim.

We're all a long way off, having a chat over intergalactic radio, but we're immortal so the time lag isn't much of a worry.

We're also both moving at different speeds relative to Jim.

I do my calculations, and work out that in my frame, the Jim that is synchronous with me is (to pick a random number) 21,080 years old.

But when you do your calculations you get 18,900.

If we try and consider an ephemiral, transient Jim we have to consider that he's both 21,080 and 19,800 years old. For a 3D, transient Jim this is paradoxical.

But eternal four-dimensional-worm Jim has a part of him that is every age, so this is okay.

 

 

If we had a preferred frame we could say we're all 3d, existing only in the now (in that frame), and the laws of physics are just conspiring to make us think some times that are not now, are actually now. This is -- in essence -- the Lorentz Ether theory that I've been mentioning. However, if you go down that road you find an endless series of little holes that need patching so that the conspiracy can trick you in every experiment we've done. Most scientists find that unpalatable, so instead of the myriad little theories, concepts and patches to keep this un-measurable preferred reference frame, they use the 4D model.

 

 

 

Aside: A good reason to think that our experiences will be 3 dimensional in appearance in this 4D world is that all of the interactions between different world lines are along our light cone (slight misnomer really, as this is the four dimensional equvalent of a cone). Also remember that everything we perceive (sans gravity) is mediated by photons. Even when you grab something, it's still the electromagnetic force.

 

Other aside: A mental image which might help with a conception of interactions which doesn't include a notion of evolution is this:

Imagine a series of strings, pulled taught. Like a very coarse net. Normally if we were to pull it tight, all of the cells/sections of the net would be squares, but if we were to tie a piece of thing string from one part of the net to another, the two bits of the net will be interacting with each other, even if the net is static.

[owl]

Schrodinger's hat:

If you were to follow your jousting lasers experiment through to its conclusion you'd find that it implied a non-constant speed of light. I would cover this in a series of thought experiments, but I need a common base of assumptions to work from.

 

I did complete the illustration, and ‘C’ stays constant. The task was to answer when each observer would see the others’ laser light (how much time would elapse) and where along the one Au “track”, i.e., distance traveled by each observer. They are in symmetrical relation to each other, so the figures are the same for both.

I picked the one Au distance between them for its commonly known length, which does not change during the run. That length is 8 light minutes, rounded off for simplicity. Their velocity is 1/2 lightspeed, and, of course, their laser beams are traveling at ‘C’ toward each other.

 

In 8 minutes each observer would have reached the midway point and each laser beam would have traveled the whole track to the opposite end from their starting points. So the “rewind” was required to answer the questions. After 4 minutes each observer would have traveled 1/4th of the track and their light beams would have reach the midway point. After 6 minutes the observers would have traveled 3/8ths of the track while their light beams would have traveled 3/4ths of the track, having already passed the opposite observer. So, each observer would be between their 1/4 and 3/8ths marker on the track (out from their respective starting points) . That would be just over 5/16ths out from each starting point when they see each other’s light, which had traveled just over 5/8ths of the way in each case. Each would be just over 5 minutes out. (Feel free to specify fractions down to 1/32nd of the track if you like.... and how many seconds over 5 minutes elapsed.)

 

So, there it is again in words. (I have no graphics capacity on my computer.) The speed of light stayed constant from both lasers (not gaining more velocity with the 1/2 ‘C’ observers' velocities. No distances (lengths) “contracted.”

Edit; Ps; An interesting comment by Schrodinger's hat above:

*Ether theories are ones in which there is a universal 'still' frame and a speed of light which appears to be constant in all frames, but actually is not. They also share a result in that objects moving relative to this frame do physically contract, as opposed to relativity which posits that length contraction is a phenomenon caused by measuring things without taking the time coordinate into account.

(my emphasis)

So you are now saying that length contraction does not reflect an accurate measurement of objects or distances in "the real world" but rather an error of omission in calculation?

 

Still catching up with past comments... like this from Schrodinger's hat, post 390:

Both the three dimensional universe and the well universal now are assumptions you have made. They are inconsistent with a constant speed of light.

I have challenged the transition from Euclidean to non-Euclidean geometry and cosmology with many specifics, mostly in the "Ontology of Spacetime" thread, and mostly citing Kelley Ross's paper on the subject... which has been ignored in this forum, since the non-Euclidean version of 4-space has become so well accepted over so many years, since Minkowski and Einstein codified it.

 

Any realist will accept that objects (with volume) and space "itself" (as volume itself, not an ingredient in "spacetime) have three dimensions: often referenced a length, width and height. Geometrically, a line is one dimensional, a plane is two dimensional, and volume is three dimensional. Time elapses as things move, which they all do. Light travels through space at the almost universally accepted constant, with which I agree. No contradiction in all of the above. That "now is now, period"... without location restrictions is not a contradiction to the above, either.

4-D space is based on a non-Euclidean *model* which reifies time and combines it with space... all of which is very debatable, as in above mentioned thread. The fourth dimension is the *assumption* here.

Edited September 22, 2011 by owl

[Schrödinger's hat]

So, there it is again in words. (I have no graphics capacity on my computer.) The speed of light stayed constant from both lasers (not gaining more velocity with the 1/2 'C' observers' velocities. No distances (lengths) "contracted."

Do you mean something like this?

 

The x axis is distance approximately in Au, the y axis is time in minutes.

Red lines are the lights, blue are our jousters.

So you are now saying that length contraction does not reflect an accurate measurement of objects or distances in "the real world" but rather an error of omission in calculation?

 

Similar, but without conflating measurement of objects and measurement of distances.

Contracted length reflects an accurate measurement of distances, which are only an accurate representation of objects to the same degree angular size is. If one were to put a metre stick beside that object as it moved past it would be that length. One would be able to fit it in a box of that size if closing and opening the lid were very carefully timed, but it is certainly not measuring the same entity that would be measured with a meter stick in the frame at rest with the object.

 

Just as if one were to take a photo it would subtend a certian angular size. The photo represents an accurate measure of the angular size of that object, but this is not a frame or position invariant quantity. Also taking photos from different angles produces a 2d representation of a different part of the 3d object.

 

We also have to be careful what we mean by object here. I am talking of the four dimensional entity, because the length contracted version does not represent the same set of events (the back is older than the front in a frame where it's moving)

 

I can find an object's proper length by taking the length I measure in my frame, making some assumptions about it being non-accelerating/rotating, and doing some calculations based on its velocity in my frame. This is the quantity/entity that would be measured in a frame moving with the object.

To go back to my angle analogy, I could find the height of the Statue of Liberty if I had a record of its angular height (or the height on a photograph of known angle/size) and the distance from which the measurement was taken.

Edited September 22, 2011 by Schrödinger's hat

[Iggy]

if I was spot on, it was accidental or misinterpreted.

You should have run with it