Who's familiar with the conversion? - "In 15 years' ship-time they could reach Andromeda

@layman,

Quote:

For example: The frame of reference which says the earth is motionless and that the sun orbits it is NOT, FOR PURPOSES OF AN ACCURATE PHYSICAL DESCRIPTION OF THE WORLD

"just as valid" as a frame of reference that says the earth orbits the sun.

As an oversimplification, the claim of SR is that every inertial frame is equally valid. There is also General Relativity (which was Einsteins extension of SR) that says that every non-inertial frame is equally valid. But we haven't even gotten to where you accept SR yet, I don't know if we should go there.

You are using the phrase "ACCURATE PHYSICAL DESCRIPTION". I don't know why this is all in caps, nor do I know how you would define it.

The fact is that Physics can make accurate predictions in any inertial frame of reference.. including the one that at this instant says that the earth is motionless. Of course in SR the earth is not an inertial frame for more than an instant (since it has a non-zero acceleration that will be non-zero when measured by experiment in any inertial frame of reference).

By the way, you are right about one thing... I did make a misstatement (just one as far as I can see in all of these pages). The scientifically correct position is that if two theories are indistinguishable by any possible experiment (that is they make the exact same predictions in any circumstance), then they are equivalent.

Of course if there are two theories, and we can think of a test to distinguish between the two (meaning that we can run experiments where they make different predictions and then measure the results to see which one matches the experimental results), then they are not the same.... and at most one is correct. There are theories where experiments have been designed that we don't have the technology to run yet.

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@layman,

Quote:

Now, I have made (or at least tried to make) a distinction between "a frame of reference" and a "correct frame of reference." They are NOT the same thing.

This is one of the key disagreements you and I have. I claim that there is no scientific difference between "any frame of reference" and "the correct frame of reference" that can be determined by experiment.

If you believe there is such a thing as the "correct frame of reference", then please tell me what it is? The way you define a frame of reference is by telling me what isn't moving.

So please tell me... in the correct way of looking at things, the "truth", or whatever you want to call it.

What isn't moving? In the dragster example you came up with... is the Earth moving in the correct frame of reference?

(And yes.... once you make this decision about the one true correct frame of reference, I am going to insist that you stick with it.)

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@maxdancona,

BTW, let me say it again. I hope that you are going to choose the CBR frame of reference as the correct frame of reference (meaning it is the CBR that isn't moving). This is the coolest idea.

But sadly after bringing up the CBR frame, you didn't use it at all in your dragster example where you insist the crowd isn't moving. (In the CBR frame of reference anything standing on Earth is moving quite rapidly).

So pick a "correct" frame of reference, and we will stick with it. It might be fun to look at how fast this crowd is really travelling in your "correct" point of view.

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@maxdancona,

Quote:

I claim that there is no scientific difference between "any frame of reference" and "the correct frame of reference" that can be determined by experiment.

I disagree for reasons other than I have yet to state, but I'm going to leave those aside.

You didn't answer my question about a heliocentric versus a geocentric understanding of the solar system, unless what you said above is supposed to answer it. Do you agree that each is not just as valid as the other for PHYSICAL explanation purposes?

Do you understand the distinction between "correct" for physical purposes and "correct" for calculation purposes? Do you believe there is no difference?

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@layman,

Quote:

Do you agree that each is not just as valid as the other for PHYSICAL explanation purposes?

I can't agree with this. I don't know what it means and you haven't given me a definition of the term. If one was more valid than the other, how would you know which?

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Do you understand the distinction between "correct" for physical purposes and "correct" for calculation purposes?

No I don't. And, I wish you would explain it in a way that I can test.

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Do you believe there is no difference?

No.

We humans have a point of view that believes that the Earth is solid and ummoving (with the rare exception of earthquakes). We believe this because since we are born, we walk upon and interact with the Earth in this way. But this says more about the experience of human beings than it does about anything real.

As we have developed science, we have learned to look at things from other perspectives and particularly to make mathematical predictions based on other perspectives. We had to do this in order to develop things like airplanes and spaceships.

There is a scientific way to look at the world, and there are multiple philosophical ways to look at the world. The advantages of the scientific way include being able to make testable predictions. It also is alone in giving us practical things we can use like airplanes and computers and medicine.

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@layman,

Quote:

There is a scientific way to look at the world, and there are multiple philosophical ways to look at the world. The advantage of the scientific way is that it gives us things we can use like airplanes and computers and medicine

OK, let's look at what might be called a "scientific" way. If I postulate that the earth is immobile and that all the planets and constellation revolve around it, then, among other things, I would have to conclude that the "fixed stars" were moving at speeds far in excess of lightspeed.

Would that be:

1. A perfectly correct scientific view
2.A view that is "just as good as any other," for purposes of explaining the motion of the planets and stars
3.An incorrect view which science, as we know it, has to reject, or
4. None of the above?

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@layman,

Is this statement, made by physics nobel prize winner, George Smoot, a "scientific" one, ya figure, Max? I ask it partly because I'm bored and you take a long time to respond to posts (you must be thinking a lot).

Quote:

We attribute the dipole anisotropy to the motion of the Earth and Solar System relative to the universal CMB radiation field and thus the distant matter in the Universe. This would seem to violate the postulates of Galilean and Special Relativity but there is a preferred frame in which the expansion of the Universe looks most simple.

Please note that a "preferred frame" is neither an "absolutely motionless" one, nor is it a "preferred frame" for ALL purposes. I am NOT endorsing the CMB as such.

My question is, is it a "scientific" claim to say that we KNOW the earth is moving?

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@layman,

This quote is also from the Cal-Berkeley (where Smoot is) physics website:

Quote:

The theory of special relativity is based on the principle that there are no preferred reference frames. In other words, the whole of Einstein's theory rests on the assumption that physics works the same irrespective of what speed and direction you have. So the fact that there is a frame of reference in which there is no motion through the CMB would appear to violate special relativity!

However, the crucial assumption of Einstein's theory is not that there are no special frames, but that there are no special frames where the laws of physics are different. There clearly is a frame where the CMB is at rest, and so this is, in some sense, the rest frame of the Universe. But for doing any physics experiment, any other frame is as good as this one. So the only difference is that in the CMB rest frame you measure no velocity with respect to the CMB photons, but that does not imply any fundamental difference in the laws of physics.

http://www.astro.ubc.ca/people/scott/faq_basic.html

Notice the distinction being made between the validity of physical laws in a frame (there is no preferred frame for THAT) and a preferred frame for purposes of assessing motion ("a frame where the CMB is at rest...the rest frame of the Universe").

These are distinctions you seem to be unwilling to acknowledge, as you seem to do with other meaningful and significant distinctions.

Here they are saying that SR does NOT require that there be no "special" (what I am calling "correct") frames of reference and that, indeed, there ARE such "special frames." More generically, they are called "preferred frames." In SR, for example, inertial frames are "preferred frames."

1 Reply

@layman,

Quote:

1. A perfectly correct scientific view
2.A view that is "just as good as any other," for purposes of explaining the motion of the planets and stars
3.An incorrect view which science, as we know it, has to reject, or
4. None of the above?

Claims that are made that can be tested with experiment are scientific claims. Now, there is the idea of Occam's razor, which says if two theories are mathematically equivalent you take the simplest. But that doesn't mean that the mathematically equivalent theory (which is just as good at making predictions) isn't valid.

It is pretty easy to devise an experiment that will break the "fixed stars" claim, and there are many other experiments that this view will contradict with.

Any view that meets all of the experimental and observed data is a valid scientific view. Any view that doesn't meet the experimental and observed data is not a valid scientific view. Any view that isn't able to be tested experimentally is not a scientific view (and science can have no bearing on whether it is valid or invalid)

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@layman,

Quote:

I ask it partly because I'm bored and you take a long time to respond to posts (you must be thinking a lot).

I do have a life, you know.

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@layman,

Quote:

We attribute the dipole anisotropy to the motion of the Earth and Solar System relative to the universal CMB radiation field and thus the distant matter in the Universe. This would seem to violate the postulates of Galilean and Special Relativity but there is a preferred frame in which the expansion of the Universe looks most simple.

For the record, I do not really agree with this statement of Smoot's. I think I know the point he is trying to make, and I agree with it. But I don't see how "the postulates of Gailean relativity" are being "violated" at all. Galileo never claimed that "you can't tell if the earth is moving." In fact, he claimed the opposite, i.e., that it could be shown, scientifically, that the earth was moving.

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@maxdancona,

Quote:

Any view that meets all of the experimental and observed data is a valid scientific view. Any view that doesn't meet the experimental and observed data is not a valid scientific view. Any view that isn't able to be tested experimentally is not a scientific view (and science can have no bearing on whether it is valid or invalid)

Great. Are you going to answer the question (or do you think you have)? Is it 1, 2, 3, or 4?

More questions on this post later.

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@layman,

Quote:

My question is, is it a "scientific" claim to say that we KNOW the earth is moving?

Only if you can prove this by experiment.

And we have done this. We have a theory that accurately explains the motion of the Earth in several frames of reference.

There is one inertial frame of reference in which the Earth is not moving for this one instant. Of course in the previous instant it was a different inertial frame (since the Earth is changing direction in all inertial frames).

There is a non-inertial frame of reference in which the Earth is forever motionless. If you take a General Relativity class you will consider this frame. Working in this non-inertial frame of reference is a little tricky... but again the math works and accurately predicts the interaction of space and time in a way that can be predicted and measured by experiment.

Again, it is the fact that all of these frames of reference can be used to make predictions that are testable that make them scientifically valid.

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@maxdancona,

You say:

Quote:

Any view that isn't able to be tested experimentally is not a scientific view (and science can have no bearing on whether it is valid or invalid)

Are you saying then that SR is NOT a "scientific view?" As the paper I cited above said (and as virtually any knowledgeable physicist will acknowledge):

Quote:

special relativity contains an important assumption which has not and possibly cannot be tested

.

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@layman,

You are taking things out of context Layman. But let me ask you this.

If you saying that the CMB frame is the only valid frame of reference, then why did you chose a different frame of reference to work with for your drag race example?

In this case it seems like you chose a frame of reference that suited you rather than using the CMB frame? How did you know that the frame of reference you chose was valid?

Why didn't you use the "real" frame of reference, if you believe in it so much? (In case you are missing this, the Earth and the crowd are going about 1,000,000 mph wrt the CMB).

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@layman,

You are taking things out of context. Skimming over wikipedia articles to find phrases that you think support your position isn't a good way to learn, or to make a point.

Please link me to this paper again, and I will try to explain to you what it is really saying in context.

There have been many, many experiments that have confirmed SR (and the more detailed version... GR). We have already discussed several of them in this very thread.

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@maxdancona,

Quote:

If you saying that the CMB frame is the only valid frame of reference, then why did you chose a different frame of reference to work with for your drag race example?

I am NOT saying that. I DID NOT say that at any time. In fact, I just told you that such a position is NOT one which I would endorse.

1 Reply

@maxdancona,

Quote:

Please link me to this paper again, and I will try to explain to you what it is really saying in context.

http://able2know.org/topic/301703-14#post-6074305[/quote]

That paper, by Zhang, the pre-eminent expert on the topic of experiments relating to SR, and other theories of relative motion, says:

Quote:

... the one-way speed of light is not observable in any physical experiment.

Only the two-way speed of light can be measured. Einstein merely postulates, without proving, what the one-way speed of light is.

As an example of the problem:

Suppose I get the grade of C in a college course.
Assume that the course had two, equally weighted, tests which determined that grade, OK?
Does that mean I got a C on each test?

1 Reply

@layman,

Quote:

the one-way speed of light is not observable in any physical experiment.

Do you know what this means? Can you explain why this is true? Do you know what the word "anisotropic" means (I am curious if you even bothered to look it up before you posted it out of context in this thread.)

Taking phrases you found on google out of context is not a good way to gain understanding or to make a point.

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@layman,

Quote:

Quote:
If you saying that the CMB frame is the only valid frame of reference, then why did you chose a different frame of reference to work with for your drag race example?

I am NOT saying that. I DID NOT say that at any time. In fact, I just told you that such a position is NOT one which I would endorse.

For measurements relating to distant stars, astronomers routinely use the CMB as a preferred frame of reference (and thereby employ a "neo-lorentzian" theory of relative motion).

But they would not use it for measurements within the solar system. In that case, they use the barycenter for their preferred frame (once again employing a "neo-lorentzian" theory of relative motion).

1 Reply

Who's familiar with the conversion? - "In 15 years' ship-time they could reach Andromeda

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