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

@maxdancona,

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If you don't agree that the driver is not moving wrt the race car... then we have another problem.

Of course I agree with that. But that wasn't the question.

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2) The crowd is moving wrt the race car?

Well, that's the question I asked. Now you're asking it, not answering it (at this point, anyway).

We both AGREE that there is RELATIVE motion between the two. Nobody is disputing that. But, again, that wasn't the question.

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Now change the the word "wrt" (which is your word) to the phrase "in the frame of reference of" (which is the science term) and maybe you finally understand.

Are you going to answer the question, or not?

1 Reply

@maxdancona,

maxdancona wrote:

Quote:
So, are you saying, then, that if I'm the guy in the dragster (I'm in HIS "frame of reference"), and I say that "I'm not the one moving relative to the crowed, the crowd is moving relative to me, while I remain motionless," then I would be WRONG?

Do you agree that in this case?

1) The driver is not moving wrt the race car.
2) The crowd is moving wrt the race car.

I don't believe that you would be wrong to say either of these two things. Now change the the word "wrt" (which is your word) to the phrase "relative to" (which is phrase you seem to be having trouble with) and maybe you finally understand.

If you don't agree that the driver is not moving wrt the race car... then we have another problem (and our poor driver has one hell of a problem). Again, I can propose an experiment to measure any one of these claims.

I did answer the question. In fact I will answer the question in several ways that all mean the same thing.

1) The crowd is moving wrt to the racecar (and the driver is not)
2) The crowd is moving relative to the race car (and the driver is not)
3) The crowd is moving in the race car frame of reference (and the driver is not).

All of these statements are completely correct. And they all say the same thing with different words.

So yes, if the driver wants to speak from his frame of reference and say "the crowd is moving and I am motionless" he is perfectly correct to say this. Most people are completely able to understand that he is just speaking from his frame of reference.

So the answer is "No". You would not be wrong. Again, I could propose any number of experiments that would show that this is the case.

1 Reply

@layman,

Here is an experiment I would propose.

Let's get two identical handheld doppler radar guns. We give one to the driver. We give the other one to a member of the crowd. The driver's gun is pointed at the crowd member. The crowd member's gun is pointed at the driver.

The crowd member's gun clocks the driver going at 200mph. What do you think the driver's gun would read?

Now the driver takes his gun and points it at himself. What do you think it will read now?

(Hint: Doppler radar guns work in a frame of reference that assume that the gun is motionless.)

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@maxdancona,

Quote:

I did answer the question. In fact I will answer the question in several ways that all mean the same thing.

1) The crowd is moving wrt to the racecar (and the driver is not)
2) The crowd is moving relative to the race car (and the driver is not)
3) The crowd is moving in the race car frame of reference (and the driver is not).

All of these statements are completely correct. And they all say the same thing with different words

.

All you're saying here is that they are moving relative to each other. This does NOT answer the question. We agree on that part.

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So yes, if the driver wants to speak from his frame of reference and say "the crowd is moving and I am motionless" he is perfectly correct

OK, that's "an" answer, but it's not an answer to the question I was asking.

But let's look at this "answer" for a minute. It is quite qualified. You say the answer is correct" from his frame of reference."

See my next post where I ask for some clarification.

1 Reply

@layman,

What IS the driver's "frame of reference?" Please try to understand what I'm asking next:

I'm the driver. I say to myself something like the following.

1. Ya know, I could look at myself as motionless, if I wanted. I could even imagine that the crowd is moving, not me.
2. But, ****, I know damn well that I just sped up like a bat out of hell, and I know that I've still got this pedal on the floor to keep going.
3. So I know that I AM moving. From my knowledge and perspective, I'm the one moving relative to the crowd (and the earth).

Would that be a "valid" frame of reference for him? Would SR allow him to concede what he knows, i.e., that he is the one moving?

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@layman,

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Would that be a "valid" frame of reference for him?

Yes

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Would SR allow him to concede what he knows, i.e., that he is the one moving?

Only within a frame of reference. In an absolute sense... no.

By the way. This whole example has nothing to do with SR. Physicists have understood this since the 1500s (well before Lorentz).

Now the question for you.

In your idea of correctness, the Earth is fixed, right? The Earth is not moving... which is why you can say with confidence that the crowd (which is not moving wrt the Earth) is also not moving.

(Why did you ever drop the CBR frame of reference... that was the coolest thing you have brought up here... of course wrt the CBR the crowd is moving at somewhere near a million miles per hour (if I remember correctly)?)

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@layman,

Let me insert this as "2a" in my last post, to expound on what I say the driver "knows"

I am assuming the driver "knows" the basic law of inertia, for example (a body in motion tends to stay in motion"). I am assuming the driver knows that F = MA, i.e. that it takes a force to accelerate something. I am assuming the driver knows that he would not need to supply any more gas if he were "in space" and wasn't subjected to forces of friction, etc., on earth. I am assuming that he knows that, if he did let off the gas, he would not immediately STOP. He might "coast" for miles, gradually decelerating the whole time, until he eventually came to be "at rest" relative to the crowd (i.e., until was no longer any relative motion between them).

And of course the laws of physics, as well as his own everyday experience, would lead him to know a lot of other things beyond those.

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@maxdancona,

Quote:

Q: Would SR allow him to concede what he knows, i.e., that he is the one moving?

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A: Only within a frame of reference. In an absolute sense... no.

I don't quite understand your answer. You seem to be giving two answers here.

1 Reply

@maxdancona,

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By the way. This whole example has nothing to do with SR

If it hasn't nothing to do with SR, then why did you start out lecturing Oris about the "fact" that there is no way to tell which of two things is moving?

1 Reply

@layman,

Ok, let me put this into your terms.

He can know that he is the one moving wrt the Earth...

1 Reply

@layman,

Quote:

If it hasn't nothing to do with SR, then why did you start out lecturing Oris about the "fact" that there is no way to tell which of two things is moving?

This principle, that the laws of physics work the same in any inertial frame of reference, has been known since the 1500s. Newton's laws have been effective at making accurate predictions in many frames of reference... in fact Isaac Newton did just that; he made calculations wrt the Earth. He then used the same math to make equally accurate calculations wrt the Sun.

Both of these frames were confirmed by careful experimentation and measurements.

1 Reply

@maxdancona,

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In your idea of correctness, the Earth is fixed, right? The Earth is not moving... which is why you can say with confidence that the crowd (which is not moving wrt the Earth) is also not moving.

1. NO, that is not why I say with confidence that the crowd is not moving. To begin with, I NEVER said that. But if I did it wouldn't because the "earth is fixed in space."

2. What I did say is that AS BETWEEN THE CROWD AND THE CAR (not talking about the CMB here or any other 3rd "object"), it is the car that is moving. This follows from our basic laws of physics, as elaborated on in my supplemental (2a) post.

3. I'll say it for the 10th time. I am NOT talking about "absolute" motion at all. Why do YOU keep talking about it? I'm talking about relative motion.

4. I "could" say the earth is motionless. I "could" say the sun is motionless. But I DON'T say either.

5. What I DO SAY, is that, whatever else is true, they can't BOTH be motionless.

1 Reply

@maxdancona,

Quote:

This principle, that the laws of physics work the same in any inertial frame of reference, has been known since the 1500s. Newton's laws have been effective at making accurate predictions in many frames of reference... in fact Isaac Newton did just that; he made calculations wrt the Earth. He then used the same math to make equally accurate calculations wrt the Sun.

Right. I have stated as much myself. We don't disagree there. I'll go a step further.

So long as the guy in the dragster is moving at a UNIFORM rate of speed, the laws of physics will apply to any "experiment" he performs in his car. Galileo made this clear.

But that isn't the question. It's "true" but it's irrelevant.

1 Reply

@layman,

If the Earth is moving, than the crowd standing on the Earth is also moving.

Right?

1 Reply

@layman,

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But that isn't the question. It's "true" but it's irrelevant.

It is not irrelevant. It is science.

Science deals with things that can be tested by experiment. If you have some version of "truth" that can't be tested by an experiment, then it may be "true"... but it isn't scientifically true.

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@maxdancona,

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If the Earth is moving, than the crowd standing on the Earth is also moving.

Right?

Yes, of course.

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@maxdancona,

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It is not irrelevant. It is science.

Heh. It's irrelevant to answering the question that I'm asking.

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@maxdancona,

You said:

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Science deals with things that can be tested by experiment. If you have some version of "truth" that can't be tested by an experiment, then it may be "true"... but it isn't scientifically true.

OK. Did you read the scientific article I posted which demonstrates that SR contains an assumption that has not been, and cannot be, tested? If so, why would you say SR is "true?"

Beyond that, if you want to continue to base your answers on what you assert that "science" is, or is not, please answer the following question, which I asked way back:

Quote:

You say: "A theory is correct if and only if it can make predictions that are confirmed by experiment that no other theory can make"

1. First you say SR is "correct" ONLY IF it makes predictions that no other theory can make
2. Then you say LR makes the same prediction that SR does.
3. Then you say "That is why the scientific community accepts it as the correct theory."

What's up with that?

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@maxdancona,

Quote:

He can know that he is the one moving wrt the Earth...

OK, thanks.

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. And each one is not "just as valid as any other" for PHYSICAL purposes. They may be "just as valid" for the VERY LIMITED purpose of making certain mathematical calculations, sure. But that's not "just as valid" for every purpose.

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.

Do you agree?

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@maxdancona,

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LET and SR are equivalent theories because they always give the same answer under any conditions... which is why you can't run an experiment to say which is correct...

As an aside, Max, I note that you have frequently made exactly the opposite claim in the past. You have routinely claimed that ONLY SR is capable of making (at least some of) the correct predictions it makes.

In response, I have repeatedly urged you to "do some research." You refused. When I handed you the sources, and quoted them, you denied that they said what they said (which is the very thing you now positively assert).

I can see that you are learning some things from your participation in this thread. I'm happy to see that.

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

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