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

@layman,

1. All 4 would be moving
2. If all 4 were shot at the same speed, then all would be moving at the same speed.
3. If different, then different.

Since you seem to not understand this, let me add:

1.NONE of the 4 bullets would just "remain motionless" while the other 4 items (CMB and other bullets) moved away from it
2. A fortiori, ALL 5 things would not remain motionless.

Agree?

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@layman,

layman wrote:

If you were at rest with respect to the CMB, and if you shot 4 bullets in 4 different directions, then, RELATIVE to the CMB:

1. All 4 would be moving
2. If all 4 were shot at the same speed, then all would be moving at the same speed.
3. If different, then different.

Now what? Do you have a point?

Yes, I have a point. I am trying to clarify your view of the universe. This is the point I want you to either agree with or explain why you don't agree

Consider particle A is shot from a gun attached to the Earth in the direction of the Earth's motion (wrt the CMB frame) and particle B is shot in the opposite direction. Both are shot at the same speed wrt the Earth. Is it correct that particle B will be going slower (wrt the CMB frame) than particle A.

Tell me if this is correct or not.

If it will help, we can return to the dragster example. Consider a car going at 90mph. On the car is mounted a gun that shoots a baseball at 50mph (wrt the car). If I shoot the car forward it will be going at 140mph wrt the crowd. If I shoot it backwards it will be going at 40mph wrt the crowd. The forward shot baseball will always be faster than the backwards shot baseball (as long as the car is moving).

Is this correct to you?

1 Reply

@maxdancona,

Quote:

Consider particle A is shot from a gun attached to the Earth in the direction of the Earth's motion (wrt the CMB frame) and particle B is shot in the opposite direction. Both are shot at the same speed wrt the Earth. Is it correct that particle B will be going slower (wrt the CMB frame) than particle A.

Tell me if this is correct or not.

Yeah, sounds right.

1 Reply

@layman,

Ok so now we agree that a particle shot forward from a gun attached to the Earth will go faster than a particle shot backwards from the same gun attached to the Earth (both going the same speed wrt the earth).

Do you agree that in that case a particle shot forward will have a greater time dilation than a particle shot backward?

Or in another sense. As long as the gun is attached to the Earth, do you agree that in your view of the universe the direction the particle is shot will determine how much time dilation each particle experiences?

Do you still agree?

1 Reply

@maxdancona,

Quote:

Do you agree that in that case a particle shot forward will have a greater time dilation than a particle shot backward?

Depends on the frame of reference. In the ECI frame, yes (but that might still depend on whether you're talking east vs west rather than north vs south).

See the Hafele-Keating experiment.

According to SR, it would make no difference which direction they were shot. But that is wrong.

1 Reply

@layman,

Quote:

Depends on the frame of reference. In the ECI frame, yes (but that might still depend on whether you're talking east vs west rather than north vs south.

Really? You are changing frames of reference on me now? My understanding of your view of the universe is that the CMB frame the one that really matters.

Assuming (as I understood was your position) that the CMB frame is the valid frame.

A particle shot forward wrt to the Earth will have a greater time dilation than a particle shot backwards wrt to the Earth. This is because the particle shot forward is going faster than the particle shot backwards. (In the CMB frame).

Yes or no. According to your understanding of the Universe, is this correct or not?

1 Reply

@maxdancona,

Quote:

Really? You are changing frames of reference on me now? My understanding of your view of the universe is that the CMB frame the one that really matters.

WRONG!! I have already said it is NOT! Do you ever read my posts?

1 Reply

@layman,

I do read your posts... I guess sometimes they aren't very clear.

You said that there was a correct frame of reference where an object is actually motionless or actually moving. And when I asked you which that was, you said the CMB frame.

Now please be patient with me and let's start again.

You are saying that an object is either motionless or not motionless, right? Consider a object that is actually motionless. What is the motion of the Earth wrt that object?

I am asking very specific questions because I want to see if your view of the Universe makes sense or not.

2 Replies

@maxdancona,

Quote:

Really? You are changing frames of reference on me now? My understanding of your view of the universe is that the CMB frame the one that really matters.

You kept bringing up the topic of absolute motion and asked me *my* views. I told you the whole topic, in general was irrelevant to the points under discussion. I nonetheless answered that I personally don't think absolute motion can be detected.

I mentioned that physicists (Nobel-prize winning ones, at that) claimed that the CMB was close to a "motionless" point on a UNIVERSAL (that's capitalized because it's a key word) scale. I didn't say every scale, and I didn't even say I agreed.

Way before that, I told you that the "preferred" frame to be used by LR would depend on what you were trying to measure and calculate.

1 Reply

@layman,

Quote:

Way before that, I told you that the "preferred" frame to be used by LR would depend on what you were trying to measure and calculate.

But something that is motionless in one frame would be moving in another frame, right? A few pages you seemed to say that there was only one valid frame... now you are accepting that there are multiple valid frames of reference.

At least that's progress.

3 Replies

@maxdancona,

Quote:

You are saying that an object is either motionless or not motionless, right?

No, not really. Yes, everything is, in theory, either moving or it isn't, just as a matter of logic.

But as between two particular objects neither has to be considered to be motionless in order for one (say a rocket) to be the one be the "moving' one.

The same is NOT true in SR.

1 Reply

@maxdancona,

Now here is a further question for you that will help further our agreement (maybe).

The pilot of Spaceship A sees Spaceship B and measures that the distance between the spaceships is decreasing at a rate of 2,000 mph. The pilot of Spaceship B sees Spaceship A and also measures that the distance is decreasing at a rate of 2000 mph.

How does either pilot no what the "preferred" frame of reference it is? Can you imagine an experiment or a piece of equipment that would tell them?

Is the CMB frame the correct frame in this case?

1 Reply

@layman,

Quote:

No, not really. Yes, everything is, in theory, either moving or it isn't, just as a matter of logic.

Please explain this apparent contradiction.

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@maxdancona,

Quote:

But something that is motionless in one frame would be moving in another frame, right?

Maybe, but we're way off track here. Did you read any of my posts? Did you read the paper published in Applied Physics Research?

I have asked you a lot of questions which you have simply ignored. I have made a lot of explanatory posts which you have neither challenged nor acknowledged.

Read the thread. If you see particular issues to discuss, raise them. You don't do that. You just pop in when you think you have some irrebutable refutation and post it. Then, when your assertions get challenged, you just fade away. If you discuss anything at all, you always try to change the topic.

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@maxdancona,

Quote:

How does either pilot no what the "preferred" frame of reference it is? Can you imagine an experiment or a piece of equipment that would tell them?

This question isn't properly phrased. But I'm going to rephrase it in the way I think you mean it:

Q: Can either one know which one of them is "moving faster?"

A: Not always. But not never, either. Fundamental physical laws can often tell that.

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@maxdancona,

Quote:

Please explain this apparent contradiction.

I already have. Read the post it was made in.

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@maxdancona,

I'm going to address what I assume that you think the problem is, Max. I think I know, because I've heard it from a hundred SR supporters (at least) before. These are assertions/objections that have been handed down, generation to generation, for about 100 years now. They never change. They are articles of faith and part of the accepted dogma and holy scripture of SR.

The objection: We can't detect a "motionless" point, therefore...

I'll leave out what follows "therefore," for now.

I will instead go back in history to Newton. Newton himself said all these things long before any "relativists" came along. According to Newton, ALL detectable motion was relative. We could never know our absolute speed through "space."

So what did he do then? Just quit physics and turn to alchemy or black magic? No, he worked out laws of gravity and planetary orbits in the solar system which still get us to the moon today. But how could he tell what was moving? The earth, the sun, or anything?

See next post:

1 Reply

@layman,

Newton started by simply positing a point that he was going to call "motionless" for purposes of analyzing motion in the solar system. That point was the solar barycenter--the center of all mass in the solar system, which the sun itself revolves around. With respect to THAT point, everything else in the system was moving, but IT did not move.

He acknowledged that the whole solar system might itself be moving (as we now know it to be). But that was irrelevant for his purposes. Why? Because the whole system shared that motion. It had no effect whatsoever on the relationships between them (the sun and planets), so it could be ignored (again, for his particular purposes, at least).

Having chosen his motionless point (the barycenter), he then chose the background against which to measure planetary motion from this point--the fixed stars. He said that, although the fixed stars might not be a perfectly motionless background, it was a "good approximation."

He kept time constant. He was not dealing with objects travelling anywhere near lightspeed, so it made absolutely no practical difference. From this he deduced his "law of gravity." Given this framework, he also developed his fundamental laws of motion and his mechanics--still viable today.

What he did was "science." For all practical (if not ideal) purposes it worked just fine. All with the initial concession that he could never detect absolute motion--that wasn't necessary.

He thought that a "motionless" point must exist at the center of all mass in the universe. But he said that, even if it did, we wouldn't know it if we saw it. That didn't stop him.

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@maxdancona,

The point?

Well, I'm just saying the same things over and over. If I've bought a ticket, boarded a train, felt myself accelerating as it leaves the station, know that it takes energy to both reach AND maintain a uniform speed of, say, 80 mph then I know that RELATIVE to the earth's surface, I am moving, not the earth. The law of inertia tells me that I haven't just suddenly STOPPED the second I quit accelerating. The basic formula of F=MA tells me that the coal burning in the engine isn't moving the earth--it's causing the TRAIN (and me) to move at a uniform speed of 80 mph.

If I want to know who's watch has slowed down, as between mine and a guy's who I see sittin by the tracks as I pass, I KNOW it's mine, not his. And, guess what? This can be tested.

And, guess what? It has been tested. How? Just use atomic clocks and measure to SEE whose clock slowed down (a la Hafele Keating). And, to know this, I don't need to know a damn thing about how fast I (or the earth) is moving with respect to some distant galaxy, Mars, or the CMB. Those aren't even relevant questions in connection with this particular analysis.

A theory that REQUIRES me to deny that I'm moving, one that requires me to contradict the guy sittin by the tracks (who is, by experiment, right if he says my watch has slowed down), is NOT a theory that provides a good "physical explanation," however mathematically consistent it might be.

I have tried and tried to get you to see and understand the (very limited) role that the math (the LT) plays in all of this analysis. You came in and posted THE FORMULA and basically claimed it "proved everything" you were trying to claim. It doesn't. Not even close. I then addressed a whole lot of posts to that claim.

Have you read any of them? Is there anything you don't understand, or disagree with, in those posts? Do you, for example, claim that the LT formula IS a force of nature which causes things to speed up or slow down? Do you claim that a frame of reference is a determinative "force" insofar as actual physical motion is concerned?

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@layman,

By the way a "preferred frame" is not necessarily an absolutely motionless frame. According to wiki:

Quote:

Although there is no preferred inertial frame under Newtonian mechanics or special relativity, the set of all inertial frames as a group may still be said to be "preferred" over noninertial frames in these theories, since the laws of physics derived for inertial motion only work exactly in this special category of frames.

https://en.wikipedia.org/wiki/Preferred_frame

So an inertial frame (any inertial frame) is a preferred frame (in these theories), but they are not "motionless."

Quote:

In theoretical physics, a preferred or privileged frame is usually a special hypothetical frame of reference in which the laws of physics might appear to be identifiably different (simpler) from those in other frames.

I would take this another step and say that one frame is a "preferred frame" if it allows you to make a correct prediction over others which don't. By that definition the earth is "the" preferred frame in the twin paradox (not the rocket frame). In practice, this means that, in order to be correct in any predictions it might make, the rocket frame has to acknowledge the preferential status of the earth frame and concede that IT is moving, NOT the earth frame.

You can play mathematical tricks and juggle the books using SR to make the predictions come out right. But those mathematical "explanations" make absolutely NO sense from a physical standpoint. Changing frames of reference, for example, might provide a mathematical justification but it has NO physical import. As a matter of physics, these "explanations" are simply utterly absurd.

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

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