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

@maxdancona,

Quote:

Those other theories were dropped because they have trouble explaining the results of Michelson Morley and other experiments of the time. This is why Relativity was accepted by the physics community.

As I said there have since been many confirmations of relativity that break the earlier theories. There is no other theory that matches the mathematical results found by experiment or observation.

By the way, the so-called "twin paradox" has been confirmed by experiment (using two atomic clocks). This actually happens as predicted by the theory.

I have already responded to this post, Max, but without elaboration. Your first two claims are just wrong, and I won't bother addressing them in this post. But you have, several times, challenged me to address the twin paradox (which you say proves SR to be correct). So I will address it in more detail.

In fact it proves that SR in INCORRECT.

First, the "paradox:" The travelling twin claims the earth twin is aging more slowly while, at the same time, the earth twin claims that the travelling twin is the one who is aging more slowly.

So how is this "paradox" resolved? Here's how: Every physicist ends up saying that it is in fact the travelling twin who ages more slowly, NOT the earth twin. In other words, the earth twin was right, and the travelling twin was wrong when claiming the contrary.

This is tantamount to saying that in this case the correct frame of reference is the earths twin's frame. His frame gives to the right answer, so it is the right one. The travelling twin's frame is the wrong one, plain and simple.

Why does the travelling twin age less rapidly? Because, according to Feynman HE is the one (as between the two) who is moving. That's exactly what the LT says, i.e. that the moving clock will slow down. That's exactly what lorentzian relativity says (without the appearance of any "paradox").

2 Replies

@layman,

layman wrote:

Quote:
Those other theories were dropped because they have trouble explaining the results of Michelson Morley and other experiments of the time. This is why Relativity was accepted by the physics community.

As I said there have since been many confirmations of relativity that break the earlier theories. There is no other theory that matches the mathematical results found by experiment or observation.

By the way, the so-called "twin paradox" has been confirmed by experiment (using two atomic clocks). This actually happens as predicted by the theory.

I have already responded to this post, Max, but without elaboration. Your first two claims are just wrong, and I won't bother addressing them in this post. But you have, several times, challenged me to address the twin paradox (which you say proves SR to be correct). So I will address it in more detail.

In fact it proves that SR in INCORRECT.

First, the "paradox:" The travelling twin claims the earth twin is aging more slowly while, at the same time, the earth twin claims that the travelling twin is the one who is aging more slowly.

So how is this "paradox" resolved? Here's how: Every physicist ends up saying that it is in fact the travelling twin who ages more slowly, NOT the earth twin. In other words, the earth twin was right, and the travelling twin was wrong when claiming the contrary.

This is tantamount to saying that in this case the correct frame of reference is the earths twin's frame. His frame gives to the right answer, so it is the right one. The travelling twin's frame is the wrong one, plain and simple.

Why does the travelling twin age less rapidly? Because, according to Feynman HE is the one (as between the two) who is moving. That's exactly what the LT says, i.e. that the moving clock will slow down. That's exactly what lorentzian relativity says (without the appearance of any "paradox").

This analysis is quite clear, Lay. Congrats.
But moving a step forward doesn't mean winning the battle. Wink

1 Reply

@layman,

Quote:

First, the "paradox:" The travelling twin claims the earth twin is aging more slowly while, at the same time, the earth twin claims that the travelling twin is the one who is aging more slowly.

To be clear, perhaps I should have put it this way:

First, the "paradox:" According to SR (but not LR), the travelling twin claims the earth twin is aging more slowly while, at the same time, the earth twin claims that the travelling twin is the one who is aging more slowly.

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@oristarA,

Quote:

But moving a step forward doesn't mean winning the battle.

I thought you had left this thread, never to return, Oris (after starting all the trouble to begin with). Have you been reading it all along? Many "steps" have been made so far, if you've been following.

In any event, I'm happy to see that you can recognize common sense and simple logic when it is presented to you.

1 Reply

@layman,

layman wrote:

Quote:
But moving a step forward doesn't mean winning the battle.

I thought you had left this thread, never to return, Oris (after starting all the trouble to begin with). Have you been reading it all along? Many "steps" have been made so far, if you've been following.

In any event, I'm happy to see that you can recognize common sense and simple logic when it is presented to you.

I only took samples and read em; didn't read it all along.
I prefer reading Scientific American to reading your posts, Lay.

2 Replies

@oristarA,

Quote:

I only took samples and read em; didn't read it all along

Well, Oris, if you're interested in the topic at all, you could read the following post and the 2-3 that follow it. They (indirectly) summarize the difference in views between me and Max. They're not very long or complicated.

http://able2know.org/topic/301703-19#post-6076648

Quote:

I prefer reading Scientific American to reading your posts, Lay.

And if you like scientific articles, you could look at the following post (and the two that follow it). That would tell you about all you need to know to decide for yourself, I figure.

http://able2know.org/topic/301703-18#post-6075848

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@oristarA,

As I've said, for purposes of calculation, SR is fine. There's nothing wrong with the math, per se.

The problem only enters when those who are enamored of the theory want to take the unwarranted step of claiming that their math techniques reflect objective physical reality.

In SR, each and every "frame of reference' (of which they are an infinite number) is required to be treated as though it is absolutely motionless. Again, this is fine for calculation purposes but it CANNOT reflect reality. Yet SR's adherents can't resist claiming that, as a matter of objective reality, all views are "equally valid."

Every single object in the universe cannot be "motionless" and it still have objects which are said to be "in motion."

1 Reply

@layman,

As a historical matter, long before Einstein, Lorentz developed the concept of "local time," which Einstein was later to claim was "real time."

Again, long before Einstein, Poincare noted that the "local time" concept established a "subjective" relativity." He explained that if every observer was unaware of, or chose to ignore, his own motion, then the notion of relativity could be superficially preserved.

Einstein was not the first to realize this. But both Lorentz and Poincare refused to accept the notion of "local time" as a matter of physical reality, to their dying day. Lorentz said local time was a mere "mathematical fiction," with no correspondence to reality. He said that it was nonetheless quite useful as a means of simplifying certain calculations, and that's the reason he developed it.

Einstein, who at the time was a devout disciple of the proto-positivist of physical theory, Ernst Mach, decided to simply define "time" as "what we measure it to be." At the time he thought that seemed to be a valid "operational definition" of time.

Einstein later totally rejected his prior positivist views, calling them "nonsense." Heisenberg used Einstein's own notions to argue against Einstein himself. Einstein even said that his biggest regret was that, perhaps in large part due to the "success" of his early theories, science took a bad turn toward positivism. He regretted that his name was being used to dignify, accept, and perpetuate positivism in science.

Too late, Al.

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@layman,

Quote:

The LT ONLY tells you that it is the MOVING clock which slows down. Being nothing more than a stupid math formula it doesn't, and can't, tell you which one is moving.

It the clock that had undergone a period of acceleration that is moving.

1 Reply

http://math.ucr.edu/home/baez/physics/Relativity/SR/acceleration.html

Can Special Relativity Handle Acceleration?

It's a common misconception that special relativity cannot handle accelerating objects or accelerating reference frames. Sometimes it's claimed that general relativity is required for these situations, the reason being given that special relativity only applies to inertial frames. This is not true. Special relativity treats accelerating frames differently from inertial frames, but can still deal with accelerating frames. And accelerating objects can be dealt with without even calling upon accelerating frames.

This idea that special relativity cannot handle acceleration or accelerated frames often comes up in the context of the twin paradox, when people claim that it can only be resolved in general relativity because of the acceleration present. Their claim is wrong.

The only sense in which special relativity is an approximation when there are accelerating bodies is that gravitational effects such as the generation of gravitational waves are being ignored. But, of course, there are larger gravitational effects being neglected even when massive bodies are not accelerating, and these are small for many applications, so this is not strictly relevant. Special relativity gives a completely self-consistent description of the mechanics of accelerating bodies neglecting gravitation, just as newtonian mechanics does.

One difference between general and special relativity is that in the general theory all frames of reference, including spinning and accelerating frames, are treated on an equal footing. In special relativity accelerating frames are different to inertial frames. Velocities are relative but acceleration is treated as absolute. In general relativity all motion is relative. To accommodate this change, general relativity has to use curved space-time. In special relativity space-time is always flat.

In special relativity an accelerating particle's worldline is not straight. This isn't difficult to handle. The particle's 4-vector acceleration can be defined as the derivative with respect to proper time of its 4-velocity. It is possible to solve the equations of motion for a particle in electric and magnetic fields, for example.

Accelerating reference frames are a different matter. In GR the physical equations take the same form in any co-ordinate system. In SR they don't, but it's still possible to use co-ordinate systems corresponding to accelerating or rotating frames of reference, just as it is possible to solve ordinary mechanics problems in curvilinear co-ordinate systems. This is done by introducing a metric tensor. The formalism is very similar to that of many general relativity problems, but it is still special relativity as long as the space-time is constrained to be flat and minkowskian. Note that the speed of light is rarely a constant in non-inertial frames, and this has been known to cause confusion.

An example is a rotating frame of reference used to deal with a rotating object. The transformation of the metric into the rotating frame leads to "fictitious" forces: Coriolis forces and centrifugal forces. But this is no different from ordinary mechanics.

A simple task is to solve for the motion of a rocket that accelerates "uniformly". What does this mean? We don't mean that its acceleration as measured by an inertial observer is constant. We mean that it is moving such that its acceleration measured in a "momentarily comoving inertial frame" is always the same; this frame is an inertial frame travelling at the same instantaneous velocity as the object at any moment. If you were on board such a uniformly accelerated rocket, you would experience a constant "G force". The motion of this rocket can be found in several ways. One way uses the four-vector acceleration along the rocket's worldline, since this has constant magnitude. Alternatively, the rocket is passing constantly from one inertial frame to another in such a way that its change of speed in a fixed time interval is always the same. From our understanding of adding velocities, we can see that the rapidity r of the rocket must be increasing at a constant rate a with respect to the rocket's proper time T. The rapidity is related to velocity v by the equation

v = c tanh(r/c)
From this we derive the equation

v = c tanh(aT/c)
For other acceleration equations see the relativity FAQ article on the relativistic rocket.

2 Replies

@BillRM,

Quote:

Special relativity treats accelerating frames differently from inertial frames, but can still deal with accelerating frames.

This is somewhat misleading. Strictly speaking "special relativity" does not "deal with" accelerating frames. In such cases physicists simply abandon SR and adopt the LR approach. Unlike SR, LR can and does make accurate predictions with respect to accelerating bodies.

Why do I say they're using LR? Well, I'm not even the one saying it, he is. He says:

Quote:

Note that the speed of light is rarely a constant in non-inertial frames, and this has been known to cause confusion.

In other words, the second postulate of SR gets dropped. Put simply: inertial and accelerating observers don't reciprocally see the other's clock slowing down. Both see only the accelerating clock (the moving clock) as slowing down and both see the inertial clock as going faster (staying constant).

The same is true in LR, except there it's not ONLY in accelerating frames. It's all frames, including inertial ones.

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@BillRM,

Quote:

In special relativity accelerating frames are different to inertial frames. Velocities are relative but acceleration is treated as absolute.

Yes, this is another serious problem with the article Oris initially inquired about. I've already said it several times, but without elaboration.

Even "in SR," accelerating motion is ABSOLUTE motion, not "relative motion." This means that the accelerating object will be seen as accelerating in ALL frames of reference, including its own.

The article completely ignores this fact. The proposition is that it is continuously accelerating for a period of "23" years (which it wouldn't be, even in the ship's frame of reference). And, the presumption is that, even though it would reach light speed in less than a year, it will NEVER exceed the speed of light even though it supposedly "just keeps on accelerating." This claim is made with the erroneous assumption that even the "frame of reference" of an accelerating object should be considered to be motionless.

There are other serious problems with the conclusions stated in the article, which have already been addressed. This is simply one more reason that it shouldn't even be claimed that SR allows a spaceship to go 14 billion light years in just 23 years WITHOUT ever exceeding the speed of light.

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@BillRM,

Quote:

It the clock that had undergone a period of acceleration that is moving.

If I'm reading you right, yeah, I agree. It is then going faster than any non-accelerating object that it has left behind.

Unfortunately (for SR), SR refuses to treat it that way, at least not once it stops accelerating and starts "coasting" by virtue of inertia.

1 Reply

@layman,

In order to "explain" the dubious concept of the "relativity of simultaneity" Einstein had to resort to the device of having a passenger on a moving train (Al himself said it was moving) deny that he was moving.

What idiot would ever really think that, I ask ya?

1 Reply

@layman,

Suppose I hop on my motorcycle and get to cruising across town. I'm passing condemned buildings, trash cans on the sidewalk, whores on the street corners, stop signs which I ignore, and alla that there, ya know? Then I get to thinking I'm actually moving.

WRONG, says SR. I aint goin nowhere. All them things is passing me. They're the ones who took to moving, not me. I best get my head straight if I ever expect to understand SR. For some damn reason, God only knows why, I still aint quite getting it.

So, then, next day, while ridin the train, I asked that train conducter: "Does the town of Podunk stop here?" He said: "What?"

He aint no college boy, I could tell that from jump street.

1 Reply

@layman,

Question was not your cycle at one point at rest with the buildings etc before you used you engine to accelerated your motorcycle?

Your frame of reference of the motorcycle was an accelerating one it would seems just as the clock on a spaceship.

2 Replies

@BillRM,

Quote:

Question was not your cycle at one point at rest with the buildings etc before you used you engine to accelerated your motorcycle? Your frame of reference of the motorcycle was an accelerating one it would seems just as the clock on a spaceship.

Yeah, Bill, I agree, it would be.

But SR tells me that, once I get to cruising, I aint movin no more. Once I'm travelling inertially, I am at absolute rest. I am the ether. Anything in the universe that moves relative to me is moving. Anything that aint, aint.

That's how it is with the clock on the spaceship. Hence the so-called "twin paradox," ya know? Them ignorant buildings think THEY aint movin.

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@BillRM,

Bertrand Russell once said:

Quote:

Special Relativity is the Lorentz transformation.

He was largely (but not completely) right. But it is for this reason, I think, that many people think that applications of LR are instead SR at work. Both rely on the Lorentz transformation, but relatively few people are aware of the existence, let alone the efficacy, of LR as an alternate theory of relative motion.

The twin paradox is not unique is this regard. Ironically, many claim that the resolution to the twin paradox "proves" SR when it in fact basically refutes it. The same is true of the Hafele-Keating (clocks on airplanes) type of experiment. SR is incapable of explaining the actual clock differences found by experiment, so LR is used. Then it's advocates claim that SR has been proven by the experiments. The same is true of the practical application of the global positioning system.

These DO show that the Lorentz Transformation is accurate. But they don't "prove" SR.

1 Reply

@layman,

Layman wrote:

The twin paradox is not unique is this regard. Ironically, many claim that the resolution to the twin paradox "proves" SR when it in fact basically refutes it. The same is true of the Hafele-Keating (clocks on airplanes) type of experiment. SR is incapable of explaining the actual clock differences found by experiment, so LR is used. Then it's advocates claim that SR has been proven by the experiments.

Reality wrote:

The Hafele–Keating experiment was a test of the theory of relativity. In October 1971, Joseph C. Hafele, a physicist, and Richard E. Keating, an astronomer, took four cesium-beam atomic clocks aboard commercial airliners. They flew twice around the world, first eastward, then westward, and compared the clocks against others that remained at the United States Naval Observatory. When reunited, the three sets of clocks were found to disagree with one another, and their differences were consistent with the predictions of special and general relativity.

https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

1 Reply

@maxdancona,

The guy is making the very mistake I just mentioned. He is calling the Lorentz transforms "special relativity." Wrong, in this case. This experiment confirmed the validity of the LT (which he is erroneously calling "special relativity") but NOT SR itself.

You call a wiki article writer's mischaracterization "reality!?"

Why don't you try reading the original paper?
Why don't you try thinking for yourself?
Tell ya what, why not trying to read the whole wiki article, instead of just the erroneous conclusions spoonfed to you by someone who wrote a wiki page?

Here, Max, I'll help you get started. From that very wiki article itself:

Quote:

Considering the Hafele–Keating experiment in a frame of reference at rest with respect to the center of the earth, a clock aboard the plane moving eastward, in the direction of the Earth's rotation, had a greater velocity (resulting in a relative time loss) than one that remained on the ground, while a clock aboard the plane moving westward, against the Earth's rotation, had a lower velocity than one on the ground.

That is NOT what SR predicts. It does not predict that motion in two different directions will produce difference clock rates in vehicles going away from the starting point at the same speed.

That's why they had to use a PREFERRED frame of reference, in wiki's words " a frame of reference at rest with respect to the center of the earth," i.e., the ECI frame, was used. Only that "correct" frame of reference correctly "predicted" the actual time differences.

It should be clear to you, if you understand SR at all, that this is NOT using SR. Using a preferred frame is what LR does, not SR.

Thanks for helping me make my point about people confusing SR with the LT, and calling the application of LR the application of SR. Many people don't know the difference. Do YOU?

3 Replies

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

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