New and improved.

How does science work? And what's all this about quantum mechanics?

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uwot
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New and improved.

Post by uwot » Thu Mar 16, 2017 5:52 pm

I am currently overhauling my blog/proto book. If you thought it was a bit rubbish, I have to say you have a point. Thanks to those too polite to say so, but thanks especially to those that did. I have taken the criticisms into account and have tried to incorporate them into the the new edit. It's a work in progress, naturally, but the development can be assessed by looking at '1. Where did the universe come from?' in the usual place: http://willijbouwman.blogspot.co.uk Feel free to tell me exactly what you think, and have no fear that I will be offended.

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Noax
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Re: New and improved.

Post by Noax » Thu Mar 16, 2017 11:15 pm

uwot wrote:I am currently overhauling my blog/proto book. If you thought it was a bit rubbish, I have to say you have a point. Thanks to those too polite to say so, but thanks especially to those that did. I have taken the criticisms into account and have tried to incorporate them into the the new edit. It's a work in progress, naturally, but the development can be assessed by looking at '1. Where did the universe come from?' in the usual place: http://willijbouwman.blogspot.co.uk Feel free to tell me exactly what you think, and have no fear that I will be offended.
OK, My complaint still stands: The symmetry of the situation is not expressed in the blog post, and that is only going to mislead. Stickwoman should also be bouncing a ball which appears to take a longer path from Einstein's POV, and her mental processes are also slowed from his POV. Time is not objectively going faster or slower for either person compared to the other since there is no such thing as objective velocity, and that fact needs to be expressed to ground a foundation for the understanding of relativity.

In the first panels, from stickman's POV, the train is stationary and the world is whizzing past at 100kmph, and the fast-travelling clocks and brains on the world outside run slower than the ones on the stationary train.

Things only get complicated when you pan back from the local view (as you do in the illustration) because outside the local environment, neither the train nor the world outside the train actually travel in a straight line, and special relativity is all about the special case of things not accelerating.

Kindly tell me to piss off if my comment are not welcome.

uwot
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Re: New and improved.

Post by uwot » Fri Mar 17, 2017 8:20 am

Noax wrote:Things only get complicated when you pan back from the local view (as you do in the illustration) because outside the local environment, neither the train nor the world outside the train actually travel in a straight line, and special relativity is all about the special case of things not accelerating.
You are quite right to say that referencing special relativity is misleading, it is after all premised on a Euclidean worldview, which Einstein himself consigned to the dustbin with general relativity. It is an idealised, Platonic almost, treatment of premises that do not obtain in the real world. But what I am trying to do is give the non-physicist an overview of what actually happens, and I think the thing that people most associate with special relativity is time dilation. If you take special relativity literally, then the different observers can watching each others atomic clocks ticking, agree that they have ticked the same number of times and when they compare them, agree that they tell different times. No one has successfully explained that anomaly by adhering to special relativity. Most attempts, in my view, involve sleight of hand manoeuvres in which the observers are somehow distracted by an acceleration.
The point I am making, I suppose, is that atomic clocks do not count time, they count vibrations (to put it crudely) of caesium atoms, and the reason the clocks were different in Hafele-Keating, is not that they magically compensated for the same number of ticks, as a literal interpretation of SR would compel you to believe, but rather that they simply counted a different number of ticks. But then, as you point out, H-K was not an exercise in SR, it also measured gravitational dilation and it wasn't conducted in the idealised conditions that exist nowhere in the universe.
Noax wrote:Kindly tell me to piss off if my comment are not welcome.
On the contrary, it is salutary to be reminded to keep the reasoning tight. Thank you.

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Noax
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Re: New and improved.

Post by Noax » Fri Mar 17, 2017 1:11 pm

uwot wrote:You are quite right to say that referencing special relativity is misleading, it is after all premised on a Euclidean worldview, which Einstein himself consigned to the dustbin with general relativity. It is an idealised, Platonic almost, treatment of premises that do not obtain in the real world.
I merely think of SR as part of the story, not the general case. Einstein wanted to publish his work and handn't yet worked out all the math for the general case. Regular acceleration was there, but gravity made it more complex.
But what I am trying to do is give the non-physicist an overview of what actually happens, and I think the thing that people most associate with special relativity is time dilation. If you take special relativity literally, then the different observers can watching each others atomic clocks ticking, agree that they have ticked the same number of times and when they compare them, agree that they tell different times. No one has successfully explained that anomaly by adhering to special relativity.
Well that's because nobody can compare times under SR. I have two clocks that were synchronized, and they move relative to each other. Each clock runs slower in the frame of the other. Which is actually slower? SR gives no answer since it gives no way to compare the two clocks. SR has the ambiguity of simultaneity which means it is impossible to determine the current time 'over there' where the other clock is.
Most attempts, in my view, involve sleight of hand manoeuvres in which the observers are somehow distracted by an acceleration.
The point I am making, I suppose, is that atomic clocks do not count time, they count vibrations (to put it crudely) of caesium atoms, and the reason the clocks were different in Hafele-Keating, is not that they magically compensated for the same number of ticks, as a literal interpretation of SR would compel you to believe, but rather that they simply counted a different number of ticks.
Physics does not say this. It says clocks measure actual time, that is, temporal distance between two events, and what happens in the H-K experiment is not sleight of hand. Time is just another dimension and the clock is another form of tape measure, and like the tape, it gives accurate results only if pulled straight between the two points being measured.
If you're going to post a different interpretation in your blog (that clocks do not accurately measure time), then don't title this an explanation of relativity. Without the clocks, how does one distinguish (measure) 'actual' time? If you can't measure it, perhaps what you thing of as time doesn't really exist.
Einstein's clock cannot be the slow one since in his frame, stickwoman's clock is the slower one, except you don't give her a clock, which was my protest. If one of the clocks is actually slower than the other, then this symmetry would not exist. In physics, moving clocks don't run slower, they just measure a shorter temporal distance.
But then, as you point out, H-K was not an exercise in SR, it also measured gravitational dilation and it wasn't conducted in the idealised conditions that exist nowhere in the universe.
That experiment didn't need idealized conditions unless it wanted results accurate to a few more digits. It was a successful demonstration of clocks measuring from point A to B via different paths, and the most straight path (on the westbound aircraft) measured the longest time as predicted. The experiment illustrated GR, not SR, because SR does not cover acceleration, and there is no way to compare clocks without acceleration.

If you think not in terms 3D space that perdures, but rather 4D spacetime with arbitrary assignment of the four axes (X, Y, Z, and time), then relativity is actually quite simple, and the twins un-paradox is actually easy to visualize. For visualization purposes, most concepts can be reduced to only two dimensions, one spatial and the other temporal. But two orthogonal axes can still be arbitrarily oriented, which is what SR is describing. I've never found a better way of illustrating the twins aging that that. Any two points in spacetime are separated in one of three ways: By pure space, in which case there is exactly one distance between them and no temporal distance, by pure time, in which case there is exactly one temporal distance between the two and no spatial displacement, or right on the boundary in which case both measurements are meaningless, but their vectors are not.

uwot
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Re: New and improved.

Post by uwot » Fri Mar 17, 2017 4:55 pm

Noax wrote:I merely think of SR as part of the story, not the general case. Einstein wanted to publish his work and handn't yet worked out all the math for the general case.
To be honest, Einstein hadn't even worked out the maths for special relativity in 1905, that was developed by Poincaré and Minkowski.
Noax wrote:...nobody can compare times under SR.
Of course not. The conditions don't exist.
Noax wrote:Physics does not say this. It says clocks measure actual time...
It depends on the physics you are doing, but the most general definition of 'time' is 'the stuff that clocks measure'. They do this by counting events. For all I know, there is some objective (I won't say 'absolute') time, but if there is, we currently have no means of recording it.
Noax wrote:Time is just another dimension and the clock is another form of tape measure, and like the tape, it gives accurate results only if pulled straight between the two points being measured.
Well yes, that is pretty much the Euclidean Minkowski interpretation.
Noax wrote:If you're going to post a different interpretation in your blog (that clocks do not accurately measure time), then don't title this an explanation of relativity.
That is a fair point. It will definitely raise some hackles.
Noax wrote:Without the clocks, how does one distinguish (measure) 'actual' time? If you can't measure it, perhaps what you thing of as time doesn't really exist.
I have no idea what time is, other than a sequence of events. Which is what clocks count.
Noax wrote:In physics, moving clocks don't run slower, they just measure a shorter temporal distance.
Again: depends on the physics.
Noax wrote:[H-K] was a successful demonstration of clocks measuring from point A to B via different paths, and the most straight path (on the westbound aircraft) measured the longest time as predicted. The experiment illustrated GR, not SR, because SR does not cover acceleration, and there is no way to compare clocks without acceleration.
Hafele-Keating accounted for both kinematic and gravitational dilation. You are quite right that it is misleading to ascribe kinematic dilation to special relativity, but time dilation due to motion is generally accepted by physicists.
Noax wrote:If you think not in terms 3D space that perdures, but rather 4D spacetime with arbitrary assignment of the four axes (X, Y, Z, and time), then relativity is actually quite simple, and the twins un-paradox is actually easy to visualize. For visualization purposes, most concepts can be reduced to only two dimensions, one spatial and the other temporal. But two orthogonal axes can still be arbitrarily oriented, which is what SR is describing. I've never found a better way of illustrating the twins aging that that.
I'm not suggesting there is one for people with the inclination to study physics, but they are not my intended audience.

uwot
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Re: New and improved.

Post by uwot » Fri Mar 17, 2017 5:12 pm

Come to think of it, Hafele-Keating was primarily a test of kinematic (I may never say special relativity again) dilation, because the two jets were flying at a comparable altitude, so although general relativity was an issue when comparing with the ground based clock, it had negligible influence on the comparison of the clocks that actually went round the world.

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