Time Explained

[Trolldor]

Christ, I feel like I'm in a room full of actors and one science major.

[Farsight]

Farsight..come back.. youre the time expert...Help us out with Barbours "Alpha points" ....

Sorry Mr Jobby. I'll move rationalia up my favourites list. What are those alpha points? I read Julian Barbour's The End of Time back in 2001 and found it very interesting. In 2006 I got into a spat about the speed of light, whereafter I thought time is the key and resolved to really look into it. So I read The End of Time again, plus Paul Davies' About Time along with other material, and then wrote the first version of Time Explained. I don't concur with Barbour's take I'm afraid, which is rather a block-universe timeless view. I take a more mundane view. We see space and motion through it. That's it.

There's some interesting stuff kicking around about supermassive black holes, such as they may even be involved in galaxy formation. However black hole spin is rather... interesting. Because they don't spin! But that's one for another day, or maybe another thread. Sorry I've got to go. I'll be back tomorrow. Again, apologies for being absent for a while.

[LaMont Cranston]

Farsight, I am not sure what the current thinking is about gravity. I was a math and science whiz as a kid, particularly chemistry, but I got interested in other things. When it comes to understanding things like time, gravity, dark matter, dark energy, black holes, string theory, etc., I consider myself to be an interested student and a seeker of information.

If you have a current take on gravity, I'd like to know more about that.

[ChildInAZoo]

Childin the Zoo...Dont go away.. do u understand Barbours alpha points ?

I'm sorry, but I am a little busy. I will have to take another look at Barbour before I comment on alpha points.

[colubridae]

It's really comforting to know that despite any furore, unreality rolls gently on....

[lpetrich]

Christ, I feel like I'm in a room full of actors and one science major.

Who might that science major be?

[lpetrich]

You get rather a different view of time as something that's an emergent property of motion through space.

However, motion is defined in terms of time - change of space-coordinate values as a function of time. When one wants to measure time, one measures it with some effect with a nonzero time derivative -- is such an effect automatically "motion"?

Furthermore, both Galilean and Lorentz boosts mix space and time coordinates.
A Galilean boost:
x' = x - v*t
t' = t
Newtonian mechanics is Galilean-invariant.
A Lorentz boost:
x' = (x - v*t)/sqrt(1 - v2/c2)
t' = (t - v*x/c2)/sqrt(1 - v2/c2)
Special relativity is Lorentz-invariant.

Lorentz invariance can be expressed by constructing a space-time vector X = (t,x1,x2,x3) and setting c = 1 for convenience. The space-time interval is
ds2 = dX . g . dX
where the metric g = diagonal matrix from (-1,1,1,1) or (1,-1,-1,-1), depending on one's signature convention.

The most general Lorentz transform may be expressed with 4-matrix R; it includes Lorentz boosts, rotations, and mixtures of them. It satisfies:
RT.g.R = R.g.RT = g
(transpose of R)
in analogy with rotations: RT.R = R.RT = I

A space-time point transforms as:
X' = R.X

Lorentz-invariance is a VERY successful paradigm, and Farsight cavalierly discards that.

This then makes you shift your position on special relativity from space-time to space-motion, and you get a different handle on Minkowski's wrench, relating the magnetic field to motion through an electric field so you can "see" the geometric disposition of the electron's electromagnetic field.

Pure hand-waving.

One can easily get that "result" by working out what a Lorentz-boosted electromagnetic field looks like - what is necessary to get Maxwell's equations from boosted coordinates.

Then you read On Physical Lines of Force and see Maxwell's vortices and realise he got it back to front -

Maxwell's vortices are a completely unsupported speculation.

they're not in the intervening space, they're what the particles are, and you bump in the Einstein-de Haas effect that demonstrates that spin angular momentum is the same as classical angular momentum.

How does it do so? Why would quantum-mechanical elementary-particle spin be incapable of causing the EdH effect?

[mistermack]

Can someone help me out here?
Two observers a and b, carrying super-accurate clocks, pass each other in empty space, well clear of gravity effects.
Their closing speed is 100,000 mph. Who's clock is going slower? Special relativity says you can regard a as stationary, and b as moving, or vice versa. The moving clock should go slower than the stationary clock.
So the clock of a should be going faster, and slower, that that of b?

I know it's wrong, but why? ( I've read the twin paradox stuff, I don't want to hear about stopping and returning, it just clouds the question ). I just want to know in the example I've mentioned, do the clocks actually run at different speeds, and if so, how, and why?
.

[ChildInAZoo]

Can someone help me out here?
Two observers a and b, carrying super-accurate clocks, pass each other in empty space, well clear of gravity effects.
Their closing speed is 100,000 mph. Who's clock is going slower? Special relativity says you can regard a as stationary, and b as moving, or vice versa. The moving clock should go slower than the stationary clock.
So the clock of a should be going faster, and slower, that that of b?

I know it's wrong, but why? ( I've read the twin paradox stuff, I don't want to hear about stopping and returning, it just clouds the question ). I just want to know in the example I've mentioned, do the clocks actually run at different speeds, and if so, how, and why?
.

The clocks runs at different speeds because they are in motion relative to each other, that's all. It's one of the physical laws of the universe that when we are considering the time that things happen for events or a series of events that are separated in space, we are limited in the relationships that we can assign to the times. One limitation is that we cannot assign to the two clocks you describe synchronized readings in every scenario. The big difference really is that when clocks are separated, they do not necessarily behave like we imagine they do when they are right nest to each other.

In special relativity, assuming that the clocks are the same kind of clock operating in the same way, we can describe the scenario as one clock being stationary and the other clock running slower or we can describe the scenario as the other clock being stationary and the first running slower. Or we can describe is as both clocks in motion and each slowed to a different extent. This all works out because in determining time-relations at distance, we also have to determine(effectively) what distances are and what we consider to be simultaneous to events. Different scenarios assign different lengths to different objects and assign different sets of simultaneous events.

In general relativity, we can cook up a scenario where the clocks are perfectly synchronized, but in so doing we are creating a new background in which to describe physical laws and we have to introduce all sorts of strange geometric effects to the background geometry in which one describes physics in order to account for the motion imparted into this background by tying it to two or more classes of clocks that are in motion relative to each other. GR allows one to do all sorts of crazy things with clocks, but at the cost of radically changing the way we write the equations of our physics. In this case, the GR scenario would build back in all the differences in measurement and temporal ordering that we get from the SR scenario by introducing what one might call a curved spacetime to distort physical interactions between the two clocks.

[ChildInAZoo]

This then makes you shift your position on special relativity from space-time to space-motion, and you get a different handle on Minkowski's wrench, relating the magnetic field to motion through an electric field so you can "see" the geometric disposition of the electron's electromagnetic field.

I have asked you in another thread to explain yourself on Minkowski's uses of "wrench" but you only dodged the question and then quit responding. Here you are using it again to support your point while you still have dodged the question about just what Minkowski actually means. He specifically claims that he uses "wrench" as an analogy and you have never said just exactly what it is in his work that is an analogy to wrench. MInkowski's paper is a mathematics paper (based in number theory*), so it may be that you simply do not have the mathematical knowledge to understand the paper. Regardless, you should not use Minkowski as a citation unless you can say exactly what Minkowski has written and why. So far, you have only picked out on claim of an analogy and not explained what Minkowski was doing with the analogy in his paper.

* For those interested, Minkowski was working on developing some sort of graph for use in number theory, but recognized that it had immediate application for special relativity. At least, as far as I can remember. The historical details are in Minkowski Spacetime: A Hundred Years Later in the paper "Hermann Minkowski: From Geometry of Numbers to Physical Geometry" by Yvon Gauthier.

[Farsight]

Can someone help me out here? Two observers a and b, carrying super-accurate clocks, pass each other in empty space, well clear of gravity effects. Their closing speed is 100,000 mph. Who's clock is going slower? Special relativity says you can regard a as stationary, and b as moving, or vice versa. The moving clock should go slower than the stationary clock. So the clock of a should be going faster, and slower, that that of b? I know it's wrong, but why? ( I've read the twin paradox stuff, I don't want to hear about stopping and returning, it just clouds the question ). I just want to know in the example I've mentioned, do the clocks actually run at different speeds, and if so, how, and why?

The answer to this is simpler than you might think. It's all to do with motion, and motion is relative.

What does a clock clock up? The answer isn't time, it's motion. It's motion that is local to the clock. And what do the observers have in relation to each other? The answer is motion, and you don't know whether a is doing the moving, or b is doing the moving. You only know that their motion is relative to each other. In similar vein the motion of their respective clocks is only relative to each other. So as far as a is concerned, b's clock is going slower than a's clock, and as far as b is concerned, a's clock is going slower than b's clock. There's no paradox here, that's how it is, because motion is relative, and clocks clock up motion.

Take a look at the Simple inference of time dilation due to relative velocity and say to yourself that a and b are using parallel-mirror light clocks. Imagine they've got lasers and misted chambers or something, and can see their own light beams. They each see their own light beams looking like this:



If they could see each other's light beams when they pass, they'd each see the other's light beams looking like this:



So they each claim that the other one's clock is running slower than their own. And they're both right, because their linear 100,000 mph motion is relative to each other, as is the local motion of their respective clocks. They cannot resolve their difference until they agree on which of them is "really moving". They can only settle their disagreement by agreeing on some common reference, such as the earth, or the CMBR. If they agree that a is really moving, then they can agree that a's clock is running slower, and that the rate of motion within his clock is reduced by his linear motion through the universe. it has to be, it's a light clock, and that beam of light travels at c whether it's following a path like this: || or a path like this: /\.

[Farsight]

Farsight, I am not sure what the current thinking is about gravity. I was a math and science whiz as a kid, particularly chemistry, but I got interested in other things. When it comes to understanding things like time, gravity, dark matter, dark energy, black holes, string theory, etc., I consider myself to be an interested student and a seeker of information. If you have a current take on gravity, I'd like to know more about that.

My pleasure, Lamont. One new thread coming up.

[Farsight]

However, motion is defined in terms of time...

This is an axiomatic assumption, and it's wrong. Look at the official definition of the second and the NIST fountain clock. We count 9,192,631,770 incoming microwave peaks and then we define a second. Time is defined using the motion of light. When the light moves slower, the second is bigger. You might try to say the motion of light is nothing to do with it, and point back to the hyperfine transition of the caesium atom. But the hyperfine transition is an electron spin-flip, the Einstein-de Haas effect, where a current rotates a coil, tells us "spin angular momentum is indeed of the same nature as the angular momentum of rotating bodies as conceived in classical mechanics". So that spin-flip is an electromagnetic movement. When the light moves slower, that moves slower too. Come on Loren, look to the evidence. I don't discard Lorentz Invariance. I explain it. We don't see time flowing. We don't see motion through time. We see space and motion through it. Time is just a cumulative measure of that motion, and that motion is through space.

[mistermack]

The clocks runs at different speeds because they are in motion relative to each other, that's all.

But do they? 'a's clock' can't both run faster AND slower than 'b's'.
If SR says that both clocks run faster AND slower at the same time, then SR is not giving us reality. It may WORK both ways, but that's not the same as reality.
I did ask if the clocks ACTUALLY run at different speeds.
SR is saying that there is no 'actually', only an infinite number of 'apparently's, all perfectly valid, depending on your choice of reference frame.
I want to know what ACTUALLY happens. And a clock can't ACTUALLY run faster AND slower than another at the same time.

I'm not saying SR is wrong, I'm saying it works perfectly, but it's not reality. Obviously, clocks are just there to measure time. So SR is really saying that time for 'a' can run slower AND faster than 'b', simultaneously.
I appreciate that we can never experience true simultaneousness, ( is that a word? ) but that doesn't mean it's not there, or that we should ignore it.
.

[mistermack]

Farsight, thanks for that. But I'm not sure the first half of what you said makes a difference, and I'll have to work on the second half.
Picture one of the clocks. If you say it's travelling at 100,000 mph, the 'light' inside the atoms is travelling laterally, so rotates less, showing slower apparent time?
If it's stationary, it rotates more. So the question remains, which ACTUALLY happened? SR is saying both are valid.
But are both circumstances REAL?
.