Relativity Discussion Thread

[Sam5]

Originally Posted by milli360

Good one, Sam5.

Thanks.

Hmm, there were different editions of both Optics and the Principia.

The Question 20 in the 1704 Edition is not the same as what that guys says is in the 1706 Edition.

I think the apparent discrepancy lies in the difference between the terms “medium” and “matter”.

The term “the fictitious matter” in the 1706 Edition suggests a physical substance such as a thin gas or vapour, and this is what Newton was objecting to in that Edition.

However, the term “the Aetherial Medium” referred to in the 1704 Edition is not made up of physical “matter”. This “Aetherial Medium” is generated by the physical matter of the astronomical bodies, and he is saying the “medium” fills the space in-between the bodies. That is, the “medium” is essentially the gravity “fields” of space, but at that time (1704) the term “field” had not yet been invented, so in its place Newton used the term "Atherial Medium”.

These two words, “medium” and “matter”, are very tricky when used in terms of the “ether”, and in some early science publications they seem to be used almost interchangeably, even though they are actually quite different.

[daver]

Originally Posted by SeanF

But as milli360 pointed out (at least, I think this was his point), you have to assume that there's no dilation perpendicular to the direction of travel in order to derive the equations that way, don't you?

The way he does it in the 1905 paper actually leads to the conclusion that there's no perpendicular dilation.

If I understand what you're getting at, you can get consistent equations by assuming either a spatial contraction perpendicular to the velocity vector or a time dilation. A thought experiment should be sufficicient to demonstrate that a space contraction doesn't make sense.

[Normandy6644]

Originally Posted by milli360

Yep, the method Normandy6644 is talking about, I think, is the same as the one Eroica brought up originally.

SeanF and I do a lot of thinking, because you never know, on the BABB.

I think it is, and yes you do have to make those assumptions. The reason it's still nice to look it is because you can derive the basic equation in a very simple manner. It won't hold up under intense scrutiny, but if someone ever randomly asks you to prove the time dilation equation on a napkin or something (happens all the time, I know), you can do it without too much trouble.

Also, Lorentz derived the transformations, but as has been said, he didn't know why they worked. Minkowski actually explained them the best, allowing Einstein to use his methods to formulate GR.

[Eroica]

This site has links to PDFs of most editions of Newton's works:

The Online Newton Project

Newton's Opticks

[oriel]

Banned poster content deleted

[Kaptain K]

... I expect to be banned from the forum...

Why? Is it because you dropped the "36" from your nickname when you rejoined and expect the BA to figure it out soon?

[Sam5]

Originally Posted by oriel

Mach: on Newton's Absolute Time

"This absolute time can be measured by comparison with no motion; it
has therefore neither a practical nor a scientific value; and no one
is justified in saying that he knows aught about it. It is an idle
metaphysical conception."
Mach, Analyse der Empfindungen, 6th ed.

Why do you suppose that Mach would compare “absolute time” to “no motion”, since no motion means “no time”? Absolute time is merely “steady motion”, where the gaps in between the motion-related events are all of the same duration, whether we measure time by a linear device, counting the increments in inches, or by means of the usual vibratory method, counting the number of vibrations with the duration in between each vibration cycle being exactly the same as the previous one.

There would be such a thing as "absolute time", if we could find something that moved in a straight line at a steady speed or vibrated or rotated steadily, forever, but apparently nothing in the universe does that.

One problem I see with Newton’s short description of “absolute time” is that it tends to suggest time as an independent entity that sort of “permeates” the universe. Whereas I see time is being strictly a local phenomenon, that transpires only where things move and vibrate. Since there are so many things that move and vibrate, all around us, and at fairly steady rates, this tends to give us the impression that “time itself” permeates the universe, but I say it doesn’t. I say it occurs only when and where things are moving. If we could stop things from moving in a small part of space, then all of “time” in that small part of space would stop.

Newton might have known this, but he just didn’t say it in any of his books, and he seemed to think of time as flowing even without motion, especially when he said:

“Absolute, true, and mathematical time, of itself, and from its own nature flows equably without regard to anything external, and by another name is called duration: relative, apparent, and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion, which is commonly used instead of true time; such as an hour, a day, a month, a year.”

But I disagree. I say motion causes time. Motion generates time. No motion, no time. Steady motion equals steady time. I see time as a product of motion and motion as a product of kinetic energy. Thus, in my view, time starts with energy, energy generates motion, and time is a numerical accumulation of motion-related events, a counting of the events in sequence, and it is localized to the thing that is moving or vibrating. Absolute time would be steady motion or vibration with the same duration in between the events. When motion stops, let’s say within a single mechanical clock, that particular time stops. However, all of time does not stop in the area around the clock, since many other things continue to move and vibrate. In fact, the atoms and molecules inside the clock continue to vibrate and oscillate. Only the time that was being generated by the turning of the hands and the gears stops in the clock. But the rest of time doesn’t stop.

About being banned, just try not to get into any serious personal fights and arguments, and I think everything will be ok.

Uhh, what is your overall point?

[oriel]

Banned poster content deleted

[Normandy6644]

Hey guys, keep in mind this thread is for discussing mainstream relativity as it now stands, not quibbles with the theory. If you want to start debating certain points of it, please go to the Against the Mainstream topic that Tensor started. Thanks.

[oriel]

Banned poster content deleted

[oriel]

Banned poster content deleted

[Kaptain K]

I apologise Sam5 for making a mess of the posting by putting the thing entirely in 'quote',I am new to that feature and unfortunately when posting I was required to resubmit my password.

There is an "edit" button in the top right corner of your post. Click on it and you can correct your errors.

[The Bad Astronomer]

What is it with some people who cannot stay away from here? Sheesh. I have deleted what he wrote, because it's a very bad idea to come back here after being banned and posting something.

[Sam5]

Originally Posted by oriel

Newton's Absolute Time

Uhh, nevermind.

[Celestial Mechanic]

Darn! I only saw one of He Who Will Not Name Einstein's posts in his new incarnation before the BA deleted them all! Of course, a leopard does not change his spots, so I imagine it was the same old same old about the Equation of Time, the sidereal rotation being a kludge, cosmic modelling, physics being a total wasteland after 1905, etc., etc.

[Kaptain K]

Nope. Just long rambling disertations about Newton. See some of Sam5's responses to HWSNNE for quotes.

[milli360]

Originally Posted by Sam5

This is generally based on Einstein’s deduction in 1911 that the “tick rates” of atomic clocks tend to follow the speed rate changes of light.

Sam5, I was browsing our high school library, and guess what was on the shelves?

Apparently, Einstein wrote up an article in 1912 On the Special Theory of Relativity, and was set to publish it when the first world war, or something, intervened. When they finally got around to it, he'd published his General Theory, and they decided to not publish the 1912 article. It was published in facsimile in 2000. The great thing about it is that he crossed off whole paragraphs throughout the article--but they are included in the new book. Check it out. There are some interesting comments about the speed of light, crossed out.

Here it is at Amazon.com. The editorial review and the customer review seem to assume that it is the original theory article. One of them mentions publication history--I'd have sworn that it said it hadn't been published before this. O well.

[Sam5]

Originally Posted by milli360

Check it out. There are some interesting comments about the speed of light, crossed out.

Here it is at Amazon.com. The editorial review and the customer review seem to assume that it is the original theory article. One of them mentions publication history--I'd have sworn that it said it hadn't been published before this. O well.

Thanks very much for the information. I’ll try to track down a copy of that book. Apparently Einstein did publish an article in the Annalen der Physik in 1912, modifying the original 1905 SR theory. This is what Max Abraham said in a paper of his that was published in 1912:

“Already before period of one year A. Einstein, by accepting an influence of the gravitation potential on the speed of light, gave up the postulate of the constant speed of light essential for his earlier theory 1); in a work appeared recently 2)......

1) A. Einstein, Ann. d. Phys. 35. p 898. 1911.
2) A. Einstein. Ann. d. Phys. 38. p. 355. u. 443. 1912.”

This type of stuff is what I’ve been investigating. Einstein made a major switch-over from the basic “relativity theory” (the 1905 SR theory), to the GR theory of 1916. This switch-over began in 1911 when he realized his 1905 theory contained errors and when he realized that the speed of light is variable and not “constant”. He actually started examining gravitation and accelerative effects as early as 1906-07, but he didn’t make a major breakthrough until his 1911 gravitational redshift theory.

Why don’t you post some quotes from that book?

[milli360]

Originally Posted by Sam5

Apparently Einstein did publish an article in the Annalen der Physik in 1912, modifying the original 1905 SR theory. This is what Max Abraham said in a paper of his that was published in 1912:

Yes, you've posted that before. That's why I thought you'd be interested. Einstein was on a quest almost from day one--he dallied in quantum mechanics, but returned to the general relativity pursuit.

This type of stuff is what I’ve been investigating. Einstein made a major switch-over from the basic “relativity theory” (the 1905 SR theory), to the GR theory of 1916.

Of course. No one denies that.

This switch-over began in 1911 when he realized his 1905 theory contained errors and when he realized that the speed of light is variable and not “constant”.

I disagree. There is a constant trend throughout his works, it appears to me. It's like going from learning to catch fish from the river, to learning to catch different fish from different parts of the river. It's unfair to characterize it as an error, when there is no evidence for that, other than supposition.

He actually started examining gravitation and accelerative effects as early as 1906-07, but he didn’t make a major breakthrough until his 1911 gravitational redshift theory.

I would say he started earlier than that. Too, he was influenced by the philosophy, and physics, of Mach.

Why don’t you post some quotes from that book?

I don't have it. It's a reference book, left in the library.

[Sam5]

Originally Posted by milli360

I disagree. There is a constant trend throughout his works, it appears to me. It's like going from learning to catch fish from the river, to learning to catch different fish from different parts of the river. It's unfair to characterize it as an error, when there is no evidence for that, other than supposition.

Yes, you are right about the "constant trend". I have Volume 2 of the “Collected Papers”, and I’m surprised by how many “atomic” papers he wrote. He was quite an expert on the inner workings of atoms, and in fact he was fairly well known in theoretical physics before he wrote the first 1905 relativity paper. Volume 2 contains some of his earliest attempts to add “acceleration” to his basic first relativity theory.

I think he did not include acceleration in the first theory because he imagined the “stationary system” to be the surface of the earth, as in the Michelson Morley experiment, and so he wanted to consider a steady relative speed and velocity before he began to inquire about the effects of acceleration. He made several interesting attempts in 1907 and ’09, but he kept getting some of the SR principles mixed up with some of the newly emerging GR principles. The two are not compatible. This is why he said in his 1911 paper:

”To avoid unnecessary complications, let us for the present disregard the theory of relativity, and regard both systems from the customary point of view of kinematics, and the movements occurring in them from that of ordinary mechanics.”

He had to actually start over by leaving out some of the incorrect principles of the 1905 paper. In the 1911 paper, he returned to some of the original relativity ideas that Lorentz had proposed in his 1895 book. By 1911 Einstein realized that “fields” and “acceleration” must be considered in a true relativity theory, and they can not be left out, as they were in his first 1905 relativity paper.

Based on what I’ve read, he actually started his “relativity” thinking as far back as his high school years, and that 1895 Lorentz book influenced him quite a lot. He apparently worked on his first relativity theory for years, long before he first published it in 1905. However, as he began to consider fields and acceleration more an more, he gradually began to realize the 1905 theory contained errors. He finally officially split the theories into two different versions, when, in 1916, he called the first theory, the one without fields and acceleration the “special” theory, and the ones in which he did consider fields and acceleration, he included them in his “general” theory.

So, the 1911 paper fits into the “general” theory, even though he was still calling all his relativity papers “the relativity theory” in 1911. But after 1916, the 1911 paper became classified under the General theory heading. That is why his statement about “the velocity of propagation of light varies with position” is included in the General relativity section of his 1916 book, and not with his earlier Special relativity secti