# Naked Science Forum

## Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scherado on 17/10/2017 21:29:20

Title: What does "time-like" mean in the following sentence?
Post by: scherado on 17/10/2017 21:29:20
First point is that the term is an English translation of the original. From the Publisher's Note, page viii:

`...--The papers were originally published by the Querido Verlag in Amsterda. In fairness to Professor Einstein, his American publishers would like to make it clear that although they have his full authorization to translate the German text as published in Holland, and although the documents from which the original publication was made have his authentication, there has been no further collaboration by him....`

The subject term is at the end of the passage quoted below.

From page 82 Essays in Science, essay Notes On The Origin Of The General Theory Of Relativity, by Albert Einstein, published 1934:

`--A material point, which is acted on by no force, will be represented in four-dimensional space by a straight line, that is to say by a line that is as short as possible or more correctly, an extreme line. This concept presupposes that of the length of a linear element, that is to say, a metric. In the special theory of relativity, as Minkowski had shown, this metric was a quasi-Euclidean one, i.e., the square of the "length" ds of the linear element was a definite quadratic function of the differentials of the co-ordinates.     If other co-ordinates arrew introduced by means of a non-linear transformation, ds² remains a homogeneous function of the differentials of the co-ordinates, but the co-efficients of this function (guv) cease to be constant and become certain functions of the co-ordinates. In mathematical terms this means that physical (four-dimensional) space has a Riemannian metric. The time-like extremal lines of this metric furnish the law of motion of a material point which is acted on by no force apart from the forces of gravity.`

What is the meaning of "time-like?"
Title: Re: What does "time-like" mean in the following sentence?
Post by: Colin2B on 18/10/2017 08:46:25
It has to do with the spacetime interval. If two events are timelike separated, then it is possible to  travel from the first event to the second event with a velocity v<c. In a spacetime diagram, future timelike events will always be within the upper portion of the diagram and within the light one.

Edit: Whoops, just noticed predictive text says light one, which should be light cone!
Title: Re: What does "time-like" mean in the following sentence?
Post by: jeffreyH on 18/10/2017 17:39:13
There is a related point to consider. The problem of time. This is the distinction between how QM and GR see time. This is absolute for QM and relative for GR.
https://en.m.wikipedia.org/wiki/Problem_of_time
Title: Re: What does "time-like" mean in the following sentence?
Post by: jeffreyH on 18/10/2017 18:00:47
The solution to this dilemma could lie in relativistic quantum mechanics. This could be via either the Schrodinger or Heisenberg picture of quantum mechanics.
https://en.m.wikipedia.org/wiki/Relativistic_quantum_mechanics
Title: Re: What does "time-like" mean in the following sentence?
Post by: yor_on on 27/10/2017 21:08:53
By Neutrino
"
If two events are time-like separated, then an object can travel from the first event to the second event with a velocity v<c.

Events separated by a time-like interval are always arranged in the same order in time. That is, if an observer O deduces that event A happens before B, then another observer O', moving relative to O, will also come to the same conclusion. There is a before and after. And there is a possibility that that event A will influence event B. (Cause and Effect.)

In a space-like interval, an object can be present at both events only if it travels at a velocity v>c. Since no object with mass can travel at such a speed, the two events are not causally connected. Also, there is no particular order between A and B(in time) if they are space-like separated.

On a spacetime diagram, for time-like events A and B, B will be within the light-cone of A and vice-versa. For space-like intervals, one event is outside the light-cone of the other.  "

And light propagate at 'c', which is a definition made by a ruler and a clock
Title: Re: What does "time-like" mean in the following sentence?
Post by: scherado on 02/01/2018 19:32:57
In a space-like interval, an object can...
.
Keeping with the theme introduced by, uh, was it "Global Moderator?", yes, I believe it was: "space-like" seems combative in a thread that was created to resolve the term that appeared in one of legendary Albert Einstein's essays, "time-like"; that is, the English translation of the term, "time-like".
Title: Re: What does "time-like" mean in the following sentence?
Post by: jeffreyH on 02/01/2018 20:21:35
Or you could just try having a conversation.

P.S. What I said in the other thread was confrontational and not combative. You have modified it so that you look like the victim. If you need to vent that much against others then I think you need to talk to someone about your situation. Being under constant stress is never good either physically or emotionally.
Title: Re: What does "time-like" mean in the following sentence?
Post by: Colin2B on 02/01/2018 22:36:51
I thought @yor_on was right to introduce space-like. I didnt mention it in my reply, but it is helpful to anyone trying to understand the spacetime interval regions.
Light-like is also worth following up.
Title: Re: What does "time-like" mean in the following sentence?t thought that comes to
Post by: opportunity on 30/01/2018 12:12:42
First thought that comes to mind with "time-like"........"does that equate with quantum entanglement"? Is that what Schrödinger picked up on? Well, he capitalised on the use of words.

At a glance then, it means the statement has already been taken advantage of.
Title: Re: What does "time-like" mean in the following sentence?
Post by: Colin2B on 31/01/2018 14:32:41
First thought that comes to mind with "time-like"........"does that equate with quantum entanglement"? Is that what Schrödinger picked up on?
No, the meaning is as in earlier reply https://www.thenakedscientists.com/forum/index.php?topic=71638.msg525642#msg525642
Title: Re: What does "time-like" mean in the following sentence?
Post by: opportunity on 31/01/2018 17:43:21
No problem. I was thinking maybe Einstein was trying to carry the idea of the same time frame of reference, and so maybe Schrödinger tried to address that.
Title: Re: What does "time-like" mean in the following sentence?
Post by: jeffreyH on 31/01/2018 19:36:32
Here https://www.quora.com/How-do-you-explain-quantum-entanglement-to-someone-in-laymans-terms you will find discussion of entanglement with different coloured objects in two identical boxes. You open one you know the contents of the other. Well, no. If you put a red ball on in one box and a green ball in another and your friend takes the red one he is equally likely to find it contains the green ball when opened. Think flavour change with quarks. It is that strange. Hence Schrödinger's cat.
Title: Re: What does "time-like" mean in the following sentence?know if IFind how that
Post by: opportunity on 01/02/2018 08:41:27
I couldn't agree more. I was though looking at what Einstein remarked about "time-like", and how debate back then, at that time, regarding his theory, and so on, took a direction among others, based on the wording of his works, for a further "need to address" the "time-like" statement. I'm not sure if the point I'm making is a relevant one as others could see it, its just an observation. I was thinking of just adding an observational angle.

I know if I had a theory and it used terms that weren't rock solid, I would expect others, peers, to jump all over it with advances of their own; I'm sure the same happened to Einstein with his comment about "time-like".

Einstein ultimately labels his critics ideas as "spooky" (spooky action at a distance). If there is anything that needs to have theory to it, today, its quantum entanglement, violations of "c". Find how that works, that "immediacy", despite the distance of space, and I'm sure a theory of everything is forthcoming.
Title: Re: What does "time-like" mean in the following sentence?
Post by: Colin2B on 01/02/2018 09:48:38
@opportunity . “I would expect others, peers, to jump all over it with advances of their own;”

With ‘time-like’ this was developed by Minkowski in his spacetime maths, but the meaning remained the same as far as i can see, and is now a solid part of GR.

Quantum entanglement was born from the EPR paradox and is part of QM not GR.

I think time-like will remain as it is because of it’s inherent utility, but it’s relationship - and that of light like and space like - with entanglement and QM is sure to attract debate.
Title: [quote author=Colin2B lRe: What does "time-like" mean in the following sentence?
Post by: scherado on 08/02/2018 22:23:09
With ‘time-like’ this was developed by Minkowski in his spacetime maths, but the meaning remained the same as far as i can see, and is now a solid part of GR.
developed by Minkowski?

I give a quote by the Big Cheese Himself, Albert Einstein, published, 1934, and Uttered some time previous to the publication. We all can agree on that point. No? YES.

What did Einstein mean by "time-like"? The question is asked outside the mathematical realm.

The purpose of this thread is clear.
Title: Re: What does "time-like" mean in the following sentence?
Post by: Colin2B on 09/02/2018 10:28:21
developed by Minkowski?

I give a quote by the Big Cheese Himself, Albert Einstein, published, 1934,

Yes, Minkowski.
Why else do you think Big Cheese mentions him in the quote you gave in the op? The 2 of them were in full agreement on the meaning of time-like, which is also the meaning i gave in my reply #1.

What did Einstein mean by "time-like"? The question is asked outside the mathematical realm.
LOL, that’s like asking what Pythagoras Theorem means outside the mathematical realm, they are inseparable. Spacetime interval is just Pythagoras in 4d.

Reread my reply #1 and ask questions if you dont understand it.