Is time a constant?

Originally posted by twhitehead
I didn't realize that. Surely if in one inertial frame of reference, a proton exists at x,y,z,t then it exists in every other inertial frame of reference at some x1,y1,z1,t1? In fact, surely it exists in every frame of reference, inertial or not? If so, how would I refer to it mathematically? How would I then refer to another point in space time?

Bu s it understandable? Is there a better way to express it? Does it violate relativity?

How would I then refer to another point in space time?

If you want to know at what point in spacetime x,y,z,t something in intertial frame A is in some different intertial frame B, you apply a Lorentz transformation.

As for your second paragraph, I don't understand where "universal now" comes in. It is true that those light cones (i.e. the set of timelike intervals) are unique for every frame of reference.

If the frames of reference are not intertial things become pretty complicated and I haven't studied this math, so I can't really comment on what happens exactly.

Originally posted by KazetNagorra
[b]How would I then refer to another point in space time?

If you want to know at what point in spacetime x,y,z,t something in intertial frame A is in some different intertial frame B, you apply a Lorentz transformation.

As for your second paragraph, I don't understand where "universal now" comes in. It is true that those light cones (i.e. the ...[text shortened]... licated and I haven't studied this math, so I can't really comment on what happens exactly.[/b]

If there is a "universal now" and it is a common point among all points of
reference does this change anything in how we view things?
Kelly

Originally posted by KellyJay
If there is a "universal now" and it is a common point among all points of
reference does this change anything in how we view things?
Kelly

I think everyone should read the latest Scientific American article about time. It posits time may be an illusion. It makes a metric of the way we view time now, as a box where time slices go from left to right or Vice-versa as in the frames of a movie. His new idea is to slice the box not into vertical slices like we would view each frame of a movie but to slice left to right horizontally, giving new definitions to causality and such. I am not competent to give the whole article here. Maybe I can find a link.

Here is a link but it does not give the whole article, just an overview:
http://www.scientificamerican.com/article.cfm?id=is-time-an-illusion

The piece in the print magazine is titled 'Is time an illusion?'

Has anyone here besides me read this one?
Would like opinions about it.

The issue in question is the June 2010 issue of Scientific American.

Originally posted by sonhouse
I think everyone should read the latest Scientific American article about time. It posits time may be an illusion. It makes a metric of the way we view time now, as a box where time slices go from left to right or Vice-versa as in the frames of a movie. His new idea is to slice the box not into vertical slices like we would view each frame of a movie but to ...[text shortened]... ike opinions about it.

The issue in question is the June 2010 issue of Scientific American.

Read it, and it does make me think this topic is more complex than some
here have let on. 🙂
Kelly

Originally posted by KazetNagorra
If you want to know at what point in spacetime x,y,z,t something in intertial frame A is in some different intertial frame B, you apply a Lorentz transformation.

Lets say we are talking about a single inertial frame.

Would my rules make any sense?

As for your second paragraph, I don't understand where "universal now" comes in. It is true that those light cones (i.e. the set of timelike intervals) are unique for every frame of reference.
I said it wrong. I intended to say that one point should not be inside another points light cone - not that both points are not in the same light cone.
I disagree that light cones are unique for different frames of reference. If light leaves the sun and hits the earth, it does so whatever the frame of reference. The earth enters the suns light cone regardless of the frame of reference. Time and space may be measured differently in the various frames of reference, but the physical lines of intersection of various light cones does not vary.

I would like to know from someone who understands relativity better than I , given an inertial frame of reference, whether for any given point in space time, there exists a set of points that cover all of space such that none of the points are contained in another points light cone.

Originally posted by sonhouse
Here is a link but it does not give the whole article,

From the summary, it is nothing new. I have several times said similar things in this forum - partly based on ideas from past Scientific Americans.
We distinguish past from future, not because the past is unchangeable and the future is flexible, but because it appears that way to us due to The Second Law.
Essentially the past is more predictable - but not entirely so. The most interesting parts of Quantum mechanics is all about the fact that the past is not actually fully predictable and thus all possible pasts must be taken into account.
The future is only different in that the number of possible futures is greatly increased thus leading to a dramatic reduction in our ability to predict it - essentially giving the illusion that it 'has not happened'.

Originally posted by twhitehead
From the summary, it is nothing new. I have several times said similar things in this forum - partly based on ideas from past Scientific Americans.
We distinguish past from future, not because the past is unchangeable and the future is flexible, but because it appears that way to us due to The Second Law.
Essentially the past is more predictable - but n ...[text shortened]... ion in our ability to predict it - essentially giving the illusion that it 'has not happened'.

So you are saying like in the fairy tale, if Humpty Dumpty fell off a wall, and even if you had a high speed digital video of it you couldn't run time backwards and put it back together again?

Originally posted by twhitehead
The future is only different in that the number of possible futures is greatly increased thus leading to a dramatic reduction in our ability to predict it - essentially giving the illusion that it 'has not happened'.

Wow. That statement is awesome. It makes my brain slosh it's chemicals around!

Originally posted by sonhouse
So you are saying like in the fairy tale, if Humpty Dumpty fell off a wall, and even if you had a high speed digital video of it you couldn't run time backwards and put it back together again?

Yes. The implications of the two slit experiment are that there are several possible pasts - and that we have no way of knowing which one actually happened. In fact, we could say that the past has not happened, we can only attempt to predict it. We could even go further and claim all possible pasts have happened - but I won't go into that for now.

For a given starting condition - say five uniform balls in motion, if we were to use physics to work out the possible pasts and futures over a 10 minute period either side of the starting time we would find that there are say 10 possible pasts and 1000000 possible futures. This is a direct result of the Second Law of thermodynamics. The illusion of time is created by the fact of the very few possible pasts. We might even be able to say for certain an approximate region in which each ball resided in the past, but we will be far less accurate about the future. But what is important to note, is that neither past nor future is exactly predictable from initial conditions.

If you knew what would happen tomorrow with the same accuracy as you 'remember' yesterday, the illusion of time would disappear.