Imagine the sun, moving along the time axis of spacetime.

Now imagine a tennis ball, moving along the same path, but a year
behind.

What, if anything, might happen to the tennis ball.

Answers that do not discuss entropy will not be marked.

Barry

"Barry" wrote in message
ps.com...
| Imagine the sun, moving along the time axis of spacetime.

A spinning bullet is a helix in spacetime. Nothing *moves* in spacetime.
The bullet (or the sun) exists everywhen.

| Now imagine a tennis ball, moving along the same path, but a year
| behind.

You cannot do that in spacetime. The coordinates of the
sun are (x,y,z,t), the coordinates of the tennis ball are (x,y,z, t+1)
and the ball is at the same place at a different time.
Two aircraft can be at the same latitude and longitude but
do not collide at the same time if they have different altitude.
Also they can be at the same place at a different time.


| What, if anything, might happen to the tennis ball.

Nothing.


| Answers that do not discuss entropy will not be marked.

Entropy is irrelevant.


'Really, this is what is meant by the Fourth Dimension, though some people
who talk about the Fourth Dimension do not know they mean it. It is only
another way of looking at Time. There is no difference between Time and any
of the three dimensions of Space except that our consciousness moves along
with it.' -- Herbert George Wells - "The Time Machine" - 1895.

"The secret to creativity is knowing how to hide your sources." --Einstein

Androcles

Barry wrote:
Imagine the sun, moving along the time axis of spacetime.

So, are we to conclude that it's at rest in space? Where is it in
space?

Now imagine a tennis ball, moving along the same path, but a year
behind.

Again, is it at rest in space? Where is it in space?

What, if anything, might happen to the tennis ball.

Depends on the relative positions of the sun and the ball.

Answers that do not discuss entropy will not be marked.

And just how does entropy figure into this?

"Igor" wrote in message
oups.com...
|
| Barry wrote:
| Imagine the sun, moving along the time axis of spacetime.
|
| So, are we to conclude that it's at rest in space?

He said "spacetime", ****head.

Barry a écrit :
Imagine the sun, moving along the time axis of spacetime.

Let's choose the sun's frame, placing it at the origin.

The trajectory of the sun is therefore the set of the
events (0,0,0,t) [meaning, "at time t the sun is at coordinates
(0,0,0)"]

Now imagine a tennis ball, moving along the same path, but a year
behind.

Is the ball comoving with the sun ? What "a year behind" means since
you didn't provide any external reference ? Aren't you assuming some
kind of absolute space here ?

BTW, whatever, if one consider the ball comoving with the sun, being
at any time at distance d from the sun on the z axis, one could always
make the first reference frame so that its trajectory is the set of
events (0,0,-d,t).

What, if anything, might happen to the tennis ball.

What do you mean by "happen" ? That something you assumed before is
in fact untrue ?

Answers that do not discuss entropy will not be marked.

Is it some kind of joke ?

Spacetime is a set of EVENTS. Spacetime is not a "container" in which
objects "move". Restate your question in terms of EVENTS.



Barry wrote:
Imagine the sun, moving along the time axis of spacetime.

Now imagine a tennis ball, moving along the same path, but a year
behind.

What, if anything, might happen to the tennis ball.

Answers that do not discuss entropy will not be marked.

Barry