Dirk Van de moortel wrote:
"TomGee" wrote in message oups.com...
Worms doesn't know, that's why he sent you to a website. Spacetime is
a fictional place invented as a math construct so that we can calculate
the motion of objects through time.

According to Einsein, every object has a so-called "world line" which
indicates the object's past, current, and future position wrt its
motion through the universe.

This has nothing whatsoever to do with Einstein.


So you say.


A wordline is just a way of describing the path of an object by
giving its place as a function of time.


That's exactly what I said when I called it a math construct and not a
real place. Apparently you're having a problem with what is being
said.


Example:
{ x = 0
{ y = v0 cos(pi/3) t
{ z = v0 sin(pi/3) t - 1/2 g t^2
are the parametric equations of the wordline of a bullet, shot in the
y-direction with initial speed v0, tilted to an angle of 60 degrees
and where the acceleration due to gravity is given by g.

The start of the bullet at time t=0 is given has (x,y,z) = (0,0,0),
So in the coordinate system that we have chosen, this event in
spacetimes gets the coordinates (t,x,y,z) = (0,0,0,0).

This way the past, present and future of an idealized point-object
is described by its worldline.

The set of all possible events happening at all places and at all
possible times is called spacetime.
Since in this spacetime one needs 4 numbers to describe events,
we call it 4-dimensional.


And a set of anything is a math construct, is it not? Arithmetic, like
2+2=4. Not a real place, location, and not real, just a set of real
numbers. Does not exist adjacent nor parallel to nor out in the space
of our universe. It is a figment of the mind - a math construct.


None of this has anything to do with relativity or with Einstein.
This could be lesson 1 in every elementary physics course.


So what if it doesn't, even though that's your own opinion? Does that
make it any more real and existing somewhere other than in our minds or
as a graph or as a set of numbers?


AE invented a universe having the same exact dimensions which our own
universe contains, i.e., length, width, depth, and time. He did it to
show that he was not talking about our universe but an imaginary one.
His lemmings, however, insist he was talking about a real place and
they talk about it as if it exists. Go figure.

So, if you are so utterly ignorant about baby physics, what
do you think you are doing here?


Pot. Kettle. Black.