Originally posted by amolv06
Jaywill,
The idea is that objects travel along paths called world lines through space and time. Imagine a flat, two-dimensional piece of paper. Call it spacetime, with the vertical axis being time, and the horizontal axis being space. The natural path of an object (a path without any forces acting on that object) plotted on this graph is it's world line ...[text shortened]... ad an intimate relationship since special relativity, and general relativity extends this idea.
=============================
Jaywill,
The idea is that objects travel along paths called world lines through space and time. Imagine a flat, two-dimensional piece of paper. Call it spacetime, with the vertical axis being time, and the horizontal axis being space. The natural path of an object (a path without any forces acting on that object) plotted on this graph is it's world line.
==================================
I have seen diagrams like this for long time.
Now when you talk about traveling along world lines, does this have to do with Newton's idea that moving things should not stop moving unless some force forms resistence to their velocity?
I am trying to grasp if your leading up to an idea that everything is traveling (hence velocity).
===============================
This path would be a straight line whose slope would be the inverse of its velocity.
===============================
A straight line .... whose slope ... ?
Inverse of its velocity ?
I have seen the flexible graph picture for many years. It helps a tiny bit. But I guess I don't know enough about velocity or the mathematics it takes to demonstrate these concepts.
Don't be discouraged. I'm here and there trying to pick up more understanding. Maybe you could help by talking just a wee bit more about the inverse of velocity.
====================
Now, if instead, someone took the paper, and bent it, the world line would become curved, and follow a strange looking path. It would still follow the straightest path to get from a to b but now its path would be curved to do this. (The curved path is known as a geodesic) This is due to the curvature in our paper that we call spacetime.
============================
Can you say a little bit about how
time figures into this "falling" object on this curves spacetime grid.
Okay, I get a glimmer of the curvature of space. How does time factor into gravity. Just a few words. I can understand that you can't in a forum post really make it totally clear to a novice.
======================================
In reality, mass-energy curves not only the space dimensions, but the time dimension as well, analogous to the two dimensional example. Space and time have had an intimate relationship since special relativity, and general relativity extends this idea.
=====================================
Thanks for your effort.