QUOTE (yiming2000 @ Jun 6 2011, 11:37 AM)
Planetary orbital paths are not straight lines, are they?
Please define your straight line??
If here on earth you use a beam of laser light to determine a straight line
then in space-time, that same laser beam would also follow the straight line in space time ..
it just wouldn't look it from outside the system.
Think about an object following its inertial .. it would continue in a straight line unless acted upon by an outside force.
Gravity is often called a force but in Einsteins world .. gravity bends space-time
So, the object continues to go in a straight line in space-time ... it just doesn't look it from outside the system.
Yeah, it is a bit of a stretch. And, Einstein's world is not easy to grasp.
Like when you get smaller and smaller, there are more dimensions in the sub atomic world
An electron can get from here to there without going through the space in between the two points.
How? I don't know. It just can.