Reply to thread

Message

<blockquote data-quote="freyar" data-source="post: 6677979" data-attributes="member: 40227">If you recall the idea of inertial motion from introductory physics like I mentioned in my answer --- the idea that objects move in a straight line at constant speed unless acted on by an outside force --- that's all freefall is.&nbsp; In space, very far from a large mass, there's &quot;no gravity&quot; (in relativity, spacetime is flat), and a free object will just move along at constant speed in a straight line.&nbsp; It's just that near a large mass (like a star or planet), the curviness of spacetime means that &quot;inertial motion&quot; includes behavior like falling toward a planet or orbiting it.&nbsp; I don't think you can really say there's a cause of freefall or inertial motion.&nbsp; It's just how things work, and I think it's really important to remember that &quot;freefall&quot; in general relativity is the same idea as Newton's laws, just in a broader framework.In your example, the ball and the funnel are pushing (exerting force) on each other, so that's how the ball can roll around the edge of the funnel.&nbsp; But, yes, eventually it would run out of funnel and move off inertially --- in empty space, that would be a straight line, but, near a planet, that might be an orbit.Good questions.&nbsp; Maybe if there are more follow-up questions, it would be good to post a new thread in the Misc. Geek Talk forum.&nbsp; Thanks!</blockquote>

[QUOTE="freyar, post: 6677979, member: 40227"] If you recall the idea of inertial motion from introductory physics like I mentioned in my answer --- the idea that objects move in a straight line at constant speed unless acted on by an outside force --- that's all freefall is. In space, very far from a large mass, there's "no gravity" (in relativity, spacetime is flat), and a free object will just move along at constant speed in a straight line. It's just that near a large mass (like a star or planet), the curviness of spacetime means that "inertial motion" includes behavior like falling toward a planet or orbiting it. I don't think you can really say there's a cause of freefall or inertial motion. It's just how things work, and I think it's really important to remember that "freefall" in general relativity is the same idea as Newton's laws, just in a broader framework. In your example, the ball and the funnel are pushing (exerting force) on each other, so that's how the ball can roll around the edge of the funnel. But, yes, eventually it would run out of funnel and move off inertially --- in empty space, that would be a straight line, but, near a planet, that might be an orbit. Good questions. Maybe if there are more follow-up questions, it would be good to post a new thread in the Misc. Geek Talk forum. Thanks! [/QUOTE]

Verification