Yes, half an orbit for an elliptical major axis of 1 AU (vs. a full orbit for an elliptical semi-major axis of 1 AU).Chris Peterson wrote:I think he's just using the time it takes to fall 1 AU under the gravitational acceleration of the Sun.Markus Schwarz wrote:Interesting. Where did you get that?
Throw a ball up in the air and the ball follows a slightly curved space-time trajectory at the speed of light that falls back to Earth. What we perceive is a slow parabolic trajectory of the ball in space over time... but space itself can be thought of as actually falling back into the earth (carrying the ball with it).Chris Peterson wrote:
As you say, that is how bodies with mass behave under gravitation, which is modeled as a distortion of spacetime. It doesn't describe the motion of spacetime itself. Indeed, as I understand GR, the motion of spacetime isn't even a defined concept. I don't know- physically or mathematically- what it means for "space to disappear" into a black hole or any other mass. Under GR, space is a coordinate system, not a physical thing.
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Rather, the Earth goes around the Sun due to the collapse of space (i.e., the dynamic image of space "a waterfall cascade") into the Sun as time proceeds.
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Pucker, n.
- 1. A fold; a wrinkle; a collection of folds.
2. A state of perplexity or anxiety; confusion; bother; agitation.