Timeline for Isn't A Singularity Inevitable Given Infinite Time?
Current License: CC BY-SA 3.0
5 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 26, 2019 at 19:19 | vote | accept | Ethan The Brave | ||
| Apr 26, 2019 at 19:19 | comment | added | Ethan The Brave | that actually clears up a lot for me, even some of the other comments on the question itself. I suppose if the rate of, let's say, 'gravity decay' is high enough per-second that it could outpace the speed decay of the object, it would go from 11.0 km/s to 10.9-something km/s and possibly never even see 10.8. Thank you! | |
| Apr 26, 2019 at 14:48 | comment | added | Javier | @Ethan: the first point is not easy to explain, but the basic idea is that if the density is constant in time (instead of decreasing as the universe expands), the pressure must be negative. And this pressure, which also generates gravity, overwhelms the density and creates a net repulsive effect. And you can argue all you want, but I can solve the equations of motion and show that if the speed is large enough, the rock literally never comes back, because gravity decreases with distance. | |
| Apr 26, 2019 at 14:33 | comment | added | Ethan The Brave | I know it has been a while but I find myself thinking about this again - Can you expand on "Gravity doesn't always pull. A constant energy density will in fact have a repulsive effect."? Also, you argue that the rock will never come back in your first example - I argue that given enough time, yes it will. If gravity even exerts 1x10^-(some arbitrarily large number) force as acceleration, eventually it will win out. | |
| Apr 25, 2018 at 17:44 | history | answered | Javier | CC BY-SA 3.0 |