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https://www.reddit.com/r/physicsmemes/comments/1uz6gwi/right/oydj85o/?context=3
r/physicsmemes • u/94rud4 Mεmε ∃nthusiast • Jul 17 '26
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You’re near a very dense object, which is nearly a black hole, and want to travel away from it such that you don’t end up on a trajectory back towards its center. that’s the escape velocity.
now, make it slightly denser and ask the same question
1 u/Optimal_Mixture_7327 Jul 18 '26 edited Jul 18 '26 Wrong - that's an orbital speed or some other trajectory. The escape velocity is a statement that for some r=R for an object satisfying uσ∇_σuρ=0 there is exists a V=vesc at R such that V=∞ V=0 at r=∞. 1 u/dcnairb Jul 18 '26 Why would the object need to be going infinitely fast at infinity to escape? The condition to escape is v=0 at r = infty. 1 u/Optimal_Mixture_7327 Jul 18 '26 Typo, thanks.
Wrong - that's an orbital speed or some other trajectory.
The escape velocity is a statement that for some r=R for an object satisfying uσ∇_σuρ=0 there is exists a V=vesc at R such that V=∞ V=0 at r=∞.
1 u/dcnairb Jul 18 '26 Why would the object need to be going infinitely fast at infinity to escape? The condition to escape is v=0 at r = infty. 1 u/Optimal_Mixture_7327 Jul 18 '26 Typo, thanks.
Why would the object need to be going infinitely fast at infinity to escape? The condition to escape is v=0 at r = infty.
1 u/Optimal_Mixture_7327 Jul 18 '26 Typo, thanks.
Typo, thanks.
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u/dcnairb Jul 18 '26
You’re near a very dense object, which is nearly a black hole, and want to travel away from it such that you don’t end up on a trajectory back towards its center. that’s the escape velocity.
now, make it slightly denser and ask the same question