Stuck in the Well


by Brian Koberlein | 30 April 2018 | Physics

This is a companion discussion topic for the original entry at


sir is this possible that a rotating object can create gravity??


The rotation of an object can affect gravity, such as through the frame dragging effect, but mainly gravity is a result of an object’s mass.


It occurs to me that the thicker atmosphere of these “super-earths” might also sufficiently obscure starlight to diminish the possibility that such beings would even develop a science of astronomy.

There’s probably a good SF story waiting to be written with that as a hook. Too bad I’m not an Asimov or Heinlein…


The delta-v needed to escape a planet depends upon its surface gravity, or how strongly a planet’s gravity pulls you to the surface.

Well… that’s not entirely correct. Saturn has nearly the same surface gravity of Earth, but its escape velocity is 35.5 km/s (3.172 times larger than Earth’s). I would rather say that the delta-v depends only on mass and radius despite the surface gravity.


What about atmosphere? It can be much denser than our planet. In a way as you say. Gas giant can have relatively less mass in core->surface but rest of mass is actually contained in atmosphere. Overall matters.