Just a thought, if an event happened well beyond the observable universe that caused entire galaxies to be destroyed radiating from a point source event, what would it look like from our perspective and how close could it get on our observable horizon while still being unable to reach us due to expansion of the universe?...
If the sphere of destruction is propagating at the speed of light, then any observable effect reaches you at the same time as the sphere itself. Either you donāt observe it because youāre far enough away to be safe, or you donāt observe it because youāre dead the instant it becomes observable.
Incidentally, you might be interested in looking up the idea of false vacuum decay - although if you tend to get anxious about end-of-the-world hypotheticals you might prefer to give it a miss.
Iāve read that at the center of large celestial bodies thereās zero gravity (or close to). While confirmation would be nice, if true, Iām wondering how large that area can actually be and moreover, does it scale up with more mass and/or even size - that is, does the sun have a larger center area of low (zero?) gravity than...
If you had a planet that was hollow in the center*, the entire hollow region would have zero gravity. You could have a thin-skinned planet with the entire interior an empty weightless void. I doubt any planets like this actually exist.
Assuming radial symmetry. If you can represent the planet as concentric spherical shells then youāre good.
Yeah itās a pretty counter intuitive result. Iād expect a greater pull of gravity towards the nearer side, but it turns out to be exactly cancelled out by the greater mass on the further side.
E: oops, looking at your edited comment, I should stress this is only for hollow bodies. Your comment pre-edit was correct for non-hollow bodies. If youāre part way to the middle of a planet, you can think of the planet as two sections, a small sphere for the part thatās below you, and a larger hollow shell for the rest. You experience no gravity from the outer shell, so only feel gravity of the smaller mass below. 10m from the earthās center, you feel equivalent gravity to if you were on a 10m radius iron sphere.
Why were dinosaurs huge?
I mean, why evolution selected dinosaurs to become that huge?
If it were possible for some event to destroy the fabric of spacetime at the speed of light, could we still observe and be safe bc expansion?
Just a thought, if an event happened well beyond the observable universe that caused entire galaxies to be destroyed radiating from a point source event, what would it look like from our perspective and how close could it get on our observable horizon while still being unable to reach us due to expansion of the universe?...
xkcd #2821: Path Minimization ( startrek.website )
Link to comic: xkcd.com/2821/
Area of gravity at the center of large, dense celestial bodies...
Iāve read that at the center of large celestial bodies thereās zero gravity (or close to). While confirmation would be nice, if true, Iām wondering how large that area can actually be and moreover, does it scale up with more mass and/or even size - that is, does the sun have a larger center area of low (zero?) gravity than...