🧵 Gorvity
Anonymous at Sat, 15 Mar 2025 06:40:39 UTC No. 16619536
Okay, suppose you create a universe with a single astronaut with a gun that holds a single bullet. For simplicity, let’s suppose that astronaut is locked in their position in said universe. The laws of gravity work the same in this universe as they do in ours, but we’ll also negate any added effects, such as dark energy. The universe has no boundary, or at least one that would allow this situation to enact in full.
If the astronaut were to fire the gun in any direction, how long would the bullet travel and for how long until the gravity of the astronaut causes it to reverse direction and eventually kill the astronaut? The astronaut will not die unless killed by the bullet.
Anonymous at Sat, 15 Mar 2025 07:38:35 UTC No. 16619549
>>16619536
The bullet would be well beyond escape velocity. It wouldn't come back.
Anonymous at Sat, 15 Mar 2025 08:16:05 UTC No. 16619568
>>16619549
Yes, kinda. Gravity has an infinite range that gets exponentially weaker the further an object gets. To say that “escape velocity” implies it would never come back is a falsehood. That’s why I removed all other objects from the equation, like stars and planets.
We can say in our universe that the bullet wouldn’t come back because it would find itself pulled into another object at some point, but in my question there are no other objects for it to get pulled into. Therefore, the only thing having any gravitational impact on the bullet would be the astronaut.
Although the gravitational effect would constantly get weaker, the initial velocity of the bullet would never increase and could only decrease. Since gravity’s effect will get smaller and smaller, but never reach 0, even the smallest effects would cause the bullet’s velocity to reach 0 and begin returning. This could obviously take an insane number of years and allow the bullet to travel some unfathomable distance, but it would have to happen at some point.
Anonymous at Sat, 15 Mar 2025 09:06:46 UTC No. 16619578
>>16619568
No, you're comparing infinities without mathematics
The fact that gravity has infinite field doesnt mean its potential difference (and thats the work it will do on the bullet) from one point to infinite is infinite
In fact the integral of that graph you posted from 1r to infinite is finite
https://m.youtube.com/watch?v=099F-
Anonymous at Sat, 15 Mar 2025 09:11:01 UTC No. 16619580
>>16619578
*Potential enegy difference
Anonymous at Sat, 15 Mar 2025 11:29:09 UTC No. 16619659
>>16619578
Well said