2
$\begingroup$

I was reading this question on the Worldbuilding SE about stray bullets eventually hitting other things, like a space station or another ship, somewhere else in the same solar system. The consensus is that while the odds are extremely small (because Space is Big), it's still plausible if the plot demands it. Until it hits something, or burns up in some atmosphere, a bullet fired in the vacuum of space will just keep going.

But space isn't really a vacuum. There's lots of particles floating around in a solar system, and even the remotest corner of interstellar space still has a few hydrogen atoms flying around. My question is, would these particles slow down a projectile and eventually stop its forward motion? Would that happen within the same solar system, or would the process take too long?

$\endgroup$
  • $\begingroup$ In space things orbit other things or are destroyed. These are only options for your bullet. $\endgroup$ – Mithoron Jul 11 '18 at 21:57
  • $\begingroup$ This is about scale. Sure there is some drag. So what? The solar system is in excess of four billion years old quite small objects have not seen their orbits spiral into the sun because the drag is vastly smaller than other effects. You need a sense of perspective in these matters. $\endgroup$ – dmckee Jul 11 '18 at 22:08
2
$\begingroup$

Well, the mass of a hydrogen atom is very low and the density of hydrogen atoms in space is almost ignorable at most places.

But theoretically, after a very long time, your projectile will stop (relatively) if it is unaffected by the gravity of another solar object which it will never be.

The time it will take for the projectile will mainly depend on the projectile's mass and the density of the hydrogen atoms in the area of space you are talking about.

I think you can safely assume your projectile won't stop and if it does, it will stop a long time away not in the same solar system.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.