As far as I know, we can't deflect any big rocks coming at us either, yet...

@jakekimdsΨ We're working on it. llnl.gov/news/…

PBS Space Time presented 5 ways to stop a killer asteroid.

This answer states "you couldn't do it by aiming directly at the sun", but that wasn't the claim. The claim was just that it'd be possible to hit the sun.

So far we have not discovered any evidence of prehistoric, dinosaur-run space programs, but that doesn't mean...

@BlueRaja-DannyPflughoeft I'm not a native speaker. But to shoot at something usually means pointing at it, doesn't it?

@Jens not really; if you're shooting long range, for example, you might have to point the barrel to the side of the target to compensate for the wind. I'd say shoot at something means shooting with the intention to hit it.

Amusing nitpicK; actually T-rex's brain was quite a bit bigger than a human's, although its structure was rather different.

@Jens my point is that, as far as I know, you call both situations "shooting at something".

@WetSavannaAnimalakaRodVance An adult T-Rex brain is only 12.4% the volume of an adult man's brain.

While I agree the shot will miss spectacularly on the other hand I doubt the bullet has enough velocity to escape from the Sun gravity wheel so will it not end falling on the Sun?

@CeesTimmerman I'd check the trustworthiness of that particular site. In particular, check who's behind it. Anyhow, google "T-rex brain cast". There's one at the Powerhouse museum in Sydney, and it's about the size and shape of a thickened thigh bone. I don't know what that fossil on the creationist site is meant to be: T rex brains are known from x ray tomography of skulls that are way too valuable to cut up; I'm not sure we evenhave any fossil brain casts, only 3D prints of tomographs.

+1 just for "T-rexen" (not really, but.. nice)

@WetSavannaAnimalakaRodVance D'oh. I fell for the only clear result i could find. I managed to stay awake long enough to find that indeed they lied, according to this boring piece.

@CeesTimmerman don't worry - I fell for exactly that site too. I came across the same image looking for a reference for my comment and was intrigued. It was a good five minutes of reading before I knew where I was. It's a very craftily made and slick site.

@uhoh The real question is do we have evidence of Ancient Aliens?

@jakekimdsΨ - which means that we're no smarter than T-Rex, despite having more brains. Perhaps it is not the quantity of brains which matter, but quality...

@jean No it will not fall into the Sun. You need to take into account the gain in velocity when falling towards the Sun (down the gravity well). There comes a point (called perihelion) when the bullet is so fast, it starts rising again. That's what happens for all elliptical orbits.

Nitpick: Since we currently (until Falcon Heavy is certified for human transportation, that is) cannot get astronauts further than a low earth orbit you'll need 30 km/s plus almost earth's escape velocity (more precisely: at least a velocity sufficient to escape earth's Hill Sphere); i.e. probably around 40 km/s.

@Jens, Re, falling down the gravity well; The question is, where is the perihelion? If the astronaut uses the specialized gun described in Russel Borogrove's answer, then the bullet's perhelion potentially could be inside the Sun. Bull's Eye!