Not likely. Even traveling to a planet as "nearby" as Neptune by conventional means would take 12 years. Hardly within shooting range, and who knows whether our civilization will survive long enough for us to make it to even the edge of our solar system.
And the OP was referring to a nearby star system, within "sublight year" range. Even < 1 light year could mean very, very far away.
They are referring to a single system... Here is the quote:
>> And to think that there is likely an Easy Mode system out there.
>> A habitable planet on the low end of the mass spectrum needed for a stable atmosphere with other habitable planets in-system. And all that close to another star with habitable planets, possibly in the sub-lightyear range.
Yes, they mentioned another star system as an additional point, but that wasn't the main idea.
> Hardly within shooting range
Mars is only 6 months away. We have the technology today to launch boulders weighing hundreds of tons to Mars. Those make for pretty good weapons.
100+ tons to Mars. Doesn't require any major technological breakthroughs. It's just really big.
If you want a rocket that has already been built, the Saturn V could have launched a ~50 ton boulder to Mars. Not quite hundreds of tons, but that was also built 50 years ago.
If the Earth was suddenly facing interplanetary war with Mars, I imagine we would start building some very impressive rockets quite quickly. And they would all obey the rocket equation :)
BFR is unproven, no one knows whether it could take a payload of hundreds of tons.
But yeah, in theory you could just build a bigger rocket. But even going from 50 to 100 tons increases the size significantly, let alone going to hundreds of tons like you said. Maybe that's not possible with today's technology, multi stages and all.
And the OP was referring to a nearby star system, within "sublight year" range. Even < 1 light year could mean very, very far away.