Space

There is essentially no way we are the only ones in the entire universe. It would have to be the most astounding and amazing luck for that to be the case…. Vanishingly small, might as well be zero, chance of being the only ones. The universe is an absolute monster in size. There is no way for our monkey brains to even fathom how big it is. We need abstract numbers to even talk about it, which make it so anything that could exist most likely does.

However, those extraterrestrial peers of ours may be so far away that we might as well be alone. Even if we traveled for millions of years and kept our warring civilization from destroying itself, we may only explore a small percentage of this one single galaxy. Even if we managed to catalogued the entire thing, there are still 200 billion more galaxies out there. Our alien buddies may be on one of those that will soon blip out of existence due to universal expansion before we could get there, even if we traveled at maximum speed, never to be seen or heard from again.

When we talk about actually attainable and achievable exploration goals, the chances of other intelligent life existing get sort of really small. That is what I find to be not terrifying, but somewhat depressing to think about.

If we expand into the galaxy, even into just our local bit of galaxy, we will make a new threat out of some of the colonies.

I feel like humanity would be more likely to fast track world war 3/4/whatever we're on by then, nuclear winter, and near (if not complete) human extinction. But I also have little faith in humanity, so there's that. 🤷‍♀️

In the mind-bogglingly unlikely event that a Venus-sized object was on a collision course with Earth, I'd guess we'd likely have a couple of years' warning. Maybe a decade. It's not easy to detect objects out beyond Neptune, even when they're sizeable.

The odds are so incredibly small that they're not worth worrying about even abstractly, IMO. The Solar System has gone for 4.5 billion years without any of the Terrestrial planets in it being smacked by a rogue planet (I suppose it's possible one of the gas giants might have swallowed a small one in the distant past, though even then I'd expect signs of such an event to remain on its moons) so the chance that one might happen to come along right at this instant in time is vanishingly small.

I don't really have a good answer for this and frankly it's probably not rational or coherent or succinct so I'll just say it comes down to mortality, knowing how small and insignificant we are and desperately clinging to a meaningless life on a meaningless planet in a meaningless etc. etc. etc.

There's so much out there that we don't know and probably never will and it's all growing faster than we could ever hope to catch up with and we'll all be dead so soon relative to the lifespan of the universe and it'll just keep going on long after our meat sacks stop functioning and turn into nothingness until maybe everything turns into nothingness and then there's never anything ever again or maybe that won't happen but we'll all still be long, long gone.