We’re due for another meteor strike like the one that killed the dinosaurs (or bigger). The last really huge one was 65 million years ago, but about every 5 million years or so mass extinctions are caused by large meteors.

Mars is believed to have no atmosphere because it is smaller than Earth, so its molten iron core cooled and solidified quicker than Earth’s is doing. The movement of the molten iron core of Earth generates its magnetic field, which acts as a shield from solar winds. It is believed that when Mars’ core solidified, it stopped generating its magnetic field, and solar winds gradually tore away its atmosphere. This is one of the ways Earth will eventually become inhospitable.

The moon is slowly moving away from the Earth, and its gravity is responsible for our 24-hour day, the tides, the seasons, and our stable rotational axis. Eventually, if the moon were to eventually break free of its ordit, we’d be screwed.

Of course, none of these thing are likely to happen any time soon, and geologically speaking, not for a very long time, but I think they will happen long before the sun burns us. With the possible exception of the moon scenario. And some believe the moon will stabilize at 1.6 times its current orbit, leaving us with a 55 hour day. I guess as long as it is still there to keep us stable on our axis, we might be ok. And we’ll be able to get more done by noon then we get done all day right now!

It won’t happen in our lifetimes, but it will happen. The Earth can’t continue to overpopulate without either a global totalitarian government to control it (such as China does now), or a place for many of us to go. Terraforming Mars is not out of the question, and maybe not even that hard. But it will probably take several hundred years, at least, and maybe a few thousand.

Within a hundred years, we will probably have robots autonomous enough to go out in ships looking for life, find resources in other solar systems on unihabited worlds, use them to build more ships, and launch new expeditions to other solar systems. This could go on forever, in all directions, until life, or at least habitable planets are found. Of course, this will take a long time, unless we discover new technology to make faster ships.

I think that within a hundred years energy-producing technologies will be incredibly efficient (do a search for fusion energy technology) and robots able to do virtually any type of job. This will mean that energy plants can be built and maintained entirely by robots, robots can make other robots as well as any other product. Everything will eventually be free. At least after a long period in which politics keeps things status quo, and virtually the entire planet is unemployed and civilization on the verge of collapse.

With free labor and free energy, what’s to stop us from creating incredibly huge ‘domed’ cities on other planets? We have the technology already to make oxygen and water from rocks on the moon. We are developing the technology right now to make hostile environments way more comfortable than the Arctic or the Gobi Desert. What’s the attraction to colonizing space? How about a life less crowded? A controlled environment that never gets too cold, too warm, or aggravates your asthma? Maybe, on one of Saturn’s moons, a beautiful view of the ringed planet up close. Or maybe just that spirit of adventure that won’t be denied. Man is the ultimate adaptor. It’s what we do. And as the technology gets there, we will move into nice, comfortable homes in the
Arctic and the Gobi.

Odd that you mention the idea of “put[ting] our cells into space pods, launch[ing] them and hav[ing] them re-breed us in a billion years” – that’s very similar to one of the things Charlie said.

One other thing:

But it is a fact that humans, or at least our descendants thousands of years from now, realizing they have life and civilization to cling to, will have to leave this planet and its dying sun.

The “thousands of years” is wayyy off. Assuming we stop screwing up our planet (which, I admit, is unlikely), we should be able to stay here for a REALLY long time before needing to worry about the sun going poof. According to the Wikipedia article, the sun won’t be entering its red giant phase for 4-5 billion years… at which point, most of the water on the Earth will be boiled away, and the majority of our atmosphere will escape into space. In other words, it will be at that point that the inhabitants of Earth will be.. ahem.. fraked.

Remember that a century ago, we could barely fly, had only rudimentary motorized transport and no computing at all. But it is a fact that humans, or at least our descendants thousands of years from now, realizing they have life and civilization to cling to, will have to leave this planet and its dying sun. Unless we actually want to disappear, we have to go.

I realize you want to see it happen now (hey, me too, man!) but that’s just not going to happen any time soon. And if it does, it may well happen totally different from what we can now imagine. Maybe we just put our cells into space pods, launch them and have them re-breed us in a billion years. If you have the right technology, maybe time and distance won’t even matter anymore…