The truth is that there are a huge number of cataclysms that could come along and wipe us out before we even knew what hit us.

A small black hole. We would not even see it coming.
An unknown meteor. If it's large enough.. and there are many that are... we could not do a darn thing about it.
A supernova too close. There would be nothing we could do either.

That is why many people, including myself, feel that sooner or later we have to move on from our beautiful world to inhabit others. If we don't, we cannot survive in the long run.

However, that long run could be long indeed. The Earth has endured billions of years so far, so the odds are good on our scale. The human race has only been around for less than a million years. A hiccup in the scale of things.

That is also why I believe technology is important. It has some major drawbacks, don't get me wrong, but in the end our future depends on it.

I'm sceptical that we could get off the Earth in any sustainable way.. in the short to medium term. Even if we put a colony on Mars for example, it would be more exposed to a local supernova than Earth would be, so there is no gain there. Venus wouldn't give much bang for buck either. We'd be looking at building a colony in a giant underground fridge on Mercury for us all to live in as a sort of supernova shelter - and hope that the Sun's magnetic field could keep the ISM (& gamma ray emissions?) from such supernovae at bay, and the planet's surface enough protection from the Sun's heat/flares. Not a promising prospect.

The only alternative would be to build colonies way beyond the solar system, 100s of light years away, which would be a much less feasible challenge. Grim as it may sound, our best bet is to sit tight on this rock for as long as we can until something comes along and extinguishes us, be that in a million or a billion years time. Heck though, if we get lucky and survive for another 5 billion years, there might be a case in the far future of colonising the outer rims of the solar system when the Sun expands into a red giant, but worrying about that now is a bit naff to say the least...

Anyway, that all said, I think there's no point in expediting the situation by putting our planet under unnecessary risk with LHC-type experiments, and forcing ourselves to an emergency evacuation that we are not technically ready for as a civilisation. Assuming there's a risk that is.

I wouldn't say it sounds grim. The only real threat for highly advanced civilization is probably an invisible black hole (I say "probably", because there is no proof that such objects of small size travel here and there in space). Everything else has one solution or another.
Living happily on this planet, an advanced civilization can:
- easily destroy/change direction of any asteroid coming to earth.
- create shields in space in order to minimize the chance of direct hit of gamma ray bursts.
- the knowledge in medicine/biology will be high enough to prevent the spread of any disease.
- create underwater/underground self sustained cities in case of hostile environment (caused by whatever reason) at ground level.

And I believe we can achieve this technological level in less than 1000 years.