Answer: No life forms could flourish indefinitely. In an isolated system, entropy always increases. Life tries to push entropy in the opposite direction. When life is created, entropy decreases in the cave but nature demands a greater entropy increase offset. The cave, being sealed, would mean that entropy would reach its max, thus energy necessary to sustain and generate new life would be unavailable. Maybe we should learn a lesson from this. Available energy is mandatory. Wealth may equate to available energy. If you want to live in a nation that is prospering make sure that its available energy supply is abundant.

Entropy is one of “Physics Foibles”

Your answers are appreciated.

The problem is how much of the planetary atmosphere actually gets ejected from the planet? For impactors less than ~100 km the answer is probably not much. The ejecta travel through the atmosphere and may reach escape velocity. That does not necessarily mean that they impart such a velocity to the gas molecules themselves.

I think Phil has already moved on. From what I can gather the cometary threat is poorly understood but it may be significant. And we will not typically receive decades of warnings before impact as we do with asteroids. For comets following nearly hyperbolic orbits the warning period may be only a matter of months.

http://www.lpl.arizona.edu/~marcus/CollinsEtAl2005.pdf

“Currently, the relative importance of comets to the Earthcrossing impactor flux is not well-constrained. The Near-Earth Object Science Definition Team (2003) suggests that comets comprise only about 1% of the estimated population of small NEOs; however, there is evidence to suggest that, at larger sizes, comets may comprise a significantly larger proportion of
the impactor flux (Shoemaker et al. 1990).”

“Filming ‘Independence Day’ movie the bit where the saucer crashes with Wil Smith either flying it or forcing the alien to crash! “I could’da been at a barbecque!”

Am I right?

D’oh! Turns out I’m not.

But Phil about that 10km *Comet* threat – any response? Please?

Oh & no one has anything to say on slamming the Near Earth Asteroids into Venus and using that as a terraforming tool either? Is it too dumb or something in the idea or ..?

“The dinosaurs that pushed the KT event rock into the planet will be back… one day…”

Yeah, that has already happened & been stopped by the Doctor in Jon Pertwee incarnation a coupleof times actually : the Silurians and the Sea Lizards.

Close? Sure, if by close you mean off by a factor of 10 trillion. We are currently a type 0.7 Kardashev civilization. To get to type 2.0 status we need to increase our energy output by a factor of 1.0E13.

No, that’s the wrong way to think about it. The probability that any given human being is killed by an asteroid or a comet of 1 in 700,000 (more likely to by 1 in 15,000 as I’ve shown) is dominated by extremely rare events (i.e., impacts of large objects). If you included just the small impactors (100 meters or less in size) then the odds are reduced by a factor of 20. So the events that are likely to actually happen within a person’s lifetime make up only 5 percent or less of the statistic. The extremely rare events make up 95 percent of the statistic, even though they never happened in your lifetime, your father’s lifetime, your grandfather’s lifetime, or even during recorded history.

That doesn’t change the statistic at all. The assumption that these events never occurred during all of human history and therefore can never occur in the future, is entirely an illusion. Tomorrow may be entirely different than anything anyone has ever experienced before.