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Comment by progrus | Hacker News Reader

Seems like maybe our ability to find and divert these asteroids might make all that burning of energy worth it, no?

Not really, since there are only a few known instances of asteroids hitting earth in hundreds of millions of years, but climate change is an immediate threat within the next 50. The odds we live to see an asteroid hit us are slim.

> The odds we live to see an asteroid hit us are slim.

Presumably this is based on a belief that humans are likely to go extinct. I don't agree; I think we're extremely unlikely to go extinct and, following from this, an impact is definitely something worth worrying about.

It doesn't even have to be a "planet-killer," a smallish impactor could wipe out a city.

The question is really how likely are we to be hit within the relevant time period. Had we taken a slower growth curve, we'd avoid climate change at the cost of an extra 50 or 100 years before being able to divert asteroids. That seems like a good bet. I am much more worried about climate change and irreversible destruction of ecosystems than getting hit with an asteroid in a very limited time period

Slim, but not zero; we can and probably should do both.

Well, maybe. It really comes down to the specific numbers. (At least for the objective part of the consideration.)

How realistic it to divert an asteroid of this size?

It doesn't necessarily need to be diverted entirely. Simply breaking it up into smaller components significantly reduces it's impact force.

Smaller pieces burn up more readily in the atmosphere and create smaller impacts (I believe exponentially smaller)

some of these asteroids we only have days warning. that's the scary part. To divert an asteroid you need to do it before it comes near so it has a long path to begin drifting in a new direction. ie it's only gonna nudge it slightly. Slightly adds up over many millions of miles, not so much when its a week out.

Now you're begging the question of how hard it is to break it up!

Significantly harder than diverting it slightly.

If you know find out years in advance then you barely have to change it's velocity to make it miss Earth. Probably a kinetic impactor would be sufficient, otherwise thermonuclear warheads exist.

Capable with current technology if intercepted early enough. I think most people visualize an asteroid hitting earth like a ball hitting the ground when dropped at arm's length. In reality, orbits of celestial objects are elliptical, and they're constantly moving. A small force, like that produced by an ion thruster, applied to an asteroid 15km in diameter for months or years would be enough to change it's orbit such that it wouldn't impact earth.

when did we learn it was heading our way, and how far away is it at detection? hours, days, months, years before impact? that's key things to know.

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