Comments on: TED x ME

By: Bob’s Junkmail, #222 « xpda

Bob’s Junkmail, #222 « xpda — Fri, 16 Dec 2011 16:35:52 +0000

[...] http://blogs.discovermagazine.com/badastronomy/2011/10/… [...]

By: Lisa Sample

Lisa Sample — Wed, 07 Dec 2011 18:24:31 +0000

Considering the varied densities of these space bodies, I think the gravity leash would be safest. Some of the bodies in the asteroid belt aren’t solid, they’re a collection of smaller rocks held loosely together by gravity — a nuke hitting one of those would just scatter the rocks at best.

I’m just glad none of the NEOs we’ve cataloged so far are the size of Vesta or Ceres…

By: Steve Grimsley

Steve Grimsley — Sun, 04 Dec 2011 12:04:08 +0000

That was excellent. The line about the space program coupled with your remark about voting is classic. I guess the laughter came about because of the recent political climate, no pun intended.

By: slemke

slemke — Mon, 24 Oct 2011 03:36:39 +0000

Great speech. I wonder if the current plans of NASA to land a person on an asteroid will yield any useful information that could help us in defending against an impact. I would hope that it would not be all for nothing. Another thought, if an oncoming asteroid could be nudged just a bit to get caught in the Moon’s gravity pull, then we could just let the asteroid hit the moon instead of us. It is our natural Dustbuster, anyway.

By: Yojimbo

Yojimbo — Fri, 14 Oct 2011 17:57:39 +0000

So – nobody is going for Phil and TED’s Excellent Adventure?

[Sigh!] It must be my bas sens de l’humour

By: Hemogoblin

Hemogoblin — Fri, 14 Oct 2011 14:19:55 +0000

@ 18. konrad

a couple of stupid questions: if we can hit an asteroid to change its orbit, is it possible that the chicxulub asteroid did the same to earth? (if not, how big would an asteroid capable of that have to be?) could it have had (or would such an impact have) any implications on our climate, or would any such change be so small as to be practically insignificant?

Every impact changes the Earth’s orbit ever so slightly, but the difference would be insignificant.
First off, the difference in mass is… well… massive.
The Chicxulub impactor is believed to have been a rocky (density of about 3000 kg/m^3) asteroid with a radius of roughly 5 km. The Earth has (thanks to its dense core) a mean density of about 5500 kg/m^3 and a mean radius of about 6000 km. Now remember: for spheres, mass scales with the cube of the radius!
All in all, that makes for a mass ratio of more than a billion to one in the Earth’s favor.

Second, our changing of the asteroids’ orbits is significant because all we care about is if they hit us or not. The Earth is a tiny, fast-moving (~30 km/s!) target in the vastness of space, so even a miniscule change in an asteroid’s velocity can mean the difference between a hit and a miss.

However, for purposes of climate, the same change applied to the Earth would be entirely unmeasurable. The Earth has an elliptical orbit where the difference between aphelion (closest point to the sun) and perihelion (farthest point from the sun) is around 5 million km, but even that enormous change only results in a few percent change in insolation (received solar energy).

EDIT: Arrgh, no tags

By: Titan

Titan — Thu, 13 Oct 2011 23:58:41 +0000

Phil: Didn’t we put Dawn into orbit around Vesta? Surely we could do the same with a nuke.

By: ?

Thu, 13 Oct 2011 23:09:14 +0000

deleted/duplicate

By: WDM

WDM — Thu, 13 Oct 2011 23:07:25 +0000

This speech was way too optimistic. Phil knows better, I know, because I read his book.

But if I heard nothing more than what Phil said in this presentation, I would have left TED believing that NASA had the problem well in hand, and that there was really nothing to worry about.

Nothing could be further from the truth. Assuming we don’t destroy the environment ourselves, we face _certain_ extinction (as a species) from an impact from space. Nothing we can conceive of would be of use in stopping an impact like Shoemaker-Levy 9, or any large comet, given that comets can come out of nowhere on highly elliptical orbits.

People need to know and thus fear the truth, so that we can get all of our eggs out of this one basket.

By: Yoav Landsman

Yoav Landsman — Thu, 13 Oct 2011 22:05:23 +0000

Great speech, but red shirt…as a Star Trek fan you should know better…