4 ms·

What's the criteria for that? It's complicated. Depends on the cross-sectional area and the materials the boulders are made of. Ice, for example, burns up (mel

What's the criteria for that? It's complicated. Depends on the cross-sectional area and the materials the boulders are made of. Ice, for example, burns up (melts) on reentry much more readily than iron! Also depends on the angle of attack. Heading straight down (perpendicular to the ground beneath it) passes through much less atmosphere than a glancing blow, so has a lot less time to burn up.

mydriasis 3y ago
Interesting, thank you!
golemotron 3y ago
I wonder how often perpendicular to the ground impacts occur? I seems that they could only occur if an asteroid approached in a head on collision with our orbit or perpendicular from a higher or lower orbit as it passes or is passed by the earth. That makes it statistically unlikely, doesn't it?
- chongli 3y ago
  The statistical likelihood depends entirely on the timeframe. Within our lifetimes? Extremely unlikely for any large impact. Over the next billion years? A lot more likely!
  - deleted 3y ago
    [deleted]
  - golemotron 3y ago
    Nope. I was referring the likelihood of perpendicular collisions out of the set of all possible collisions. No time dimension.
- deleted 3y ago
  [deleted]
inamberclad 3y ago
Not to mention asteroids made of iron would be much harder to knock boulders off of.
- chongli 3y ago
  Yeah if there's some solid iron asteroid out there heading right for us we're totally screwed. That's like a core of a planetessimal! Very dense stuff! It could also be some lighter rock (a matrix) with iron clasts, created from a collision between a huge, light asteroid and smaller iron planetessimal fragments. Then if our planetary defense system breaks off a bunch of boulders, some could contain the heavy iron fragments and some might not, so different things would happen on reentry for each boulder.
  - JumpCrisscross 3y ago
    > if there's some solid iron asteroid out there heading right for us we're totally screwed Isn’t this among the easier to deflect? You literally smash other asteroids into it without much fear of it breaking up.
    - chongli 3y ago
      No. That’s going to be extremely difficult to deflect due to the momentum. You’d have to catch it much earlier. As for smashing “other asteroids” into it, that’s likely not feasible due to the vast distances between asteroids and the masses involved.
      - JumpCrisscross 3y ago
        > going to be extremely difficult to deflect due to the momentum Momentum is a function of mass and velocity. The momentum of two similarly-massive asteroids, one rock the other metal, is the same. Given existing technologies, deflecting a solid-ish body is easier than a loose pile of gravel.
        3y ago

mydriasis 3y ago

Interesting, thank you!

golemotron 3y ago

I wonder how often perpendicular to the ground impacts occur? I seems that they could only occur if an asteroid approached in a head on collision with our orbit or perpendicular from a higher or lower orbit as it passes or is passed by the earth. That makes it statistically unlikely, doesn't it?

chongli 3y ago
The statistical likelihood depends entirely on the timeframe. Within our lifetimes? Extremely unlikely for any large impact. Over the next billion years? A lot more likely!
- deleted 3y ago
  [deleted]
- golemotron 3y ago
  Nope. I was referring the likelihood of perpendicular collisions out of the set of all possible collisions. No time dimension.
deleted 3y ago
[deleted]

inamberclad 3y ago

Not to mention asteroids made of iron would be much harder to knock boulders off of.

chongli 3y ago
Yeah if there's some solid iron asteroid out there heading right for us we're totally screwed. That's like a core of a planetessimal! Very dense stuff! It could also be some lighter rock (a matrix) with iron clasts, created from a collision between a huge, light asteroid and smaller iron planetessimal fragments. Then if our planetary defense system breaks off a bunch of boulders, some could contain the heavy iron fragments and some might not, so different things would happen on reentry for each boulder.
- JumpCrisscross 3y ago
  > if there's some solid iron asteroid out there heading right for us we're totally screwed Isn’t this among the easier to deflect? You literally smash other asteroids into it without much fear of it breaking up.
  - chongli 3y ago
    No. That’s going to be extremely difficult to deflect due to the momentum. You’d have to catch it much earlier. As for smashing “other asteroids” into it, that’s likely not feasible due to the vast distances between asteroids and the masses involved.
    - JumpCrisscross 3y ago
      > going to be extremely difficult to deflect due to the momentum Momentum is a function of mass and velocity. The momentum of two similarly-massive asteroids, one rock the other metal, is the same. Given existing technologies, deflecting a solid-ish body is easier than a loose pile of gravel.
      - 3y ago