3 ms·

The scaling with meteor size is impressive. A 100 m object will flatten some trees in Siberia. A 10 000 m object will kill 75% percent of all species on the p

by gaur 11y ago

The scaling with meteor size is impressive. A 100 m object will flatten some trees in Siberia. A 10 000 m object will kill 75% percent of all species on the planet (the KT event).

elorant 11y ago
The problem with the latter is that it will cause a nuclear winter. So that 75% will not die instantly but in 2-3 years after the impact. Add an order of magnitude or even half of that and then you have an extinction level event. It could kill organisms even at microbe level.
- EGreg 11y ago
  Ok simple... figure out what will disperse all the ash to prevent the nuclear winter! Lets start testing this stuff now... may also solve the greenhouse gas problem.
- deleted 11y ago
  [deleted]
- njharman 11y ago
  It wouldn't be a NUCLEAR winter...
mikeash 11y ago
Keep in mind that when taking about the diameter of a three dimensional object, the amount of stuff scales with the cube. The second one is a million times more meteor.
mirimir 11y ago
Velocity matters too. E ~ mv^2 after all. I'm reminded of Killing Star by Charles R. Pellegrino and George Zebrowski. Even without aggressive aliens, stuff falling toward the galaxy's central black hole may get ejected at relativistic velocity. Very unlikely. But we wouldn't see it until it was almost here.
- raattgift 11y ago
  Well, we're getting photons and probably cosmic rays from Sagittarius A, so not that unlikely. :-) You're right about small mass but macroscopic objects though, since Sag A's rotation is very sub-extremal, its mass is sufficiently high (higher mass means less curvature just outside the horizon), and its accretion structures and jets are sufficiently dim that there is essentially no chance for a rocky object to get any sort of gravity assist, much less to relativistic speeds. Much smaller black holes are likely sources of "dangerous" gravity assists, but they also usually have accretion structures whose ICS-boosted radiation would probably disintegrate candidate objects. On the other hand, even a fairly small chunk of rock boosted to near the speed of light would pretty much end Earth. (Time to dig up https://what-if.xkcd.com/1/ https://what-if.xkcd.com/1/ :) )
  - mirimir 11y ago
    Yes, I get that Sag A is pretty quiet. But there was an X-ray flash about 60 years ago, based on echos seen in Chandra images. Also, there is this: http://www.space.com/19748-hypervelocity-stars-milky-way.html http://www.space.com/19748-hypervelocity-stars-milky-way.htm... The impact description in Killing Star is similar to xkcd's, for what it's worth.
    - raattgift 11y ago
      "up to 2 million miles per hour" is pretty slow compared to the speed of light :-) These stars are in Kepler orbits so the speed tells us the relationship between their mass and the central mass. We can also use their periastrons to trace out the minimal radius of the central mass. Whatever's there is almost certainly a supermassive black hole. Gas or dust or a swarm of smaller black holes in the same radius would undergo gravitational collapse (and light up LIGO! and probably put out a lot of electomagnetic radiation too... but Sag A* is not very bright). The UCLA Galactic Centre Group has a bunch of cool information about this sort of thing. You might enjoy: http://www.galacticcenter.astro.ucla.edu/animations.html http://www.galacticcenter.astro.ucla.edu/animations.html

by gaur 11y ago

The scaling with meteor size is impressive. A 100 m object will flatten some trees in Siberia. A 10 000 m object will kill 75% percent of all species on the planet (the KT event).

elorant 11y ago

The problem with the latter is that it will cause a nuclear winter. So that 75% will not die instantly but in 2-3 years after the impact. Add an order of magnitude or even half of that and then you have an extinction level event. It could kill organisms even at microbe level.

EGreg 11y ago
Ok simple... figure out what will disperse all the ash to prevent the nuclear winter! Lets start testing this stuff now... may also solve the greenhouse gas problem.
deleted 11y ago
[deleted]
njharman 11y ago
It wouldn't be a NUCLEAR winter...

mikeash 11y ago

Keep in mind that when taking about the diameter of a three dimensional object, the amount of stuff scales with the cube. The second one is a million times more meteor.

mirimir 11y ago

Velocity matters too. E ~ mv^2 after all. I'm reminded of Killing Star by Charles R. Pellegrino and George Zebrowski. Even without aggressive aliens, stuff falling toward the galaxy's central black hole may get ejected at relativistic velocity. Very unlikely. But we wouldn't see it until it was almost here.

raattgift 11y ago
Well, we're getting photons and probably cosmic rays from Sagittarius A, so not that unlikely. :-) You're right about small mass but macroscopic objects though, since Sag A's rotation is very sub-extremal, its mass is sufficiently high (higher mass means less curvature just outside the horizon), and its accretion structures and jets are sufficiently dim that there is essentially no chance for a rocky object to get any sort of gravity assist, much less to relativistic speeds. Much smaller black holes are likely sources of "dangerous" gravity assists, but they also usually have accretion structures whose ICS-boosted radiation would probably disintegrate candidate objects. On the other hand, even a fairly small chunk of rock boosted to near the speed of light would pretty much end Earth. (Time to dig up https://what-if.xkcd.com/1/ https://what-if.xkcd.com/1/ :) )
- mirimir 11y ago
  Yes, I get that Sag A is pretty quiet. But there was an X-ray flash about 60 years ago, based on echos seen in Chandra images. Also, there is this: http://www.space.com/19748-hypervelocity-stars-milky-way.html http://www.space.com/19748-hypervelocity-stars-milky-way.htm... The impact description in Killing Star is similar to xkcd's, for what it's worth.
  - raattgift 11y ago
    "up to 2 million miles per hour" is pretty slow compared to the speed of light :-) These stars are in Kepler orbits so the speed tells us the relationship between their mass and the central mass. We can also use their periastrons to trace out the minimal radius of the central mass. Whatever's there is almost certainly a supermassive black hole. Gas or dust or a swarm of smaller black holes in the same radius would undergo gravitational collapse (and light up LIGO! and probably put out a lot of electomagnetic radiation too... but Sag A* is not very bright). The UCLA Galactic Centre Group has a bunch of cool information about this sort of thing. You might enjoy: http://www.galacticcenter.astro.ucla.edu/animations.html http://www.galacticcenter.astro.ucla.edu/animations.html