WOW! Just wow....

[fivemack]

Originally Posted by Xyzzy

How big would a meteorite have to be to make it all the way to the ground?

It depends what you mean by 'all the way'. It's not going to land gently on the ground in any case, it's got enough kinetic energy to heat itself to well above boiling point - orbital velocity gives a kinetic energy equal to twelve times the object's weight in TNT, and it has to lose that pretty much between the top of the stratosphere and ground level.

Looking at the video, the thing comes in glowing white-hot and constantly brightening, and then there's the flash significantly brighter than the Sun which I think corresponds to the point of maximum deceleration - I suspect that's when the asteroid tumbled into a particularly unaerodynamic position. The 'contrail' of vaporised and condensed rock stops at that stage because the rock had stopped boiling; it's still glowing hot and surrounded by plasma when it leaves the camera frame.

I do hope someone got a high-altitude aircraft (a MiG-25 would work well if they had one around) with sampling equipment up to the vicinity of the trail before high-altitude winds blew it away.

The hole in the ice on the lake a hundred miles further down the track is produced by a rock falling not much faster than had it been dropped from an airliner; the asteroid had broken into pieces and the pieces are moving at the terminal velocity of a large rock in air, which is still enough to make a mess.

If an asteroid came straight down, it would punch through the atmosphere in a couple of seconds and still have quite a lot of its decent atom-bomb's worth of energy at ground level. Which would be unfortunate for anyone at ground level.

[LaurV]

Originally Posted by firejuggler

Every meteorite fall on earth mapped; or at least those we know about.

I wonder why no meteorite felt into the ocean.... :whitsle:

[Uncwilly]

Originally Posted by LaurV

I wonder why no meteorite felt into the ocean.... :whitsle:

A while back I saw a day-time bolide (that I reported). That if it survived would have landed in the ocean.
I knew where I was standing to within a about 5 feet on the north-west axis and I ranged ~15' on the east-west axis. I was looking through some clerestory windows, so I had a confined viewing angle.

[akruppa]

Originally Posted by fivemack

and then there's the flash significantly brighter than the Sun which I think corresponds to the point of maximum deceleration - I suspect that's when the asteroid tumbled into a particularly unaerodynamic position.

... or the point where the asteroid fragments and the pieces suffer greater combined drag than the complete thing did, along with greater surface area to emit light.

[jasong]

Originally Posted by akruppa

... or the point where the asteroid fragments and the pieces suffer greater combined drag than the complete thing did, along with greater surface area to emit light.

Which is better for the people on the ground, the asteroid exploding near the ground, or hitting the ground nearly intact?

And I'm asking from a survival perspective, not a scientific perspective, if you get my meaning.(since, technically, even a survival analysis requires science. The scientific perspective would mean the scientists studying it were happier, even if people affected by it weren't)

[bcp19]

Originally Posted by jasong

Which is better for the people on the ground, the asteroid exploding near the ground, or hitting the ground nearly intact?

And I'm asking from a survival perspective, not a scientific perspective, if you get my meaning.(since, technically, even a survival analysis requires science. The scientific perspective would mean the scientists studying it were happier, even if people affected by it weren't)

From a logical point of view, I would say hitting the ground would be more survivable, but only by degrees. The atom bomb dropped on Japan detonated at ~2000 feet IIRC, which caused far greater damage from the shockwave then if it had exploded at ground level.