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Norwegian skydiver nearly struck by meteorite

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Re: Norwegian skydiver nearly struck by meteorite

#101

Post by jccooper »

dclowd9901 wrote: post #47

I'm... skeptical. If you look at the frames of the meteorite falling, it looks like each frame has the fragment at about 3 feet from its last position. If that's a 60fps camera (I think it is?), that's 180 f/s speed or 122mph. That seems really slow for a rock flying into the atmosphere from space, and far slower than a rock would have to be going for it to "cut him in half." My guess: a rock that fell off the underc…

Terminal velocity for a small flat rock is not all that fast. 200-400mph: http://www.amsmeteors.org/fireballs/faqf/#8

Considering the skydiver also has a significant speed, that corresponds reasonably well with your estimate.

The rock also looks very much like fragment of a meteorite with classic "fusion crust".

And probably they would have known if an airliner was in the area, considering they were essentially right above a general aviation airport. And probably airliners would not choose to fly over that area.

I think the meteorite identification is much more plausible than anything else.

Re: Norwegian skydiver nearly struck by meteorite

#103

Post by roc »

FatalLogic wrote: post #98
dredmorbius wrote: post #82

Earlier quoted context omitted.

As others have said: the distribution of the planes over the Earth (and their speed -- one Yahoo site I ran across suggested they're harder to hit because they're moving fast -- that's also irrelevant, not to mention that pretty much everything on Earth is moving at about 20km/s relative to an asteroid) doesn't matter. Because meteorites aren't aimed. Odds are they'll land pretty much anywhere on the planet. I'm not…

>one Yahoo site I ran across suggested they're harder to hit because they're moving fast -- that's also irrelevant, Indeed, it's not as if they're trying to dodge. However, doesn't a faster plane actually have a higher probability of intersecting the same space as a falling rock? Comparable to: http://news.bbc.co.uk/2/hi/uk_news/magazine/4562132.stm ('...So running fast actually makes us wetter according to this anal…

Running makes you wetter than walking over an equivalent time period. The main goal of running in the rain is to get to a shelter -- to minimize that time.

Something your link covers, and points out. [1]

So it would be with a plane: Flying faster means less time in the air, where meteorite strikes are particularly dangerous (as opposed to strikes while taxiing, or sitting idle). So while a faster-flying plane is more likely to encounter a meteorite than a slower-flying plane, if flying faster means less time in the air it's going to be "safer" overall.

[1] "So here we have it - more mathematical advice to avoid getting wet. Because we divide by VP in this equation, maximising our velocity now emerges as a good idea, assuming there is a shelter available."

EDIT: grammar

Re: Norwegian skydiver nearly struck by meteorite

#104

Post by lifeisstillgood »

FatalLogic wrote: post #98
dredmorbius wrote: post #82

Earlier quoted context omitted.

As others have said: the distribution of the planes over the Earth (and their speed -- one Yahoo site I ran across suggested they're harder to hit because they're moving fast -- that's also irrelevant, not to mention that pretty much everything on Earth is moving at about 20km/s relative to an asteroid) doesn't matter. Because meteorites aren't aimed. Odds are they'll land pretty much anywhere on the planet. I'm not…

>one Yahoo site I ran across suggested they're harder to hit because they're moving fast -- that's also irrelevant, Indeed, it's not as if they're trying to dodge. However, doesn't a faster plane actually have a higher probability of intersecting the same space as a falling rock? Comparable to: http://news.bbc.co.uk/2/hi/uk_news/magazine/4562132.stm ('...So running fast actually makes us wetter according to this anal…

>> However, doesn't a faster plane actually have a higher probability of intersecting the same space as a falling rock?

I'm pretty certain thats true - against my intuition.

If a meterite will be crossing 35,000 feet at 300 km/hr it will be in the layer of the atmosphere the height of a Boeing for say 1/10th second. (300km/h ~ 8m/s, Boeing 747 about 8m tall in body if you squint)

so an aircraft that is stationary (!) in the air, will consume 1 airframe's worth of space in that 1/10th of a second.

A plane that travels its own length in 1/10th of a second will consume two airframes worth of space in the same 1/10th so doubling its chances of getting hit.

A Boeing 747 is approx 70m long which would mean to double its chances of getting hit it would have to travel 700m/sec or about twice the speed of sound (340m/s)

Wow.

Re: Norwegian skydiver nearly struck by meteorite

#105

Post by jameshart »

dclowd9901 wrote: post #69
allthatisgold wrote: post #54

Earlier quoted context omitted.

Camera isn't stationary.

Even if it's not, the relative speed is what's the issue here. The thing I take most issue with is his statement that this rock would've killed him. If it's only moving 120 or so mph in relation to his speed, it probably wouldn't kill him, let alone cut him in two.

Let's say that meteorite is about the size of a baseball. 120mph is faster than a fastball baseball pitch, and getting hit by a fastball? That can do damage, which is why baseball players wear protective gear (the catcher's padding is not for show). An iron nickel meteorite is maybe five-six times denser than water; a baseball? Well baseballs float - they're about 2/3 as dense as water. So the meteorite is maybe 3-4 times as dense as a baseball, going 20% faster than the fastest fastball ever recorded; so it's carrying more than 4 times the kinetic energy of a fastball. If that hit you, it could certainly be immediately fatal, or at least cause severe injuries; I would imagine that becoming severely injured while skydiving comes with a significantly increased risk of death.

But maybe he's just being a drama queen.

Re: Norwegian skydiver nearly struck by meteorite

#106

Post by JohnBooty »

FatalLogic wrote: post #98
dredmorbius wrote: post #82

Earlier quoted context omitted.

As others have said: the distribution of the planes over the Earth (and their speed -- one Yahoo site I ran across suggested they're harder to hit because they're moving fast -- that's also irrelevant, not to mention that pretty much everything on Earth is moving at about 20km/s relative to an asteroid) doesn't matter. Because meteorites aren't aimed. Odds are they'll land pretty much anywhere on the planet. I'm not…

>one Yahoo site I ran across suggested they're harder to hit because they're moving fast -- that's also irrelevant, Indeed, it's not as if they're trying to dodge. However, doesn't a faster plane actually have a higher probability of intersecting the same space as a falling rock? Comparable to: http://news.bbc.co.uk/2/hi/uk_news/magazine/4562132.stm ('...So running fast actually makes us wetter according to this anal…

roc is correct and, additionally, remember that part of the reason that you pick up more moisture per second while running is because while running you lean forward - by changing your orientation from the vertical, your cross section relative to the path of the rain increases as well.

whereas with a plane, it's exposing the same cross section to the meteor whether it's flying level at Mach 2 or sitting on a runway.

Re: Norwegian skydiver nearly struck by meteorite

#107

Post by doorhammer »

NAFV_P wrote: post #72
dclowd9901 wrote: post #47

I'm... skeptical. If you look at the frames of the meteorite falling, it looks like each frame has the fragment at about 3 feet from its last position. If that's a 60fps camera (I think it is?), that's 180 f/s speed or 122mph. That seems really slow for a rock flying into the atmosphere from space, and far slower than a rock would have to be going for it to "cut him in half." My guess: a rock that fell off the underc…

$ If that's a 60fps camera (I think it is?), that's 180 f/s speed or 122mph. That seems really slow for a rock flying into the atmosphere from space, and far slower than a rock would have to be going for it to "cut him in half." A slushie travelling at 120mph into a windshield: http://www.discovery.com/tv-shows/mythbusters/videos/soda-cu... Regarding the speed, the atmosphere will slow the rock down considerably, aer…

The high speed/slowmow internal shot of the slushie at 120mph:

http://www.discovery.com/tv-shows/mythbusters/videos/soda-cu...

Re: Norwegian skydiver nearly struck by meteorite

#108

Post by dang »

vegardx wrote: post #92
darkarmani wrote: post #74

Earlier quoted context omitted.

Agreed. When is the last time you saw a bullet videotaped on a normal camera? This is moving 10x faster than a bullet?

Did you actually read the article? The stone/object they filmed was within the atmosphere, thus going around terminal velocity, depending a little on the size of it, which varies a little on the estimations.

All: please don't say testy things like "Did you actually read the article?" on HN.

This is one of those phrases that can always be deleted with instant improvement in comment quality. Check out how much more substantive and neutral this comment is without it.

Re-read what you've posted and, if you notice phrases that add nothing but testiness to your comment, edit them out. That's what I do.

Re: Norwegian skydiver nearly struck by meteorite

#109

Post by InclinedPlane »

woodchuck64 wrote: post #60

Shouldn't we be expecting a rock that has just been heated to plasma stage by atmospheric friction only seconds earlier to be glowing, steaming or leaving little molten fragments of itself behind? Update: maybe not. The last stage of flight is "dark and cold" according to this: http://www.meteorite-recon.com/en/Meteorite_fusion_crust_1.h...

Small rocks will experience substantial heating around their outside and will form a melt crust, but this cools down very quickly once the rock has slowed down. Most small meteorites are still cold in their interiors when they land.

Re: Norwegian skydiver nearly struck by meteorite

#110

Post by dang »

lotsofcows wrote: post #43
lotsofcows wrote: post #15

April Fool?

Presumably the downvote means, "No, but I'm not going to tell you why"? Any Nordic types following this story?

Comments that are (a) really short and (b) not obviously substantive almost always get downvoted. If instead you had written: "Could this be an April Fool?", people would have probably have recognized it as a sincere question.

Please don't add comments about getting downvoted, though. As the guidelines say, it makes for boring reading.

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