Norwegian skydiver nearly struck by meteorite | Hacker News Reader

Norwegian skydiver nearly struck by meteorite

nrk.no

150 pointsoyvind115 comments

I did some quick googling and found this interesting research from Oberlin, with a history of meteorite injuries and deaths:

     1420 BC  Israel - Fatal meteorite impact.
     588 AD China - 10 deaths; siege towers destroyed.
     1321-68 China - People & animals killed; homes ruined.
     1369  Ho-t'ao China - Soldier injured; fire.
     02/03/1490 Shansi, China - 10,000 deaths.
     09/14/1511 Cremona, Italy - Monk, birds, & sheep killed.
     1633-64 Milono, Italy - Monk killed.
     1639 China - Tens of deaths; 10 homes destroyed.
     1647-54 Indian Ocean - 2 sailors killed aboard a ship.
     07/24/1790 France - Farmer killed; home destroyed; cattle killed.
     01/16/1825 Oriang, India - Man killed; woman injured.
     02/27/1827 Mhow, India - Man injured.
     12/11/1836 Macao, Brazil - Oxen killed; homes damaged.
     07/14/1847 Braunau, Bohemia - Home struck by 371 lb meteorite.
     01/23/1870 Nedagolla, India - Man stunned by meteorite.
     06/30/1874 Ming Tung li, China - Cottage crushed, child killed.
     01/14/1879 Newtown, Indiana, USA - Man killed in bed.
     01/31/1879 Dun-Lepoelier, France - Farmer killed by meteorite.
     11/19/1881 Grossliebenthal, Russia - Man injured.
     03/11/1897 West Virginia, USA - Walls pierced, horse killed, man injured.
     09/05/1907 Weng-li, China - Whole family crushed to death.
     06/30/1908 Tunguska, Siberia - Fire, 2 people killed. (referenced throughout paper)
     04/28/1927 Aba, Japan - Girl injured by meteorite.
     12/08/1929 Zvezvan, Yugoslavia - Meteorite hit bridal party, 1 killed.
     05/16/1946 Santa Ana, Mexico - Houses destroyed, 28 injured.
     11/30/1946 Colford, UK - Telephones knocked out, boy injured.
     11/28/1954 Sylacauga, Alabama, USA - 4 kg meteorite struck home, lady injured.
     08/14/1992 Mbole, Uganda - 48 stones fell, roofs damaged, boy injured.

http://www.oberlin.edu/faculty/bsimonso/group9.htm

Hey, I took that class in 2004!

I grew up in Oberlin and was friends with Bruce's kids, so this is cool to see in this context.

I've seen the Sylacauga meteorite (2nd from the last) in person. It currently resides in Smith Hall, the museum of natural history, at The University of Alabama in Tuscaloosa.

The data are interesting on their own if you start with the idea that meteor strikes are random across centuries, but the information collection and preservation isn't. For instance, with two data points you might claim there were more monks than princes in Renaissance Italy, but they were both surrounded by literate people who kept records compared to the even more numerous peasants. However, I suppose interpreting small datasets so that they fit preconceived notions isn't very productive.

It does seem strange that there are ten 19th century events and eight in the 20th century. Not so much because the numbers are different, but because there was twice the population, and literacy and communication were so vastly improved.

More people are working indoors in tall buildings and traveling in cars. So they are more concentrated where they live and travel. And each sighting is counted only once, regardless of how many people saw it.

Relative to the entire population, humanity is more urbanized, but that seems irrelevant to me compared to how many single square miles on the earth's surface contain a human who is connected to the global community.

While the decreasing number of people needed to farm a square mile seems like it would matter enough to decrease the newsworthiness of meteor strikes in some agricultural regions, it still seems likely that there has been a net increase in total area that includes the lower bound of population density where a meteor strike would be sufficiently newsworthy to make this list.

Take Las Vegas over the past 50 years as an example. It's a prime example of people being increasingly insulated from the outdoors, yet the footprint and total area of settled land has grown dramatically. It hardly matters whether you're inside or not, if a meteor strikes your block.

Edit: I was curious about the data and found this Google Earth file[1]. It looks like there definitely are many more recorded events, and it's just that the bar for being newsworthy has risen. However, what's strange is the preponderance of events in NW Texas and north of there. If records were population-based, then it should look like population density maps. I can't figure out off hand what causes the density of events, other than flat land and maybe tornado observation equipment, but that would seem to apply to other areas as well.

[1]https://productforums.google.com/forum/#!topic/gec-places/59...

A related question: what's the probability of an aircraft being struck by a meteor. Seems this question was asked in the wake of the Air France flight 447 disappearance (since resolved as pitot tube freezing combined with pilot error and control feedback failures of the Airbus design).

But still, the odds of a strike on _an_ aircraft over the next 20 years are about 4%:

http://blog.revolutionanalytics.com/2009/06/how-much-of-a-th...

at any given time, airliners cover 2 billionths of the Earth's surface. There are 125 meteors an hour, each with probability 2x10-9 of striking some airplane. In 20 years, that's about 22 million independent possible impact events. The chance that every one of those meteors misses every airplane is: ppois(0,2e-922e6)*

(Using R).

So the odds of an asteroid flying past a skydiver aren't as infinitesimal as one might otherwise think.

It also makes one wonder at the possibility of space-junk collisions being the cause of past aviation accidents. There's little enough evidence this would leave, particularly for a flight which disappeared entirely without a trace, or whose wreckage was only found much later.

That would be under an assumption that the distribution of planes around the globe is even. Given most jetliners are flying in corridors, I would say the actual probability is much much lower. The same can be probably said about meteorites - I guess their geographic distribution is uneven as well.

If the meteorite strikes are evenly distributed, and if the planes aren't actually stacked (i.e., flying directly above one another) very much, then I don't think the plane positions matter for this calculation.

If the distribution of meteors is perfectly even and all of the planes are parked next to each other in the desert, then the probability should be the same 4% expectation within the next 20 years of one of those parked aircraft being hit.

While staying within corridors would not matter, the distribution by latitude probably does, and my guess is that they align enough to actually increase the odds.

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 entirely sure this is the case -- because the Earth orbits the Sun, the eastward-facing side should be sweeping through more debris than the west, which means that if you could concentrate your flights on that side, you'd be at higher risk. As it is, most flights tend to operate during daylight hours, with the before-noon flights being at greater risk. More reasons to catch the afternoon flight if you prefer to play things safe, or the morning flight if you feel like making history (or low-grade mysteries of the unknown TV programmes).

>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 analysis')

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

>Flying faster means less time in the air, where meteorite strikes are particularly dangerous (as opposed to strikes while taxiing, or sitting idle).

That's a very good point: for a plane, reaching the ground is the equivalent of a runner reaching shelter from the rain.

But I suppose planes generally spend about the same amount of time in the air, no matter how fast they go. The faster plane just travels further in that time. There's no obvious reason a fast plane would spend more time safely on the ground than a slow plane.

Perhaps flying faster is safer for individual passengers, but more dangerous for the plane?

reaching the ground is the equivalent of a runner reaching shelter from the rain.

A meteorite capable of striking a plane in flight is just as equivalent of striking it on the ground. It's already passed through the ablative portion of its entry, and is falling at terminal velocity. So the probabilities of a strike don't actually change.

The implications for the aircraft, passengers, and crew, are rather different, however, when the plane is at-rest and on the ground.

>The implications for the aircraft, passengers, and crew, are rather different, however, when the plane is at-rest and on the ground.

Yes, that's so. A 300km/h 5kg rock striking any part of a plane in flight must have a very high probability of proving fatal for all aboard. On the ground the risk of injury for each passenger must be much lower - the plane might even be empty.

However, while the plane is in the air, it seems that a faster plane moves through a greater volume of space per unit of time, compared to a slower plane, therefore it is at greater risk of passing through the space occupied by a meteorite in any particular hour. So, assuming that faster planes spend about the amount of time airborne as slower planes, the risk of an accident is higher for faster aircraft.

The risk for an individual passenger is not increased in the same way (I guess it is not much affected by aircraft speed), because the faster aircraft gets them to their destination in less time, so they spend less time vulnerable to meteorite impacts on the aircraft.

>> 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.

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.

It's not the leaning forward (which reduces your forward cross-section), but your forward motion (which increases your _effective_ cross-section relative to the rain, which is the relevant factor in the running example.

In the case of an aircraft, since the frontal surface area is smaller than the topside area, the effect of velocity is to reduce the apparent interface.

You can skip to the photo collage to get a better look at it.

http://www.youtube.com/watch?feature=player_detailpage&v=jfE...

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 undercarriage panel of an airliner, and was carried by strong winds. Or a particularly slow meteorite.

These rocks slow down considerably when they move through the atmosphere (Unless they are massive and this one was not). What is also interesting is most the time they are cold to the touch immediately after impact.[1][2]

[1]http://misconceptions.us/are-meteorites-hot-or-cold-when-the... [2] http://curious.astro.cornell.edu/question.php?number=215

GoPros have high frame-rate modes.

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.

By the time it has reached the kind of altitude that skydivers would be operating it, a meteor would have lost most of its speed to atmospheric compression and friction. According to this faq [1] the terminal velocity for a small meteorite is 200-400 miles/hour, which is not far from your estimate.

[1] http://www.amsmeteors.org/fireballs/faqf/#12

> If that's a 60fps camera (I think it is?) ...

The camera appears to be recording at a rate of about 10 frames per second. This is a way to reduce memory consumption in a portable device in which recording duration has a higher priority than recording frame rate.

AT 10 FPS, the rock's sequential positions seem consistent with a falling rock.

And, lo and behold:

http://gopro.com/cameras/hd-hero3-silver-edition

Quote: "Features video resolutions up to 1080p60, 10MP photos up to 10 frames per second, enhanced low-light performance and built-in Wi-Fi. Waterproof to 131’/40m."

According to the above, ten frames per second is the highest available frame rate.

> Or a particularly slow meteorite.

Not a meteorite until it gets to the ground.

So even slower. At 20 mph, it could've simply come out of his parachute.

> So even slower. At 20 mph, it could've simply come out of his parachute.

It seems you're missing the point that the rock passed him by at a fairly high horizontal speed, while descending past him. That's not consistent with the rock coming out of his canopy.

The 1080p60 means 1080p video at 60 frames per second. I would guess they are taking videos and not capturing stills, but who knows.

That's 1080p (~2MP) at 60fps, or stills at 10MP at 10fps.

$ 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, aerodynamic drag is proportional to the square of the speed.

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

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

Er, the actual direct link: http://www.discovery.com/tv-shows/mythbusters/videos/soda-cu...

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.

> Did you actually read the article? The stone/object they filmed was within the atmosphere

OH! They were parachuting inside the atmosphere!

I read the article, watched the video, and read other content related to it, so the answer is yes. Somewhere i ran into that crazy speed estimate.

I am very skeptical. Although quite stupid, it wouldn't be hard for the other guy to have thrown some kind of junk and get it on camera, then claim it was a meteorite.

I bet nobody ever finds any evidence of said "space rock".

So they wasted the time and money of a few geologists, and spent a day or more with a group of friends/family searching around the forests for a meteorite.. because of a stunt for fame?

HN skeptics. The shit they say, I swear.

>> it looks like each frame has the fragment at about 3 feet from its last position

How did you arrive at this number? What distance do you estimate between the camera and the falling rock?

> If that's a 60fps camera (I think it is?), that's 180 f/s speed or 122mph.

Are you assuming the skydiver is stationary?

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.

This site has more information. It's in Norwegian, but there are some charts and graphics which give an idea how they've been trying to locate the rock by analyzing the video and checking wind speed records.

http://norskmeteornettverk.no/wordpress/?p=1329

They estimate the speed of the falling rock at 280km/h (vertical) and the speed of the guy in the wingsuit at 148km/h (at 37 degr). It seems like they're still uncertain about the exact speed, though. The wind speed was about 5m/s.

One document in the video suggests the altitude that the rock passed him was 1200m... so the rock would have hit the ground 15 seconds later at 280km/h

The research website mentioned in the article is linked on that page, but it isn't up yet.

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...

I imagine the rushing air can cool a rock pretty rapidly. The increase in terminal velocity will also tend to partially counteract the increased volume:surface-area ratio of larger rocks.

It has to be a pretty big rock to be hot when it hits the ground. Smaller pieces, on landing, are often found to be quite cold, entry heating not being long enough to remove the in-space cold soak, and the upper atmosphere being chilly.

As I understand it, the rock doesn't get especially hot. The hot surface ablates, and the rock underneath remains relatively cool (doesn't have time to heat up).

From http://en.wikipedia.org/wiki/Atmospheric_reentry#Blunt_body_... (admittedly about spacecraft rather than meteorites):

"Through making the reentry vehicle blunt, air cannot 'get out of the way' quickly enough, and acts as an air cushion to push the shock wave and heated shock layer forward (away from the vehicle). Since most of the hot gases are no longer in direct contact with the vehicle, the heat energy would stay in the shocked gas and simply move around the vehicle to later dissipate into the atmosphere."

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.

They keep talking about how lucky he is it missed him, but I almost think the opposite is true: He'd have to have been staggeringly unlucky to have been hit by it.

In fact, he was doubly lucky. Firstly, he was incredibly lucky to have witnessed a meteorite passing a few meters from him. Secondly, he was very lucky not to be killed by the meteorite that was passing a few meters from him.

Triple lucky for capturing those events in video!

Is it me or does it look like the "meteorite" is moving quite slow. Shouldn't it be moving so fast that you'd need a high speed camera to see it in that detail?

Also...his parachute is always above him, maybe it fell out of that.

Yep; so slow that there is no motion blur.

Odds of a meteor are absurdly really low. Much more likely this is a fake or a rock packed in his chute.

My understanding is that chutes are packed with great care since they're the only thing stopping one from going "splat!"

I could believe that it's an intentional fake, maybe, but unintentionally packing a good-sized rock seems unlikely... although, I guess it's not as improbable as a meteor sailing past your head while you're skydiving!

It's probably not a fake or packed inside the chute, since he was under canopy for some time when this occurred. Low odds are not zero odds, but then again, it can be a clever April fools segment.

Also, chutes are not packed with great care. A main (the parachute you generally use) takes an experienced packer 5-10 minutes to fully pack and some people hurry through it to get on the next load. Outside of two things you need to get right (make sure the slider is up, make sure lines aren't over the fabric), it will open. Most of the packing is all about reducing the pack volume and slowing down the opening, not ensuring it.

A reserve however (the second chute sport jumpers wear), gets packed by a certified packer and gets re-inspected and repacked at least once every 180 days.

Video was shot on 17 June 2012 according to video at 0:44, so strange april fools timing.

Motion blur is a function of distance travelled in screen space per frame and shutter duration, which can be very short for go pro type cameras in bright sunlight. So I wouldn't necessarily expect obvious motion blur.

> Odds of a meteor are absurdly really low

Odds that I win the lottery this week are absurdly low. Odds that someone will win the lottery this week are quite high.

Once the friction of the atmosphere has had a chance to slow it down, what then is the terminal velocity of a rock that size? Not fast is my intuition.

As for falling out of the parachute, and whether it really is a meteorite, the article discusses that: probably not, and almost certainly yes.

It had already entered the atmosphere, and probably slowed down significantly due to friction, then based on its mass it reached a low terminal velocity.

https://en.wikipedia.org/wiki/Terminal_velocity

Ram pressure, not friction

To get really technical, it's wave drag. ;) There's a fascinating discussion here:

http://cosmoquest.org/forum/showthread.php?35327-meteors-ram...

The article states that the meteorite already slowed down to around 300 km/h because the incident happened at a low altitude and the heavy braking was already over.

That seems about right... It looks like it travels roughly a meter or so between frames, and the GoPro was likely recording at 60fps, so it was traveling somewhere around 60m/s relative to the parachutist. So add another 10 m/s for rate of descent of the camera and you come up with 252 km/h.

I just spent a while looking up the maths on this and was really surprised to find that the terminal velocity of a spherical rock (diameter 10cm, density 2.5g/cm^3) at this altitude is remarkably close to 300 km/h (I got 340).

Aside: up until now I had imagined that if a skydiver were to ever drop a rock of that size (or a dense piece of equipment like a DSLR) during freefall they would never be able to catch it, but as the terminal velocity of a skydiver in "dart" position is about 320km/h that's not the case. Pretty cool.

It's right after his parachute opens, so he hasn't slowed down that much yet.

Yeah, Occam's razor tells me that it's much more likely that a stone got stuck somewhere in their skydiving apparatus than having a meteorite fly right past you while you're skydiving.

Maybe I'm underestimating the quantity of meteorites falling on the earth but since the newspapers aren't exactly filled with news of people getting killed by falling rocks I'm not yet ready to believe that was a meteorite.

I am not sure how you are using Occams razor there. It's well known that metorites falls to earth. Also see top comment right now.

He explains in the video why it's not possible to have been from the aircraft or other flyers.

The first guy's chute was open. The rock flew past the first guy. Then a second guy (with his chute not yet open) flew past the first guy. When the rock flew past the first guy, the second guy was above him, and whatever aircraft the second guy jumped from must have also been above him.

If you look at how a parachute is packed, and how it unfolds when deployed, what you described is definitely not the simpler explanation preferred by Occam's razor.

Well, since it seems I'm in a minority here I'll accept that I might be misjudging the odds on this one, especially since I know nothing about skydiving.

I guess it goes to prove that since nowadays we're almost all carrying video recorders with us at all times the probability of catching the most elusive events on video gets increasingly large. I expect to see a video of someone standing at the foot of a rainbow any day now.

It could have fallen from or (if they are being stupid) been thrown by the other guy, who happens to appear in the frame just after the object.

Even low probability events happen. It just means we can be less certain about when they will/might happen.

Occam's razor tells me it's much more likely the winner of the lottery cheated, because the odds of winning are so low.

No it did not fell out of the parachute. To the obvious:

If it would have been in the parachute, it would be moving at the same velocity as both the parachute and the man. It obviously can't have been under the parachute, it would have droppped instantly, it doesn't.

If it would have been on top of the parachute it would have gotten a push upwards to reduce speed (but its still moving _downwards_ unless some magic explosion happened).

Now according to the video, from the time the parachute opens, it takes roughly 8 seconds (!) until the rock passes. During that time the mans velocity decreased substantially due to the parachute...

Well just do the math.

Seems strange that the other diver is following the same path as the meteorite and passes by just a few seconds later. Could he have dropped it and it accelerated to a speed faster than he was travelling?

ie, thrown it? That does seem far more likely than it being from space.

If he threw a rock of that size at his buddy ... what a jerk

People are stupid, sometimes. Especially on internet videos.

Possibly. A small rock would have a lot less air resistance than a person, and those suits are designed to increase air resistance. So it might end up with a higher terminal velocity and fall slightly faster.

http://www.wired.com/2013/10/do-heavier-objects-really-fall-... http://www.physicsclassroom.com/mmedia/newtlaws/efar.cfm

> A small rock would have a lot less air resistance than a person, and those suits are designed to increase air resistance. So it might end up with a higher terminal velocity and fall slightly faster.

This is a bit more complicated than it appears at first glance. Other things being equal, a 3D object's mass increases as the cube of a single dimension's increase, but its surface area increases only as the square. Therefore a smaller object's atmospheric terminal velocity can be expected to less than that for a large one. This is why many kinds of small animals can fall great distances through the atmosphere and land unharmed.

(Until objects approach terminal velocity, they all fall with the same profile. Only when approaching terminal velocity do their speeds change.)

On the other hand, a typical rock (non-metallic) has 3.5 times the density of a human, so that argues in favor of a greater terminal velocity.

A full analysis would need to take into account the human's flight suit, which turns vertical kinetic energy into horizontal kinetic energy, and the rock's size, shape and composition.

But without any of this and a priori, the idea of a rock flying past a human, as in the video, is perfectly reasonable.

One more thing. The picture of the rock passing by the human is actually most likely a person flying horizontally past a rock that's dropping vertically.

A wingsuit has a forward speed of around 100mph and your arms are bound. It definitely didn't come from a friend. It looks like it has significant forward speed like the jumpers. Throw from the aircraft stops at around the 10 second mark into freefall on a wingsuit jump it's likely they were 2 minutes or more after exit making the forward speed of the rock likely to come from neither another jumper or the plane.

JFYI To be hit by a meteorite you would either need to be close to the Earth's surface or for somebody strong to throw it. Technically it is not a meteorite until it impacts with the Earth's surface, therefore this object may actually be a meteoroid.

Ah, technically correct.. the best sort of correct.

It seems to me though that a meteoroid that has evidently survived reentry but has not yet reached "the surface" properly might be something of a previously unhandled edge case. Normally you would avoid naming meteoroids to be meteorites until after you have found them safely on the ground because it is possible that they burned up during their observation, but this one was observed well after the point where it may have burned up. Also from a delta-v perspective, it had already performed the majority of its transition (from kilometers per second to likely less than a hundred meters per second).

> Technically it is not a meteorite until it impacts with the Earth's surface, therefore this object may actually be a meteoroid.

Not quite. Before entering Earth's atmosphere, it's a meteoroid. While passing through the atmosphere, it's a meteor. After landing, it's a meteorite.

http://www.livescience.com/27183-asteroid-meteorite-meteor-m...

> While passing through the atmosphere, it's a meteor.

Just to be an absurdly pedantic, it's actually only the flash of light that is the meteor and not the rock itself.

http://hubblesite.org/reference_desk/faq/answer.php.id=22&ca...

Meteor is a description of the burning in the atmosphere not the object itself, which is still a meteoroid.

> Meteor is a description of the burning in the atmosphere not the object itself ...

Yes, fair enough. Unless the object is consumed in the process of generating the visible presentation (often true), which makes it a meteor -- or perhaps I should say "turns it into a meteor".

I don't know why everyone is assuming it was so close. It looked further away from the dude to me... i'd guess ~100 feet or more.

In any case, given camera optics, you can only solve for size or distance given the other.

I wonder if it's possible to use computer vision techniques on the video footage to calculate the position and altitude of the skydiver at the time, and then also estimate the trajectory of the rock?

Some analysis going on here at least (text in norwegian though): http://norskmeteornettverk.no/wordpress/?p=1329

Go to 2:12 if you want to skip the fluff.

The fluff is actually worth watching as well. The guy is clearly taken back by this experience.

It's extremely hard to discern but it looks like there was possibly another smaller piece that goes flying by just before the camera stabilizes and the main meteor comes into view.

That would make sense; it's clearly a fragment from a larger object that broke up during entry, probably late in the heating phase. (There is a visible dark "outside" and light "inside" on the piece we see.) So there are likely to be other pieces nearby.

He almost got taken out by 1/100bn odds.

We all do.

Could it be Blue Ice[0] or a similar leakage from an airplane flying above the skydivers?

[0] http://en.wikipedia.org/wiki/Blue_ice_(precipitation)

Could it have fallen from some other plane, they weren't aware of, that was above their altitude or do the principles of terminal velocity and gravity not support that hypothesis?

I accidentally downvoted you, sorry :-(

No problem ... it happens.

I've neutralized the errant downvote.

Isn't it more likely that the rock fell out of their plane?

He says at 1:20 that the plane is below them the entire time. That was my initial thoughts too, though.

The plane is well below the skydiver (about to land) when the rock passes by. There's no way it came from the plane.

He addresses that in the video: other jumpers and the plane are not above him at this point, so odds are the rock came from elsewhere.

The presumes a reliable narrator, but it seems plausible. This is one guy with an in-flight asteroid sighting. Not as if they're crawling out of the woodwork. And the experts called in seem to find this credible. Though people hamming up an act for cameras is also not unheard of.

Given its a wingsuit jump he's likely miles from where they exited the plane. The rock would have a more straight down trajectory as well. You can tell the forward speed when the other jumper comes by.

April Fool?

Presumably the downvote means, "No, but I'm not going to tell you why"?

Any Nordic types following this story?

Not April fools'. The story was published by NRK today, 3. of April.

This was published by NRK, the Norwegian equivalent of BBC on April 3rd, and the guys in the video seem sincere. I suppose it could convievably be an elaborate April fools prank by the skydivers if they talked to NRK on the 1st, I suppose. But I suppose they would have come clean by now.

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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