Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

ESA: Small meteorite will safely impact atmosphere tonight over northern France

twitter.com

Post reply on HN
Print view View original

51–60 of 85 posts

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#51

Post by Aachen »

spenczar5 wrote: post #39
singularity2001 wrote: post #34

why are these events always forecasted so late? some hours earlier i could have witnessed it

Two related reasons. 1m is quite small, so it needs to be close for us to detect it. Since we don’t have many observations, the error in estimates of its orbital path is high. In general, it also is extra difficult to calculate the exact last little bit of a trajectory that will impact earth because the force models start getting really wild as something gets very close to earth - approximations stop working.

> it also is extra difficult to calculate the exact last little bit of a trajectory that will impact earth because the force models start getting really wild

What kind of forces? I assume you're talking about the space part, before atmosphere, so I would assume it's the same gravity effects that you also get in space, just that gravity is a bit larger value. I wrote a gravity simulator at lgms.nl/p/badgravity so I have a bit of an idea but am definitely no expert (the thing doesn't do any sort of collisions and assumes 2d point masses), so I'm curious what you mean. Especially with the earth dominating the gravity and not needing to use N-body physics anymore, it should get more accurate if anything.

Could you elaborate or do you have a link? Or do you simply mean the compounding effect of having used N-body approximations for the interplanetary space part of the trajectory leading to different starting points for the final approach?

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#52

Post by bl0rg »

idlewords wrote: post #29
throwanem wrote: post #20

Earlier quoted context omitted.

The continuous-rod warhead in a Sidewinder will rip the hell out of an aircraft, which is made of tinfoil wrapped around complications. A rock from space, by contrast, is made out of rock wrapped around rock. Assuming charitably that the missile could generate an intercept, you would probably get some sparks, maybe more or less depending on how much of the rock is actually nickel and iron. But basically, the rock is…

This site truly is where humor goes to die.

I thought it was pretty funny.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#53

Post by mnw21cam »

Aachen wrote: post #41
tehc-uk wrote: post #33

I happened to be up watching the Super Bowl in the UK, saw the ESA tweet across my timeline and was able to pop outside to see it at the time they predicted - was also able to grab a video [0]. So cool to see how far our detection of these objects is coming along, especially for something as small as this was. [0] https://twitter.com/teh_c/status/1624967399131824130

Would you be willing to share your exact location, perhaps in an email to sar2667observation@lgms.nl? From a sibling comment: > Got so lucky finding that Brighton video as the 2nd result earlier. Spent another 15 minutes looking for a third angle but the "looking east", "looking south" indicated angles are either implausible or too inaccurate to be useful. A Paris video is of such quality that I couldn't for the life…

There's a moon in that video. That'll give you the angle more accurately than a building.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#54

Post by dmurray »

mnw21cam wrote: post #53
Aachen wrote: post #41

Earlier quoted context omitted.

Would you be willing to share your exact location, perhaps in an email to sar2667observation@lgms.nl? From a sibling comment: > Got so lucky finding that Brighton video as the 2nd result earlier. Spent another 15 minutes looking for a third angle but the "looking east", "looking south" indicated angles are either implausible or too inaccurate to be useful. A Paris video is of such quality that I couldn't for the life…

There's a moon in that video. That'll give you the angle more accurately than a building.

How? Everywhere nearby me, the moon is in the same direction, but my building isn't.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#55

Post by dmurray »

kijin wrote: post #26
version_five wrote: post #16

Earlier quoted context omitted.

But this isnt an orbiting satellite, it's an object moving at 20 km/s (quoting another post, I dont really know in what direction or relative to what) which is ~Mach 60. I don't know how that compares to satellites - is it close enough we'd expect an anti-satellite missile to work?

Depends on what kind of warhead you have on that missile. :) A small nuke could definitely obliterate a 1-meter rock, if you don't mind contaminating a large part of Europe with radioactive dust.

This isn't fantasy, either. There were plenty of air-to-air and surface-to-air nuclear-tipped missiles. All of the ones mentioned on Wikipedia [0] have officially been decommissioned for 40+ years, a development due both to disarmament agreements and advances in targeting by conventional missiles. But I wouldn't be shocked to learn there are still some deployed.

[0] https://en.m.wikipedia.org/wiki/Category:Nuclear_anti-aircra...

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#56

Post by chmod775 »

prvc wrote: post #17

"Safely" because it is expected to burn completely before impact with the surface? If not, then fair to call it a potential hazard, even if a small one?

These things don't even need to impact the surface to cause massive damage. They can disintegrate mid-air or just pass earth closely and the resulting shock wave will already be devastating. Examples: Tunguska explosion and the Chelyabinsk meteor.

At their speeds they're impacting the atmosphere in a similar way a bullet impacts water (it disintegrates and loses speed rapidly, causing a big splash).

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#57

Post by Aachen »

mnw21cam wrote: post #53
Aachen wrote: post #41

Earlier quoted context omitted.

Would you be willing to share your exact location, perhaps in an email to sar2667observation@lgms.nl? From a sibling comment: > Got so lucky finding that Brighton video as the 2nd result earlier. Spent another 15 minutes looking for a third angle but the "looking east", "looking south" indicated angles are either implausible or too inaccurate to be useful. A Paris video is of such quality that I couldn't for the life…

There's a moon in that video. That'll give you the angle more accurately than a building.

I considered that, but I don't think that works because where the moon appears in the sky also depends on where you are. There are two unknowns (moon and meteor) and one video (one equation), if I understand the math correctly (we didn't have solving multiple unknowns in school but this is the theory I heard in relation to GPS needing 4 sats to solve for x,y,z,time).

It surprised me how many different combinations of meteor-moon constellations I saw in the various videos being posted. For some, the moon was very close; for me, the moon was like 110° removed I think (somewhere over my left shoulder). Maybe, knowing it was in England, it could help me to narrow down the scenarios (perhaps from an area down to a line?), but I don't have the experience to do that in a time-effective manner and I don't know if it would significantly help with the outcome.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#58

Post by mnw21cam »

Aachen wrote: post #57
mnw21cam wrote: post #53

Earlier quoted context omitted.

There's a moon in that video. That'll give you the angle more accurately than a building.

I considered that, but I don't think that works because where the moon appears in the sky also depends on where you are. There are two unknowns (moon and meteor) and one video (one equation), if I understand the math correctly (we didn't have solving multiple unknowns in school but this is the theory I heard in relation to GPS needing 4 sats to solve for x,y,z,time). It surprised me how many different combinations of…

The exact location of the moon in the sky depends to a very small extent on your location on the earth's surface. The tweet says near Brighton, and that's already accurate enough to tell the direction of the moon much more accurately than the size of the moon in the sky. At the time of the video (3am UK time), the moon from brighton was at a compass heading of 144 degrees (calculated by Stellarium). The observer location of "near Brighton" is accurate to within a few km.

The moon at that time had a diameter in the sky of 0.5225 degrees (it doesn't change much), so you can also get a reasonably accurate idea of the zoom level of the video, taking the size of the moon in pixels when it is most in-focus (and accounting a bit for glare).

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#60

Post by rvba »

throwanem wrote: post #20
GalenErso wrote: post #12

Could a F-22 shoot it down? /s

The continuous-rod warhead in a Sidewinder will rip the hell out of an aircraft, which is made of tinfoil wrapped around complications. A rock from space, by contrast, is made out of rock wrapped around rock. Assuming charitably that the missile could generate an intercept, you would probably get some sparks, maybe more or less depending on how much of the rock is actually nickel and iron. But basically, the rock is…

There are bunker busters but most of them are conventional bombs, or cruise missiles (with a propeller).

If they can bust few (double digit?) meters of concrete, they could bust a rock. Assuming they dont miss and assuming they dont slip.

https://en.m.wikipedia.org/wiki/Bunker_buster

Obviously it would have to be some combination of an anti sat missile (so it can fly in space) and a bunker buster (so it can crush throigh rock).

Post reply on HN