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How can a meteorite explode?


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#1 Lode   Members   -  Reputation: 981

Posted 18 February 2013 - 04:48 AM

Hello,

 

This meteorite above Russia apparently exploded with a power 30 times stronger than the Hiroshima nuclear bomb.

 

I understand that it gets hot from entering the atmosphere, and is quite big with a mass of 10000 tons, but still, it existed out of stone and iron, how can such "passive" material create such a huge explosion?

 

Also, it went at 15 km/s and exploded 30km above ground. If it exploded 2 seconds later it would have hit the ground. How likely was that?

Thanks!


Edited by Lode, 18 February 2013 - 04:49 AM.


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#2 samoth   Crossbones+   -  Reputation: 4684

Posted 18 February 2013 - 05:06 AM

A Russian meteor could conceivably explode if it was a Korean nuclear long range missle test, or if it was a telecommunication sattelite from the Cold War equipped with half a dozen missles coming down. You don't really know what it was, do you.

It could also explode if, like most real meteors, it's made of more than just a single material and gets hot enough so something inside (whatever it is) gets vaporized and the outer hull can't keep the pressure any more. Say, frozen water inside, or anything. Even "inert" materials like iron and stone will become liquid and eventually boil, if you only make them hot enough.

About the size of the explosion, just consider the formula for kinetic energy. 10k tons are a huge number for m and 15km/s is also a terribly huge number for v2

Also, it went at 15 km/s and exploded 30km above ground. If it exploded 2 seconds later it would have hit the ground. How likely was that?

Very likely, as you can tell from the fact that no civilization we know of has been wiped off the planet during the last 6,000 years. Besides, 2 seconds are an eternity at such a speed, it's not like two seconds before impact are anywhere "near the ground".

#3 Hodgman   Moderators   -  Reputation: 29489

Posted 18 February 2013 - 05:29 AM

The Tunguska event exploded at 5-10km, with the power of 1000x Hiroshima's (sad that that's a unit of energy now)... and would've taken out a city had it have hit one, rather than Siberian forest (it levelled a 46km * 46km area of trees). So, these things are definately capable of doing a lot of damage.

 

Apparently, kiloton-equivalent air-bursts occur in the upper atmosphere (at safe altitudes) around once per year!

Interestingly, this 2013 meteor is apparently a "once in 100 years event", and Tunguska (a megaton-level event) was roughly 100 years ago, so it was fairly on time wink.png

 

I'm not sure about how the explosions occur, but like with anything moving extremely fast through the atmosphere, the increase in pressure in front of the object generates a hell of a lot of heat. I've had a stone barbecue crack and fire out bits of shrapnel explosively due to heating just from a wood fire, so I can imagine that with enough heat you could explosively vaporize a giant rock...

 

A Russian meteor could conceivably explode if it was a Korean nuclear long range missle test, or if it was a telecommunication sattelite from the Cold War equipped with half a dozen missles coming down. You don't really know what it was, do you.

Care for Occam's razor?


Edited by Hodgman, 18 February 2013 - 05:32 AM.


#4 sunandshadow   Moderators   -  Reputation: 4819

Posted 18 February 2013 - 05:39 AM

If you take a frozen mug and pour hot coffee in it, it can explode pretty dramatically, and glass or ceramic are two of the most "passive" materials there are.  It's all about temperature change causing uneven expansion.  Cold meteorite burning up in the atmosphere is the same kind of temperature change.


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#5 Milcho   Crossbones+   -  Reputation: 1175

Posted 18 February 2013 - 05:48 AM

My understanding is that the meteor exploded because it essentially 'hit' the atmosphere. At the high speeds at which it was moving, hitting the atmosphere must be more like a brick wall than gently passing through it.

 

I don't think heat had much to do with it - though I don't dispute that there's a lot of heat buildup due to the pressurized air. I've read somewhere that most meteorites that fall to earth are still frozen, mostly because the short entry time  (usually in matter of seconds) doesn't leave enough time for the core to be heated up at all - the rules of convection still apply - heat only spread so fast.

 

You don't really know what it was, do you

We kinda do. There's the lot of amateur videos posted online, the analysis of scientists of the explosion and the readings that were taken by various instruments around the world. I seriously doubt it was anything other than a meteor.



#6 samoth   Crossbones+   -  Reputation: 4684

Posted 18 February 2013 - 06:29 AM

Care for Occam's razor?

Occam's razor is applicable most of the time, but that's also its danger. Or rather, it's always applicable, but it's not always right. The apparent likely cause is not necessarily the only possible one, and not necessarily the correct one.

I'm not saying that it wasn't a meteor, it probably was. But a meteor strike, being relatively unlikely itself, is only moderately more likely than some of the shit that they've been launching into the orbit during the last 50 years eventually coming down again. With North Korea having done 3 (was it 3?) nuclear missle tests that we know about during the last 1 1/2 months (and probably another 3-4 that we don't know about), this isn't an entirely impossible theory either. It might not even have happened deliberately, it could just have been a malfunctioning rocket gone astray. Everything you shoot up eventually comes down again (well, almost everything).

Had the explosion been a bit higher, say 60-100km, one could exclude that possibility since obviously the lights didn't go out. But EMPs don't happen that close to the ground. We might know in a few weeks when nobody has died from radiation, though. If you ever hear about it, that is.

And that's the problem: You would hardly ever hear it in the news if it was anything else but a meteor, not in any part of the world, but especially when it happened in Russia -- they'd never admit to that.

It is surprising that you even heard there were casualties, Russia seems to have become extremely liberal of late by their standards. You would normally have expected something like "What you saw was a successful weather experiment, everything went as intended".

#7 Vilem Otte   Crossbones+   -  Reputation: 1392

Posted 18 February 2013 - 07:03 AM

As far as I remember from physics Milcho is right - atmosphere at that speed is like hitting brick wall.

 

According to report from NASA the object had diameter of maximally 17 m, mass around 10000 tonnes (a really heavy one, because their density is often less than water density) and velocity 17900 m/s. Kinetic energy of this object is 1602050000000000 J = 1602 TJ. Energy equivalent (in TNT) of this kinetic energy value is around 383 kTons of TNT - e.g. we need at least 383 kTons of TNT equivalent energy to just stop the motion of the meteorite. Assuming that energy of explosion must be higher than just kinetic energy (it's calculated using the thermodynamic energy of detonation) - we could get somewhere to 500 kTons.


Edited by Vilem Otte, 18 February 2013 - 07:33 AM.

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#8 Olof Hedman   Crossbones+   -  Reputation: 2743

Posted 18 February 2013 - 07:12 AM

...maybe it was a NK missile...

I'd say it's extremely likely to be a meteor, considering the number of independent observations, and the world wide consensus among astronomers that it was.
It behaved exactly like you would expect a meteor of a certain size and composition hitting the atmosphere.
 
North Koreas Kim Jong Un can hardly even fart without CIA picking up the vibrations, and the purpose of their tests is mostly political, it makes no sense to do secret tests.
There was 1 missile send up (without payload), and 1 underground nuke blown up in NK the last months. Before that, I think it was over a year since they did anything major.
Also, why would they test fire it over china? the Chinese would very much not like that, and they are pretty much the closest thing NK has to an ally.
And above all, why would they fire a _live_300kton_nuke_ to explode over russia?
A ballistic missile travelling across china would be noticed...  you need a very big conspiracy to cover that up. 
A malfunctioning missile will not travel 1000s of kilometers before blowing up. specially not in opposite direction of where it would be send.
There is no sense in doing "tests" with live nuclear ballistic missiles. No-one has done that, ever.
I'd list a bunch of other reasons, but I think this is enough to say that theory is extremely unlikely.

Edited by Olof Hedman, 18 February 2013 - 07:47 AM.


#9 Bregma   Crossbones+   -  Reputation: 4986

Posted 18 February 2013 - 07:36 AM

An 'explosion' is a rapid thermal reaction with rapid expansion.  Rapid expansion often results in the loss of structural integrity.

 

How could dynamite "explode"?  Well, a rapid oxidation reaction takes place in the substance, resulting in an endothermic expansion that transfers its energy into the surrounding substrate (which could be, say, rock in a mine or a railroad trestle in front of an oncoming mail train).  A great deal of force can be imparted by this rapid endothermic reaction.  Newton's third law state the force of a reaction is proportional to the mass involved and the acceleration, and the acceleration of the products of reaction is very high indeed.  This expansion takes fractions of a second.

 

So, how could an object colliding with a gas at very high velocity explode?  Well, chances are goof that this particular meteorite was a type called a 'carbonaceous chondrite' which tends to lack structural cohesiveness.  As it hits the atmosphere at a great velocity, a couple of things happen.  The outer layers heat very rapidly due to friction with the (rather thin upper) atmosphere, heating in an exothermic reaction, and an oxidative reaction begins between the exposed carbon and the free oxygen in Earth's corrosive atmosphere, and endothermic reaction.  A great deal of heat causes the chondrite to expand rapidly and lose its structural integrity  this exposes more surface area to the axidation reaction, which causes still further exothermic reaction, until a critical mass is reached and the entire object expands very rapidly.  This can take mere seconds.

 

So that is how a meteorite such as the one over Russia the other day can "explode":  a rapid thermal expansion causes the loss of integrity of the object.  It is, indeed, rocket science.


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#10 szecs   Members   -  Reputation: 2109

Posted 18 February 2013 - 09:35 AM

And that's the problem: You would hardly ever hear it in the news if it was anything else but a meteor, not in any part of the world, but especially when it happened in Russia -- they'd never admit to that.

In the age of Youtube, Facebook, and all the other crap...

 

It couldn't be much else than a meteor. The height of the explosion can be quite easily determined (from the latency of the sonic boom). Knowing the height, it's not so hard to determine the speed from the videos (so one could fairly easily make one's own calculations and estimations to verify the meteor theory even without any instruments, like satellite images of the event, or the cloud that was left behind).

 

Not anything that humans built are big enough to leave a 400 km long (and pretty thick) smoke (and I guess jet stream) trail with that speed at that height.

 

Plus the whole thing looks just the same as bigger falling start everyone of us probably have seen (with the explosion at the end). This was only bigger.


Edited by szecs, 18 February 2013 - 09:39 AM.


#11 samoth   Crossbones+   -  Reputation: 4684

Posted 18 February 2013 - 10:41 AM

The CIA and China would notice and wouldn't like it

Both the CIA and China (and Russia) would have the greatest interest in keeping it secret if any such thing happened.

Admitting that any such thing had happened would cause widespread panic (we're talking about a panic of biblical scale -- the end of the world, we're all going to die -- that kind of thing), which is just the thing governments don't like happening. But worse... both China and Russia would have to admit that they couldn't prevent it. That's something they'd never want to admit.
And, yet worse than the previous, China and former USSR would find themselves in a position where they would have to do something, if anyone was to ever take them seriously again afterwards. Such thing (accidential or not) is a more or less compelling reason for war, and they surely wouldn't want to go to war against a communist brother state. Therefore, given such a hypothetical case, they would definitively keep it secret, and you would definitively never find out.

The Chernobyl incident was only revealed after some guy in Sweden wondered where all that radioactivity came from all of a sudden. If it had been for Russia, you would still not know today.

There is no sense in doing "tests" with live nuclear ballistic missiles.

There is no sense in most of what governments do, for example, developing weapons of mass destruction in the first place, or making the place where you live uninhabitable for humans, or taking up loans to pay interests on loans they use to pay interests. That alone doesn't mean they're not doing it anyway.

looked exactly like you'd expect

I totally agree. It looked exactly like I'd imagine a meteor coming down, too. However, that doesn't mean much. The meteor in the Armageddon movie looked pretty good to me, too. Tie fighters in Star Wars make sounds (in vacuum) just like I'd expect them, and the airplane crash sites in September 2001 looked pretty authentic on TV as well.

The problem is, all I've seen is stuff on TV and on youtube (and presumably the same is true for you), and neither source is reliable in any way. Nor is anything that "some super sapient expert" tells on TV or on the internet.

All you really know so far (and all they know) is that there exist some movies of "something" from an unknown source, with unknown editing, and unknown censorship. Some big smoke/vapor trail, and some glowing tail with a big flash in the lower third of the sky. Fine, youtube is full with all kinds of fake videos. Some seismologists might in addition have picked up some recordings that tell them there was indeed a big boom, ok, fine... but again, that boom could have been anything.

Unless you can lay hands on a big piece of molten metal with an "alien" composition that doesn't normally occur in Russia (or on Earth) in that form, that's about it, and for all it's worth, it could have been anything. Including a comet, a sattelite, a missle, or a smoke show for propaganda.

#12 Chindril   Members   -  Reputation: 170

Posted 18 February 2013 - 11:38 AM

Seriously, a conspiracy ? Did you even watched the movies ? There's not a single missile on earth that can outshine the sun. It just does not happen. And missiles don't leave a trail of fire behind them. The fact you believe it can even be a possibility is ludicrous. And then you say the movies would be part of the conspiracy ? Laughable. The movies were uploaded from many different sources minutes to a few hours after the event, so Russians had to prepare them beforehand. Yeah right.



#13 wintertime   Members   -  Reputation: 1643

Posted 18 February 2013 - 11:49 AM

I thought that was gamedev here and not the flat earth society?laugh.png



#14 szecs   Members   -  Reputation: 2109

Posted 18 February 2013 - 12:01 PM

I thought that was gamedev here and not the flat earth society?laugh.png

You were wrong. It's Hollow Earth society here



#15 szecs   Members   -  Reputation: 2109

Posted 18 February 2013 - 12:43 PM

looked exactly like you'd expect

I totally agree. It looked exactly like I'd imagine a meteor coming down, too. However, that doesn't mean much. The meteor in the Armageddon movie looked pretty good to me, too. Tie fighters in Star Wars make sounds (in vacuum) just like I'd expect them, and the airplane crash sites in September 2001 looked pretty authentic on TV as well.

The problem is, all I've seen is stuff on TV and on youtube (and presumably the same is true for you), and neither source is reliable in any way. Nor is anything that "some super sapient expert" tells on TV or on the internet.

All you really know so far (and all they know) is that there exist some movies of "something" from an unknown source, with unknown editing, and unknown censorship. Some big smoke/vapor trail, and some glowing tail with a big flash in the lower third of the sky. Fine, youtube is full with all kinds of fake videos. Some seismologists might in addition have picked up some recordings that tell them there was indeed a big boom, ok, fine... but again, that boom could have been anything.

Unless you can lay hands on a big piece of molten metal with an "alien" composition that doesn't normally occur in Russia (or on Earth) in that form, that's about it, and for all it's worth, it could have been anything. Including a comet, a sattelite, a missle, or a smoke show for propaganda.

I've seen very similar, but of course smaller falling starts (long streak than a flash, then some more streak. I saw even more flashes some time). Of course I didn't see the smoke trails because of the night (but I think it's more of a cloud/jet stream than smoke or particles from the meteor)

 

fallingstar.jpg

meteor%2520--%2520fireball.jpg

MeteorFireball_breakup_ChumackHRweb.jpg



#16 Tom Sloper   Moderators   -  Reputation: 9524

Posted 18 February 2013 - 12:44 PM

This meteorite [sic] above Russia apparently exploded with a power 30 times stronger than the Hiroshima nuclear bomb.
I understand that it gets hot from entering the atmosphere, and is quite big with a mass of 10000 tons,
Also, it went at 15 km/s

 

 

A better question: How could a meteor weighing 10,000 tons and traveling through the Earth's ever-thickening atmosphere at 15 kilometers per second NOT explode?


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#17 Lode   Members   -  Reputation: 981

Posted 18 February 2013 - 01:29 PM

Interesting, I already knew our atmosphere protected us from quite a lot, but it's good to know that it can also protect us from objects coming in at 15 km/s!

 

meteorite [sic]

 

It's a meteorite right now, so ... :P



#18 Luckless   Crossbones+   -  Reputation: 1765

Posted 18 February 2013 - 02:04 PM

Next time you're at a beach on a clam day do the following:
1. Find a fist sized rock and throw it into the water as hard as you can (in a location you're not going to hurt anyone), and observe the effects it has on the water as it hits.
2. Pick up a fist full of wet sand, and compress it as tightly as you can into a ball. Repeat step 1 with your new 'rock'.

It didn't 'explode' in the traditional stick of TNT going off, but rather rapidly compressed a huge volume of air as it hit, converting a bunch of kinetic energy into heat and sound.

Also consider the effect a super sonic fighter jet or similar craft has on household windows with a low pass. Sonic booms are a neat type of 'explosion', and very similar in many ways to what happens with a massive chunk of stuff hitting our atmosphere at exceptionally high speeds.
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#19 Prinz Eugn   Crossbones+   -  Reputation: 3579

Posted 18 February 2013 - 03:31 PM

There's so many reasons it's not a nuclear test it's actually pretty hilarious to seriously propose it could be one...

 

But just as an aside, there have been live tests of missiles with nuclear weapons: http://en.wikipedia.org/wiki/List_of_nuclear_weapons_tests#Tests_of_live_warheads_on_rockets


Edited by Prinz Eugn, 18 February 2013 - 03:32 PM.

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#20 samoth   Crossbones+   -  Reputation: 4684

Posted 18 February 2013 - 03:51 PM

The fact you believe it can even be a possibility is ludicrous. [...] And then you say the movies would be part of the conspiracy ? Laughable.

Well, that is somewhat of a distorted way of putting it, but what's really scary is that you're almost fanatic about not letting the slightest possibility it might be something different than what it looks like at first sight.

What I've said is that all you have is "some videos" on youtube. They may be fake (or edited, or whatever), or they may be "genuine" insofar as they're something people really saw on the sky and recorded. However, "something" genuinely recorded may not be the same "something" that you or someone else thinks.

Although it looks like a meteor and probably is one, that "genuine something" may still be something completely different, and you have no base to prove it, other than "but it looks like...".

About 2030 years ago, one particular government had all the first borns killed when they saw a falling star. This should be enough reason to not blindly follow the first convenient explanation and dismiss everything else without even a thought. Only because someone says it is an omen, that needs not be. Only because someone says it's a meteor, that needs not be either.

Mr. Zhirinovsky seems to be convinced that the phenomenon was an US nuclear missle because Mr. Kerry was pissed off by something. Or so he said in his speech. Whatever. Now don't concentrate on how disturbed this is or whether might be true. Just consider its immense propaganda value.

And with that propaganda value in mind, you should at least deem it not impossible that an ultra-hardline nutter who likely has a way of getting hold of a nuclear missle (if you have some spare money, you got a bomb) detonates a missle in a sparsely inhabited area. It's not like Rome hasn't burned before. Nero did it, Hitler did it, and Bush did it -- why is it impossible and entirely laughable to consider that Zhirinovsky might. I'm not saying that he did, but it is a possibility.

Yesterday, it was said that the major part of the remains after the explosion fell into lake Cherbarkul (how convenient), and today some alleged tiny pieces have been found near the lake. Apparently someone found (or made) a 6 meter hole in the ice, too. Nice facts, so there's proof it was a meteor falling into the lake.

This reminds one of Nostradamus' prophecy. Something about a burning star falling from the sky and the Mediterranean Sea evaporating in 1999, remember? Oh wait, he's a couple of years late, and it's not quite the Mediterranean either. But hey, did someone say "evaporate"?

Vilem Otte calculated a kinetic energy of 1602TJ a few posts above. Let's assume that is the correct number, and assume that only 1% of this was left in the big piece falling into the lake afterwards. In the car video, what came after the boom still looked "quite big", so that's probably a conservative assumption.

This meager 1% is still the equivalent of heating 4 million cubic meters of water by 1°C, or alternatively, making 41,000 cubic meters of 4°C cold Lake Cherbarkul evaporate (that's approximately one third of the lake!). I didn't see a huge mass of steam rise from the ground in the videos, did you? I didn't read about hundreds of people getting burns in hot steam, nor about a flood wave destroying houses near the lake, did you?

Surely the meteor must have stopped moving by now. Where did the energy go?




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