<p>The Chelyabinsk meteor didn't explode.  </p>

<p>In fact meteors in general usually don't explode, this is a common misconception.<br>
When an object at orbital speeds ($\sim11 km/s$) enters the atmosphere, this speed corresponds to extremely high mach-numbers (M$\sim 30$). This generates a strong shock-front in front of the meteor which causes the meteor to heat up enourmously.<br>
To give a feeling of how important this heat-up is, you can look up on <a href="https://en.wikipedia.org/wiki/Hypersonic_speed" rel="nofollow">Wikipedia</a> that already at Mach-numbers of 2-3 there are severe engineering problems in not letting aircraft overheat. At Mach-numbers of 30, the air in the shock is so hot that it locally ionizes the air and easily evaporates the solids away from the falling meteor. Upon reaching the ground one hears this shock as loud thunder.<br>
The other thing that happened with the Chelyabinsk meteor is that it broke up in mid-flight. This caused the total solid surface of the meteor that is exposed to the shock to momentarily increase strongly. More surface exposure to the heat causes more surface to glow. This lasts until the smaller fragments that resulted from the breakup evaporate themselves.  </p>

<p>Taken together, the mach-shock and the increase in glowing surface area upon break-up give the impression of an "explosion".<br>
Also for an explosion a reservoir of energy would need to be suddenly tapped, which is just not there.</p>

CC BY-SA 3.0
2016-04-29T22:26:14.477Z
I'm a little murky on the distinction you make between "breaking up" and "exploding" --- you seem to be using these terms in a technical way that I'm not accustomed to.
rob
CC BY-SA 3.0
2016-04-30T06:23:24.967Z
@rob: sometimes the break-up is quite non-violent. But in case of Chelyabinsk there was heavy damage to ground infrastructure, many wounded people - is that all result just of the (continuous, lengthy) shock front reaching the ground?
SF.
CC BY-SA 3.0
2016-04-30T10:26:47.687Z
@SF: The meteor still hits pretty fast. That should account for all the damage.
AtmosphericPrisonEscape
CC BY-SA 3.0
2016-04-30T10:28:53.743Z
@rob: Imagine you travel on the comet. Then you are in its rest-frame. From this perspective an explosion would generate motion in all directions equally. This needs an energy source. However a break-up is just the comet loosing its structural support and then _relatively_ gently falling to pieces.
AtmosphericPrisonEscape
CC BY-SA 3.0
2016-04-30T11:40:02.023Z
I'm completely sure that *if* a pretty solid (iron) meteorite is shaped in such a way that the air makes it enter a violent spin, the berak-up will be anything but gentle. But I have no clue how often this could occur.
SF.
CC BY-SA 3.0
2016-05-02T08:43:35.837Z
@uhoh: at energies like these the border between explosions and any other processes really gets blurred. If you light a balloon filled with a few grams of oxygen and hydrogen mix, it explodes - so if you burn several hundred kilograms per second of that mix, it's hard not to call it a continuous explosion. And if the shockwave of a breaking meteor can seriously damage brick buildings, I somehow find any argument stating 'that's not an explosion' unconvincing.
SF.
CC BY-SA 3.0
2016-05-02T08:55:59.507Z
@uhoh I think you messed up your units somewhere. 1kg TNT = 4184000J = E = 0.5*1kg*v^2 ; v=sqrt(2*4184000) = 2893m/s. So 2.9km/s, not a measly 1 mach!
SF.
CC BY-SA 3.0
2016-05-02T10:07:32.967Z
@SF. Thanks for checking my math! Indeed 1 ton is 4.2 gigaJoules not 1 *kiloton* - my v was off by √1000. But I think "even if the meteor was made of *100% pure TNT* (and not [this stuff](https://en.wikipedia.org/wiki/Chelyabinsk_meteor#/media/File:Cheljabinsk_meteorite_fragment.jpg)) and exploded, the energy released would still be only a few % of the kinetic energy dumped into the atmosphere" is ok. Still, if built-up heat & gradients -> sudden disintegration and you were moving along side and could see through the blindingly bright glowing atmosphere, it might look like a mild explosion.
uhoh
CC BY-SA 3.0
2016-05-03T13:07:42.190Z
@SF I don't know where you want to take all that chemical energy from, but a meteor sure doesn't have it. Also your violent spin will lead to piece-by-piece breakup and not a single, explosion-like event and that only for the icy-surface. In the case of the compact metal-rich meteors that we've been discussing here, no spin would break them apart. See the image uhoh attached.
AtmosphericPrisonEscape
CC BY-SA 3.0
2017-02-23T09:49:30.253Z
@AtmosphericPrisonEscape: (sorry for necromancy, kinda missed the notification and forgot about this topic). This isn't "where I want to take that chemical energy from". This is about "where a suden energy capable of toppling multiple brick buildings in a wide radius comes from". Not from direct impact of meteorite fragments, or ground impact (the fragments were quite slow when reaching the ground) - and not from continuous energy release because the disatrous effect was instantaneous, not continuous. So...?
SF.
CC BY-SA 3.0
2017-02-23T13:03:34.443Z
@SF: The comet hits with terminal velocity, the energy comes from falling down into a deep potential well, I hope that much is clear. After breakup the fragments are scattered through supersonic turbulence, which is a quite violent force, as one can see in the engineering efforts put into keeping airflow laminar at those lower mach-numbers for experimental planes. One uncontrolled maneuver can break your airplane apart, and that's at only Mach 2-3. Then of course the planes density is not that of solid rock. But to increase M by a factor of 10, increases energy dissipation by 100.
AtmosphericPrisonEscape
CC BY-SA 3.0
2016-04-29T18:07:13.483Z
2016-04-29T18:07:13.483Z
AtmosphericPrisonEscape
<p>Meteorites don't explode. To understand them properly we need to know it's stages.</p>

<ul>
<li><strong>Meteoroid</strong> <em>(small piece of rock travelling in outer space towards a planet or satellite)</em></li>
<li><strong>Meteor</strong> <em>(This is when meteoroid reaches the planets atmosphere and is travelling)</em></li>
<li><strong>Meteorite</strong> <em>(This is after the meteor has fallen on the surface)</em></li>
</ul>

<p>As I mentioned above meteorites don't explode. But, when a meteor is big enough and is still travelling in atmosphere, it produces bright flame around it.</p>

<p>There is a common misconception that the flame is produces is due to friction of meteor with atmosphere. But, the actually when the meteor travels in atmosphere, it compresses the air below it. When gas is compressed heavily it produces incandescence and glows. This is what exactly happening here also.</p>

CC BY-SA 3.0
2016-05-02T07:31:15.427Z
2016-05-02T07:31:15.427Z
Jophine
<p>Some meteorites just blaze away, streaking through the sky. This is clearly explained, as they either slow down enough for the flame to cease, or ablate in their entirety, turning to vapor.</p>

<p>But some, like the Chelyabinsk meteorite, explode violently.</p>

<p>What effect is responsible for this?</p>

<p>Can it be that with their irregular surface acting as a turbine they enter a spin of increasing speed, and once the centrifugal force reaches a certain level, it causes the meteorite to break apart rapidly, hurling parts of it in all directions at speeds far exceeding its speed so far?</p>

CC BY-SA 3.0
2016-04-29T17:51:44.800Z
answered on physics se http://physics.stackexchange.com/questions/76045/why-do-meteors-explode
James K
<meteorite>
Why do meteorites explode?
SF.
# Why do meteorites explode?

(Asked by: username_0 on 2016-04-29)

Some meteorites just blaze away, streaking through the sky. This is clearly explained, as they either slow down enough for the flame to cease, or ablate in their entirety, turning to vapor.

But some, like the Chelyabinsk meteorite, explode violently.

What effect is responsible for this?

Can it be that with their irregular surface acting as a turbine they enter a spin of increasing speed, and once the centrifugal force reaches a certain level, it causes the meteorite to break apart rapidly, hurling parts of it in all directions at speeds far exceeding its speed so far?

**Tags:** meteorite
> **Comments:**
> **username_1**: answered on physics se http://physics.stackexchange.com/questions/76045/why-do-meteors-explode  

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## 2 answers

### Answer by username_2 on 2016-04-29. Score: 2

The Chelyabinsk meteor didn't explode.

In fact meteors in general usually don't explode, this is a common misconception.  
When an object at orbital speeds ($\sim11 km/s$) enters the atmosphere, this speed corresponds to extremely high mach-numbers (M$\sim 30$). This generates a strong shock-front in front of the meteor which causes the meteor to heat up enourmously.  
To give a feeling of how important this heat-up is, you can look up on [Wikipedia](https://en.wikipedia.org/wiki/Hypersonic_speed) that already at Mach-numbers of 2-3 there are severe engineering problems in not letting aircraft overheat. At Mach-numbers of 30, the air in the shock is so hot that it locally ionizes the air and easily evaporates the solids away from the falling meteor. Upon reaching the ground one hears this shock as loud thunder.  
The other thing that happened with the Chelyabinsk meteor is that it broke up in mid-flight. This caused the total solid surface of the meteor that is exposed to the shock to momentarily increase strongly. More surface exposure to the heat causes more surface to glow. This lasts until the smaller fragments that resulted from the breakup evaporate themselves.

Taken together, the mach-shock and the increase in glowing surface area upon break-up give the impression of an "explosion".  
Also for an explosion a reservoir of energy would need to be suddenly tapped, which is just not there.

> **Comments:**
> **username_3**: I'm a little murky on the distinction you make between "breaking up" and "exploding" --- you seem to be using these terms in a technical way that I'm not accustomed to.  
> **username_0**: @rob: sometimes the break-up is quite non-violent. But in case of Chelyabinsk there was heavy damage to ground infrastructure, many wounded people - is that all result just of the (continuous, lengthy) shock front reaching the ground?  
> **username_2**: @SF: The meteor still hits pretty fast. That should account for all the damage.  
> **username_2**: @rob: Imagine you travel on the comet. Then you are in its rest-frame. From this perspective an explosion would generate motion in all directions equally. This needs an energy source. However a break-up is just the comet loosing its structural support and then _relatively_ gently falling to pieces.  
> **username_0**: I'm completely sure that *if* a pretty solid (iron) meteorite is shaped in such a way that the air makes it enter a violent spin, the berak-up will be anything but gentle. But I have no clue how often this could occur.  
> **username_0**: @uhoh: at energies like these the border between explosions and any other processes really gets blurred. If you light a balloon filled with a few grams of oxygen and hydrogen mix, it explodes - so if you burn several hundred kilograms per second of that mix, it's hard not to call it a continuous explosion. And if the shockwave of a breaking meteor can seriously damage brick buildings, I somehow find any argument stating 'that's not an explosion' unconvincing.  
> **username_0**: @uhoh I think you messed up your units somewhere. 1kg TNT = 4184000J = E = 0.5*1kg*v^2 ; v=sqrt(2*4184000) = 2893m/s. So 2.9km/s, not a measly 1 mach!  
> **username_4**: @SF. Thanks for checking my math! Indeed 1 ton is 4.2 gigaJoules not 1 *kiloton* - my v was off by √1000. But I think "even if the meteor was made of *100% pure TNT* (and not [this stuff](https://en.wikipedia.org/wiki/Chelyabinsk_meteor#/media/File:Cheljabinsk_meteorite_fragment.jpg)) and exploded, the energy released would still be only a few % of the kinetic energy dumped into the atmosphere" is ok. Still, if built-up heat & gradients -> sudden disintegration and you were moving along side and could see through the blindingly bright glowing atmosphere, it might look like a mild explosion.  
> **username_2**: @SF I don't know where you want to take all that chemical energy from, but a meteor sure doesn't have it. Also your violent spin will lead to piece-by-piece breakup and not a single, explosion-like event and that only for the icy-surface. In the case of the compact metal-rich meteors that we've been discussing here, no spin would break them apart. See the image uhoh attached.  
> **username_0**: @AtmosphericPrisonEscape: (sorry for necromancy, kinda missed the notification and forgot about this topic). This isn't "where I want to take that chemical energy from". This is about "where a suden energy capable of toppling multiple brick buildings in a wide radius comes from". Not from direct impact of meteorite fragments, or ground impact (the fragments were quite slow when reaching the ground) - and not from continuous energy release because the disatrous effect was instantaneous, not continuous. So...?  
> **username_2**: @SF: The comet hits with terminal velocity, the energy comes from falling down into a deep potential well, I hope that much is clear. After breakup the fragments are scattered through supersonic turbulence, which is a quite violent force, as one can see in the engineering efforts put into keeping airflow laminar at those lower mach-numbers for experimental planes. One uncontrolled maneuver can break your airplane apart, and that's at only Mach 2-3. Then of course the planes density is not that of solid rock. But to increase M by a factor of 10, increases energy dissipation by 100.  

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### Answer by username_5 on 2016-05-02. Score: 1

Meteorites don't explode. To understand them properly we need to know it's stages.

* **Meteoroid** *(small piece of rock travelling in outer space towards a planet or satellite)*
* **Meteor** *(This is when meteoroid reaches the planets atmosphere and is travelling)*
* **Meteorite** *(This is after the meteor has fallen on the surface)*

As I mentioned above meteorites don't explode. But, when a meteor is big enough and is still travelling in atmosphere, it produces bright flame around it.

There is a common misconception that the flame is produces is due to friction of meteor with atmosphere. But, the actually when the meteor travels in atmosphere, it compresses the air below it. When gas is compressed heavily it produces incandescence and glows. This is what exactly happening here also.


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