<p>An object hitting the Earth at high speed has a lot of <a href="http://en.wikipedia.org/wiki/Kinetic_energy" rel="nofollow">kinetic energy</a>, \begin{align}
  \frac{1}{2}mv^2
\end{align}
where <em>m</em> is the object's mass and <em>v</em> is it's velocity. If the velocity goes from lots to nothing relative to the Earth, that kinetic energy has to go somewhere. That somewhere ends up as heat.</p>

CC BY-SA 3.0
2014-02-17T17:15:03.707Z
2014-02-17T17:15:03.707Z
Marc
<p>You'll often hear that it's because of friction, but that's often not the main factor. For larger objects it's more likely the pressure they create. </p>

<p>In both cases the reason is the enormous speed, often tens of kilometers per second. When a larger object enters the atmosphere at these speed the air in front of it gets compressed so much that it becomes extremely hot. (Think of pumping up a tire; you're also compressing air and you can feel the valve becoming hot.) The compressed air will often disintegrate the object in the air, and then the debris may burn because of the heat. This is exactly what happened to the asteroid above Russia last year: it exploded with an enormous flash in the air, and left little traces on the ground.</p>

<p>This happens on other planets as well, if they have a sufficiently dense atmosphere. In 1994 the comet Shoemaker-Levy crashed into Jupiter. It disintegrated before entering Jupiter's atmosphere due to the strong gravitation, but when the fragments entered the atmosphere they could easily be seen lighting up as they burned up.</p>

<p><strong>edit</strong><br>
Remember the Space Shuttle? It had heat resistant tiles on the bottom of the craft to protect it from burning when it entered the atmosphere, even though its speed is only a fraction of a meteorite's speed when that enters the atmosphere.<br>
During the last launch of the Space Shuttle Columbia some material from the external fuel tank damaged this heat shield, and upon re-entry the heat and the highly pressurized air under the craft could enter it, causing the craft to disintegrate and kill all crew.</p>

CC BY-SA 3.0
2016-10-10T22:52:46.823Z
@stevenvh: Sorry, but your answer is wrong. That's why I downvoted it. See http://astronomy.stackexchange.com/questions/14712/why-do-meteorites-explode/
AtmosphericPrisonEscape
CC BY-SA 4.0
2020-08-03T13:47:54.627Z
@stevenvh, are you sure it isn't the friction of the air going through the rubber tire pump that causes the heat instead of the pressure?
Breakskater
CC BY-SA 3.0
2014-02-17T13:58:08.963Z
So if the speed and the air's pressure are the reason, such a thing won't happen in space itself where there is a vacuum right?
A.K
CC BY-SA 3.0
2014-02-17T14:33:40.897Z
@A.K - Right. Comets move at speeds of hundreds of kilometers per second without having any medium in which they would heat up. Note that comets may evaporate very slowly due to the sun's *radiation* though, but this is nothing mechanical.
stevenvh
CC BY-SA 3.0
2014-02-18T11:10:03.927Z
@RhysW - 'fraid not. This is knowledge I collected over several decades through several sources, including courses. I read in meta that there seems to be a need for references for some people, but I disagree (as I pointed out there).
stevenvh
CC BY-SA 3.0
2014-02-18T12:16:12.917Z
@RhysW - I didn't make this up; I definitely have heard this elsewhere, otherwise I wouldn't post it. I found [this video](http://www.youtube.com/watch?v=NFPXRnfrNSQ), which doesn't refer to the pressure per se, but talks about meteorites exploding above ground, like Tunguska. I'm also thinking about the meteorite above Russia last year. I think these can be explained easier by the pressure hypothesis than pure friction. Also see my edit on the Columbia shuttle, where speed (and pressure) were much lower than those of a meteorite. I'll try to find more material.
stevenvh
CC BY-SA 3.0
2014-02-17T12:54:01.220Z
2014-02-17T16:34:36.143Z
2014-02-17T16:34:36.143Z
stevenvh
<p>Why do all objects burn when they enter our atmosphere? is this because of our atmosphere composition? and does this happen on other planets as well?</p>

CC BY-SA 3.0
2014-02-17T12:20:51.627Z
Maybe you should better post two separate questions.
Gerald
CC BY-SA 3.0
2014-02-17T12:40:45.200Z
Please close this question and make two separate questions.
Envite
CC BY-SA 3.0
2014-02-17T14:20:15.307Z
Already separated by the OP :)
Envite
<planetary-atmosphere>
Why do objects burn when they enter earth's atmosphere?
A.K
# Why do objects burn when they enter earth's atmosphere?

(Asked by: username_0 on 2014-02-17)

Why do all objects burn when they enter our atmosphere? is this because of our atmosphere composition? and does this happen on other planets as well?

**Tags:** planetary-atmosphere
> **Comments:**
> **username_1**: Maybe you should better post two separate questions.  
> **username_2**: Please close this question and make two separate questions.  
> **username_2**: Already separated by the OP :)  

---

## 2 answers

### Answer by username_4 on 2014-02-17. Score: 10 | Accepted answer

You'll often hear that it's because of friction, but that's often not the main factor. For larger objects it's more likely the pressure they create.

In both cases the reason is the enormous speed, often tens of kilometers per second. When a larger object enters the atmosphere at these speed the air in front of it gets compressed so much that it becomes extremely hot. (Think of pumping up a tire; you're also compressing air and you can feel the valve becoming hot.) The compressed air will often disintegrate the object in the air, and then the debris may burn because of the heat. This is exactly what happened to the asteroid above Russia last year: it exploded with an enormous flash in the air, and left little traces on the ground.

This happens on other planets as well, if they have a sufficiently dense atmosphere. In 1994 the comet Shoemaker-Levy crashed into Jupiter. It disintegrated before entering Jupiter's atmosphere due to the strong gravitation, but when the fragments entered the atmosphere they could easily be seen lighting up as they burned up.

**edit**  
Remember the Space Shuttle? It had heat resistant tiles on the bottom of the craft to protect it from burning when it entered the atmosphere, even though its speed is only a fraction of a meteorite's speed when that enters the atmosphere.  
During the last launch of the Space Shuttle Columbia some material from the external fuel tank damaged this heat shield, and upon re-entry the heat and the highly pressurized air under the craft could enter it, causing the craft to disintegrate and kill all crew.

> **Comments:**
> **username_0**: So if the speed and the air's pressure are the reason, such a thing won't happen in space itself where there is a vacuum right?  
> **username_4**: @A.K - Right. Comets move at speeds of hundreds of kilometers per second without having any medium in which they would heat up. Note that comets may evaporate very slowly due to the sun's *radiation* though, but this is nothing mechanical.  
> **username_4**: @RhysW - 'fraid not. This is knowledge I collected over several decades through several sources, including courses. I read in meta that there seems to be a need for references for some people, but I disagree (as I pointed out there).  
> **username_4**: @RhysW - I didn't make this up; I definitely have heard this elsewhere, otherwise I wouldn't post it. I found [this video](http://www.youtube.com/watch?v=NFPXRnfrNSQ), which doesn't refer to the pressure per se, but talks about meteorites exploding above ground, like Tunguska. I'm also thinking about the meteorite above Russia last year. I think these can be explained easier by the pressure hypothesis than pure friction. Also see my edit on the Columbia shuttle, where speed (and pressure) were much lower than those of a meteorite. I'll try to find more material.  
> **username_5**: @stevenvh: Sorry, but your answer is wrong. That's why I downvoted it. See http://astronomy.stackexchange.com/questions/14712/why-do-meteorites-explode/  
> **username_6**: @stevenvh, are you sure it isn't the friction of the air going through the rubber tire pump that causes the heat instead of the pressure?  

---

### Answer by username_3 on 2014-02-17. Score: 1

An object hitting the Earth at high speed has a lot of [kinetic energy](http://en.wikipedia.org/wiki/Kinetic_energy), \begin{align}
\frac{1}{2}mv^2
\end{align}
where *m* is the object's mass and *v* is it's velocity. If the velocity goes from lots to nothing relative to the Earth, that kinetic energy has to go somewhere. That somewhere ends up as heat.


---

