<p>The <a href="https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/" rel="nofollow noreferrer">Earth impact Effects Calculator</a> does include relativistic effects, as noted in <a href="https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/effects.pdf" rel="nofollow noreferrer">the journal article</a> describing the website:</p>
<blockquote>
<p>In fact, the program uses the relativistic energy equation to accommodate the requests of several science fiction writers. The program does not limit the impact velocity to 72 km/s, the maximum possible for an impactor bound to the Sun; however, we have limited the maximum velocity to the speed of light, in response to attempts of a few users to insert supra-light velocities!</p>
</blockquote>
<p>So, putting in a 1.5-m-diameter icy object travelling at 30,000 km/s, we get the following results:</p>
<blockquote>
<ul>
<li>The projectile begins to breakup at an altitude of 200000 meters = 657000 ft</li>
<li>The projectile bursts into a cloud of fragments at an altitude of 67700 meters = 222000 ft</li>
<li>The residual velocity of the projectile fragments after the burst is 28800 km/s = 17900 miles/s</li>
<li>The energy of the airburst is <span class="math-container">$6.44 \times 10^{16}$</span> Joules = 15.4 MegaTons.</li>
<li>No crater is formed, although large fragments may strike the surface.</li>
</ul>
</blockquote>
<p>And even at Ground Zero, directly below the &quot;target point&quot;, the main effects on the ground is a sound as loud as &quot;loud traffic&quot;, and that &quot;glass windows may shatter&quot;.</p>
<p>Changing the impactor from icy material to iron does not substantially change the results;  the main change is that airburst is lower and that the airburst is a little more damaging (&quot;glass windows <em>will</em> shatter&quot; at Ground Zero.)</p>

CC BY-SA 4.0
2023-02-06T15:46:19.307Z
The reason I didn't use that is specifically the "indestructible" aspect. I'm specifically wondering how it would impact the earth, as well as how air compression would affect the atmosphere
Arctic
CC BY-SA 4.0
2023-02-06T18:06:27.520Z
I'm not sure you can believe that the physics in that paper is applicable to relativistic velocities and since the question invokes magic in order to make the object indestructible I'm not sure how the answer can apply in any case.
ProfRob
CC BY-SA 4.0
2023-02-06T15:37:28.773Z
2023-02-06T15:45:49.680Z
2023-02-06T15:45:49.680Z
Michael Seifert
<p>Let's say that it hits in the exact center and is somehow also incompressible and doesn't slow down upon entering the atmosphere.</p>

CC BY-SA 4.0
2023-02-06T15:21:48.653Z
I think there are a few too many hypotheticals here, since it leaves out a key thing: what is the mass of the meteor? It could be the density of air, in which case the ~0.1 kg body would have a kinetic energy of 10 kt. Or it could be made out of neutronium, in which case it would likely careen through Earth leaving some multimegaton explosions in its wake.
Anders Sandberg
CC BY-SA 4.0
2023-02-06T15:23:27.170Z
Related:  [Relativistic object impacts the Earth](https://physics.stackexchange.com/questions/3362/relativistic-object-impacts-the-earth)
Michael Seifert
CC BY-SA 4.0
2023-02-06T15:26:03.617Z
I’m voting to close this question because this question is completely Off-Topic.
Arcturus
CC BY-SA 4.0
2023-02-06T17:59:58.447Z
There isn't a question here to answer. I suppose you mean "what would the effects be of..." ?
ProfRob
CC BY-SA 4.0
2023-02-06T18:07:51.693Z
Voting to close on the basis that magic is invoked.
ProfRob
CC BY-SA 4.0
2023-02-06T18:52:14.513Z
voting to close because this isn't about astronomy and might be better on [worldbuilding.se]
Aaron F
CC BY-SA 4.0
2023-04-23T17:54:59.947Z
Just read https://what-if.xkcd.com/20/
Mithoron
<meteor><collision><hypothetical>
What if a magically indestructible human-sized rocky meteor hit the United States at 10% the speed of light?
Arctic
# What if a magically indestructible human-sized rocky meteor hit the United States at 10% the speed of light?

(Asked by: username_0 on 2023-02-06)

Let's say that it hits in the exact center and is somehow also incompressible and doesn't slow down upon entering the atmosphere.

**Tags:** meteor, collision, hypothetical

> **Comments:**
> **username_1**: I think there are a few too many hypotheticals here, since it leaves out a key thing: what is the mass of the meteor? It could be the density of air, in which case the ~0.1 kg body would have a kinetic energy of 10 kt. Or it could be made out of neutronium, in which case it would likely careen through Earth leaving some multimegaton explosions in its wake.  
> **username_2**: Related:  [Relativistic object impacts the Earth](https://physics.stackexchange.com/questions/3362/relativistic-object-impacts-the-earth)  
> **username_3**: I’m voting to close this question because this question is completely Off-Topic.  
> **username_4**: There isn't a question here to answer. I suppose you mean "what would the effects be of..." ?  
> **username_4**: Voting to close on the basis that magic is invoked.  
> **username_5**: voting to close because this isn't about astronomy and might be better on [worldbuilding.se]  
> **username_6**: Just read https://what-if.xkcd.com/20/  

---

## 1 answers

### Answer by username_2 on 2023-02-06. Score: 2

The [Earth impact Effects Calculator](https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/) does include relativistic effects, as noted in [the journal article](https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/effects.pdf) describing the website:

> In fact, the program uses the relativistic energy equation to accommodate the requests of several science fiction writers. The program does not limit the impact velocity to 72 km/s, the maximum possible for an impactor bound to the Sun; however, we have limited the maximum velocity to the speed of light, in response to attempts of a few users to insert supra-light velocities!

So, putting in a 1.5-m-diameter icy object travelling at 30,000 km/s, we get the following results:

> * The projectile begins to breakup at an altitude of 200000 meters = 657000 ft
> * The projectile bursts into a cloud of fragments at an altitude of 67700 meters = 222000 ft
> * The residual velocity of the projectile fragments after the burst is 28800 km/s = 17900 miles/s
> * The energy of the airburst is $6.44 \times 10^{16}$ Joules = 15.4 MegaTons.
> * No crater is formed, although large fragments may strike the surface.

And even at Ground Zero, directly below the "target point", the main effects on the ground is a sound as loud as "loud traffic", and that "glass windows may shatter".

Changing the impactor from icy material to iron does not substantially change the results; the main change is that airburst is lower and that the airburst is a little more damaging ("glass windows *will* shatter" at Ground Zero.)

> **Comments:**
> **username_0**: The reason I didn't use that is specifically the "indestructible" aspect. I'm specifically wondering how it would impact the earth, as well as how air compression would affect the atmosphere  
> **username_4**: I'm not sure you can believe that the physics in that paper is applicable to relativistic velocities and since the question invokes magic in order to make the object indestructible I'm not sure how the answer can apply in any case.  

---

