# An iron meteor the size of an apples hits earth at .9 c. What are the effects? **URL:** \ **Category:** Factual Questions\ **Created:** [January 17, 2013, 4:29am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469 "2013-01-17T04:29:49Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Willcross](https://avatars.discourse-cdn.com/v4/letter/w/b2d939/32.png) [@Willcross](https://boards.straightdope.com/u/Willcross)\ **Post date:** [January 17, 2013, 4:29am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/1 "2013-01-17T04:29:49Z")
I was wondering how small of an object, if accelerated to 90% the speed of light could destroy life on earth. The size of a car? An apple? A bb? Also, assume they are all made of solid iron. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [January 17, 2013, 4:36am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/2 "2013-01-17T04:36:56Z")
Start with a [baseball](http://what-if.xkcd.com/1/) and work up - the results probably are not much different - maybe a bit more mass, slightly bigger boom, but at higher altitude. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [January 17, 2013, 4:50am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/3 "2013-01-17T04:50:58Z")
Oh, and the kinetic energy scales directly with mass. At some point, the atmosphere cannot retain the blast and much of the resulting blast radiation will blow off into space. This [link](http://qntm.org/destroy) suggests you need a 5,000,000,000,000-tonne rock travelling at 90% c to destroy the earth (as in completely shatter and break it up), but you might blow off a good proportion of the atmosphere with somewhat less. Still bigger than a car, though. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [January 17, 2013, 4:51am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/4 "2013-01-17T04:51:07Z")
> [@si\_blakely](#): > > Start with a [baseball](http://what-if.xkcd.com/1/) and work up - the results probably are not much different - maybe a bit more mass, slightly bigger boom, but at higher altitude. [He did another question on a similar theme: “If a meteor made out of diamond and 100 feet in diameter was traveling at the speed of light and hit the earth, what would happen to it?”](http://what-if.xkcd.com/20/) Short answer: At 0.99c it’s an extinction event, at least with a rock that size. An apple-size hunk of iron at 0.9c might not be quite so dramatic but it wouldn’t be far off. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [January 17, 2013, 5:03am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/5 "2013-01-17T05:03:07Z")
I hadn’t seen that one. But I will note that the energetic difference between an object travelling at .9c and .99c is rather large due to both the v[sup]2[/sup] relationship between velocity and kinetic energy and the relativistic effects of getting something to that speed. ---
**Author:** ![moriah](https://avatars.discourse-cdn.com/v4/letter/m/b2d939/32.png) [@moriah](https://boards.straightdope.com/u/moriah)\ **Post date:** [January 17, 2013, 5:29am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/6 "2013-01-17T05:29:11Z")
> [@si\_blakely](#): > > Start with a [baseball](http://what-if.xkcd.com/1/) and work up - the results probably are not much different - maybe a bit more mass, slightly bigger boom, but at higher altitude. And that’s why we won’t let photons have any mass. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [January 17, 2013, 5:48am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/7 "2013-01-17T05:48:39Z")
> [@moriah](#): > > And that’s why we won’t let photons have any mass. Or take confession. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [January 17, 2013, 6:50am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/8 "2013-01-17T06:50:14Z")
> [@si\_blakely](#): > > But I will note that the energetic difference between an object travelling at .9c and .99c is rather large due to both the v[sup]2[/sup] relationship between velocity and kinetic energy Note that the v[sup]2[/sup] relationship is only a low-v approximation which isn’t good for v large compared to c, as is the case here. The kinetic energy of a relativistic meteor scales with 1/sqrt(1-(v/c)^2) which is much more dramatic. ---
**Author:** ![Tom\_P](https://avatars.discourse-cdn.com/v4/letter/t/7993a0/32.png) [@Tom\_P](https://boards.straightdope.com/u/Tom_P)\ **Post date:** [January 17, 2013, 12:02pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/9 "2013-01-17T12:02:33Z")
Using Wolfram Alpha and wiki: An iron ball 7cm in diameter (which is the size of the apple on my desk) has a mass of 1.41kg (3.12lb) The relativistic kinetic energy of this ball moving at 0.9_c_ is 1.64x10[sup]17[/sup] Joules 1.64x10[sup]17[/sup]J equals 39.2 Megatons of TNT. The Soviet Tsar Bomba (largest nuclear explosion ever detonated) was 57 Mt, so it would be smaller than that one. If we instead have an object with the same mass as a car (here defined as 1410kg for obvious reasons :)), the resulting energy would be 1000 times as large as well, so 1.64x10[sup]20[/sup]J The Chicxulub impact blamed for wiping out the dinosaurs were 4.2x10[sup]23[/sup]J, or 2500 times as powerful as the latter impact, and while most life had a bad day, our ancestors survived. ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [January 17, 2013, 1:08pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/10 "2013-01-17T13:08:21Z")
I would ask how such an impact would compare to that of an asteroid the size of an orange, but of course such a comparison cannot be made. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 17, 2013, 3:10pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/11 "2013-01-17T15:10:06Z")
> [@Derleth](#): > > Or take confession. Which is why Lucifer never did. Please say you get it. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [January 17, 2013, 5:22pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/12 "2013-01-17T17:22:32Z")
> [@moriah](#): > > And that’s why we won’t let photons have any mass. > [@Derleth](#): > > Or take confession. Yeah, but has that been _confirmed_? ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [January 17, 2013, 6:53pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/13 "2013-01-17T18:53:58Z")
> [@Leo\_Bloom](#): > > Which is why Lucifer never did. Please say you get it. I see what you did there. ---
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [January 17, 2013, 7:06pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/14 "2013-01-17T19:06:10Z")
> [@moriah](#): > > And that’s why we won’t let photons have any mass. Awww… The poor BABIES! Can’t we at least let a few of them go to church? 🙂 ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [January 17, 2013, 8:17pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/15 "2013-01-17T20:17:06Z")
Also, at that speed, it doesn’t matter what the object is made of. Iron? Diamond? It could be powdered sugar, and it would make very, very little difference. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [January 17, 2013, 9:01pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/16 "2013-01-17T21:01:15Z")
> [@Jake](#): > > Awww… The poor BABIES! Can’t we at least let a few of them go to church? 🙂 Are you kidding? They’re always trying to sneak in through the stained glass windows. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [January 17, 2013, 9:11pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/17 "2013-01-17T21:11:06Z")
> [@Leo\_Bloom](#): > > Which is why Lucifer never did. Please say you get it. Lucifer always was a polarized character, but discrete in his own way. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [January 17, 2013, 9:12pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/18 "2013-01-17T21:12:59Z")
Hitting a planet with a single, massive relativistic lump is not the most efficient way of sterilising the Earth. A single explosion, even a very powerful one, could easily waste most of its effect by lifting local atmosphere rapidly into space. Sure, it would be nasty for lifeforms near the impact, but there is a chance that some life could survive hundreds, or thousands of kilometers away from the centre of the blast. Much more efficient to split your massive impactor up into hundreds of little impactors, and spread them out evenly so that every square kilometer gets an even share of the blast. This method is described in some detail in _The Killing Star_, quoted here. [http://www.projectrho.com/public\_html/rocket/spacegunexotic.php#id--Relativistic\_Weapons--The\_Killing\_Star](http://www.projectrho.com/public_html/rocket/spacegunexotic.php#id--Relativistic_Weapons--The_Killing_Star) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 17, 2013, 11:47pm UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/19 "2013-01-17T23:47:14Z")
> [@](#): > > Hitting a planet with a single, massive relativistic lump is not the most efficient way of sterilising the Earth. A single explosion, even a very powerful one, could easily waste most of its effect by lifting local atmosphere rapidly into space. Sure, it would be nasty for lifeforms near the impact, but there is a chance that some life could survive hundreds, or thousands of kilometers away from the centre of the blast. Plus, due to Coriolis effects, any atmospheric effects will have a hard time crossing the equator. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [January 18, 2013, 3:11am UTC](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469/20 "2013-01-18T03:11:49Z")
Is it even possible for a solid object with a substantive mass to be imparted that degree of acceleration without disintegrating? This assumes the .9c would necessarily have to be imparted by a one time kinetic explosion or push of some kind not a continuous acceleration over time like a spacecraft. [Next page](https://boards.straightdope.com/t/an-iron-meteor-the-size-of-an-apples-hits-earth-at-9-c-what-are-the-effects/647469.md?page=2)