# What could I do with a cubic millimeter of neutron star? **URL:** \ **Category:** Factual Questions\ **Created:** [November 12, 2006, 6:07pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128 "2006-11-12T18:07:00Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Emilio\_Lizardo](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Emilio\_Lizardo](https://boards.straightdope.com/u/Emilio_Lizardo)\ **Post date:** [November 12, 2006, 6:07pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/1 "2006-11-12T18:07:00Z")
Imagine I run downstairs on Christmas morning and find that Santa has thoughtfully left me a small chunk of neutron star, say a 1 millimeter cube, in my stocking. According to the good folks at Wikipedia, the low end for [neutron star](http://en.wikipedia.org/wiki/Neutron_star) density is 8\*10[SUP]13[/SUP] grams per cubic centimeter. Unless I’m using my slide rule wrong, that works out to about 800,000 tons per cubic millimeter. Forgetting for a moment the practical considerations in moving such a thing, could I even store it somewhere? What would happen if I set it down on a big concrete pad. In fact, what would happen if I set it on the ground? Would it just fall through the earth as if the ground was air? ---
**Author:** ![Emilio\_Lizardo](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Emilio\_Lizardo](https://boards.straightdope.com/u/Emilio_Lizardo)\ **Post date:** [November 12, 2006, 6:14pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/2 "2006-11-12T18:14:28Z")
Just for comparison, the [Knock Nevis](http://en.wikipedia.org/wiki/Knock_Nevis) the largest ship in the world, has a displacement of about 650,000 tons when loaded. So my chunk of neutron star isn’t all that heavy. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [November 12, 2006, 6:15pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/3 "2006-11-12T18:15:52Z")
[QUOTE=Emilio Lizardo] Would it just fall through the earth as if the ground was air? [/QUOTE] Pretty much. The pressure would instantly overwhelm any normal material. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 12, 2006, 6:20pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/4 "2006-11-12T18:20:10Z")
[QUOTE=Emilio Lizardo] What would happen if I set it down on a big concrete pad. In fact, what would happen if I set it on the ground? Would it just fall through the earth as if the ground was air? [/QUOTE] Pretty much. It’s not the weight, it’s the pressure. All that weight concentrated in so small an area means your little cube of neutronium will drive itself through the concrete, the ground and the bedrock like a nail through a stick of butter. If you wanted to prevent that, you’d have to smash your sample into a thin sheet that covers a lot of surface area, so that the weight is spread out. ---
**Author:** ![Don\_t\_fight\_the\_hypothetical](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@Don\_t\_fight\_the\_hypothetical](https://boards.straightdope.com/u/Don_t_fight_the_hypothetical)\ **Post date:** [November 12, 2006, 6:27pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/5 "2006-11-12T18:27:51Z")
Going from my (admittedly rusty) memory, but I think Carl Sagan stated it would pass through the earth 100,000 times before friction stopped it. ---
**Author:** ![Alive\_At\_Both\_Ends](https://avatars.discourse-cdn.com/v4/letter/a/73ab20/32.png) [@Alive\_At\_Both\_Ends](https://boards.straightdope.com/u/Alive_At_Both_Ends)\ **Post date:** [November 12, 2006, 6:35pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/6 "2006-11-12T18:35:11Z")
Neutron star material can only exist within a neutron star, where the gravity is sufficient to keep it compressed to that extent. A cubic millimetre of neutron star material in isolation would explode out to a more normal density immediately. So it wouldn’t fall through the earth, since it wouldn’t exist long enough. I’d stand well back, though. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 12, 2006, 6:36pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/7 "2006-11-12T18:36:41Z")
First, you’d need to store it somewhere with a far stronger gravitational field than the earth’s. Here, it would play apart pretty energetically within microseconds of your receiving it. Neutronium needs a lot of force to keep itself together in the first place. Like those forces found in a neutron star, even. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 12, 2006, 6:58pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/8 "2006-11-12T18:58:25Z")
[QUOTE=Qadgop the Mercotan] First, you’d need to store it somewhere with a far stronger gravitational field than the earth’s. Here, it would play apart pretty energetically within microseconds of your receiving it. Neutronium needs a lot of force to keep itself together in the first place. Like those forces found in a neutron star, even. [/QUOTE] And let’s face it, when you want someone’s opinion on neutronium… 😃 ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 12, 2006, 7:17pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/9 "2006-11-12T19:17:02Z")
[QUOTE=Malacandra] And let’s face it, when you want someone’s opinion on neutronium… 😃 [/QUOTE] Yesssssssssssss! ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [November 12, 2006, 7:18pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/10 "2006-11-12T19:18:07Z")
[QUOTE=Qadgop the Mercotan] Yesssssssssssss! [/QUOTE] Damn, that was supposed to have my sig with it! ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [November 12, 2006, 7:53pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/11 "2006-11-12T19:53:15Z")
Assuming you could keep it stable and on the surface of the Earth ( would diamond be strong enough ? ), I expect there are scientific uses for it. For example, I expect there are particles that it would stop more efficiently than normal matter would. Such a superdense mass might be useful in gravity experiments. Would something that dense have a detectable gravity field at it’s surface ? Would vibrating it create detectable gravity waves ? Given that it’s just one object ( and an awkward to handle one at that ), I doubt you could use it for any practical industrial or military purpose, but I’d be surprised if it was of no scientific interest. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [November 12, 2006, 8:28pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/12 "2006-11-12T20:28:19Z")
[QUOTE=Qadgop the Mercotan] Here, it would play apart pretty energetically within microseconds of your receiving it. [/QUOTE] That’s another good question–if I’m going to get 1 mm[sup]3[/sup] of neutronium, how far away do I have to be to escape the blast radius? And how close can I be to it and still run away from the explosion, assuming that I start before it does and move at the speed of light? ---
**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:** [November 12, 2006, 8:37pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/13 "2006-11-12T20:37:57Z")
> [@](#): > > Would something that dense have a detectable gravity field at it’s surface ? Would vibrating it create detectable gravity waves ? Assuming you could have something that size and density? Certainly, to the first question. The Cavendish experiment which determined the value of the gravitational constant was basically measuring the gravitational field of something comparable to a cannonball, and our hypothetical neutronium-grain is both significantly smaller and far more massive. In fact, such an object would have a surface gravity of tens of thousands of gees. On the second question, the answer would be yes, but only if you could figure out a way to wiggle it fast enough, and you’d have to custom-build a detector to detect the waves, since they’d probably be much higher frequency than anything we expect from astronomical sources. The custom detector wouldn’t be all that hard, it’d just require funding, but I’m frankly at a loss as to how you could wiggle it appropriately. The best bet, I suppose, would be to get two of the things, and somehow get both of them into orbit around the Earth, and also around each other. I guess if we’re going to posit the existence of such things, we might as well assume they came from space in the first place, so we don’t have to lift them out of Earth’s gravity well. ---
**Author:** ![1010011010](https://avatars.discourse-cdn.com/v4/letter/1/ea666f/32.png) [@1010011010](https://boards.straightdope.com/u/1010011010)\ **Post date:** [November 12, 2006, 9:05pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/14 "2006-11-12T21:05:19Z")
Releasing ~10^50 neutrons is going to cause a bit of activation and subsequent irradiation. Luckily you seem the type to leave your tree up until mid-July, so most of the nastier stuff should have decayed to safe levels by that point. How about you ask Santa for something else for chrismas, just the same? ---
**Author:** ![Emilio\_Lizardo](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Emilio\_Lizardo](https://boards.straightdope.com/u/Emilio_Lizardo)\ **Post date:** [November 12, 2006, 9:54pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/15 "2006-11-12T21:54:29Z")
Imagining that something of that density did impact the Earth (say a tiny black hole) would it leave any kind of hole in its wake, or is it so small that all of the displaced material would be quickly replaced? ---
**Author:** ![Captain\_Carrot](https://avatars.discourse-cdn.com/v4/letter/c/f0a364/32.png) [@Captain\_Carrot](https://boards.straightdope.com/u/Captain_Carrot)\ **Post date:** [November 12, 2006, 10:07pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/16 "2006-11-12T22:07:40Z")
[QUOTE=Emilio Lizardo] 8\*10[SUP]13[/SUP] grams per cubic centimeter. Unless I’m using my slide rule wrong, that works out to about 800,000 tons per cubic millimeter. [/QUOTE] Not that it matters, but (ignoring the 8 because I’m dealing with exponents for the moment) 10[sup]13[/sup] g/cm[sup]3[/sup]=10[sup]10[/sup] g/mm[sup]3[/sup] =10[sup]7[/sup] kg/mm[sup]3[/sup]=10[sup]4[/sup] t/mm[sup]3[/sup] (t=metric ton). So it’s more like 80,000 tons per cubic millimeter. There are four different powers-of-ten conversions in there, but I pale at the thought of converting ounces/cubic foot to tons/cubic inch. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 13, 2006, 5:45am UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/17 "2006-11-13T05:45:35Z")
[QUOTE=Chronos] In fact, such an object would have a surface gravity of tens of thousands of gees. [/QUOTE] I worked it out to be about 1,771.1 G, actually. That sound right to you? ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 13, 2006, 9:36am UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/18 "2006-11-13T09:36:29Z")
[QUOTE=ultrafilter] That’s another good question–if I’m going to get 1 mm[sup]3[/sup] of neutronium, how far away do I have to be to escape the blast radius? And how close can I be to it and still run away from the explosion, assuming that I start before it does and move at the speed of light? [/QUOTE] As close as you like, if you can move at the speed of light. However big the blast radius, it won’t be expanding at _c_. **Der Trihs** , my off-the-wall estimate is that diamond just isn’t in the picture. You’re comparing the energy in molecular bonds to the energy in subatomic bonds. It’s like trying to stop an atom bomb going off by hosing it down with cold water. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [November 13, 2006, 4:34pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/19 "2006-11-13T16:34:55Z")
[QUOTE=Malacandra] **Der Trihs** , my off-the-wall estimate is that diamond just isn’t in the picture. You’re comparing the energy in molecular bonds to the energy in subatomic bonds. It’s like trying to stop an atom bomb going off by hosing it down with cold water. [/QUOTE] \< shrugs \> I didn’t think so, but it was the strongest non-unobtainium material I could think of. ---
**Author:** ![StinkyBurrito](https://avatars.discourse-cdn.com/v4/letter/s/b9e5f3/32.png) [@StinkyBurrito](https://boards.straightdope.com/u/StinkyBurrito)\ **Post date:** [November 13, 2006, 4:46pm UTC](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128/20 "2006-11-13T16:46:55Z")
[QUOTE=Der Trihs] \< shrugs \> I didn’t think so, but it was the strongest non-unobtainium material I could think of. [/QUOTE] Diamond isn’t particularly strong. You could crush it with a hammer. It is, however, very hard. [Next page](https://boards.straightdope.com/t/what-could-i-do-with-a-cubic-millimeter-of-neutron-star/380128.md?page=2)