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 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?
Just for comparison, the 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.
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.
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.
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.
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.
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?
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.
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?
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?
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.
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.
