So, a hypothetical: is there any known type of chemical or nuclear reaction that could cause a Krypton-sized world to explode?
(Note: I hope this doesn’t go off to Café Society, because I’m asking if something like the Krypton Event could actually happen.)
Gravitational stresses, from its Red Giant Star?
To make a planet explode, you need something on the order of the gravitational binding energy of its matter. When objects fall in on each other, they release energy–and to pull them apart requires the same energy.
I don’t know about Krypton, but we can compute the binding energy for Earth. The equation is:
-16/15*pi[sup]2[/sup]*p[sup]2[/sup]GR[sup]5[/sup]
p is the density and R radius. For Earth, that’s p=5510 kg/m[sup]3[/sup] and R=6371000. That comes to:
E = 2.24e32 J
For comparison, a 1 megaton bomb is 4.2e15 J, so you need about 50 quadrillion of them to blow up Earth.
If you can get your hands on 1.24 trillion tons of antimatter, that would do the trick. But that’s a little hard to come by.
I guess you could do it if you could somehow turn Earth’s core into a fission bomb. You would need about 2.5e17 kg of highly enriched Uranium. That’s a lot, but Earth weighs about 6e24 kg, so it’s not a high percentage. Suppose the core was made of lots of subcritical masses of U235 separated by some low-density rock or something. It’s just barely stable. Then, some extra mass is added on the surface–asteroid strikes or something. The core is compressed due to the increased pressure, and the whole thing goes critical–boom.
I think it was Niven who posited that Krypton wasn’t actually a planet itself, but a cooled white dwarf star. If that’s the case, then its explosion might have been the result of accretion above the Chandrasekhar limit.
You’d have to explain why Krypton would explode at a given time after existing for so long. IIRC DC Comics post-Crisis explanation was that terrorists planted some sort of strange matter/ proton decay catalyst into Krypton’s core, and that the chain reaction grew exponentially for a long period until it all went kaboom.
Plotonium
I think the answer is no. Assuming Dr. Strangelove’s estimate of the energy required is accurate, that is a ridiculous amount. It takes the Sun something like 10 days to create that much energy, and you need it done within hours for the event to qualify as an “explosion,” I would guess. That means you need the power output of 10 Suns. I don’t think it’s possible to create a thermonuclear device in a volume less than the Earth that could generate that kind of power output. The fact that the natural thermonuclear devices – stars – that can do it are so much larger is a strong hint.
I’m even doubtful you could do it with antimatter or a black hole, simply because I suspect you could not set up the preconditions such that the energy output would ramp up fast enough – meaning you don’t get a big messy months long “fizzle” predetonation, given in the inherent limitations of the acceleration of matter flow even under very strong gravity. It seems likely you could set up a black hole, say, with a steady-state power output of more than is needed, but that’s not an explosion, it’s a steady energy flow. It’s hard to see how you can initiate this gigantic power flow fast enough to qualify as an explosion.
There are certainly cosmological events with this much power or much, much larger, and which happen on a short enough time scale to be called explosive. It is trivial to find an event that would destroy the Earth from outside – but that’s not the same as it exploding from the inside. There are also plenty of very high energy events that take place in a very small volume, like the collapse of a stellar core during a nova or supernova – but these require initial conditions that can’t be duplicated inside a planet, and certainly not while leaving the surface peacefully habitable right up until Zero Hour.
I dont think there’s any way for a planet-sized fission bomb to be assembled in time to go boom all at once, without lots of smaller booms/fizzes happening first, and upsetting the yield.
I think I agree–but I haven’t completely convinced myself. Small bombs fizzle because they blow themselves apart before undergoing much fission. The inertial mass of the Earth might allow the reaction to complete, though.
What you’d want is a “crushable” material–one that is solid up to a given load, and then collapses down to a small volume. It’s easy to build such materials at low strengths. But something that can survive at a planet’s core seems like magic. Still, if you had such a material, you could intersperse it with subcritical cores. Surround the whole thing with a slightly weaker version of the material. When the planet’s mass exceeds a certain point, the outer section will collapse, and the planet will freefall toward the core with great momentum. When it reaches the inner core, it should be able to compress the whole thing to a critical mass in a relatively short timeframe.
Greg Bear once came up with an interesting way to destroy the Earth; collapsed antimatter. 1.24 trillion tons of anti-neutronium colliding with a similar mount of neutronium at the centre of the earth; these materials were assumed to be so dense that they would pass though solid rock like an icepick through butter.
However neutronium would immediately expand into a gas if it were ever removed from a neutron star, (and anti-neutronium would do the same if removed from an anti-neutron star, if such a thing existed) so that’s no good.
Strange matter might be the most plausible planet killer so far.
Here’s a paragraph on wikipedia about how negatively-charged strangelets might be dangerous;
some of you might remember that there was concern in some corners about the Large Hadron Collider creating negatively-charged strangelets that might breed at the Earth’s core.
One argument that seems to disprove the possibility of strangelet disaster is that certain cosmic rays that hit the Earth have much greater energy than any collision that might occur in the LHC, and the Earth is still here despite these events, so they appear to be safe after all.
In case anyone’s curious about the binding energy equation and the crazy dependence on r[sup]5[/sup] and weird constants… here’s the derivation.
First we figure out the gravitational energy for a small lump of matter. The force equation is simply:
F = G*m[sub]1[/sub]*m[sub]2[/sub]/r[sup]2[/sup]
To get energy, we integrate forcedistance, or:
E = ∫[r…inf] Gm[sub]1[/sub]m[sub]2[/sub]/r[sup]2[/sup] dr =
Gm[sub]1[/sub]m[sub]2[/sub]∫[r…inf] r[sup]-2[/sup] dr =
Gm[sub]1[/sub]m[sub]2[/sub]|[r…inf] -r[sup]-1[/sup] =
Gm[sub]1[/sub]*m[sub]2[/sub]/r
Easy enough. Now, we want to see how much energy it takes to take a layer at a time off of the planet. We integrate again over the radius, this time from the original radius down to zero, slicing off thin layers until there’s nothing left.
The mass of a thin layer is just the surface area times the thickness, times the density §, or:
m[sub]2[/sub] = 4pir[sup]2[/sup]pdr
And the mass of the rest of the planet up to a radius r is just the volume times density, or:
m[sub]1[/sub] = 4/3pir[sup]3[/sup]*p
Plug into our first energy equation and stuff inside an integral:
E = ∫(r…0) Gm[sub]1[/sub]m[sub]2[/sub]/r =
G∫(r…0) (4/3pir[sup]3[/sup]p)(4pir[sup]2[/sup]pdr)/r =
G16/3pi[sup]2[/sup]p[sup]2[/sup]∫(r…0) (r[sup]3[/sup])(r[sup]2[/sup]dr)/r =
G16/3pi[sup]2[/sup]p[sup]2[/sup]∫(r…0) r[sup]4[/sup] dr =
G16/3pi[sup]2[/sup]p[sup]2[/sup]|(r…0) r[sup]5[/sup]/5 =
-G16/15*pi[sup]2[/sup]*p[sup]2[/sup]*r[sup]5[/sup]
And there you go. The r[sup]5[/sup] and p[sup]2[/sup] factors really make for a lot of energy.
I think we are being too literal, here.
Gravitational stress could cause a break-up, & seems likely, given that Krypton has moons & is orbiting a huge Red Giant.
What’s the current theory about the formation of the asteroid belt? A common theme in SF is that it’s a former planet.
Easy - you just need to get your hands on a Illudium PU-36 Explosive Space Modulator
I think freefall would not be a quick enough. Also, wouldnt there be a problem with having lots of subcritical cores all clustered close-ish together?
If you are only looking for an event that makes the planet uninhabitable, then tidal stress could probably achieve that. But it wouldn’t put lumps of kryptonite all over the galaxy…
SF != science. Current theory is that the asteroids are leftover planetesimals that managed not to be incorporated into a planet. The entire mass of the Belt is less than that of our Moon.
As for the gravitational effects of a red giant on a planet, they aren’t significantly different than an ordinary non-giant star. Red giants are in fact ordinary stars that have had their atmospheres expanded greatly. But that atmosphere is very tenuous, in fact, a very good vacuum by Earth standards. A planet could actually orbit within that atmosphere without losing significant orbital velocity… OK, it would lose all its lighter, low boiling point components, and the minerals that make up most of the planet would mostly melt, but they would not necessarily boil away.
Neil deGrasse Tyson: How to Blow Up a Planet
According to several documentaries I’ve seen, that thing never works.
(Where’s the kaboom? There was supposed to be an earth-shattering kaboom!)
Maybe the neutrinos were mutating…