# How Do We Keep The Moon From Eating The World?

In 2053 a manned mission to the moon, using seismic sensors, discovers that it is not a natural satellite*. The moon is actually an egg of Vespula ludicrousmegagiganto. Note that the name is not truly scientific - the shape of the creature is just vaguely wasp-like, and it stuck.

By 2071 and after extensive study, the scientific consensus is that - at some point between one and ten thousand years from now - the "egg" will hatch, and the creature will devour the earth to start its next phase of life. For obvious reasons we'd prefer this not to happen.

Is it possible to move the moon elsewhere using modern technology?

Since the science is imprecise, political will exists to start it moving ASAP, using all of the world's available resources. It could theoretically hatch at any time. They are looking to accomplish this with 2071 tech - consider this equivalent to what we have in 2015, perhaps with some optimizations but without any truly groundbreaking physics advancements. So no generated gravity or reactionless drives, for example.

Success is defined as "Put the moon into orbit around another planet within 500 years". Destroying it is officially considered too risky, although conspiracy theorists point out the tremendous scientific advances that could be gathered by studying the creature.

Ideally the movement would be accomplished without excessive impacts to the moon, but if that's not viable they will consider explosive drives.

*a competing theory is that it was a natural satellite, and the creature burrowed in and grew there over time. The difference is largely academic at this point.

• "Vulgaris" has nothing to to with wasp-like (that's the "Vespula" part). "Vulgaris" just means "common". There's e.g. nothing wasp-like in this species. – celtschk Oct 6 '15 at 19:01
• @celtschk: Man it's been a long time since I've dealt with scientific names, would you go with Vespula Ludicrousmegagiganto then? – Dan Smolinske Oct 6 '15 at 19:18
• That would be a more likely name, yes; it's also in line with the fact that the most creative part of a species name is generally in the last part. – celtschk Oct 6 '15 at 19:23
• Develop a shield so we can hide from the Moon Moth, and have it fly off to Mars or something. – Oldcat Oct 6 '15 at 19:41
• @HenkLangeveld: It’s Doctor Who – Kill the Moon – Wrzlprmft Oct 15 '15 at 13:41

Let's do a bit of math.

According to Wikipedia, the mass of the moon is $7.3\cdot10^{22}\,\rm kg$ and its average orbital speed is $1.0\,\rm km/s$. That means its kinetic energy is $3.7\cdot 10^{28}\,\rm J$. According to the virial theorem the potential energy is $-2$ times the kinetic energy. To get the moon away of the earth (that is at potential energy $0$), you therefore need to add at least the same amount of energy as the moon's kinetic energy again.

So we are looking at a method to add $3.7\cdot 10^{28}\,\rm J$ to the moon. For comparison, the largest nuclear bomb, the Tsar Bomba, releases an energy of up to about $240\,\mathrm{PJ} = 2.4\cdot 10^{17} J$. That is, you would have to detonate about $1.5\cdot 10^{11}$ Tsar Bombas to get the energy; that's 150 billion bombs. Even at the height of the cold war, there had "only" been 68 000 nuclear weapons. So you are looking at an arsenal two million times the total arsenal of the cold war. And that's assuming you manage to transfer 100% of the energy the bombs release to the moon, which itself is rather unrealistic.

Another bit of trivia: A year has about 30 million seconds, therefore 500 years have about 15 billion seconds. So you'd have to build ten Tsar Bombas per second.

Or in short: Forget moving the moon. Better think of ways to kill the wasp.

• This type of question seems to always boil down to the same type of answer. "I want to do Physical Thing X to Celestial Body Y. How do I do it?". Maybe we need a canonical question for that which we can just close this type of question as duplicates of... – a CVn Oct 6 '15 at 20:05
• @MichaelKjörling It would be nice to have something to summarily explain "space is bigger than you think." However, I do have to point out that it is not always obvious why this particular question is on the wrong order of magnitude but that question is manageable. I point to XKCD's what-if for an example of some of the clever and really hard to guess order of magnitude questions ( what-if.xkcd.com/73 ). I wouldn't want to dissuade people's curiosity on such questions, because sometimes they can even stump Munroe! – Cort Ammon Oct 6 '15 at 20:10
• Note that I think your answer is likely correct, but a few questions: 1) is building 10 bombs a second actually unrealistic if we utilize all of humanity? 2) Do we actually need to reduce the potential energy to 0, or is there a point where we could get it into orbit around the sun and use orbital mechanics to transfer it elsewhere afterwards? 3) Is there any advantage from setting the bombs off at perihelion / aphelion and pushing the moon into a more elliptical orbit? – Dan Smolinske Oct 6 '15 at 20:21
• @DanSmolinske: 1) It definitely seems high to me; but then, I'm not a bomb-building expert :-). 2) The closest Lagrangian points of the sun-earth system (that's where you could reasonable say you've left earth gravity) are 1.5 million km away from earth. Given that the potential goes with $1/r$ and the moon's orbital radius is about $400\,000\,\rm km$, you can indeed save about $4/15$ of the energy. So you'll "only" need $11\cdot 10^{10}$ Tsar Bombas. BTW, if you need more than about 50 g of unenriched uranium per bomb, you're in trouble: – celtschk Oct 6 '15 at 20:50
• @celtschk: Well, as a reference, in 2012 the world built roughly 2 cars per second using only a small fraction of our resources. I am not entirely convinced it's possible to build that many bombs - or if it is, to get them to orbit - but it seems potentially possible. I mean, the world is a very big place too, and we have lots and lots of people we could rope into building them. – Dan Smolinske Oct 6 '15 at 20:55

Any experienced xenoentomologist can tell you that the natural enemy of Vespula ludicrousmegagiganto is the interplanetary parasitic wasp Proctotrupoidea corpusparadeisos, which lays its eggs exclusively in V. ludicrousmegagiganto larvae.

So if the core problem is saving the Earth from destruction, then it will suffice to merely introduce a mating pair of P. corpusparadeisos to the moon and await the inevitable grisly dénuement.

I'm sure that 500 years will be ample time for Humanity to figure out how to cram a female P. corpusparadeisos into an Apollo LEM. The male, of course, will follow on his own.

You could damage the egg with drills carrying bombs. Put some on the surface, make them drill to the egg (I suppose it can't be too deep, it has to be large enough to eat the earth after all) and detonate the bombs inside. Even if it hatches it should be damaged enough to die soon after hatching. Naturally there's the problem with carcass which falling to the surface of earth could damage it quite a bit, and debris from moon (when wasp hatches it will probably destroy the moon)

• I doubt you have to worry about debris hitting the earth. It's in stable orbit around the earth now, an explosion even the size of the largest thermonuclear warheads we have ever made would not kick it out of orbit. – jwenting Oct 7 '15 at 12:48
• I was wondering what would happen with debris when the creature would leave moons orbit. Then perhaps earth would pull some of them since they would slow a little, or could even be pushed towards earth when the creature hatches. – Piotr Kamoda Oct 7 '15 at 14:13
• This will run into the same scale issues as the question itself - it's just too big to kill in one shot like this. – Dan Smolinske Oct 7 '15 at 14:36
• You don't have to evaporate it, only drill deep enough to damage something important. That's why there should be quite a few of those drills. Like a thousand or so. – Piotr Kamoda Oct 7 '15 at 14:49

I think in all reality, were humanity to face this problem, they would just move planets. the resources needed to move a celestial body would be tremendous, even compared to moving the humans, and I'm pretty sure we need the tides that the Moon brings.