If the Moon were destroyed, what would that mean for Earth?


In 2293, while returning home from a successful mission to catalog gaseous planetary anomalies in the beta quadrant, the USS Excelsior, under the command of Captain Hikaru Sulu, was struck by a subspace shock wave. Initial investigation revealed that the shock wave resulted from the destruction of Praxis; a Klingon moon used for energy production.

With only fragments of the moon remaining, the destruction of Praxis threatened the Klingons, eating away at their ozone layer, causing the total loss of oxygen over the next 50 years. To be sure, the destruction of a moon is a violent and serious thing – enough to end decades of hostilities and a tenuous peace between two warring races. But can a moon really be destroyed? And if so, would it lead to the impending demise of the home planet? With Star Trek VI: The Unknown Country turning 30 this week, it seems like the right time to reflect on these important questions.

Blow up a moon

Since we don’t have direct observations from Praxis, it’s a fictional moon and all, we’ll be using Earth’s moon as a proxy. To detonate the Moon (or a planet), you need enough energy to overcome its binding energy, which is the amount of energy that holds everything together. The more massive the object, the more binding energy it has. And while the Moon is a relatively small object compared to something like gas giants, and even Earth, it still has a lot of binding energy. Something like 120 octillion joules – that’s a 12 with 28 zeros behind it.

But it’s a little hard to visualize, so let’s try to bring it home. A standard stick of dynamite, measuring about 8 inches long, has a megajoule of explosive energy inside. It’s a 1 with 6 zeros behind it. It’s a decent amount, certainly enough to be dangerous, but it’s ridiculously small if you’re in the exploding moon business.

If dynamite is all you have at your disposal then you will need a lot of it. The math is pretty straightforward, dividing that large number above for the Moon’s binding energy by ten simply involves subtracting a zero. Dividing it by a megajoule is like dividing by a million, so you subtract six zeros to get the total number of sticks of dynamite we need to blow up the Moon.

We would need 120,000,000,000,000,000,000,000 eight-inch sticks of dynamite. Arranged in a line, this amount of dynamite would extend beyond the edge of our solar system. It’s a lot. Not very doable. Let’s try something more powerful.

The Tsar Bomb, the most powerful atomic bomb ever deployed, had a yield of 50 megatons. However, this was reduced for the test from its capacity of 100 megatons. Let’s use as many as possible, just for fun.

A 100 megaton bomb carries 4.184 times ten in 17th joules of cosmic explosion power. If we break that down into the Moon’s binding energy, we would need – wait while I pull out the calculator – about 287 billion of these bombs. If we outfitted everyone on Earth with a cool spaceship and sent an armada of the entire human population to the Moon with bombs, we’d each get a compliment of 36 100-megaton bombs to get the job done, and that assumes that ‘there is none of this energy is lost in space and we can cram everything into the moon.

Suffice it to say that whatever the Klingons do on Praxis, it was incredibly powerful and they are all lucky to have experienced this. Assuming that we could actually detonate the Moon, whether accidentally or on purpose, would that mean impending demise for humanity?

LIVING IN A POST-MOON WORLD

The most immediate consequence of the destruction of the Moon would be a much darker night sky. The Moon is the largest and most reflective object in our sky, besides the Sun of course. Losing it would make the rest of the sky relatively brighter, which could be a pleasant side effect for ground-based deep sky astronomers. We’re going to chalk this one down to the silver liners.

Aside from missing it in the night sky, there are two main things that would change if the Moon no longer existed. First the tides.

The fact that we have tides, the displacement of water bodies of time, is a consequence of the gravitational relations between the Earth and the Moon, and to a lesser extent the Sun. As the Earth spins and the Moon spins around the Earth, it pulls on the oceans by pulling them to one side or the other. If there weren’t any more tomorrow, the tides wouldn’t totally disappear, but they would be much less impressive.

The tides we enjoy today derive about two-thirds of their movement from the Moon. On a moonless Earth, the oceans would still move under the influence of the Sun’s gravity, but it would be much smaller. As a result, coastal regions and environments could be quite drastically altered. The effect would likely be felt further offshore as well, as currents change in response to the reduced tides.

It’s unclear exactly what level of impact this would have on global ecology, but it probably wouldn’t be the best. Yet, this is not an end of the world scenario. In all likelihood we would adjust and be fine.

The other major impact of the Moon on Earth is related to its tilt. The Earth sits at a fairly stable tilt of 23.5 degrees and that’s largely because the Moon acts as a kind of walking stick that we can lean on. Because our tilt is constant, we enjoy moderately stable seasons from year to year and the polar regions remain relatively cold.

Without the influence of the Moon, the tilt of the Earth would change much more drastically. Basically, because the Moon is moderately large and close, it is the most noticeable gravitational companion we have (again, aside from the Sun). But without it, we would be at the mercy of the gravitational pushes and pulls of the other planets in our solar system. Over time, the tilt of the Earth could turn everything upside down and those snowy winters and hot summers we rely on, would be out the proverbial window.

Something like this, however, would take a long time. It’s probably not something we would notice on human timescales. All in all, if the Moon were destroyed it would be a big emotional disappointment, but it wouldn’t be life-destroying.

Let’s be clear though, destroying the Moon is an extremely bad idea and we don’t endorse it, just in case any villains or alien forces read this. We love our Moon as it is.


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