Shoot for the Moon: Would the USA’s Cold War plan to blow it out of our night sky really work? Fiona

In 1958 – the year after the Soviet Union’s Sputnik became the first object to be launched into space by humankind – 60 years ago – the government of the USA began to work on a secret plan to assert their dominance on the stage of world power: by blowing up the moon. Known covertly as “project A119”, the intention was to make the military might of the USA abundantly clear to all on earth.

Of course, the first question this raises is: would such a show of force actually be possible? Though it may look small from down here, and is supposedly made of green cheese, the moon is actually a seventy trillion megaton rock located four hundred thousand kilometers away. That’s quite a big thing to blow up, and a significant distance to send explosives. The explosion would have to have enough energy to not only break the moon into pieces, but also send them far enough away from one another that their gravitational fields – the attractive forces that act between all objects – wouldn’t be able to pull them back together. Otherwise, the single lump of geological matter we call our moon would simply be replaced by a pile of lunar rubble. It is estimated that such an explosion would be equivalent to the detonation of thirty trillion megatons of TNT; given that the Tsar Bomba – the most powerful nuclear bomb ever built – had an explosive power of fifty megatons, blowing up the moon would require six hundred billion of these. Humanity has neither the uranium supplies to build such a bomb, nor the rocket technology to get it there.

Other options include creating a “moon quake” to split apart the internal structure of the rock; this would need to be equivalent to a 16.5 on the Richter scale. The most violent earthquake recorded read just 9.5 on the Richter scale, so it’s unlikely that such a quake could be artificially produced on the moon. Alternatively, the moon could be zapped with a giant laser, however this would need to provide the same amount of energy instantaneously as the sun outputs every six minutes. Humans don’t really have the resources to power such a thing.

It seems, therefore, that blowing up the moon to assert their dominance over the space and nuclear spheres wasn’t really an option for the USA in 1958 – or even sixty years later – due to a lack of both technology and resources. However, the idea of blowing a large crater in the moon, in order to produce a giant explosion to demonstrate to the world the might of the USA, and leave behind a crater visible from earth to remind them of it forevermore was also considered. This, too, was dismissed in 1959; the reasons for this are not clear, but perhaps those in charge of the project realised how utterly ridiculous their own idea sounded.

But let’s just take a step back for a moment, and imagine if exploding the moon were possible: what would the consequences be here on earth? Would lumps of moonrock kill us all? What would life be like on a moonless planet?

So the moon has exploded. The first thing most humans notice is a big, bright cloud spreading out through the sky where the moon used to be. This is the light from the explosion illuminating the moon debris. Dust then covers the sky for a while, making daylight darker and air travel impossible for a few months. Our seas and lakes are still tidal – the sun exerts a gravitational pull on the earth that contributes to this, but does not move relative to the earth – so there will be no spring or neap tides – the water will rise to one-quarter the height of a spring tide and return to the same lower level each day. Fragments of moon start to fall to earth; some burn up as they enter our atmosphere; others hit the ground and wreak havoc where they land, though it is unlikely that this would be catastrophic for humanity, as they would move slowly in comparison to other astronomical objects that fall to earth, such as asteroids.

Once the dust clouds have cleared, the next noticeable thing is a lot more stars. The moon is by far the brightest object in the night sky, so with it out of the way, nighttime will be darker and the stars much brighter by comparison. One –or more – smaller ‘moon replacements’ may also appear in the sky, if the explosion leaves some larger chunks of rock as well as debris and dust. Of course, this debris and dust continues to rain down on the earth whenever a piece falls out of orbit.

Only after the majority of this debris has cleared – in perhaps a few thousand years – is the next major effect noticeable by humans: the earth will tip over. Gravitational interactions between the earth and the moon are what is currently preventing this; without it, the earth will tip on its axis, causing the poles to melt and an ice age to occur every few thousand years on whichever part of the planet is furthest from the sun at that point.

So, although exploding the moon isn’t really possible – and certainly wasn’t in the 1950s – it wouldn’t have utterly catastrophic consequences for the earth, just bring significant change. However, as a show of force, it still seems somewhat excessive.