Sunday, 10 May 2015

Could Ultron's plan work?

Fellow blogger Bobrownia gave me the idea for this entry. He asked if Ultron’s plan for humanity extinction was plausible from scientific standpoint. Obviously this means a spoiler for Avengers: Age of Ultron. So if you haven’t seen it just yet, you’ll have one surprise less, but I assure you the movie has more in store.

Spoiler in 3… 2… 1…

So the question is - can you wipe out humanity by dropping something very big from very high? Simple answer is - yes. Obviously, the devil is in details. Asteroids and comets typically go at great speeds - tens of kilometers per second. Ultron had no way to send his projectile that fast, so he had to go for mass, which is inconvenient since kinetic energy is ½ * m * V2, so you need a lot more mass to make up for velocity.

To play with numbers, we’ll need some assumptions based on what we saw. The “meteor” is roughly a half-sphere. The city above is negligible - buildings may seem large, but it’s mostly empty space, incomparably lighter than solid rock or dirt. To estimate mass we’ll use density of granite. Cubic meter of dirt is around 1760 kg; let’s assume Ultron picked a rocky spot, so cubic meter will be 2600 kg. If we assume that the lifted piece was 10km in diameter (I guess it’s way more than what we saw in a movie), then it’ll weigh 700 billion tonnes.

Ultron wasn’t stupid, he knew just dropping the rock wouldn’t do the job. So he installed engines to plunge it into ground faster. Given how Iron Man got squeezed to the bottom of the “meteor”, let’s assume it’s accelerates like top Formula 1 cars, less than 20 m/s2. The biggest unknown is how high he raised the city. Let’s make another “optimistic” assumption and say it was 50 km. Arbitrary boundary of space is 100 km. The highest planes go (well Blackbird SR-71) is 26 km (85 000 feet). Actually even at the altitude of just few kilometers it gets hard to breathe, but let’s turn a blind eye to this.

So… With 50 km to gather speed, Ultron’s meteor would smack the planet releasing 700 billion gigajoules of energy - that’s 150 thousand megatons of TNT. It’s the force three thousand times that of the most powerful nuclear weapon ever detonated - the Tsar Bomba. But if we compare that to the asteroid that wiped the dinosaurs, it turns out to be thousand times weaker. To match it, Ultron would need enough time to lift the city closer to 500 km; that’s higher than orbit of ISS.

So what if the energy is smaller? A big issue for the genocidal robot is that the impact point was deep inside the continent. Dropping his “meteor” near the coast, preferably close to a tectonically active area could result in an earthquake or at least a devastating tsunami increasing the damage. Still, the calculated energy should suffice to demolish most of Europe and cause a nuclear winter in which army of robots could systematically eradicate the remains of humanity.

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