Tag Archives: thesis

I Am Become Q*, Destroyer Of Worlds.

Saying that I have a Ph.D elicits a fairly predictable reaction from most people. They will, in an attempt to appear interested, ask “What subject?” and then when informed that I did Astrophysics – one of the simpler branches of physics if you don’t tangle with cosmology or relativity but which appears to have a fearsome reputation in the eyes of the layman – their eyes glaze over and they either stop talking to me altogether, or else they desperately try to change the subject before I can get a chance to pounce on them, knock them to the ground and inject pure Science into their brains via their ear canal1. There’s a second type of person out there, however; the freakish sort who are genuinely interested in science, and this second type will, after some circumspect small talk, eventually get around to asking me what my thesis was about. And this is a question to which I have gradually evolved a tried-and-tested one-sentence reply:

“I am trying to find out how much energy you need to blow up Pluto.”

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Light Gas Guns And You.


This is not what the interior of a light gas gun looks like.

 Time for something a little more hands-on. There’s all sorts of crap hurtling around the solar system — satellites, asteroids, comets and so on – and most of it is travelling at velocities that are, to put it mildly, completely insane. Supersonic jets and rifle bullets travel at about 1 km/s. Ramjets go at around 3 km/s. The average Earth-crossing asteroid, on the other hand, is hurtling through space at 20 km/s. This is Very Fast, and the reason Earth-crossing asteroids (so called because they cross the Earth’s orbit) worry people so much is because the kinetic energy of an object is proportional to the square of its velocity as per the equation


It doesn’t help that asteroids also tend to be rather heavy, and so they tend to possess a rather staggering amount of kinetic energy. Kinetic energy that would, if released on Earth somehow – say, by the asteroid hitting it – just ruin everyone’s day.

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