Tag Archives: impacts

The Quickfire Round, Redux.


I have a whole backlog of questions here and my answers to many of them are far too snappy to justify a full post, so I’m going to economise and do a three-in-one. HOLD ON TO YOUR BUTTS.

Gerry asks

I’ve noticed that when I have a string of some sort (be it a usb cord or an audio cable that I use to plug in my phone to my aux in my car stereo, or any other string-like item) it has a tendency to tangle. This happens all the time (depending on the environment) is there a branch of physics or science/math that investigates this phenomenon? (Chaos maybe?) Not to be confused with the Quantum physical term of entanglement or spooky action)

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Asteroids Again.


After spending not a few words talking about Armageddon and fake space rocks last Wednesday I was slightly surprised when an actual real-life asteroid tore through the skies above Russia and disintegrated/detonated in midair somewhere above Chelyabinsk. Thanks to the asteroid’s passage over populated areas and the modern ubiquity of smartphones with some kind of video capture capability – not to mention the uniquely Russian preponderance of car dashboard cameras to provide some protection against the now-famous driving standards in the country, as well as the notoriously corrupt traffic police – this has been by far the most well-documented asteroid “strike” in history, so I thought I’d take a little while to talk about it, and the reaction to it.

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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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