Spinning around

March 31st, 2005 by Ben Goldacre in bad science, bbc, space, very basic science | 4 Comments »

Ben Goldacre
Thursday March 31, 2005
The Guardian

· You know that kid who spoils everyone else’s enjoyment of sci-fi movies by sitting there in his glasses saying things like: “Well I don’t see how that force field can stop those laser beams from getting through because you can still see the spaceship on the other side of it, and they’re both just electromagnetic radiation with very similar wavelengths ie the visual range known to earthlings as light …”? That’s you, that is. And we love you for it.

· So a special geeky thanks goes to Steven Wallbridge for his heads up about some Bad Science that even appeared in the trailers for the new Dr Who. And lo, on Saturday, in the first episode of the new series, after a big long speech banging on about that sudden moment of enlightenment when you’re a kid and you realise that the natural world isn’t quite how it seems on the surface, and how he can feel things moving that we can’t, Dr Who announces with an air of wonder and awe: “The ground beneath our feet … is moving at a thousand miles an hour!”

· Now, putting our spectacles on and preparing for a well-deserved kicking from the other people on the sofa, I can vaguely remember that the Earth is about 8,000 miles across. Multiply that by pi, which is about 3.14, and you get about 25,000 miles for the circumference of the Earth, which just about makes sense when you think about how far away Australia is and stuff like that. Anyway, the Earth rotates through 25,000 miles once in every 24 hours, and that’s what gives us day and night. Isn’t the Bible fascinating? Oh sorry, that wasn’t in the Bible. Anyway, divide 25,000 by 24 and you get 1,041 miles an hour.

· You don’t need to be a Timelord to work that out. Except that Dr Who was in Britain when he said it, and the Earth rotates at different speeds at different latitudes: 1,000mph at the equator, but a whole lot slower than that in Shepherd’s Bush, as the average 14-year-old could have told you. In fact, with a quick bit of trig, I make it around 650mph. If I cocked up, I hope I at least get marks for showing my working out. Reader Steven Wallbridge goes on: “I note that Sylvester McCoy has much enjoyed the new Dr Who, and has reacted happily to a return to its ‘Reithian’ ideals of educating as well as entertaining.” Oh yes. I’d like to be educated about science by a bunch of humanities graduates in the BBC Drama Department, please.


++++++++++++++++++++++++++++++++++++++++++
If you like what I do, and you want me to do more, you can: buy my books Bad Science and Bad Pharma, give them to your friends, put them on your reading list, employ me to do a talk, or tweet this article to your friends. Thanks! ++++++++++++++++++++++++++++++++++++++++++

4 Responses



  1. Ryan Barrett said,

    September 8, 2005 at 11:55 pm

    It’s moving at an approximate average speed of 30km/s, according to Wikipedia (en.wikipedia.org/wiki/Earth#Earth_in_the_Solar_System).

  2. Alexei Svensson said,

    September 9, 2005 at 7:37 am

    I’d cut Dr.Who some slack on this one. Any speed is accurate in some frame of reference, so he’s technically correct, and in my opinion he’s poetically correct as well.

    Anyway, he’s within an order of magnitude, and that’s what counts in astronomy. ;)

  3. Peter Erwin said,

    September 10, 2005 at 11:31 pm

    Anyway, he’s within an order of magnitude, and that’s what counts in astronomy.

    Being an astronomer, well, I’d have to agree. ;-)

    Though if you want to get really fussy, there are at least four motions you could plausibly talk about: the rotation of the earth’s surface; the motion of the earth orbiting around the sun (as noted above, about 30 km/s — or about 67,000 miles per hour); the sun’s orbital motion about the center of our galaxy (about 220 km/s, or just under 500,000 miles per hour); and our galaxy’s motion through space with respect to the cosmic background radiation (about 600 km/s, or about 1.3 million miles per hour).

  4. Joe Ouroussoff said,

    October 18, 2005 at 2:41 pm

    The kid was wrong…….

    >· You know that kid who spoils everyone else’s enjoyment of sci-fi movies by sitting >there in his glasses saying things like: “Well I don’t see how that force field can stop >those laser beams from getting through because you can still see the spaceship on >the other side of it, and they’re both just electromagnetic radiation with very similar >wavelengths ie the visual range known to earthlings as light …”? That’s you, that is. And >we love you for it.

    Conceivably a forcefield could exist where lasers are stopped and you could see the lasering spaceship. Or at least a window. A holographic filter can filter out a very narrow band of light and pass the rest, which, amongst other things, can be used in saftey goggles used when working with lasers. Also head up displays on aircraft, a scanning laser which provides the display is reflected off the visor into a pilots eyes, while allowing the pilot to see out (useful).

    You see I was the even more annoying brainier kid.