Tim Worstall

Your Government at Work

Slartibartfast has an interesting piece on the history of the technology of navigation. Compass/log/astrolabe/sextant/clock and so on.
One little part leapt out at me, where he talks about Newton and ellipses.
As I’m told by those who understand maths, one of the major points Newton made was that planets do not move in circles, they move in ellipses. An ellipse does not have a ” centre ” it has two focal points, or if I can get my grammar right, two foci. And in the case of a planet, the Sun will be at one of those two foci.
So when the Bank of England decided to put Newton on the pound note ( before inflation made such things into coins : does that mean that inflation is the cause of the transmutation of elements ? Isaac would have been interested.) They drew a nice little picture with the old alchemist himself, a planetary orbit, along with the requisite foci.
And then put the sun in the ” centre “.

I just have to wonder, is the obvious abscence of mathematicians from those halls where the money is both counted and issued something to do with the problems we’ve had in the past over how the money is counted and issued ? And how much ?

In

6 responses

  1. Slartibartfast Avatar
    Slartibartfast

    Hell, I’d settle for a few honest accountants.
    Pretty funny bit on Newton; I hadn’t heard that one. If it’d been a truly accurate depiction of a planetary orbit, though, it’d have been indistinguishable from a circle.
    Thanks for the link; it’s nice to know that that someone, somewhere, is paying attention.

    Reply
  2. Tim Worstall Avatar
    Tim Worstall

    Went and checked.
    Here’s the link :
    http://www.cartref.demon.co.uk/eng/Boed1b.jpg

    Reply
  3. Slartibartfast Avatar
    Slartibartfast

    There could be a decent explanation. This could be a depiction of planetary orbits as seen from an angle, which would make them appear much more oblate than they really are, and exaggerate the distance of the sun from a focus. Actual planetary orbits are nearly circular, except Mercury (0.2 eccentricity) and Pluto (0.25 eccentricity). The foci of the Earth-Sun orbit are off-center about one-sixtieth of the average orbital radius.

    Reply
  4. Sean Avatar
    Sean

    Sorry, it was Kepler who deduced that the planets
    traveled in eliptical orbits. Newton explained why (gravity),

    Reply
  5. Tim Worstall Avatar
    Tim Worstall

    Fair enough. And Kepler was pre Newton ? So the bank note is still incorrect ?
    And about angles and viewing, well, maybe. But they way I read it they’ve but the sun in the ” centre”, something which doesn’t exist with an ellipse.

    Reply
  6. Slartibartfast Avatar
    Slartibartfast

    Kepler was pre-Newton, yes. And Sean has it right. But if you’ve got a roughly circular (and most planetary orbits are nearly circular) orbit seen from some other orientation than normal to the ecliptic, they’re going to look as if the sun were at the origin of an ellipse, rather than at a focus that’s very close to the origin.
    And, to be complete, by “origin” I mean the intersection of the major and minor axes.
    I think it’s fair to associate Newton with elliptical orbits, because Kepler didn’t understand the     why of it. To be fair, though, Newton couldn’t have explained the apparent behavior of Mercury; that needed Einstein.
    Hence, the title of my post: Acceptable approximations. Probably it ought to have been Successive approximations, as I have little doubt that Einstein’s theories will be extended and eventually obsoleted.

    Reply

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