5 ms·
Any time I meet some of these stuck-up physicists, that's what I'm going to lob into their face. And they'll get even more stuck up, because physics as such de
by sqrt17 16y ago
Any time I meet some of these stuck-up physicists, that's what I'm going to lob into their face.
And they'll get even more stuck up, because physics as such deals with (but doesn't control) processes which range more orders of magnitude.
And the techniques of computer science and physics are similar: deliberate simplification. Planets are turned into mass dots, or at best spheres with uniform density; and customers are required to have an all-ASCII name. The difference is that physics relegates anything that can go wrong - building bridges, machines, cars - to people called engineers, whereas the likes of Dijkstra would rather have hyperintelligent theoreticians sort out these problems.
(You can tell that he's never had an angry lynch mob of customers banging at his door because he implemented an incorrect specification instead of using common sense to find the specification error and getting back to the customer).
- jules 16y agoSimplifying the shape of planets to dots is a simplification, but amazingly you don't lose accuracy by it wrt to their movements due to gravity. If the planets were turned into dots, their trajectories would be the same.
- sqrt17 16y agoIn the case of a 3-body solar system, they wouldn't. But as soon as one of these mass dots tries to land (or stand) on one of the other mass dots, you'd see a difference. If you say that this violates the assumptions of the basic model, you're right. But if you look at all the craters on the moon, the model assumptions are violated pretty often - the trick is recognizing when you need a different model, which is always easy in retrospect, but can be difficult to anticipate.
- jules 16y agoYep, that's true. I just thought that is was interesting that the shape of a planet doesn't affect its trajectory under the laws of gravity alone (i.e. no collisions etc). It's also true that physicists do use explicit approximations often, for example in statistical mechanics, or by using a linear approximation instead of an exact quantity. That's similar to calculating the asymptotic running time of an algorithm instead of the exact number of steps it takes (except the limit in the physics case takes some quantity to zero to get a linear approximation whereas for the algorithm we take the limit of the input data size to infinity).
- tbrownaw 16y ago...hm, how many orders of magnitude down are the tidal forces this ignores?
- jules 16y agoDo tidal forces have any effect on the center-of-mass trajectories of planets?
- tbrownaw 16y agoThey should, they transfer energy between rotational and orbital velocities. For example the earth is gradually spinning more slowly (as can be seen from daily/annual growth rings in corals), while the moon is orbiting faster and getting farther away.
- Panoramix 16y agoSpheres with uniform density behave exactly the same as mass dots. Mathematicians can cook up giant numbers without blinking, like Graham's number. If that makes anyone feel good, then good for them. Somehow, all the quotes I read from Dijkstra leave an arrogant after-taste in my mouth.
- jemfinch 16y agoNice try, Alan Kay! <http://www.youtube.com/watch?v=s7ROTJKkhuI> http://www.youtube.com/watch?v=s7ROTJKkhuI> (For those who don't feel like watching: "Arrogance in computer science is measured in nano-Dijkstras.") As a Dijkstra fan myself, though, I feel duty-bound to emphasize that condemning a claim as having been stated by an arrogant man is just a somewhat more subtle way of stating an ad hominem fallacy.
- euccastro 16y agoI don't think he's using the nano-Dijkstras comment as an argument, but as a side joke. He refutes Dijkstras on empirical grounds: the US way of programming got the job done, as illustrated by the fact that most of the software in the world was being produced there.
- jemfinch 16y agoI think Kay's US-vs-EUR comparison is largely inappropriate regardless because Dijkstra had long been writing his missives from Texas.
- deleted 16y ago[deleted]