>> * Or you just get used to the fact that some numbers are not exact in >> floating point. > > This got me thinking. How many decimal places do you need to > accurately, say, aim a laser somewhere in a 180 degree arc accurately > enough to hit a dime on the surface of the moon? > > Alan
In short: it's pretty much impossible. The mirrors used in the Lunar Laser Ranging experiments are roughly the size of a suitcase (each). Data from the APOLLO (Apache Point Observatory Lunar Laser-ranging Operation) gives us some numbers to go by: it uses 1 gigawatt energy, generating a (roughly) 1-inch long "bullet" of light. By the time it hits the moon it will have distorted to a diameter of 1.25 miles (earth's atmosphere is the biggest culprit). only about 1 in 30 *million* photons will actually hit the retroflector, and by the time it gets back to the telescope on earth the beam is about 9 miles wide. Again, only 1 in 30 million *of the returning* photons will hit the telescope. Now imagine scaling the retroflector in size to a dime. To bring it back on topic: could python handle these numbers reliably? -- best regards, Robert S. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
