Steven D'Aprano <[EMAIL PROTECTED]> wrote: > Roy Smith wrote: > > Steven D'Aprano <[EMAIL PROTECTED]> wrote: > > > > >High and low tides aren't caused by the moon. > > > > > > They're not??? > > Nope. They are mostly caused by the continents. If the > Earth was completely covered by ocean, the difference > between high and low tide would be about 10-14 inches.
Yeah, I know about all that stuff. But, let's explore this from a teaching point of view. > The true situation is that tides are caused by the > interaction of the gravitational fields of the sun, the > moon and the Earth, the rotation of the Earth, the > physical properties of water, its salinity, the depth, > shape and composition of the coast and shoreline, the > prevailing ocean currents, vibrationary modes of the > ocean (including up to 300 minor harmonics), ocean > storms, and even the wind. That's a lot of detail to absorb, and is appropriate for a college-level course taken by oceanography majors. The key to teaching something is to strip away all the details and try to get down to one nugget of truth with which you can lay a foundation upon which further learning can happen. Yes, both the sun and the moon have gravitational fields which affect tides. But the moon's gravitational field is much stronger than the sun's, so as a first-order approximation, we can ignore the sun. And, yes, there's a huge amplifying effect caused by coastline shape and resonant frequencies of the ocean basins, but if you took away the moon (remember, we're ignoring the sun for now), there would be no tides at all. If you took away all the continents, there would still be tides, they would just be a lot less (and nobody would notice them!). And, yes, wind affects tide. I live at the western tip of Long Island Sound. If the wind is blowing hard along the axis of the Sound for a solid day or two, I can see that it has a drastic effect on the tides. This says to me that "The tides are created by the moon, amplified by the shapes of the land masses, and altered by the wind". Sure, "the moon causes the tides" is not the whole picture, and from a quantitative point of view, may not even be the major player, but from a basic "How do I explain this physical process to a 6th grade child in a way that's both easy to understand and fundamentally correct", I think "the moon causes the tides" is the only reasonable explanation. Once that basic idea is planted, all the other stuff can get layered on top to improve the understanding of how tides work. So, to try and bring this back to the original point of this thread, which is that Python is a better first language than C, let's think of the moon as the "algorithms, data structures, and flow control" fundamentals of programming, and memory management as the continents and ocean basins. What you want to teach somebody on day one is the fundamentals. Sure, there are cases where poor memory management can degrade performance to the point where it swamps all other effects, but it's still not the fundamental thing you're trying to teach to a new CS student. -- http://mail.python.org/mailman/listinfo/python-list
