Peter Hansen wrote: > Roy Smith wrote: > >> Steven D'Aprano <[EMAIL PROTECTED]> wrote: >> >>> High and low tides aren't caused by the moon. >> >> >> They're not??? > > > Probably he's referring to something like this, from Wikipedia, which > emphasizes that while tides are caused primarily by the moon, the height > of the high and low tides involves the sun as well: > > "The height of the high and low tides (relative to mean sea level) also > varies. Around new and full Moon, the tidal forces due to the Sun > reinforce those of the Moon, due to the syzygy found at those times - > both the Sun and the Moon are 'pulling the water in the same direction.'" > > (If I'm right about this, then the statement is still wrong, since even > without the sun there would be high and low tides, just not of the > magnitude we have now.)
Close :-) If tides are caused by the moon, then removing the moon would end tides. But this clearly isn't true: without the moon, we would still have tides, only smaller. On the other hand, the magnitude of the tides is much larger than the magnitude of the moon's effect on the oceans (up to forty times larger). So the moon is, at best, merely a minor cause of the tides. Of course, all this is quibbling. But it does illustrate exactly what Cohen and Stewart mean when they talk about "lies for children". The truth is a lot more complicated that the simple, easy to understand "the moon causes the tides". -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
