Monday, May 14, 2012

Hemispherical misconceptions

Two concepts that I believed in throughout my entire childhood turn out to be false.

1. I was told in school that the seasons are caused by the elliptical orbit of the earth around the sun.  Some months along this orbit, the earth is closer to the sun, and other times it is farther away.  When the earth is closer to the sun, it is summer and when the earth is farther away, it is winter.  When I came to the USA, I met people from Brazil and Australia who tell me that it is winter there when it is summer here.  This clearly contradicts the theory above.  It turns out the seasons are caused by the tilt of the earth in its orbit.  Half of the year the northern hemisphere is tilted towards the sun (corresponding to the warmer seasons), while the other half of the year the southern hemisphere is tilted towards the sun.  In fact, the earth is closer to the sun in the winter of the northern hemisphere than in the summer.

2. I was also told that in the southern hemisphere water flushes away in a sink in the opposite direction from that occurring in the northern hemisphere.  I have been to the southern hemisphere 3 times, but each time I forgot to do some experiments to validate this claim.  It seems that this phenomenon attributed to the Coriolis effect is only relevant under very careful conditions or at a very large scale, neither of which is present in a toilet or a kitchen sink.

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