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Equivalent Equator Empirical Experience! (Posted on 2005-03-27) Difficulty: 3 of 5
Prove that at any time there are two opposite points along the Equator, which have exactly the same temperature. Assume the temperature function varies continuously as you move along the Equator.

Counterargument: This is patently impossible. If there are such points on the Equator, there must also be similar points on any circle around the Earth, such as a meridian. But in that case, we'd have one point in the north hemisphere, in winter, and the other in the south, in summer; that doesn't make sense!

What's wrong with this reasoning?

  Submitted by Old Original Oskar!    
Rating: 2.8000 (5 votes)
Solution: (Hide)
Let f(x) be the temperature along the Equator; f(x+2π)=f(x). Let g(x)= f(x+π)-f(x); then, g(x+π)= f(x+2π)-f(x+π)= f(x)-f(x+π)= -g(x). Unless g(x) is always 0 (which would provide infinite opposite points with the same temperature) it changes sign between x and x+π, so by continuity it must be zero somewhere. QED

As to the "logical" argument, the points on the meridian could be very near the Equator, where winter and summer are very similar, or they could be near the poles, both at very low temperatures.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
No SubjectJud2005-08-16 12:56:34
No Subjectkat2005-04-06 01:15:24
SolutionSimple solutionajosin2005-03-28 16:14:58
re: SolutionCharlie2005-03-28 13:35:38
SolutionSolutionDavid2005-03-28 05:18:35
SolutionSolutionKen Haley2005-03-28 01:06:32
SolutionBolzano solutione.g.2005-03-28 00:27:13
SolutionProofLarry2005-03-27 22:23:40
counter-counterargumentTristan2005-03-27 20:27:49
A related theorem (partial spoiler)Larry2005-03-27 19:30:02
re: possiblylenny2005-03-27 14:35:20
possiblylenny2005-03-27 14:26:19
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