Archive for December, 2008

Cold weather really can make you sick

Posted December 5th, 2008 in Biology. Tags: , , .

My mother always tells me to bundle up before I go outside during the winter, because otherwise I’ll “catch a cold.” When I first learned about the germ theory of disease, I thought she was wrong. Cold doesn’t make you sick, I thought. Germs make you sick.

Recently, it’s become obvious that I was wrong and she was right. (more…)

People who argue to win annoy me

Posted December 1st, 2008 in Philosophy. Tags: , , , .

I enjoy civilized debates, but only rarely get a chance to engage in them. That’s because in my experience nearly everyone assumes they’re correct, so they only debate to beat their viewpoint into the other person’s head at all costs.

In other words, most people argue to win… and I can’t stand it. Whenever I mention this pet peeve, the response is almost always “Oh, so you argue to lose, huh?” (more…)

The Moon wobbles

Posted December 4th, 2008 in Astronomy. Tags: , , , , , .
Lunar wobbling animation

This is what you get if you take a photo of the Moon every night for a month, then make a movie out of those pictures. The Moon’s phases aren’t surprising, but the Moon also appears to grow and shrink as it orbits the Earth. This happens because the Moon’s orbit is slightly elliptical; its distance to the Earth varies by about 10%.

Also, the Moon appears to “wobble” from left to right. That’s because the Earth’s gravity pulls harder on the Moon the closer it is to the Earth, so the Moon travels faster in its orbit when it’s closer to the Earth. The Moon’s rotation rate matches its average orbital speed (which is why we only see one face of the Moon), but its orbital speed varies during the orbit while its rotation rate remains fixed, so the Moon appears to wobble from left to right.

2009-08-10 Update: I’ve noticed that many people arrive at this article by googling moon wobbles. All the other sites on the first page claim that “moon wobbles” are responsible for explosions, mass-murder, earthquakes, terrorism, etc. Sadly, I need to emphasize that the wobbling I’m describing can’t possibly result in these kinds of ludicrous effects.


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