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Planet, Gone!

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The Plutonian system: Pluto and two moons viewed from a third.
In the last general assembly of the international astronomical union, astronomers voted to demote planet Pluto, to strip it of its planetary status. The reasons for the reduced status are clear. (And it was coming for a long while!) The surprising bit, however, was the definition the particular astronomers concocted, eh, came up with. They were looking for a precise definition, and indeed found one, one which is precisely wrong. According to it, Earth is not a planet either!

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The coming of another ice-age?

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A few days ago I stumbled upon an interesting article from Time magazine, entitled: "Another Ice Age?". No it is not a recent article. It is politically incorrect to talk about global cooling these days. The article appeared in 1974, after "three decades of cooling" prompted some to believe that an imminent ice-age may be coming. It is interesting to read it in perspective, and perhaps there is a lesson we could learn from it. Here are a few excerpts from it. Read and enjoy.

Recently added articles: Stellar parameters, rowing boats, water propelled rockets.

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  • Estimate the basic stellar parameters using the tendency for energy equipartition. In particular, the temperature at the center of the sun, the mass-radius relationship of white dwarfs and their Chandrasekhar limit are all estimated. These were taken from my order-of-magnitude course notes.
  • Row Row Row your boat, but at which maximum speed? This is a classic example of an order of magnitude analysis giving a lot of physical insight (and impressive predictive power).
  • Analysis of the classic homemade water rocket, taken straight out of my first year physics majors classical mechanics notes. There is even a rocket simulator with which the trajectory can be calculated and graphed.

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