Wednesday, November 15, 2006

A tempest in a teacup

Today in Texas the wind is howling as a cold front sweeps through the area. It's a good day to get out of town, and I'll be doing that around noon as I head for observing at Kitt Peak in Arizona.

The weather reminded me of an article I saw in an astronomical journal a few days ago talking about "cold fronts" in the hot gas in a galaxy cluster. Cluster of galaxies, which can contain thousands of galaxies in an area "only" a few million light years across, often are surrounded by X-ray emitting gas that is several million degrees in temperature. A cold front can be caused by cold gas in a galaxy that has just fallen in to the cluster, or by many other complicated mechanisms. But, in many ways, they act like cold fronts on Earth -- moving through the super-hot gas and cooling it by a million degrees or so.

Astronomy is hard to do in the laboratory. We have yet to make a star, let alone a galaxy or a cluster of a thousand galaxies. So we often have to look to similar processes on Earth to learn the physics that we use to understand the Universe. I remember seeing a talk about 10 years ago by scientists who were studying storms in Jupiter's atmosphere by dropping fluorescent crayons into a rotating drum of water. Another talk I saw about 6 or 7 years ago involved studying why stirring hot tea causes it to cool faster, and how that knowledge can extend to rotating stars. And looking for life in the Universe often involves trying to look at the Earth in the same way we'd look at other planets, trying to find tell-tale signs that would prove the presence of life.

So, there is a lot we can learn about the universe from studying seeming mundane things, like hot tea or the weather.

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