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Science Snippets

Entry 354, on 2006-06-21 at 13:26:48 (Rating 3, Science)

I want to mention several interesting (I hope) little pieces of science news in this blog entry. First, the news that NASA will launch the space shuttle Discovery on 1 July, even though it has been warned by engineers that the safety problems haven't been fixed. They say the crew is not being put at risk, but that is clearly nonsense. Any space flight exposes the crew to risk, and given the history of the shuttle, it would be crazy to make a claim like this. I am a strong supporter of space exploration, but the last thing NASA needs is another shuttle accident. The bad press, accusations of incompetence, and long delays before return to flight, which would inevitably result just don't make it worth taking this risk.

Yesterday I blogged about intelligent design's challenge to evolution. In fact, there is no real challenge, but the perception among some groups is that there is. Today I read an article on the BBC world news site (one of the best web sites in the world) which discusses another link in the evolution of birds. Its a fossil of Gansus yumenensis from 110 million years ago. Previous fossils have been limited to single bones, now almost complete skeletons have been discovered. It seems that the ancestors of modern birds made the transition to water, then back to land when a competing branch became extinct. Every year we find more evidence for evolution. When was the last time anyone announced a startling new discovery supporting intelligent design? That's right. Never.

Today is mid-winter (in the southern hemisphere, mid-summer in the northern) and we have forecasts of snow to low levels. In some parts of the country we have had the most snow for several years. Maybe its related to global climate change, maybe its just a random occurrence. Most likely its a combination of natural climate change, change caused by human activity, and random fluctuations in weather patterns.

Mid winter day, more correctly known as the winter solstice (southern hemisphere) is when the Earth faces a point furtherest south. The Sun reaches its furtherest apparent distance north (its overhead on the Tropic of Cancer at noon local time) and it doesn't rise at all for points south of the Antarctic Circle. Another astronomical factor in our seasons is the distance of the Earth from the Sun. This doesn't vary much, but we are closest on 4 January which is close to mid summer (southern) on 23 December, and furtherest near mid winter (southern) so we would expect southern seasons to be more extreme than northern. It doesn't quite work this way because the uneven distribution of land and sea in the two hemispheres has a greater effect.

The geometry of the Earth-Sun-Moon system is quite interesting when studied using something like an orrery (a motorised model Solar System). I used one a lot when teaching astronomy many years ago. Now I would tend to use an astronomy computer program instead. These allow the virtual observer to "stand" anywhere on the Earth, on another planet, or even in space and look at where other objects, such as the Sun, are.

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