Comments here and at Serendipity by Kooiti Masuda remind me yet again of the internationality of science. Not news to people in the field, but perhaps for younger readers. And the small world that science is.
Here, Masuda observed: Precise description of the polar motion by Hisashi Kimura (who led observations at Mizusawa) was a moment of demonstration that the Japanese can substantially contribute to the international scientific enterprise.
Today, of course, it's no surprise. But in 1899, when this was happening, Japan was new to the world science scene. The US wasn't exactly an old hand itself. While we'd had some individual excellent scientists before then (Ben Franklin, for instance), it wasn't until after the land grant universities (founded in 1850s and 1860s) had been at work for some decades that the US was noticeable in international science. Japan had an even later start and more rapid run up. Today, there are other countries going through the process of building their science infrastructures to the point of making significant contributions internationally.
Over at Serendipity, part of Masuda's comment is:
It reminded me another thought. There was a great development of computational geophysics in the latter half of the 20th century, including both climate modeling (Manabe, Arakawa, Kasahara), meteorological data assimilation (Sasaki, Miyakoda) and quantitative seismology (Aki, Kanamori), largely contributed by Japanese-American (born in Japan and emigrated to the USA) scientists. They made innovation by amalgamating the oriental tradition of precise numerical computation and the western tradition of rigorous logical mathematics. (I have not yet substantiated this interpretation, though.)
The very small world effect involved -- I have a connection with almost every person he names. Manabe would probably even remember me :-) after our chats in the 1990s, where I'd tell him how bad the sea ice was in his model and he'd cheerfully agree and then tell me about how good his results were anyhow. We were both right. Miyakoda, I've never met, but he's the reason that I've had sushi. My graduate advisor knew Miyakoda and apparently Miyakoda had a comment that nobody could be an oceanographer who hadn't had sushi. So after I'd successfully defended my thesis, my advisor took me out to a sushi place, thereby finishing my qualifications. Kanamori I wouldn't count except for some jr. high students. Namely, I'd attended a presentation of Kanamori's when I was in graduate school. Quiet a few years later, I went to talk to a jr. high science class. It turned out they were studying earthquakes, and their textbook had a personal profile of Kanamori. The kids were shocked/amazed/bewildered when I mentioned his sense of humor coming through in his presentation. The notion of a scientist having a sense of humor was pretty strange to them.
18 March 2011
17 March 2011
Where is north?
Where is north is actually intensely tied to the question of What is a day?. At least we wind up defining it in much the same way(s) as we define the day. In the previous post, I gave a definition for north/south. Namely, the line of a shadow cast by the sun at solar noon (itself define by the fact that it's the shortest shadow of the day) is north/south.
As happened for the day, we find our most accurate definition from examining the stars other than the sun. The 'pole star' isn't actually one that we use for this. It's almost a full degree away from the actual pole of the earth's rotation.
What we do instead is look for day to day differences in the location of stars passing overhead or nearly so. This approach dates farther back than Seth Carlo Chandler, in the 1890s. But we'll be coming back to Chandler. If the earth has wobbled a little to the north, then the star will pass the zenith a little to the north of where it did yesterday. If you've got a good telescope and other instruments, you can observe this to pretty good precision. Chandler was working with accuracy of 1 second of arc or somewhat better for single measurements. Because of the power of using multiple measurements he was able to examine earth wobbles that were less than 0.1 seconds of arc.
This turned out to be quite useful, as the earth wobbles by about 0.3 seconds of arc. It's how he discovered what was promptly called the Chandler Wobble. This translates to about 3 meters motion in where the pole is.
The orientation of the earth is, as with the rotation rate, tied to where the mass is and where it moves to. The earth's orientation is believed to have changed by some millionths of an arc second due to the earthquake. The variations of a few tenths of a second of arc are caused by ... other things. Atmosphere and ocean circulations are what I'm most concerned about, but also the earth's inner core, and the moon, and .... It's a messy business.
As for the length of day, your scientific source for observations is the International Earth Rotation Service. Which, itself, owes something to Chandler.
As happened for the day, we find our most accurate definition from examining the stars other than the sun. The 'pole star' isn't actually one that we use for this. It's almost a full degree away from the actual pole of the earth's rotation.
What we do instead is look for day to day differences in the location of stars passing overhead or nearly so. This approach dates farther back than Seth Carlo Chandler, in the 1890s. But we'll be coming back to Chandler. If the earth has wobbled a little to the north, then the star will pass the zenith a little to the north of where it did yesterday. If you've got a good telescope and other instruments, you can observe this to pretty good precision. Chandler was working with accuracy of 1 second of arc or somewhat better for single measurements. Because of the power of using multiple measurements he was able to examine earth wobbles that were less than 0.1 seconds of arc.
This turned out to be quite useful, as the earth wobbles by about 0.3 seconds of arc. It's how he discovered what was promptly called the Chandler Wobble. This translates to about 3 meters motion in where the pole is.
The orientation of the earth is, as with the rotation rate, tied to where the mass is and where it moves to. The earth's orientation is believed to have changed by some millionths of an arc second due to the earthquake. The variations of a few tenths of a second of arc are caused by ... other things. Atmosphere and ocean circulations are what I'm most concerned about, but also the earth's inner core, and the moon, and .... It's a messy business.
As for the length of day, your scientific source for observations is the International Earth Rotation Service. Which, itself, owes something to Chandler.
16 March 2011
What is a day?
Some friends have been puzzled about how an earthquake or a tsunami could change the length of a day. This question comes, of course, from the tremendous earthquake in Japan. I trust you're all aware of it, the severity, and are doing what you can. Given how late I am to comment at all, I'll take up my friends' puzzlement.
As is common in science, once you get detailed about just what you are talking about, you also understand much about the thing. So: What is a day? There are really at least 4 different definitions of 'day' that we can fairly easily point to. Only two of them are still in serious scientific use. One is commonly used, kind of. And the one with the longest history is no longer in use.
What we need, in order to define a day, is something that takes 1 day to happen. The longest history for a meaning of 'day' is: "The time between maximum elevations of the sun." Almost equivalent would be time between sunsets or sunrises. Maximum elevation of the sun is a much easier and accurate measurement to make. Don't look at the sun! You also don't need to. Get yourself a stick and put it straight in to the ground (on a desk, sheet of paper, ...). Be sure that the ground is flat and the stick is vertical. Every so often through the day, mark where the shadow ends. At some point, the shadow will reach itsgreatest shortest length. That's solar noon. The direction of the shadow (if you're in the northern hemisphere mid or high latitudes) is north. (There's more fun to be had by repeating this exercise many days through the year.)
This notion of 'day' is affected by earthquakes, since it depends on how fast the earth is rotating. (This also makes it one of the more obscure ways of showing that the earth does rotate.)
As is common in science, once you get detailed about just what you are talking about, you also understand much about the thing. So: What is a day? There are really at least 4 different definitions of 'day' that we can fairly easily point to. Only two of them are still in serious scientific use. One is commonly used, kind of. And the one with the longest history is no longer in use.
What we need, in order to define a day, is something that takes 1 day to happen. The longest history for a meaning of 'day' is: "The time between maximum elevations of the sun." Almost equivalent would be time between sunsets or sunrises. Maximum elevation of the sun is a much easier and accurate measurement to make. Don't look at the sun! You also don't need to. Get yourself a stick and put it straight in to the ground (on a desk, sheet of paper, ...). Be sure that the ground is flat and the stick is vertical. Every so often through the day, mark where the shadow ends. At some point, the shadow will reach its
This notion of 'day' is affected by earthquakes, since it depends on how fast the earth is rotating. (This also makes it one of the more obscure ways of showing that the earth does rotate.)
14 March 2011
Running in the rain
It was raining, of course, this past Sunday when I went to the track for my second run since breaking my wrist while running last fall. (First having been Thursday.) I've previously talked about running with lightning (i.e., don't!). But my negativity about being electrocuted* should not be taken to apply against running in the rain. A number of my favorite runs have been in the rain. Probably a higher fraction than in 'nice' weather.
Running in the rain becomes pleasant once you make some attitude adjustments, and perhaps do some physical preparations. Bonuses are that you can congratulate yourself for your tremendous virtue in being out in spite of the unpleasant weather. And if you race, it's a plus because even though you could arrange to do all your training in nice weather, you cannot ensure that all races will have nice weather.
The main attitude adjustment is one suggested by a fellow trail runner. We were going to run on trails during moderately heavy rain, after 2 days of steady, heavy rain. Our path was all dirt except for a stream crossing. In other words, after all that rain, no question that we were going to be soaked, and muddy, and soaked again (by the stream). As he said, it was time to let our inner child out to play -- splash through the puddles (which were numerous) and enjoy the mud. I won the contest for having the mud highest on my body (up near the shoulder blades) without having fallen.
Physical preparation starts with the fact that you are going to get soaked. So relax about that part. During the run, get wet and don't worry about it -- assuming that you're not running with too little clothing on, and temperatures are low enough to make hypothermia an issue. (If that sort of thing is a consideration, get out of the rain immediately.) But a spring rain, like I had Sunday, with a warm house or car nearby, and adequate clothing ... enjoy. The thing is, have two sets of clothes. One for running in, and one for immediately after you finish running.
Running in the rain becomes pleasant once you make some attitude adjustments, and perhaps do some physical preparations. Bonuses are that you can congratulate yourself for your tremendous virtue in being out in spite of the unpleasant weather. And if you race, it's a plus because even though you could arrange to do all your training in nice weather, you cannot ensure that all races will have nice weather.
The main attitude adjustment is one suggested by a fellow trail runner. We were going to run on trails during moderately heavy rain, after 2 days of steady, heavy rain. Our path was all dirt except for a stream crossing. In other words, after all that rain, no question that we were going to be soaked, and muddy, and soaked again (by the stream). As he said, it was time to let our inner child out to play -- splash through the puddles (which were numerous) and enjoy the mud. I won the contest for having the mud highest on my body (up near the shoulder blades) without having fallen.
Physical preparation starts with the fact that you are going to get soaked. So relax about that part. During the run, get wet and don't worry about it -- assuming that you're not running with too little clothing on, and temperatures are low enough to make hypothermia an issue. (If that sort of thing is a consideration, get out of the rain immediately.) But a spring rain, like I had Sunday, with a warm house or car nearby, and adequate clothing ... enjoy. The thing is, have two sets of clothes. One for running in, and one for immediately after you finish running.
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