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Re: Delta-T
From: Omar Reis
Date: 2004 Dec 6, 12:20 -0200
From: Omar Reis
Date: 2004 Dec 6, 12:20 -0200
>>Of DeltaT, Omar R wrote: >>"I wonder why can't this value be deterministic, like everything else in astronomy ?" >Frank Reed wrote: >Can you predict the dust storms on Mars? How about the shape of the next sunspot? You would probably counter that those things are "weather" not astronomy. And I think that's basically how we define traditional computational astronomy. Anything that is subject to computation in the foreseeable future, we count in, otherwise it's out. Changes in delta-T derive from the complexities of the Earth's weather and its interior, channeling angular momentum from one part of the total system to another. The net angular momentum of the Earth, if we could measure it, presumably shows a much more "deterministic" decline since it's under the influence of the luni-solar tides. But even there, the exact damping effect depends on the shapes of the ocean basins (which are changing on a geological time scale). I was talking about positional astronomy. I guess it is the closest thing to the deterministic world that Newton imagined in his natural philosophy. A few sciences can make predictions a thousand years into the future and past. This is so because the number of objects in its models is much smaller than in weather forecast or economy or sociology. But the DeltaT seems to be influenced by butterflys, flapping their wings in Hong Kong .... Omar