Re: Sandbox stuff and Teesside White Water Course edit
What is a 'gravity' course ? Aren't they all gravity courses ? Isn't gravity just the same as saying 'not pumped' ?
I would argue that the Teesside White Water Course should not be called 'Tidal Power' because tidal water is not normally, if ever allowed above the Tees Barrage and hence can never 'power' the white water course. It could be called a 'flow diversion' course or a 'gravity' course, or perhaps it is both.
As for the tidal aspect - yes it is tidal but this is a limitation on the operation of the course rather than something that drives the white water course. When it is high tide in the lower part of the Tees there is not much head of water (if any) on the barrage to power the course and the course gets partially flooded. The course is in a flooded state on Wikimapia: http://www.wikimapia.org/#lat=54.5657268&lon=-1.2843812&z=18&l=0&m=h Perhaps the course is a flow diversion gravity fed course with tidal limitations. But even that is due to change.
Tees white water course itself is actually in the Borough of Stockton-on-Tees rather than in Middlesbrough and currently takes the form of a 'U' shaped loop. After current modifications it will become a hybrid pumped / gravity course in the form of a loop or loops.
Is there a Wikipedia template for white water courses? - if not, then why not have one.
John
test for Little Boy talk page edit
[1] User_talk:Hawkeye7#Little_Boy_change_on_August_4.2C_2013
The Schematic Drawing edit
This widely used drawing is misleading. It implies that the mid-ocean high tide (away from the influence of continental shorelines) should occur when the moon is overhead. This would be true only if the moon were in geostationary orbit, in fixed position over a single meridian of longitude. Since the earth rotates 28 times faster than the moon orbits, the tides are about 45 degrees out of phase with the sublunar and antipodal positions.
When I lived in Honolulu, I noticed that high tide came about three hours after the moon passed overhead, or underfoot. Even though the maximum lifting force comes when the moon is overhead, or underfoot, water is heavy, and tidal currents have momentum. At a given meridian, water continues to pile up after the moon has passed on (actually, after the earth has rotated that location out from under the moon). This distinction is important, because it explains why the moon is slowly getting farther away.
Since the high-tide bulge of open-ocean water is always about 45 degrees of longitude east of the sublunar position, it tends to pull the moon forward, thereby raising it into a higher orbit.
The oversimplified diagram may be easier to understand, but it is wrong enough to cause confusion. I suggest a modification.
- Never mind. I see from sources in the above discussion that the tidal bulge supposedly lags the sublunar longitude meridian by only 3 degrees, or 12 minutes time, not 45 degrees and 3 hours as my diagram depicts, and as I have observed anecdotally. (I gather the small 3 degree lag is, in fact, what drives the moon into an ever higher orbit, getting farther away at the rate of fingernail growth.)
- However, if there is anywhere on earth where this 3 degree lag can be observed, a tropical island in the mid-Pacific, like Wake Island, should be the place. I am mystified as to why the tidal bulge arrives at Wake Island 3 hours late. We know it travels at over 1000 miles per hour, to keep pace with the moon at the equator, and that the actual movement of water toward the sublunar meridian, which causes the water to pile up into the tidal bulge, is not very fast in the open ocean. The inertia explanation for a significant time lag seems to make intuitive sense.
- I have found global color-coded contour maps showing the tidal amplitude around the world. Has anybody made such a map for time lag between the sublunar meridian and the tidal bulge? It would be helpful.
- There are many conflicting explanations about how the tides work -- and lots of people explaining how every theory but their own is incorrect. The Wikipedia policy of requiring citations breaks down here, because every theory comes with ample citations, from articles, textbooks, and the like.