Question: How ‘flat’ IS the earth?
- Actually, friction with the earth’s atmosphere over eons of time and the greater moisture at lower latitudes has caused more erosion — the end result of which is that the earth has actually gotten ‘skinnier’, (equatorial diameter less than that between the poles), not flatter and fatter!
- just one 13,000th: the distance between the poles is about 1600 feet less than the equatorial diameter.
- Flat as a pancake. Yessiree. All this orbit stuff’s a big hoax.
- Even solid rock has some give when 24 sextillion tons are being rotated around at a few hundred knots. The ‘flattening factor’ is one 297th. To a rough approximation, we are flying around over an oblate spheroid, not just a sphere! If you’re a REAL purist, it’s more like a pear, or even ‘the geoid’.
The answer, of course, is number 4.
Question: Does a bathtub REALLY drain clockwise in the Northern hemisphere, and counter-clockwise down under?
- Absolutely. I saw it on the web. (Sinks work better, though.)
- Coriolis force can be apparent on smaller scales only when there are absolutely no currents or internal eddies within the body of fluid. If you let the tub settle for about an hour or so, then could somehow make the plug vanish without causing any disturbance, yes it would drain clockwise in the Northern hemisphere and the other way in Southern latitudes.
- No. It’s a myth. You’d need a bathtub the size of a stadium.
- Actually, in a totally stable fluid body, there IS no spiral motion towards any opening at the bottom.
The answer is number 3. (On this scale, frictional and viscous forces greatly eclipse Coriolis forces, and a draining bathtub is really just cyclostrophic flow (a balance of pressure gradient and ‘centrifugal’ forces.) When we see clockwise flow around an atmospheric high (up in the Northern hemisphere) we are really looking at a broader category called ‘geostrophic’ motion–again a balance of pressure gradient and Coriolis forces. Coriolis forces (an apparent force, really, as it cannot cause a motion) only show up in nature at a scale of several hundred meters. This might be compressed down to dozens of meters in a fluid with absolutely no ‘vorticity’, in a controlled chamber. My intuition tells me also that it would ‘work’ better using a fluid that was less dense than water. Not good grounds for a funding request, though. (See Coriolis Who?! for a full explanation.)
Now for one on GPS:
Question: What change in GPS would triple the accuracy available to the ‘user segment’, but has been dropped by the Air Force?
- End-of-week rollover errors caused too many problems with the computer, so my Uncle Al wrote a letter to the President and George said ‘OK, we won’t need it, anyway.’
- Crosslink. The GPS IIF ‘follow on’ series (not to be launched for a few more years) was originally supposed to have the ability to relay nav updates to the ‘control segment’ via relay vehicles, which would have greatly reduced the ‘age of data’ (from a day to three hours or so) of each constellation vehicle’s OWN position, and thus would improve signal accuracy to the user. Alas, it’s not to be. The Air Force dropped it from their specs due to funding cutbacks.
The answer is number 4. I mean, number 3. (I was the lead engineer on GPS IIF crosslink, so I know!)