In uk.transport.london message ,
Fri, 15 Feb 2008 01:33:44, John Rowland
n.co.uk posted:
Tom Anderson wrote:

Anyway, my proposal is for *all* heights to be measured as distance
from the centre of mass of the earth. SOLVED!

Why not measure heights from the centre of mass of the earth-moon system?
That would abolish the need for tide tables because the tide would be at a
fixed height... although the land would go up and down.


Earth radius 4000 miles, Moon distance 240000 miles. Ratio of masses
81. The barycentre is therefore 3000 miles from the Earth's centre,
1000 miles down. So you're suggesting a tidal range of 6000 miles from
high to low.

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