
485Newtonian Gravity and Newtonian Cosmology
© 2010 Taylor & Francis Group, LLC
with water, the tangential force components would cause the two tidal bulges to sweep
around the globe with the moon. This picture explains the twice daily ebb and ood of the
tides, but the actual motions depend in a complicated way on the response of the oceans as
the Earth rotates and on features of local topography.
We can estimate the equilibrium height of the tide easily. In equilibrium, the surface
of the water must be an equipotential surface. We can thus calculate the height h(θ) as a
function of the angle θ to the moon’s direction (see Figure 14.8). Because ...