Jellby wrote:
> Yes, but we "notice" tides in relation to the solid earth, so the liquid
> sphere being deformed while the solid one remains rigid is what we call
> tide, isn't it (in a broad sense)?

Cetainly, speaking informally, the tide cannot "go out" if there's no 
solid beach from it to go out from.

But if you measure the shape of a world made entirely of liquid, you 
still get two bulges. And if you have a world entirely of solids, you're 
still have less apparent gravity at two places instead of one. And if 
you're tidally locked (like the moon is with the earth) but with liquid, 
you get "tides" that don't move.

That's generally the sort of thing people mean by "tides" when they're 
talking about the astrophysics of things.

> Also, it is the tidal force (wich in truth also works on solid bodies),
> which has made the rotation periods of the Moon around itself and around
> the Earth to match, so that we see always the same face of the Moon. 

It's also what makes the gaps in saturn's rings, makes the Lagrange 
points stable, and lots of other effects as well.

-- 
   Darren New / San Diego, CA, USA (PST)
    Neither rocks nor slush nor salted rims
    shall keep us from our appointed rounds.

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