Re: How does Santa do it?

Nick Odell <gurzhfvp.jbexfubc@xxxxxxxxxxxxxxxxxxxx> writes:
In Our Time last Thursday was about -erme- time. ...

I'm not too sure I understood the melon-in-the-bedsheet analogy of
gravity as a distortion of the space-time continuum, though. It made
sense until I realised that the analogy only works because of gravity.
Does that make gravity a tortology?

it's an analogy: the sheet is a two-dimensional space which gets
curved by the presence of the melon.

einsteinian space is a four-dimensional space that gets curved by the
presence of matter.

in both cases, the curvature means that things travelling through the
space don't do exactly what one might expect -- the pea on the
bedsheet, or the light beam passing by a star.

the curvature of the bed-sheet is purely a geometric distortion.
einstein's innovation was to treat gravity as if it was just a
geometric distortion, too.

And Merry Christmas from me too.

it's actually christmas, now. best wishes to all umrats, of whatever
faith or (like me) of none.
--
Robin Fairbairns, Cambridge
.

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