Dear Axel

I'm glad things stay put for you--because sometimes round my house I can't find anything when I want to lay my hands on it! But seriously...

The easy answer to your question is inertia. (Look it up in a reference book or talk about it with someone who enjoyed high school physics.) But 'inertia' isn't really an answer at all--it's really just a description of 'why things stay put'. No one actually knows the answer but there are some theories. Here's my favourite.

Some American scientists recently extended the ideas of a famous Russian scientist who is now dead (Andrei Sakharov). I don't understand it fully (the maths is beyond me) but I'll try to explain as best I can. Try this for brain-boggling!

A 'thought experiment':

Confused? So am I.

It's a deep question. Alice wants to know the answer, too.

By the way. Not everything stays put! Liquid helium when it's cooled to near absolute zero doesn't stay put. All by itself it climbs up out of any container it's in and slides down the sides! Plenty of mass. Little inertia!

Yours sincerely 

Virginia R. Claire


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