I have a radio controlled blimp that a friend gave me while I was
recovering from surgery. It's been a blast to play with.

Filled it back up with He a couple of weeks ago and parked it on
the ceiling at home. (without the drive unit)

It has deflated slowly. At first it was slammed hard against the
ceiling, but as time passes, it settled tail down a bit, then more
until it hung vertically.

Last night it started wandering around the house all by itself.

This morning it was floating along the living room about 3 feet off
of the floor. As it came into the "computer room" where the temp is
several degrees cooler, it settled down to about 1 foot and nosed
around checking everything out.

Then it turned around and floated back into the living room - and
rose back up to near 3 feet again!

While I understand the principles involved (temperature/pressure), I've
never seen such a clear demonstration of them.

Fascinating....

Richard