20190127_145056 Instructions for making an instrument out of a plastic bottle
20190127_144731 Playing the bottle-and-membrane instrument
20190127_144631 Inserting a straw into the hole in the bottle
20190127_144507 Putting paper tube into the bottle's narrow end
IMG_20180312_184942 Enacting planet movement at the McDonald Observatory
Children enact planet movement at the McDonald Observatory lecture on Solar system. The presenter (left) invited volunteers from the audience, gave each one a ball representing one of the solar system planets, and asked each of them to complete one or several orbits around the Sun (the Sun being another child volunteer) -- all at the same time. Their speeds had to be proportional to the speeds of the actual planets. So, for example, Mercury goes around the Sun approximately 4 times for every time the Earth goes around the Sun, so the holder of the Earth had to complete a circle four times slower than the holder of Mercury.
The organizer called up five children to the stage, going as far as Jupiter, but, needless to say, he had to sacrifice the scale for that. But the Jupiter-child acted realistically at least in that he completed only a quarter of a circle around the Sun while the Earth completed three.
In this picture E (second from the right) is representing Mercury, and the boy to the left of her is holding the Sun.