Science in a Pop Bottle

So a year or 2 ago I picked this Pop Bottle Science kit second hand at the thrift store. He has pulled it out a couple of times but last night he actually tied an experiment. Water, herbs, the bottom part of the bottle and a pencil are all he needed to see how the galaxy is spinning.
He LOVED it! He did it all by himself and spent a good hour exploring it. Then he ran down to me and exclaimed "MOM! Its like the spinning thing in the air!" We talked about it. I don't know how much this costs new but I do recommend it.