24th of March, 2011 (My brother's 21st birthday today!)
The hydraulic earth mover is made with syringes.
It is similar to the way a real earth movers works.
On our hydraulic earth mover toy, there are some syringes which, when pressed, push oil (or in our case, water) out into another syringe. As the syringes move in and out, it pushes or sucks the liquid and when the liquid is getting pushed or sucked, the internal pole moves in or out.
This is another one of the Supercharged Science experiments from the Online Science course.
Here is a video of our toy earth mover which we made.