I learned about two inventions and two engineers this week. The two inventions are the Heliocentric theory and the pencil. The two inventors are Nicholas Copernicus and Andreas Vesalius. First, I learned about the Heliocentric Theory. The Heliocentric Theory is the theory of Copernicus. The Heliocentric Theory revealed the structure of the solar system and helped begin space exploration. Second, I learned about Nicholas Copernicus. He believed science was possible because God sustains the universe. Without Copernicus we would not have the GPS. Third, I learned about Andreas Vesalius. He published a crucial essay on anatomy in 1543. He introduced a method of investigation to the field of anatomy. Finally, I learned about the pencil. Pencils are graphite rods encased in wood. They make durable markings. They are cheap to make and use.