Explain how one scientist builds on the discoveries of a previous scientist to make new advances.

Example: Galileo and Copernicus

Explanation:

Copernicus had come up with the idea of heliocentrism. Back then, everyone had believed the other planets revolved around the Earth, but Copernicus had done the math and realized the Earth and everything else revolved around the Sun. The Sun was the center of our solar system, not the Earth. But because he was accused of blasphemy from the Catholic church, he didn't share his ideas until his book published right before he died. Years later, Galileo took his idea, observed and researched, and found evidence backing Copernicus's theories. That's why today we know the truth about how the Sun is at the center of everything. Galileo built on Copernicus's discoveries and ideas, found evidence, and proved it was true.

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)