All of these people are mathematicians, astronomers, musicians, and scientists in their own ways. They have made great contributions as to the location of the Earth within the Solar System and how the Earth revolves in such manner that it experiences night and day. These are their major contributions:
Ptolemy - used his knowledge in Geography and located several points from ancient maps to determine the size of the Earth and why it behaves in such ways.
Copernicus - he was one of the first people who have come-up with a model that the Sun is the center of the Universe.
Kepler - believed that the solar system is created by a divine source, hence his studies are known as "celestial physics." He constructed the idea that the solar system is modeled out from a grand plan and that it is made in the image and likeness of God. The solar system is modeled out in the Holy Trinity, where the sun is the Father, the astronomical sphere is the son, and the spaces in between is the Holy Spirit.
Newton - the last man to remove all the doubts about the Heliocentric model, where the sun is the center of the solar system. He has proved this from his numerous studies on the motion of objects on Earth and related that celestial bodies move through the same principles.
Microbes. Bacteria, for example, convert nitrogen and carbon dioxide from the air into usable components that plants and animals can use as essential building blocks. A loss of all microbes would be terrible news for living organisms that can't create or take in these essential nutrients on their own.
