Much of the early scientific discoveries made about our solar system came from the great Italian mathematician Galileo Galilei. This extraordinary figure in the history of astronomy and physics played a vital role in the understanding we currently have of the cosmos, and particularly own solar system. Indeed, the most esteemed physicist of the 20th century, Albert Einstein called him the “father of modern science”. Galileo began at the University of Padua in the late 16th century teaching mathematics, until he heard of a lens maker in Holland who made a special glass used to visually magnify objects. In 1609, he constructed his own version of a telescope, which had been in existence in various other forms made by others since the late 1500s. Galileo’s version is considered to be the first complete astronomical telescope, capable of peering into the heavens and observing other planets.
Galileo used his new device to quickly begin making revolutionary observations about the nature of the moon and solar system. In 1610, he published his first scientific research based on some of the profound discoveries he had made with his telescope in Siderius Nuncius, which translates into the Starry Messenger.
The first of Galileo’s observations was regarding the texture of the moon’s surface, which had previously been thought to be smooth sphere. Galileo noted the existence of mountains, valleys, and craters on the surface of the moon, and even drew charts estimating such geological aspects.
The second major observation Galileo made was the discovery of the four moons orbiting Jupiter. The moons, now named Callisto, Io, Ganymede, and Europa are known as the Galilean satellites, or the Galilean moons. This was a crucial discovery as it revealed a flaw in the belief held for centuries in Aristotle’s observation that everything in the heavens circled the Earth, as the moon does. Galileo contradicted this prevailing view by proving with the moons of Jupiter that it is possible for a planet to have smaller planets orbiting around it. This observation would go on to play a vital role in Galileo’s understanding of the solar system.
Galileo made the profound discovery that the Milky Way is actually comprised of a vast array of separate stars, rather than the cloudy blur that it seemed to be while viewed by the human eye from Earth. This meant that there were a much larger number of stars in the galaxy than any scientists to that point had considered.
One of Galileo’s other very important observations was that Venus had phases similar to the moon. This observation led to serious questions about the prevailing view at the time that the sun and other planets revolved around the Earth. While it took much longer for the world to embrace the reality that the planets revolve around the Sun, this was a major step in that direction to uncover the truth about the motion of planets in the solar system.
In addition to these breakthroughs, Galileo was among the earliest to observe sunspots, which proved that the solar system contained imperfections and anomalies. He also made critical discoveries in physics, such as Galileo’s law of inertia and his observation that objects fall at the same rate regardless of their weight, all of which contributed to the body of scientific knowledge that would enable other scientists to determine planetary motion. Most notably, Galileo’s work in physics helped build the case for understanding of the orbits that the planets travel in around the sun. This idea that was later proven by future astronomers was the most controversial of Galileo’s observations, and the source of his contentious relationship with religious leaders of his era.
Galileo made an enormous impact on mankind’s ability to grasp and comprehend the complexities and elegance of our solar system through his revolutionary discoveries and courage to explore the unknown. The world's understanding of the solar system is powerfully influenced by the observations made by Galileo in the early 17th century.