Galileo Galilei and Astronomy

Jaime R. Angueira Juarbe

Out of all the physicists that we hear about today, one of the most important and revolutionary to the science we study today was the Italian physicist Galileo Galilei (1564-1642). He was not only physicist; he was also a mathematician, an astronomer, a philosopher, and has been nicknamed as “the father of modern observational astronomy,” “father of modern physics,” and “the father of science.” If it were not for Galileo, we might not have developed modern science the way we up to today.

Galileo was able to improve the function and mechanism of a telescope to further expand his astronomical observations. Utilizing a previous primitive model of the telescope, he was to modify it to zoom up to 30x an upright magnified image. Utilizing this device, he discovered the phases of Venus, Jupiter’s four biggest satellites, and sunspots. AS he observed Jupiter, he saw three fixed stars that crossed Jupiter, which he said were invisible. They were invisible because they could not be perceived by the naked eye. One day he noted that one of them had disappeared, concluding that it was hiding behind Jupiter and that the stars where actually orbiting the planet. He later realized that he had in fact discovered three o Jupiter’s largest satellites (discovering the fourth on a later date). During this time period, it was believed that all heavenly objects circled around the Earth; therefore, this was not accepted by the common public. Galileo was a believer of Coppernicanism, who believed that the sun was the center of the universe and not the Earth. Observing Venus he discovered its phases which he related to the phases of the moon. He was misguided thinking that Venus might be orbiting the Earth or perhaps a double cycle between the Earth and the Sun; either way, he provided facts of observations which greatly helped in the understanding of space.

For some time, he observed Saturn with his telescope and noticed three smaller planets around it. As one disappeared he concluded that they were orbiting it and missing one was behind the large planet, like in Jupiter’s case. However, as he focused further on it, he saw the image of the ring which only confused his previous observation. Besides discovering sunspots, he also observed the moon to learn about its surface. He recorded that its surface was rough and uneven like the earth, referring to its mountains and craters. Into the night sky, he recorded the discovering of many dim stars that were unable to be seen without a telescope, including one which was later discovered to be the planet Neptune of our own Milky Way. He also attempted to measure the diameter of certain bodies in comparison to the sun. He was the first to propose that star were in fact suns. He said that they were not spherically placed around the Earth but instead were randomly aligned throughout the galaxy. He argued that brighter stars were closer suns and dimmer stars were further away. Using this light emission theory he attempted to estimate the distance at which these suns were in comparison to our sun. He noted that some were a few hundred distances away from us while others were up to two thousand distances away. These are very small approximations compared to today’s standards; however, they were much larger than believed at the time and much further away than planetary distances which was an important comparison aspect.