Astronomy 101: Modern Astronomy

Lesson 3: the Rise of Modern Astronomy

galileo and telescope
Galileo Galilei began the era of modern astronomy when he turned a telescope to the sky. His actions unleashed events that reverberated into the 20th century. Library of Congress.

Tycho Brahe has often been called the Father of modern astronomy, and for good reasons. However, I think that title really belongs to Galileo Galilei for his pioneering use of the telescope to magnify the view of the sky. However, Brahe did advance the science more than anyone in the past, simply by using his senses, rather than philosophy to study the sky.

The work that Brahe began was continued and expanded by his assistant, Johannes Kepler, whose laws of planetary motion are among the foundations of modern astronomy.

There are many other astronomers since Galileo, Brahe, and Kepler who have advanced the science:  Here, in brief, are some of the other bright lights who helped bring astronomy to its current place.

  • Edmund Halley (1656-1742) was a British astronomer who was also a big fan of Sir Isaac Newton. After encouraging Newton to write his Principia, Halley then published it at his own expense. Not stopping to rest on the fame of another, he went on to calculate the orbits of comets, including the one named after him.
  • Sir William Herschel (1738-1822), though born in Germany, was a British astronomer. He discovered Uranus in 1781 coined the word "asteroids". He also cataloged about 2,000 nebulae, discovered several satellites of Uranus and Saturn, studied the rotation of planets. Discovered and studied binary stars. He discovered two satellites each orbiting Uranus and Saturn. He studied the rotation period of many planets, the motion of double stars, and nebulae. He cataloged more than 800 double stars and contributed new information on the constitution of nebulae. Herschel was the first to propose that these nebulae were composed of stars. He is considered the founder of sidereal astronomy.
  • Albert Einstein (1879-1955) was a German-born American physicist and Nobel laureate. He may be the most well-known scientist of the 20th century. In 1915, he developed his general theory of relativity, which states that the speed of light is constant and that the curvature of space and the passage of time are linked to gravity. Thinking the universe was unchanging, he inserted a  cosmological constant "fudge factor" into his calculations to make them fit his viewpoint.
  • Willem de Sitter: (1872 - 1934), a Dutch astronomer, removed Einstein's cosmological constant from his calculations and used the theory of relativity to show that the universe may always be expanding.
  • Georges-Henri Lemaitre: (1894 - 1966) was not only a Belgian astronomer, he was also a Jesuit priest. Discovering the writings of Russian mathematician, Alexander Friedmann, Lemaitre took his solution for an expanding universe and theorized that if the universe is expanding, if we follow it back to the starting point, then our universe began as a great "cosmic egg" which exploded and expanded outward. Lemaitre is often referred to as the father of the Big Bang theory.
  • Edwin P Hubble (1889-1953), American Astronomer. In the 1920s, Albert Einstein stated, "I have made my greatest blunder." This pronouncement came when Hubble demonstrated that the universe was not static and Einstein's cosmological constant was not necessary. Utilizing improved telescopic devices, he was also able to confirm that those "fuzzy" objects astronomers had seen for years were in fact other galaxies.
  • Thomas Gold (1920 - 2004) was an American astronomer. Though it is generally believed that Gold's "steady state" theory of the universe is incorrect, he made many major contributions to our knowledge of the universe, including the nature of pulsars as rotating neutron stars, and the origin of planetary hydrocarbons.

    These are just a few of the astronomers and their findings in the pre- and early 20th century history of astronomy. There have been and are many other great brains in the field of astronomy, but it's time to get away from history for now. We'll meet some of these other astronomers throughout the rest of our lessons. Next, we'll look at numbers.

    Fourth Lesson > Big Numbers > Lesson 4, 5, 6, 7, 8, 9, 10


    Edited and updated by Carolyn Collins Petersen.