The 10 Greatest Astronomical Discoveries, page 1

Hello everyone... Astronomy has always amazed me, and it has also been a hobby of mine for quite some time. I'm certainly no expert in the field, and I admit that there are many here on ATS that are more knowledgeable in the area of astronomy than I am. I came across an article that lists the 10 greatest astronomical discoveries ever, and I wanted to share it with others who share a love for astronomy and the exploration of our universe.

I did an ATS search and couldn't find any similar threads, so enjoy!

Link to Article

1. On The Revolution Of The Heavenly Spheres

When the Polish astronomer Nicolaus Copernicus (1473-1543) declard that the Earth orbits the Sun rather than vice versa, he revolutionized the way people view the world. Today we take his statement for granted and it is difficult to conceive how radical this assertion was at the time. Ptolemy, (c. AD 90 -c. 168) the Greek astronomer and mathematician had earlier asserted that the Earth stood still while other planets rotated around it. Copernicus boldly stated that the Earth orbits the Sun and completes one full rotation around its axis every day. Copernicus successfully devised a mathematical explanation which provides the essential elements of our modern theory. The paper De Revolutionibus Orbium Coelestium - On the Revolution of the Heavenly Spheres was published the year of his death and delivered to him on his deathbed.

2. Orbits Are Elliptical

The German astronomer Johannes Kepler (1571-1640) attempted to determine if the paths of the planets could be described with a curve. Kepler discovered that an ellipse with the Sun at one focus could in fact accurately describe the orbit of a planet about the Sun. Kepler's studies revealed that planets do move on ellipses, but they are nearly circular. Comets on the other hand may have very elliptical orbits. During 1605-1609, Kepler created mathematical models, which allow unprecedented accuracy in predicting the track of planetary motion. Kepler's theory was met with scepticism in the world of science. Even Galileo and Descartes ignored his work which today is known as Kepler's 1st Law: orbits are Elliptical.

3. Jupiter Has Moons

Galileo Galilei (1564 - 1642) discovered that Jupiter, like Earth has moons. His discovery showed that our planet was not unique. The Catholic Church ordered Galileo to withdraw his vies, claiming that they are false and contrary to the Scriptures.

4. Halley's Comet

Astronomer Edmund Halley (1656-1742) identified the correct period of time for the return if what today is known as Halley's Comet. Halley maintained that the comets observed in 1531 an 1607 were one and same object that passes our Sun every 76 years. His predictions were confirmed with the return of the comet in 1758.

5. The Milky Way Is A Great Cluster Of Stars

Astronomer William Herschel (1738-1822) studied the Milky Way with his self-built very large telescopes, at his home known as Observatory House, in Slough, England. By measuring the approximate distance to as many stars as possible, Herschel concluded that most of the stars are located in a disk of stars. Herschel's observations proved that the Milky Way is a great cluster of stars. Herschel thought that our solar system is at the centre of the galaxy. Today we know this is not the case. According to modern observations, the Milky Way is a huge cluster of about four hundred billion stars. Most of these stars are in fact concentrated in a flat spiral disk, with a large bulge in the middle. Herschel's findings were surprisingly accurate.

6. General Relativity

Albert Einstein (1879-1955) announced his theory of general relativity according to which gravity, as well as motion can effect the intervals of time and space. General relativity was the first major new theory of gravity since Isaac Newton more than 250 years earlier. Einstein's theory was proved during a solar eclipse in 1919. An experiment confirmed that light rays from distant stars were indeed deflected by the gravity of the Sun, in the same amount Einstein predicted in his theory of general relativity.

7. The Universe Is Expanding

In 1929, astronomer Edwin Hubble measured the distance separating Earth from several distant galaxies. Hubble observed that the farther away these galaxies are, the faster we move away from them. According to his observations, the redshift of distant galaxies increased as a linear function of their distance. The only explanation for this observation is that the Universe is expanding.

8. Big Bang Relic Radiation

In 1965, Arno Penzias and Robert Wilson of Bell Labs, discovered cosmic background radiation, which is the strongest evidence that something like Big Bang did really happen. The existence of cosmic background radiation was predicted by cosmologist George Gamov in 1948. Gamov asserted that Universe should be filled with "relic radiation left over" from the Big Bang.

9. Planets Around Alien Suns

In 1992, the Polish Professor Aleksander Wolszczan discovered extrasolar planets or planets orbiting distant stars. Professor Wolszczan, who was also the co-discoverer of pulsar planets demonstrated that our solar system is by no means unique.

10. Accelerating Universe

Instead of gradually slowing down under the force of gravity, the Universe is accelerating. If astronomers' observations are accurate, then in the near future, we will no longer be able to see distant galaxies. Astronomers have recently announced that the Universe appears to be expanding at an accelerating rate.

Well, there's your 10 greatest astronomical discoveries of all time. I'm sure the case can be made for some that aren't included on this list. I would argue that the topic of my other thread should be on this list now. I welcome everyone's thoughts and opinions on this list...