Theories of Moon Formation 9/14/16 Question: How was the moon formed? What are the 4 different theories of moon formation? https://www.youtube.com/watch?v=sjestosgiig List 10 facts about the Moon: Describe each theory: 1) 1873 Co excretion Theory by Edward Rosch 2) 1878 Fission Theory of Lunar Origin by George Darwin 3) 1909 Capture Theory by Thomas Sea 4) 1974 Giant Impact Theory by William Hartman 1
1) 1873 Co excretion Theory by Edward Rosch The Co Excretion Theory provided the idea that the moon formed along side the Earth. Materials such as rocks and dust were all revolving around the Sun. Gravity pulled these materials together. This theory would mean that the Moon and Earth were formed from the same materials. The problem was the Earth had a high iron content but there was no iron content in the rocks on the moon. This discrepancy meant that this theory could not be correct. 2
2) 1878 Fission Theory of Lunar Origin by George Darwin Darwin figured out that the moon is moving farther and farther away from the Earth. The rate is about 3.8 cm each year. If we made a movie you would see the moon moving away from the Earth. Darwin imagined moving the movie backwards. As the moon moves back toward the Earth, both must connect and Darwin theorized that this point of impact would be the beginning of the moon. Darwin did the mathematical calculations that showed the moon would travel around the earth 5 6 times a day. His calculations could not bring the moon in contact with the Earth. Scientists concluded the Earth would have been spinning too fast for this theory to be correct. In addition, Darwin's calculations did not show evidence of joining of Earth and Moon. Finally, The Fission Theory does not explain the difference in iron content between the Earth and the moon. 3
3) 1909 Capture Theory by Thomas Sea Sea was an American who created a theory that the moon and Earth were actually created separately. The moon orbited the Sun in a different position from the Earth. Sea imagined that the gravitational pull of the Earth captured the Moon. This would explain the difference in iron content. An invisible force he called the "resisting medium" would slow down the moon in its path and allow the moon to be captured by the Earth. This theory was not supported because there is no evidence of a "resisting medium." It is also very unlikely that the force of Earth's gravity could capture anything as large as the moon. 4
Table of contents date Title for Lesson 8/17/16 8/18/16 1 Welcome to Astronomy 2 Meteors?? 8/19/16 3 More Meteors?? CW Perseids: Bright Meteor Shower 8/22/16 4 Radio Waves & Meteors 8/23/16 5 Meteor Quiz 8/25/16 6 The Sun Video 8/30/16 7 Parts of the Sun 9/2/16 8 Sun Observations 9/3/16 9 Turn in Sun Diagram 9/7/16 10 Solar Quiz 9/8/16 11-12 Solar Eclipse 9/13/16 13 Reasons for seasons 9/14/16 14-16 Theories of Moon Formation page 5
4) 1974 Giant Impact Theory by William Hartman When astronauts brought back moon rock samples, now the scientists could examine what the moon was made of. They found basaltic rocks...which are volcanic. They also found Breccia which are formed during asteroid impacts. The rocks and soil samples indicate the moon was covered by a deep ocean of lava. The rocks also lacked volatile elements. If you compare Earth rocks to Lunar rocks, the moon rocks have lost their volatile elements. The isotopes of oxygen in moon rocks had EXACTLY the same make up as Earth rocks. William Hartman ran a computer program and theorized that about 4.5 billion years ago, a collision occurred. Another planet (Theos) about the size of Mars crashed into Earth and blew off part of the Earth into space which coalesced into the moon. It started the Earth spinning and created our 24 hour day. The entire surface of the Earth would become liquid. When the impactor hits the Earth, the iron from the planet forms the Earth's core. The program shows the moon would have formed in less than a year. 6