19th Century Geology and Science: Wright
For nineteenth-century geologists, the last glacial period was explained by two opposing viewpoints. The first was an astronomical theory that explained the solar system is moving through space. Frederick G. Wright argued that from the Tertiary Period (65 million years to 1.8 million years ago) to the beginning of the last glacial epoch, the earth was traveling through warm stretches of space; glacial epochs occurred when the solar system moved through a cold areas of space. There are also unknown electrical forces in the sun that make the temperature rise and fall on earth. The second theory of the causes of a glacial period is an unequal attraction of the planets and the orbit of Earth changes, moving closer and further from the sun. The earth will be colder when away from the sun and warmer when closer to the sun.