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Old 04-24-2017, 09:05 PM
Jet Jaguar Jet Jaguar is offline
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Join Date: Jan 2001
Location: Monster Island
Posts: 1,369
Somewhere I have an astronomy book from ~1910. Highlights include:

- The Sun is on the order of tens of millions of years old and the heat is caused by the gravitational compression of it's gasses. It will continue to burn for another 10 million years. (Nuclear fusion was unknown at the time.)

- The Milky Way galaxy is the extent of the known Universe. It is debated what lies beyond, if anything. (Galaxies were believed to be a type of spiral nebula within our own galaxy at the time.)

- Mars has a water cycle as evidenced by seasonal variations visible in vegetation growth. The canals are vegetation-lined waterways and it is debated whether these are natural rivers or artificial irrigation channels. Venus may also have vast oceans of water because the surface is continuously obscured by cloud cover.