ISP209s8 Lecture 21-2-Clicker Questions•Do you believe the Earth has been visited by aliens? A- yes B - no•Do you think there is life elsewhere in the Milky Way Galaxy besides the Earth? A- yes B – no• Why?
ISP209s8 Lecture 21-3-Are we alone in the Universe?•There are approximately 200 billion other stars in the Milky Way. For reference, we can see only about 20,000 stars, and only if it is very dark.•There are roughly 200,000,000,000 other galaxies (200 billion)•It seems like there is plenty of opportunity for other life. Is it possible? Why haven’t we seen it?•The fields that try to answer this question are astrobiology and exobiology
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