Suppose it turns out that one in 1 million stars has a planet that at some point in its history is home to an advanced civilization. Then the total number of civilizations that have arisen in our galaxy would be closest to ________. Assume there are about 100 billion stars in the Milky Way galaxy.
A) 100,000
B) 10,000
C) 1,000
D) 100
E) 10
F) 1
A) 100,000
Physics & Space Science
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What do we currently believe was the main source of the Earth's oceans and atmosphere?
A) impacts by icy planetesimals B) outgassing by volcanoes C) material directly accreted from the solar nebula D) melting and vaporization of polar glaciers
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Herbig-Haro objects at opposite ends of bipolar jets can span a(n) ________ across
Fill in the blank(s) with correct word
Physics & Space Science
Consider a situation where a skater pulls her arms inward, causing her rotation rate to speed up.Kinetic energy __________ conserved
Fill in the blank(s) with correct word
Physics & Space Science
One pg (picogram) of 40K has how many nuclei?
a. 
b. 
c. 
d. 
e. 
Physics & Space Science