Which was not one of the four elements the ancient Greeks believed comprised the world?
Earth
Air
Spirit
When did scientists first measure the motion of groups of moving galaxies?
1900's
1930's
1960's
The universe's expansion seems to be ________.
Slowing down
Accelerating
Changing directions
Today's best measurements estimate that about ___% of the universe is dark matter.
13
27
42
String theories can explain the universe but
You cannot check them out by now
They can explain only the dark matter
Both are correct
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