How did ancient Greeks such as Aristotle know that Earth is round?
A) From the ancient manuscripts of authors such as Homer.
B) By noting that ships drop below the horizon as they go out to sea.
C) By triangulation (measuring the distance between 2 points, and measuring 2 angles, to determine the distance to a 3rd point).
D) Careful measurements of the distance, along Earth's surface, between two widely separated points showed it to be longer than the straight-line distance.
E) Actually, the ancient Greeks thought that Earth is flat.
B
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Instructions: On occasion, the notation 
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Given that 
and 
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A.
B.
C.
D.
E.
You find yourself in a very low-density gas that is extremely hot. In fact, the temperature of the gas is so high that it is emitting lots of X-rays
There are no stars anywhere within about 10,000 light-years of you, but at slightly greater distances, your sky is brightened by hundreds (perhaps thousands) of beautiful, star-filled structures, some with majestic spiral shapes. Where are you? A) You are in the universe about 380,000 years after the Big Bang when the cosmic microwave background radiation was formed. B) You are in intergalactic space within a rich cluster of thousands of galaxies. C) You are in the center of the Milky Way Galaxy, looking outward into the Local Group. D) You are in the universe when it was about 500 million years old, just before galaxies began to form. E) You are in the outskirts of a galaxy whose nucleus is a powerful quasar.
An object, located 90 cm from a concave lens, forms an image 30 cm from the lens on the same side as the object. What is the focal length of the lens?
a. -150 cm c. -36 cm b. -45 cm d. -180 cm
The process of expanding a parison with air pressure to form a bottle is called ___________molding.
Fill in the blank(s) with the appropriate word(s).