What was one obstacle Newton encountered in developing his theory of universal gravitation from his observation of heavenly bodies?
a. He had to prove that Earth was nearly spherical.
b. He had to figure out why the Moon doesn't fall down.
c. He had to spend many years observing the movement of the planets.
d. He had to prove that the mass of the Earth acts as if it was concentrated at the planet's center.
e. He had to prove the inverse-square law.
d
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The average density of Earth is ________.
A. about 1 g/cm3 B. about 1 cm3/g C. about 5.5 g/cm3 D. about 5.5 cm3/g
Mars currently lacks surface habitability mostly because of
A) the chemical composition of its atmosphere B) its distance from the Sun C) its small size D) the chemical composition of its surface
When you blow some air above a paper strip, the paper rises. This is because
A) the air above the paper moves faster and the pressure is higher. B) the air above the paper moves faster and the pressure is lower. C) the air above the paper moves faster and the pressure remains constant. D) the air above the paper moves slower and the pressure is higher. E) the air above the paper moves slower and the pressure is lower.
The mass found by gravitational lensing in these colliding galaxy clusters is in a separate physical location from the hot gas that resulted from the collision.
II) Dark matter does not strongly interact with regular matter, other than through gravity. III) Hot intracluster gas makes up the majority of the mass of galactic clusters. A) Only I B) I and II C) I and III D) I, II, and III