In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?
A) He proved this by observing individual Cepheid variable stars in Andromeda and applying the period-luminosity relation.
B) He was able to measure the parallax of the Andromeda Galaxy.
C) He found that the universe is expanding, and therefore concluded that Andromeda must lie outside our own galaxy.
D) He was the first person ever to look through a telescope at the object we now call the Andromeda Galaxy.
A
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The corona of the Sun can be observed
a. during a lunar eclipse. b. with a coronagraph. c. using filtergrams. d. during a lunar eclipse and with a coronagraph. e. none of the others.
The most powerful agent of erosion is
A) stream flow. B) glacial action. C) action from waves and ocean currents. D) wind.
You are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. What force caused you to slide forward from the point of view of the observer on the ground?
A) the force that Earth exerts on you B) the force exerted by the floor of the bus on you perpendicular to the floor C) the force exerted by the floor of the bus parallel to the floor (the friction force) D) There is not a force causing you to your fall.
Spreading centers occur along
A) trenches. B) transform faults. C) mid-ocean ridges. D) the northern and western margins of the Juan de Fuca Plate.