Ancient Astronomers Often Had Difficulty Explaining _____, the Occasional Westward

question 43

Multiple Choice

Ancient astronomers often had difficulty explaining _____, the occasional westward motion of the planets.

• A) parallax
• B) eccentrics
• C) retrograde motion
• D) deferents
• E) epicycles

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Definitions:

Vesicles

Small cavities in volcanic rocks that are formed by gas bubbles trapped during the solidification of the rock.

Shield Volcanoes

Large, broad volcanoes with gentle slopes, built by the eruption of low-viscosity lava that can flow long distances.

Fluid Lava

Magma that has reached the surface through a volcanic eruption and flows easily due to its low viscosity.

Viscous Lava

Lava that is thick and slow-moving due to its high silica content, which increases its viscosity.