Nicholas Copernicus, Greek astronomer, was the one who famously proposed the heliocentric theory -- the theory by which the sun was in the center of the solar system and the planets orbited it circularly.
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Answer:
Oxygen is an element that can be a solid, liquid or gas depending on its temperature and pressure. In the atmosphere it is found as a gas, more specifically, a diatomic gas. This means that two oxygen atoms are connected together in a covalent double bond.
The answer is a 6.0 anything above 7 is alkaline
Since a vacuum is empty space, there is no medium for the sound to travel through. The speed of sound in air mainly depends on the temperature of the air. On average, it is about 343 meters per second (1,125 feet per second),