1. When our Galaxy was forming why was the center dense?
Answer: <u>Stars are believed to originate as from gas clouds in space. Gravitational forces cause this gas to contract forming a dense center of gravitational force.Eventually this extreme pressure at the center of the star causes nuclear fusion reactions to occur.</u>
2. Why did hydrogen atoms collide in the dense center of the Galaxy?
Answer: <u>Compression would heat the gas to temperatures above 1,000 kelvins. Some hydrogen atoms would pair up in the dense, hot gas, creating trace amounts of molecular hydrogen. The hydrogen molecules would then start to cool the densest parts of the gas by emitting infrared radiation after they collide with hydrogen atoms.</u>
There is no list, but possibly evaporation.
That is false because every type of plastic can biodegrade
