The mesosphere is the coldest layer because it doesn't have any special to trap heat.
gases
clouds
ions
wind

gases

Explanation:

greenhouse gases bounce light from the sun back and forth in the atmosphere keeping the light stuck in the atmosphere like a ping pong ball on a ping pong table heating up the air

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

like poles repel so keep pushing north to north and repels funny to see this