Atmosphere Questions

• How can there be clouds in winter when it is too cold for water to stay a vapor?
• How do plants get their nitrogen from the air?
• How do trees give earth all its oxygen?
• How does a cloud fill up with water?
• What makes meteorites so hot that you can't touch them?
• What makes the Sahara the largest desert in the world?
• Why does the air only contain water vapor and not other kinds of vapors?
• Why don't I feel the miles of air above me that are crushing me down?
• Why don't the gases in the atmosphere separate out according to mass?