1. What Makes a World Habitable?

2. Temperature
The temperature has to be between 15 Celsius and 115 Celsius
This is controlled by 3 things:
The distance from the sun
Our distance from the sun is 150,000,000 km
The thickness and composition of the atmosphere
Our atmosphere is 78% Nitrogen, 21% Oxygen
How hot the star is

3. Liquid Water Life is not possible without liquid water. Here is why:
Liquid water transports nutrients, oxygen, and food in living organisms
Chemical reactions that are necessary for life happen in water
Water helps moderate temperatures (it is like a buffer)
Juneau, Alaska

4. Atmosphere What does the atmosphere do for us?
Protects from meteors and UV rays
Mount Everest, K2, Etc.
Source of atoms for building molecules
Moderates temperatures
Without this effect alone we would not be able to live here. For example the moon is the same distance from the sun, but because it does not have an atmosphere, temperatures can range from -387 Fahrenheit during the night to 253 Fahrenheit during the day. Wouldn’t want to live there would you?