Before cyanobacteria, Earth’s atmosphere had no oxygen and there was no ozone layer to protect organisms from the sun’s rays.

When cyanobacteria came into existence, they filled the atmosphere with oxygen as a waste product of photosynthesis. Some of this oxygen formed ozone.

Earth could now sustain life with the oxygen that was present and the protection from the ozone layer.

All of the matter and energy of the universe was contained in a tiny spot called a singularity. It began to inflate and expand very quickly, scattering debris to form the universe.

Our galaxy is the Milky Way galaxy. It is a spiral galaxy with many stars and planets.

Some clumps of matter dispersed by their internal motions, others grew by attracting other nearby matter.

Panspermia means “seed everywhere”. It was the idea that life came from somewhere other than Earth. People who believed this idea believed that meteorites crashing into Earth brought organic compounds with them.

Stanley Miller was a biochemist who investigated the origin of Earth’s early organic compounds.

In his experiment, he simulated the conditions of the early earth to determine whether organic compounds that make up living things could come from inorganic compounds like the ones present on the early Earth.

He found that organic compounds could come from inorganic compounds and gave support to the idea that life came from on Earth.