８７ Snowball earth【Past and Future】Dialogue with the Universe
・For about 5～600 million years at the last Precambrian age Earth entered the time of the snowball earth, and near the equator was covered on ice.
・Most lives on Earth of this time were bacteria.
・The time of the dramatic life evolution "Cambrian explosion" had come after the snowball earth.
・There is also an opinion it is supposed that the earth will be in the state of the snowball earth again in the future.