Over hundreds of millions of years, life spread through the seas and over Earth’s surface. The first life-forms were small and simple. Later forms were more complicated and diverse.
od National Geographic Society (blogs)
Timeline of Telescopes and Lenses
Informal division of Precambrian time occurring between about 4.6 billion and about 4.0 billion years ago. The Hadean Eon is characterized by Earth ’s initial formation—from the...
File:Artist’s impression of two white dwarf stars merging and creating a Type Ia supernova.ogg
Wide Field and Planetary Camera 2 - Wikipedia, the free encyclopedia
Human Migration map