4.5 billion years ago

http://www.youtube.com/watch?v=ZUOZvAPtASo

http://www.youtube.com/watch?v=2NNT8_QDMwc

http://www.youtube.com/watch?v=CHj5EWXqQjI

http://www.youtube.com/results?search_query=Giavedoni+Eric&aq=f

http://www.youtube.com/watch?v=Mq6Ku2siI4w