<Tr> <Td> About 54 galactic years ago </Td> <Td> Birth of the Milky Way </Td> </Tr> <Tr> <Td> 20.44 galactic years ago </Td> <Td> Birth of the Sun </Td> </Tr> <Tr> <Td> 17--18 galactic years ago </Td> <Td> Oceans appear on Earth </Td> </Tr> <Tr> <Td> 16.889 galactic years ago </Td> <Td> Life begins on Earth </Td> </Tr>

Our solar system orbits the center of the galaxy with approximately what period