Cambrian period Earth
If we travel back in time 500 million years we reach planet Earth in a most amazing period at the very beginning of what is called the Paleozoic era (Greek for Old life).
Cosmologists estimate today that the entire Universe is about 13.75 Ga (Gigayears ago) old and that iot all began with a really Big Bang.
We believe that God of Israel created the Universe and our home Milky Way in it. Science tells us that our Galaxy exists soon after the Beginning and is estimated to be over 13 Ga old.
Our Sun with its planets were formed only about 4.5 Ga, i.e. about one third of the age of the entire Universe.
The surface of Earth cooled some 3 Ga ago and there actually are some intriguing signs of bacterial life in pre-Cambrian rocks like granite.
However, in the Cambrian period some 542 ± 0.3 to 488.3 ± 1.7 Mya life really took off on our planet in a still unexplained manner. The change in life is so massive in comparison to previous geological eras that the the phenomenon is often called Cambrian explosion of life.
Name of Cambria
The name of the Cambrian period brings to mind ye good ol' England and the veritable Cambridge.
That is not so far off.
However, the name actually comes from the Roman period district of Cambria corresponding to modern Wales in SW British Isles. The Roman occupiers took the old Welsh name of the region Cymre in the Old Welsh form combro (land, comrade). It sounded in their Latin ears like Cambria.