What the numbers mean
Our species arrives just before midnight.
Compress 4.54 billion years into one day. Using about 300,000 years for Homo sapiens, our species occupies the final 5.7 seconds. All of our recorded history fits inside that already tiny interval.
Read the sourcesMake deep time imaginable
A day has 86,400 seconds. Divide Earth's estimated 4.54 billion years by that number and each second represents about 52,500 years. One minute spans roughly 3.15 million years. This clock lets us compare stretches of time that are otherwise hard to picture, all on the same scale. [1]
Our ancestors go back much further
The Smithsonian dates Homo sapiens, the species all living people belong to, to about 300,000 years ago. Earlier human species existed before us. Evolution happens across populations and generations, so the date is approximate. The clock marks the span of our species; our wider family history reaches much further back. [2]
How can anyone date a planet?
Radioactive atoms change at measurable rates, leaving products that scientists can compare with what remains. USGS describes how these natural clocks in rocks and meteorites help date Earth. The oldest surviving Earth rocks give only a minimum age because the planet recycles its surface. Ancient Solar System material helps fill the gap. [1]