The Earth is more than 4.5 billion years old. This is a very large
number. One way to understand this amount of time, is to use seconds
instead of years. If you looked at a watch, it would take a little more
than 11.5 days for a million seconds to go by. Now remember that a
billion is one thousand times one million. This means that it takes
almost 32 years for a billion seconds to go by! Even if you canít
visualize the time, just remember the Earth has existed for a long time.
This picture shows the history of the Earth as if it took place in 24
hours. The creation of the major types of animals was not until 20:00.
Humans have only been on the Earth for a very short period, only 30
seconds before 24:00!
24 hour clock