Radioactivity also gave the history of life an absolute calendar.
He came up with that figure by estimating how long it had taken for the planet to cool down to its current temperature from its molten infancy.
But Kelvin didn't, and couldn't, know that radioactive atoms such as uranium were breaking down and keeping the planet warmer than it would be otherwise.
Life is well over 3.5 billion years old, and until about 600 million years ago, the planet was dominated by microbes.
Radioactive clocks have shown that evolution can change its pace the Cambrian Explosion of about 535 million years ago saw the relatively rapid emergence of many major lineages of animals in just a few million years.
There may be more information on why The Bakhshali Manuscript comes from three different time periods but, an official report of the results have not yet been published. Researchers do know that the document was found in 1881 by a farmer in Bakhshali, a small village in Pakistan, buried in a field.
In 1902, The Bakhshali Manuscript was transferred to The contains simple arithmetic exercises, most likely for determining profitable exchanges.
Some of these methods have helped to pin down the evolution of our hominid ancestors; anatomically modern humans evolved about 100,000 years ago.
While that's nearly 20 times older than the Earth was once thought to be, it's a geological eye blink.
Researchers were able to use radiocarbon dating on The Bakhshali Manuscript because it was made out of birch bark, an organic material.