Earthdating com going from long time friends to dating
Kelvin calculated the age of the Earth by using thermal gradients, and he arrived at an estimate of about 100 million years.
He did not realize that the Earth mantle was convecting, and this invalidated his estimate.
According to modern biology, the total evolutionary history from the beginning of life to today has taken place since 3.5 to 3.8 billion years ago, the amount of time which passed since the last universal ancestor of all living organisms as shown by geological dating.
In a lecture in 1869, Darwin's great advocate, Thomas H.
Their values were consistent with Thomson's calculations.
This led him to estimate that Earth was about 75,000 years old.This was a challenge to the traditional view, which saw the history of Earth as static, He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface temperature gradient to decrease to its present value.His calculations did not account for heat produced via radioactive decay (a then unknown process) or, more significantly, convection inside the Earth, which allows the temperature in the upper mantle to remain high much longer, maintaining a high thermal gradient in the crust much longer.Thus the age of the oldest terrestrial rock gives a minimum for the age of Earth, assuming that no rock has been intact for longer than the Earth itself.In 1892, Thomson had been made Lord Kelvin in appreciation of his many scientific accomplishments.