What evidence refutes Kelvin’s claim that the Earth is only 20 million years old?. Earth & Marine Sciences

Kelvin didn’t know that Earth’s interior was dynamic—that within it hot rock was rising, cooling, and sinking. He assumed the planet was a rigid sphere, so his model didn’t account for the greater heat flow that results from this movement. More importantly, scientists figured out a way to measure the absolute age of rocks using decay rates of isotopes. Radiometric dating indicates that Earth formed as part of a dust cloud around the sun 4.568 billion years ago.