Dating the age of dinosaurs

Rated 4.55/5 based on 770 customer reviews

For biologists, even 100 million years seemed much too short to be plausible.In Darwin's theory of evolution, the process of random heritable variation with cumulative selection requires great durations of time.Even more constraining were Kelvin's estimates of the age of the Sun, which were based on estimates of its thermal output and a theory that the Sun obtains its energy from gravitational collapse; Kelvin estimated that the Sun is about 20 million years old.Geologists such as Charles Lyell had trouble accepting such a short age for Earth.These had assumed that the original heat of the Earth and Sun had dissipated steadily into space, but radioactive decay meant that this heat had been continually replenished.George Darwin and John Joly were the first to point this out, in 1903.Because the exact amount of time this accretion process took is not yet known, and the predictions from different accretion models range from a few million up to about 100 million years, the exact age of Earth is difficult to determine.

It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites.His value of 56 million years added additional evidence that Thomson was on the right track.By their chemical nature, rock minerals contain certain elements and not others; but in rocks containing radioactive isotopes, the process of radioactive decay generates exotic elements over time.He did not realize that the Earth mantle was convecting, and this invalidated his estimate.In 1895, John Perry produced an age-of-Earth estimate of 2 to 3 billion years using a model of a convective mantle and thin crust.

Leave a Reply