The earth has been determined by radiometric dating to be Laman chats sex
He proposed that geologists might learn about Earth's history by sifting through layers of rock, which were laid down over the course of millennia and provide a backward chronology of our planet.
[Dear Science: Where do old spacecraft go when they die?
For example, about 1.5 percent of a quantity of Uranium 238 will decay to lead every 100 million years.
By measuring the ratio of lead to uranium in a rock sample, its age can be determined.
Scientists discovered that rocks could be timepieces -- literally.
Many chemical elements in rock exist in a number of slightly different forms, known as isotopes.
But for humans whose life span rarely reaches more than 100 years, how can we be so sure of that ancient date? Even the Greeks and Romans realized that layers of sediment in rock signified old age.
But it wasn't until the late 1700s -- when Scottish geologist James Hutton, who observed sediments building up on the landscape, set out to show that rocks were time clocks -- that serious scientific interest in geological age began.
He created a catalogue of strata (which all got colorful names such as Lias Blue, and Ditto White) and argued that each one represented a distinct time in Earth's history — a principle known as fossil succession.Using fossils as guides, they began to piece together a crude history of Earth, but it was an imperfect history.After all, the ever-changing Earth rarely left a complete geological record.The same geologic forces that operate today, like deposition, erosion and uplift, have been shaping the Earth for ages with “no vestige of a beginning, no prospect of an end.” Science provided a new way of thinking about Earth's history; it made the distant past knowable.
Rather than assume the planet was the product of bygone catastrophes, such as a massive global flood, scientists could explain the ancient rock record with phenomena that exist today.
Geologist Ralph Harvey and historian Mott Greene explain the principles of radiometric dating and its application in determining the age of Earth.