Origins of the Earth

Origins of the Earth

It is now believed that the Earth was formed from colisions among the countless meteors that made up the early solar system The man who first proposed this hellish origin for the planet was the Victorian scientist Lord Kelvin A British expert in thermodinamics, Kelvin believed that the Earth was slowly cooling down. The fires of the planet’s interior visible in volcanic eruptions suggested to him that the planet had once been completely molten. He reasoned that the molten planet would need nearly 20 million years to cool to its present temperatures. This figure was a colossal underestimate. Kelvin was unaware of a key source of heat inside the early Earth that prevented the planet from cooling as he predicted; radioactivity. In the early Earth radioactive particles of uranium, torium and potasium were in huge abundance. The heat produced from the decay of these particles would keep the Earth extremely hot for an extremely long time. But although these particles confounded Kelvin’s calculations, they would eventually prove the keys to unlocking the true age of the Earth. In 1911, a gifted 21-year-old geology student Arthur Holmes used radiation to revolutionaze our understanding of Earth history. Radiometric dating was simple in principle. It was based on the discovery that traces of the radioactive element uranium found throughout the rocks of the Earth decayed into another element land. By measuring the proportion of uranium to land in chrystals trapped in ancient rocks Holmes could accurately calculate their ages. Collecting data from samples from all over the world would be a lifetime’s work but as Holmes grew older so did the Earth. Its calculated age extended first to 1 then 3 then finally to 4.5 billion years. Today 4.5 billion years is stil the accepted age for the Earth. The search for the age of the Earth was over and the results had opened a window on the past. For the first time scientists could put rocks into correct order look deep into the Earth’s past and tell its story.