How Old is the Earth?
"Have you ever wondered how old the Earth is? Universe Today publisher Fraser Cain explains how early scientists tried to get an answer for this puzzling problem, and how modern science has finally given us an answer - by looking at meteorites.
Based on this article:
http://www.universetoday.com/75805/ho...
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Did you ever wonder how old the Earth is?
Scientists estimate the Earth is four-point-five-four billion years old, the exact same age as the rest of the Solar System.
It's no coincidence, since it all formed from the solar nebula, billions of years ago.
In the early Solar System, small particles of dust collected into larger and larger objects until there were many planetoids.
These planetoids collided into one another, forming the Earth.
So, how do we confirm the Earth is four-point-five-four billion years old?
It's surprisingly hard to tell.
We believe the oldest rocks on Earth are four to four-point-two billion years old and plate tectonics are constantly resurfacing the planet, hiding the evidence.
In the past, scientists have come up with an assortment of creative ways to determine the age of the Earth:
Benoit de Maillet was a French anthropologist in the seventeenth century who noticed fossils high up in the mountains.
He guessed that those areas were once covered by oceans, and so calculated that it would take two billion years for the oceans to evaporate to their current levels.
William Thompson, also known as Lord Kelvin, assumed that the Earth was once a ball of molten rock the same temperature of the Sun.
He calculated that it would take between twenty and four-hundred million years for the Earth to cool to its current temperature.
Charles Darwin calculated that a chalk formation in England would have taken 300 million years to weather to its current state, setting a minimum age for the Earth.
Darwin's son, George assumed that the Moon formed out of the Earth and drifted to its current location, taking at least fifty-six million years to reach its current distance.
Astronomer Edmund Halley assumed that the salinity of the oceans explained the age. Based on the amount of salt flowing into the ocean from rivers, he estimated that it would take eighty to one hundred and fifty million years for the oceans to reach their current level of salinity.
Each of these ideas was totally wrong. I admire their creativity, and their ability to produce and attempt to test theories with only a fraction of knowledge and equipment available today.
Modern science eventually provided us a method for determining the age of the earth... by using meteorites.
Scientists can tell the age of the space rocks by measuring the ratios of trace radioactive isotopes.
No matter the origin of the meteorites, they're all the same age: four-point-five-four billion years old.
And we know that everything in our solar system was formed at the same time from the primordial solar nebula. The age of the Earth, just like the meteorites and everything else in our solar system is four-point-five-four billion years old.
