One should never ask someone’s age but the Earth is so fascinating, surely we must know how old it is? Throughout history, many have come up with ideas about how old our planet is, but now science has given us a definitive answer.
Specifically, using radiometric age dating has given us the answer – and it's mucholder than you might think.
Read on to discover how old the Earth is, exactly how this was figured out, and also when the earliest form of life first appeared on our planet.
How old is Earth?
The Earth is 4.54 billion years old, give or take 50 million years. This means that the Earth is under half the age of the Milky Way Galaxy, 11-13 billion years old,and around a third of the age of the Universe (10-15 billion years old).
How do scientists know how old the Earth is?
Scientists have been able to determine the age of the Earth using a technique called ‘radiometric dating’.
Essentially, the method allows researchers to measure the last time that the rock being dated was either melted or disturbed sufficiently to alter its radioactive elements.
The Canyon Diablo meteorite found in Arizona,USA, gives us the best plausible age of the Earth.
How old did people used to think Earth was?
Many different theories have come and gone about how old the Earth is, with some wildly different estimates appearing over the centuries.
A famous example of an early theory is that of physicist William Thomson (1824-1907). Thomson believed that the Earth had “solidified from an originally molten state” and that, based on cooling times, Earth was between 20 and 40 million years old. Radioactive decay was not yet known in Thomson’s time.
It was a controversial opinion, and one that Charles Darwin did not agree with, but other scientists of the time – including Hermann von Helmoltz, Simon Newcomb, and George H Darwin (son of Charles) – concluded similar results based on different factors. Mainly, the time taken for the Sun to condense to its then current diameter and tidal friction.
In 1900, Irish physicist and geologist John Joly, meanwhile, theorised that the Earth is at least 80-100 million years old. This was based on the rate salt appears in the ocean due to the erosion process.
Outside of geological research, some fundamental Christian bible scholars claim, by apparently using hints from the account of Genesis, that the Earth and Universe are about 6000 years old.
When did life first appear on Earth?
The earliest form of life appeared on Earth between and 3.77 billion years 4.28 billion years ago.
There is some debate over this age, but scientists haven't yet found animal fossils dating back beyond 890 million years old. However, In 2017, Palaeontologists at University College London claimed they found evidence of life from tiny bacteria fossils dating 3.77 billion years ago.
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