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How Old is the Universe?, by David A. Weintraub

Reviewed by Peter Rogerson

There is a consensus among astronomers that the answer to the question posed by the title of this book is about 13.7 billion years. Professor Weintraub tells us how this figure was arrived at, beginning with Aristotle, who dealt with the problem by asserting that the universe had always existed and would always continue to exist.

It was not until the 18th century that natural philosophers started to make the first scientific attempts to estimate the age of the Earth, instead of relying on interpretations of the Old Testament. However, real progress had to await the discovery of radioactivity towards the end of the 19th century.

For example, the study of the properties of radioactive elements in rocks can be used to determine the time which has elapsed since they solidified. In the case of the decay of potassium 40 to argon 40, the argon will escape into the atmosphere until the rock solidifies, when it will become trapped as it is formed. From this time the ratio of argon 40 to potassium 40 increases from zero, so that the ratio when the rock is examined will be a measure of the time since solidification, as the half-life (the time taken for half of the atoms of a particular radioactive substance to decay) of potassium 40 is known.

The oldest rocks found on Earth are about 4.4 billion years old, and the oldest known meteorites in the solar system are 4.56 billion years old, so the universe must be much older.

Read the original article at: Magonia Blog

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