Previously she was an assistant editor at Scholastic's Science World magazine.

Our planet was pegged at a youthful few thousand years old by Bible readers (by counting all the "begats" since Adam) as late as the end of the 19th century, with physicist Lord Kelvin providing another nascent estimate of 100 million years.

Kelvin defended this calculation throughout his life, even disputing Darwin's explanations of evolution as impossible in that time period.

Also, because Earth formed as part of our sun’s family of planets – our solar system – scientists use radiometric dating to determine the ages of extraterrestrial objects, such as meteorites.

These are space rocks that once orbited our sun, but later entered Earth’s atmosphere and struck our world’s surface.

Many great thinkers throughout history have tried to figure out Earth’s age.

For example, back in 1862, Lord Kelvin calculated how long Earth might have taken to cool from its original molten state.

In 1898, Marie Curie discovered the phenomenon of radioactivity, in which unstable atoms lose energy, or decay, by emitting radiation in the form of particles or electromagnetic waves.

By 1904 physicist Ernest Rutherford showed how this decay process could act as a clock for dating old rocks.

Meanwhile, Arthur Holmes (1890-1964) was finishing up a geology degree at the Imperial College of Science in London where he developed the technique of dating rocks using the uranium-lead method.