Foucault's Pendulum The Device That Lets You See The Earth Turn

Nikunja Bihari Sahu


Today, the fact that the Earth is rotating about its own axis is accepted and well-established — an astronaut returning from the Moon can even witness how the Earth is rotating. We can also accurately clock the period of Earth's rotation using atomic clocks to a precision of few milliseconds.

But that was not the case nearly two thousand years ago when people were looking at the moving starry sky with awe and wonder with their reference frames fixed on a stationary-looking Earth. It was really hard for them to believe that their own platform was in violent motion in space. Various models were put forward to explain the daily motion of the starry sky and the motions of the Sun and the Moon.

The Greeks believed that the Earth was static and that the whole celestial sphere, in which the stars were fixed, rotates around the Earth in its daily motion. This idea was first put forward by the Greek philosopher Aristotle in the 4th century BCE. This was later supported by another eminent Greek astronomer Ptolemy (2nd century CE), who thought that the Earth would be devastated by violent storms if it rotated.

In 499 CE, the Indian astronomer Aryabhata suggested that the spherical Earth rotates about its axis daily and that the apparent movement of the stars is a relative motion caused by the rotation of the Earth. He provided an analogy that just as a man traveling in a…read more on NOPR