Lunar eclipse

A solar eclipse happens when the Moon gets between the Sun and the Earth. Swap the places and you get another kind of eclipse.

As the Moon goes round the Earth, sometimes the Earth comes between the Sun and the Moon and blocks the sunlight from reaching the Moon. This is a lunar eclipse (in Hindi, चंद्र ग्रहण). We see the Earth's shadow creeping over the full Moon.

When the Moon is completely inside the Earth's shadow, it is a total lunar eclipse. The bright Moon slowly turns dark red, and stays that way until it moves out of the shadow. (People sometimes call this a 'blood moon'.)

When only part of the Moon is in the Earth's shadow and the rest is still bright, it is a partial lunar eclipse.

One big practical difference from a solar eclipse: you can safely watch an eclipsed Moon with your naked eye. The Moon only reflects sunlight, and that is not strong enough to harm your eyes.

To find out when the next solar or lunar eclipse will be visible from where you live, try the free computer version of the Stellarium app.

The book ends with two Indian places and a scientist:

• The Kodaikanal Solar Observatory, in the Palani hills of southern India, set up in 1899, has collected data about the Sun for over 100 years; it is run by the Indian Institute of Astrophysics, Bengaluru.
• M.K. Vainu Bappu, the father of modern Indian astronomy, set up telescopes at Manora Peak near Nainital and at Kavalur in Tamil Nadu, studied stars, discovered a comet, and travelled the world to study solar eclipses.