Chapter 6: Why Do We Have Day and Night?

A gentle note: “the Sun goes around the Earth”

Long ago, many people believed the Sun travelled around the Earth, because that is how it appears from the ground. It is a very natural thing to think. But careful study by scientists showed that it is really the Earth that spins, and the Earth that travels around the Sun. Watching the sky and then checking our ideas with care is exactly what makes someone a scientist.

Story Time — The Torch, the Globe and the Secret of Night

Sara · Goa

Sara had a question at bedtime that would not go away. “Amma, where does the Sun go at night? Does it switch off?” Instead of answering, her mother fetched a globe — a small model of the Earth — and a torch. “Let us find out together,” she said.

She switched off the room lights and shone the torch at the globe. “The torch is our Sun,” she said, “and this little sticker here, on India, is us.” One side of the globe was brightly lit; the other lay in shadow. “When our side faces the torch, what do we have?” “Light!” said Sara. “Daytime!”

“Now watch closely.” Slowly, her mother turned the globe. Sara's little sticker moved out of the bright side and into the dark, shadowed side. “Oh!” Sara said. “We have gone into the dark. Is that night?” “Yes. That is night. And notice — the Sun did not switch off at all.”

“So we turn away from the Sun?” Sara asked. “Exactly. The whole Earth spins slowly, like a top, all day and all night. When our side faces the Sun, it is day. When our side turns away, it is night. Then we turn back towards morning again.”

Sara turned the globe herself, watching her sticker pass from bright day into dark night and back into day. The Sun was not going anywhere; it was the Earth, quietly turning beneath the sky.

“And how long does one full turn take?” her mother asked. Sara thought. “One whole day?” “One whole day,” her mother smiled, tucking her in. “You are turning through space this very moment, as you fall asleep.”

Story Time — Morning There, Night Here

Manjeet · Amritsar, Punjab

Manjeet's cousin lived far away in another country, and one evening his father let him make a video call. Outside Manjeet's window in Amritsar it was dark, and the stars were coming out. Yet on the screen, his cousin's room was full of bright morning sunshine.

“Why is it morning there and night here?” Manjeet asked. “You are both on the same Earth.” His father smiled. “This is one of my favourite things to explain. It happens because the Earth is round, and it spins.”

“Right now,” his father said, “our side of the Earth has turned away from the Sun, so we have night. But your cousin's side, far around the ball of the Earth, is facing the Sun, so they have day.”

Manjeet imagined the whole round Earth turning slowly in space, carrying India into the dark while carrying the other country into the light. “So when we go to sleep, they are waking up?” “Exactly. And in a few hours, as the Earth keeps turning, it will be the other way around.”

Manjeet said goodnight to his sunlit cousin and looked out at his own starry Amritsar sky. He was not standing still, he realised. He was riding upon a giant, spinning Earth, and on the far side, the day was only beginning.