The Universe And The Earth 7th Class Pdf Official

One of those planets was .

For a billion years, Earth was a water world with volcanic islands. Then, a new kind of magic happened deep in the oceans. Near volcanic vents, tiny, single-celled life forms appeared. They figured out a trick called —using sunlight to make food. Their waste product? Oxygen . the universe and the earth 7th class pdf

Long ago, before there was time, space, or a single star, there was nothing. Not even empty space. Then, about 13.8 billion years ago, something miraculous happened: . One of those planets was

At first, Earth was a nightmare: a molten ball of lava, constantly bombarded by comets and asteroids. It had no air, no water, just fire and rock. But over millions of years, Earth cooled. A thin, rocky crust formed on its surface. Heavier metals like iron and nickel sank to the center, creating a dense . Lighter rocks formed the thick mantle and the thin crust where we live. Near volcanic vents, tiny, single-celled life forms appeared

From the outside, Earth looks like a blue marble. But inside, it’s still restless. The crust is broken into giant puzzle pieces called . They float on the hot mantle, grinding together to build mountains, pulling apart to create valleys, and causing earthquakes.

Today, you live on a 4.5-billion-year-old planet. Your body is made of stardust—carbon from that ancient supernova. You are protected by a thin blue sky. Beneath your feet, a molten core churns. And above you, the universe continues to expand, filled with a hundred billion galaxies, each with a hundred billion stars.

Slowly, oxygen filled the atmosphere. The sky turned blue. The ozone layer formed, shielding the land from the sun’s deadly ultraviolet rays. Finally, life could crawl onto land.