Astronomy is one of the oldest subjects in human history. From ancient times, people have looked at the sky with curiosity. They wanted to know how stars move, why days and nights happen, and how planets travel in space. But for many centuries, humans had the wrong understanding of our universe. The real change came when one great scientist introduced a completely new idea. This man is known as the Founder of Modern Astronomy, and his name is Nicolaus Copernicus.

This PDF book summary will help you understand his life, his discoveries, and how his ideas changed the world forever. The language is kept simple so that students, beginners, and general readers can understand everything easily.

🌟 Who Was Nicolaus Copernicus?

Nicolaus Copernicus was a Polish astronomer born in 1473. During that time, Europe was still following old beliefs about the universe. People trusted the ancient Greek model made by Ptolemy, which said that Earth is at the centre of the universe and everything — the Sun, Moon, and planets — moves around Earth. This was known as the geocentric model.

Copernicus was educated in many subjects. He studied mathematics, medicine, astronomy, and even law. But his heart always stayed with astronomy. He kept asking one question: What if the old belief is wrong?

🌞 The Revolutionary Idea — Sun at the Centre

After many years of observing the sky, Copernicus proposed a bold idea:

“The Sun is at the centre of the universe, and Earth moves around the Sun.”

This was called the heliocentric model.

This idea was shocking for people in the 16th century. Nobody could imagine that Earth, which feels still under our feet, is actually moving. Copernicus explained that:

His theory changed everything. For the first time in history, astronomy moved from blind belief to scientific observation.

📘 His Famous Book – De Revolutionibus Orbium Coelestium

The most important work of Copernicus was his book De Revolutionibus Orbium Coelestium (meaning On the Revolutions of the Heavenly Spheres). This book is considered the foundation of modern astronomy.

However, he was afraid to publish it during his life because his ideas were against popular beliefs and religious systems. Finally, the book was printed in 1543, the same year Copernicus died.

This book changed the direction of scientific thinking. Many future scientists like Galileo Galilei, Johannes Kepler, and Isaac Newton used Copernicus’s ideas to develop their own discoveries.

🌍 Why Copernicus Is Called the Founder of Modern Astronomy

Nicolaus Copernicus is called the founder of modern astronomy because he brought a scientific shift. His work did not only talk about the Sun being in the centre — it introduced a new style of thinking:

1. Use observation, not belief

2. Use mathematics to explain the universe

3. Question old ideas and explore new ones

Before him, astronomy was based on religion and philosophy. After him, it became a science.

His heliocentric model laid the foundation for:

• Newton’s laws of motion

• Kepler’s planetary laws

• Galileo’s telescope discoveries

• Modern astrophysics

• Space science and modern satellites

Without Copernicus, our understanding of planets, galaxies, and the universe would not have grown so fast.