1. What is Gravitation?
Gravitation is a natural force of attraction that exists between any two objects that have mass. Whether the objects are as small as grains of sand or as large as planets and stars, they pull each other with a force known as gravitational force. This force acts everywhere in the universe and plays a major role in shaping the motion of celestial bodies as well as everyday objects around us.
You experience gravitation constantly—when you drop something and it falls to the ground, when the Earth orbits the Sun, and even when you stand on the floor feeling your weight.
1.1. Why Does Gravitation Exist?
Gravitation exists because all matter attracts all other matter. The Earth attracts you, and you also attract the Earth—but the Earth's mass is much larger, so you feel the pull strongly, while your pull on the Earth is extremely tiny.
1.1.1. Simple Examples
- A dropped stone falls because the Earth pulls it downward.
- The Moon stays in orbit because Earth's gravity keeps it from flying away.
- The planets revolve around the Sun due to the Sun’s gravitational pull.
2. Gravitation in Daily Life
Although gravity plays a huge role in astronomy, it also affects your normal daily activities. Without gravity, walking, sitting, standing, or even drinking water would be impossible. Gravity keeps everything anchored to the Earth's surface.
2.1. Familiar Experiences
- Objects fall downward when released.
- Rainwater flows towards the ground.
- Your weight changes slightly at different places on Earth.
- You feel heavier when climbing stairs and lighter when coming down due to gravitational effects.
2.2. What if Gravity Did Not Exist?
If gravity suddenly disappeared, everything—humans, buildings, oceans—would float away from the Earth. Even the Moon would drift into space. Gravity is essential to the stability of life on Earth.
3. Gravity vs Gravitation: Are They the Same?
The terms gravitation and gravity are related but not identical. Gravitation refers to the general attraction between any two masses anywhere in the universe. Gravity usually refers specifically to the force by which the Earth attracts objects toward itself.
3.1. Key Differences
- Gravitation: Universal force acting between any two masses.
- Gravity: Special case of gravitation—Earth’s pull on objects near its surface.
4. Historical Understanding of Gravitation
People have observed falling objects for thousands of years, but the deeper understanding of gravitation came much later. Ancient thinkers believed objects fell because they 'wanted' to be on the ground. It was Isaac Newton who provided a scientific explanation.
4.1. Newton’s Insight
Newton realised that the same force that pulls objects to the ground also keeps the Moon in orbit. This remarkable idea led him to propose the Universal Law of Gravitation, linking Earth-based motion and celestial motion for the first time.
5. Why Gravitation is a Universal Force
Gravitation acts everywhere—between stars, planets, galaxies, and tiny dust particles. Its range is infinite, meaning it never becomes truly zero even at very large distances. This universality makes gravitation fundamental to understanding the structure and motion of the universe.
5.1. Effects of Universal Gravitation
- Planets orbit stars.
- Moons orbit planets.
- Ocean tides occur due to the Moon’s gravitational pull.
- Galaxies form and stay bound due to gravitational attraction.
6. Why Studying Gravitation is Important
Studying gravitation helps us understand a wide range of natural phenomena—from why objects fall to the ground to how satellites stay in orbit. It also provides the foundation for space travel, astronomy, atmospheric science, and many modern technologies.
In the next topic, we explore gravity and gravitational force in detail, explaining how objects attract each other and how this universal force works.