Question: “What holds the planets in their orbits around the sun?”
Answer: The main force that keeps planets in their orbits around the Sun is the gravitational force. Let’s understand this in detail:
1. Gravitational Force:
The Sun’s gravitational force is the power that keeps the planets revolving around it in their orbits. This force is the attraction between two objects, depending on their mass and the distance between them. The Sun has a very large mass, so its gravitational force is very strong.
2. Kepler’s Laws:
Johannes Kepler provided three important laws of planetary motion, which explain how planets move around the Sun:
- First Law (Law of Ellipses): Every planet moves in an elliptical orbit with the Sun at one focus.
- Second Law (Law of Equal Areas): A line that connects a planet to the Sun sweeps out equal areas in equal times. This means that planets move faster when they are closer to the Sun and slower when they are farther from the Sun.
- Third Law (Law of Harmonies): The square of the orbital period of any planet is proportional to the cube of the average distance from the Sun.
3. Centripetal Force:
A centripetal force is also at work, keeping the planets in their orbits. This force pulls objects towards the center. In this case, the centripetal force is provided by the Sun’s gravitational pull.
4. Inertia and Velocity:
Newton’s First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. For planets, they continue moving forward, and the Sun’s gravitational force pulls them inward, causing them to orbit in a curved path.
Example:
Imagine swinging a ball tied to a string. The string pulls the ball towards the center while the ball’s motion tries to move it outward. Similarly, the Sun’s gravitational force keeps the planets in their orbits around the Sun.
Also, read: Full Form of ISRO: Indian Space Research Organisation
Source: LPI