How do planets maintain their orbits around the Sun?

Planets maintain their orbits around the Sun due to the balance between gravitational pull and their own inertia.

The orbits of planets around the Sun are a result of two fundamental physical phenomena: gravity and inertia. The Sun, being the most massive object in the solar system, exerts a strong gravitational pull on all the planets. This force of gravity pulls the planets towards the Sun. However, the planets also have their own inertia, which is the tendency of an object to continue moving in a straight line at a constant speed unless acted upon by an external force.

The balance between these two forces - the Sun's gravitational pull drawing the planet in, and the planet's inertia trying to keep it moving in a straight line - results in the planet moving in an elliptical orbit around the Sun. This is known as Kepler's First Law of Planetary Motion.

The speed at which a planet moves in its orbit (its orbital speed) also plays a crucial role. If the orbital speed is too great, the planet's inertia will overcome the Sun's gravitational pull and the planet will move off into space. If the orbital speed is too small, the Sun's gravity will overcome the planet's inertia and the planet will fall into the Sun.

However, for all the planets in our solar system, their orbital speeds are just right - they are in what is known as a 'stable orbit'. This means that the gravitational pull of the Sun is exactly balanced by the planet's inertia. As a result, the planet continues to move in its orbit around the Sun without spiralling inwards or drifting away.

In essence, the delicate balance between gravitational pull and inertia, coupled with the right orbital speed, allows planets to maintain their orbits around the Sun. This intricate dance of celestial bodies is a testament to the fundamental laws of physics that govern our universe.