No, the solar system is not held together by inertia. While inertia plays a role in the motion of planets, the primary force holding the solar system together is gravity.

Here's why:

* Inertia: Inertia is the tendency of an object to resist changes in its motion. It's what keeps planets moving in a straight line. However, inertia alone wouldn't be enough to keep them orbiting the sun.

* Gravity: The sun's immense mass creates a powerful gravitational field that pulls on all the planets. This gravitational force constantly pulls the planets towards the sun, preventing them from flying off into space. The planets' inertia, their tendency to move in a straight line, counteracts this pull, resulting in a curved path – an orbit.

Think of it like this: Imagine a ball attached to a string being swung in a circle. The string represents the gravitational force, pulling the ball inwards. The ball's inertia, its tendency to move in a straight line, resists this pull. The combined effect of these two forces creates the circular motion.

So, the solar system is held together by a delicate balance between the sun's gravitational pull and the planets' inertia.