The Sun doesn't actually "stop exploding" in the way we usually think of explosions. It's constantly undergoing nuclear fusion in its core, which releases immense energy and creates outward pressure. This outward pressure is what keeps the Sun from collapsing in on itself.

Here's a breakdown of the forces at play:

* Gravity: The Sun's immense mass creates a powerful inward force of gravity. This force tries to pull all the Sun's matter towards its center.

* Nuclear Fusion: In the Sun's core, hydrogen atoms are fusing to form helium, releasing enormous amounts of energy in the process. This energy creates outward pressure, pushing against gravity.

These two forces are in a constant state of equilibrium. The outward pressure from nuclear fusion perfectly balances the inward pull of gravity, preventing the Sun from collapsing or exploding.

So, it's not a single force that stops the Sun from exploding, but rather a balance between two opposing forces. This balance is what allows the Sun to burn steadily for billions of years.

It's important to note that the Sun will eventually run out of fuel for nuclear fusion. When this happens, the outward pressure will decrease, and gravity will take over, causing the Sun to collapse and eventually become a white dwarf.