What Would Happen if the Sun Stopped? Part 3: The Photon Traffic Jam

(This is Part 3 of a series on what would happen if the Sun stopped. Read Part 1 and Part 2 first.)

Imagine you're standing in the middle of a crowded room. Not just any crowded room. A packed one. Shoulder to shoulder. So crowded you can't take more than a single step in any direction before bumping into somebody. And every time you bump into someone, you get spun around to face a brand new random direction. You can't see the walls. You can't see the doors. All you can do is push, bump, spin. Push, bump, spin.

You can feel your blood pressure climbing already. You want out. Now. How long does it take you?

The answer depends on how big the room is, naturally, but it also depends on something subtler. You aren't walking out of the room. You're random walking out of the room. Every step lands in a completely random direction. Half the time you're blundering deeper into the crowd without realizing it. Sometimes you go in circles. Sometimes you make a little progress and then immediately undo it.

There's some math describing how long this takes, and the math is frustrating, especially if you happen to be in a hurry. It says that to cover a given distance by random walk, you can't just take the number of steps a straight walk would need. You have to take the square of that number. If the door is 4 steps away on a normal walk, it's 16 steps away on a random walk. If it's 10 steps in an empty room, it's 100 in a packed one.

Every photon born in the core of the Sun is in exactly this predicament. Worse, actually. The Sun's interior isn't a gas, it's a plasma, every atom stripped down to bare nuclei and free electrons drifting everywhere. And photons absolutely love to interact with free electrons. A photon born in the core travels about one centimeter before slamming into an electron, scattering off in a completely random direction, traveling another centimeter, slamming into another electron, scattering again. And again. And again.

One. Centimeter. The Sun's radius is 70 billion of them. That's the straight-line, empty-room, normal-walk distance. For a photon actually stuck inside the Sun, it's 70 billion squared steps.

If you tried to count them off at one per second, it would take you longer than the current age of the universe. Several times over.

Each step takes only a fraction of a nanosecond, which is good. But there are a staggering number of them, which is bad. Run the arithmetic, and a photon born in the core of the Sun takes around 100,000 years to claw its way out to the surface.

If photons could simply stream straight out, the trip would ta