It takes one tenacious photon to travel from the sun’s core all the way to the earth. It all starts in the Sun’s 27-million-degree-Fahrenheit core of plasma, a gas-like state of matter that conducts electrical current. In the core, nuclear fusion drives pairs of protons to collide and create deuterium atoms, which are composed of one proton and one neutron. If a separate, singular proton collides with a deuterium atom, a Helium-3 nucleus is formed. And that’s where you come in: a photon, in the form of a high-energy gamma ray.
Soon after your formation you escape the sweltering core and enter the radiative zone of the sun. However, this territory is going to be a bit more challenging to traverse compared to the core. Unlike the core, the radiative section is densely packed with protons. In fact, the protons are so tightly packed together that every time you try to move you end up hitting a proton. You do not intentionally run into other protons– it is inconvenient for both you as a photon and for the protons–but the protons are so densely packed that it is impossible to travel very far without colliding. In the process of colliding with a proton, you lose some energy and scatter in a random direction. And when you scatter in a random direction, you hit another proton, lose some more energy, scatter in a random direction, hit another proton, lose some more energy. This makes the process of traveling significantly harder and more time consuming. As a result, it will take you anywhere from a few thousand to a few million years to escape the radiative zone.
When you finally leave the radiative zone, you may think, “Oh, yes, finally, I’m almost there!” However, the journey is not over yet. Now, you enter the convection zone. Coming from the radiative zone, you have become a less energetic photon, having lost quite a bit of energy from all the collisions in the radiative zone of the sun. Therefore, you have shifted from a gamma ray to a visible ray of light. The convection zone acts like an enormous pot of boiling water; the bottom part of this layer (the one on top of the radiative zone) is significantly hotter than the upper part of the layer (which faces the sun’s surface). The entire surface of the sun is covered in convection cells, which is a result of the cycle of hot rising material and sinking cold material in the sun. The hot cells rise to the surface of the sun, and you rise with this hot cell.
Now that you have reached the sun’s surface, you may think that this wonderful adventure is over and you can travel to the earth and shed light as a visible photon. However, the sun’s surface itself serves as yet another layer for the photon to travel through. Luckily, the sun’s surface is less dense than previous layers, so there are not too many protons to run into.
After leaving the sun’s surface, it is time to travel through the final stage of the sun: the sun’s atmosphere. You have three layers in your way before reaching the freedom of outer space: the photosphere, the chromosphere, and the corona. Finally, when you leave the corona, you can head to earth as a visible proton. This is probably the easiest part of the journey– it only takes about eight minutes to get from the sun’s atmosphere to the earth.
And that concludes your journey from the center of the sun to the earth! It only takes a few thousand years and a significant amount of effort and dedication, but if you are a patient photon and are not claustrophobic, it should not be a problem at all.
About the writer: Eliana Petreikis is a member of the class of 2020 at The Bishop's School in San Diego.