If you have seen pictures of the night sky filled with green, pink, and purple lights, you might have wondered what causes them. That glow is called the aurora borealis, or northern lights, and it has inspired stories and legends for centuries. The real reason, though, is not magic or angry gods. It all begins with our sun.

The sun is always sending tiny bits of itself into space. This flow of charged particles, mainly electrons and protons, is called the solar wind. It travels millions of miles and eventually hits Earth’s magnetic field. Luckily, this field works like a huge shield and blocks most of the solar wind. However, near the North and South Poles, the magnetic field is weaker. Some particles get through and travel down into our upper atmosphere.

When these particles reach our atmosphere, they hit gas molecules such as oxygen and nitrogen. These collisions give energy to the gases, which then release it as light. It is similar to how a neon sign works. Different gases make different colors. Oxygen high up in the sky creates red light, but lower down it glows green, which is the most common color. Nitrogen makes blue and purple lights. The result is a huge light show powered by the sun, even though it is ninety-three million miles away.

So when can you see this happen? You need to be far north or far south, away from city lights. In the northern hemisphere, the best places are Alaska, northern Canada, Iceland, Scandinavia, and Russia. The season runs from late August to early April because you need long, dark nights. The sky has to be clear too. Clouds will ruin the view no matter how active the aurora is. Also, the lights are strongest around the equinoxes in September and March. That is when the solar wind tends to hit Earth at just the right angle.

You also need to pay attention to solar activity. The sun goes through an eleven year cycle, and at its peak, called solar maximum, you get more sunspots and solar flares. That means stronger solar winds and more frequent, brighter auroras. We are heading toward one of those peaks soon, so the next few years are a great time to plan a trip.

In the end, the aurora borealis reminds us that our planet is not alone. Earth is always interacting with the sun through particles and magnetic fields. If you ever get the chance to stand under a moving curtain of green light, remember that you are seeing the solar wind meet our atmosphere. That is a pretty amazing thing to witness.