There’s an Irish saying, “There’s a pot of gold at the end of every rainbow.”

But it used to say, “you’re as likely to find a pot of gold as the end of the rainbow.”

That’s because if you go looking for its end, the rainbow vanishes.

Rainbows occur when water droplets—from rain, mist, waterfalls, even sea spray—hang in the air.

When sunlight enters the droplet, some will reflect off the back side and pass again out the front.

As sunlight passes twice through the water, the different wavelengths that make it up bend at different angles, which splits the entering white light into the spectrum of rainbow colors.

Your position, in relation to the sun and the water droplet, affects how much and which light reaches your eyes. Meaning, you determine how much rainbow you see.

If the sun is directly behind you, and low in the sky, the largest amount of light is reflected back toward you, and you’ll see a strong rainbow.

If the sun is 90 degrees to your right or left, you’ll see less reflected light and a weak rainbow.

If the sun is high in the sky or on the other side of the water droplets, no light reflects back to you, and you’ll see no rainbow.

This also means that, as you move, the amount of rainbow you see changes.

If you travel far enough toward what appears to be its end, the rainbow, and your pot of gold, will gradually disappear.