HOW ON EARTH

A circumhorizontal arc, or "fire rainbow," in Japan.

As the saying goes, you can’t have a rainbow without a little rain. But you can have parhelia and circumhorizontal arcs.

An image of Earth from 1 million miles away snapped on July 6, 2015 by a camera on NASA's Deep Space Climate Observatory spacecraft.

How much do you know about the blue marble we call home? From how our planet formed to just how many species there are, here are 100 things you need to know about Earth.

Two people can, however, look at the same photo of a rainbow.

How do rainbows form? It’s all about light waves, water, and angles—and that includes the angle from which you see one.

Calving is one way that glaciers lose ice.

If you want to behold some of the world's most majestic glaciers on six continents, you better act fast.

Lenticular clouds in Cape Town, South Africa.

The next time somebody points out a UFO-shaped cloud, you can whip out the word ‘lenticular.’ They’ll love it.

Deep-sea urchins are seen in an ocean trench near New Zealand.

Just a handful of people have ever been to the deepest part of the ocean, but what we've learned about life in the hadal zone is astonishing.

The small torn of Peshtigo, Wisconsin, before being destroyed by fire.

On October 8, 1871—the same day the Great Chicago Fire killed 300—a far deadlier wildfire swept across Wisconsin.

HOW ON EARTH

What Causes a Rainbow If There Isn’t Any Rain?

100 Facts About Earth

Rainbow Disconnection: Why No Two People Can Ever See the Same Rainbow

12 Disappearing Glaciers Around the World

8 Strange Cloud Types and What They Mean

8 Surprising Facts About the Deepest Part of the Ocean

The Great Peshtigo Fire: The Deadliest Blaze in American History