Almost all mammals live for around 1 billion heartbeats. For a rabbit, which has a quick pulse, it takes about 3 years to reach a billion heartbeats, but a slow-pulsed elephant can go more than 80 years. Only humans can push their hearts past 2 billion, thanks to modern medicine, food preservation technology, and water purification. (, , )

If you’re traveling through the fog and the sun is at your back, you might just see a white rainbow. Fogbows are like rainbows without color. Though rare, they occur in the fog because the water droplets, which would normally form a rainbow, are too small to reflect the light wavelengths that create colors. (, , )