## Pick An Emoji To Learn Something New

Though you'd never know it from the way they waddle around as if their pants are around their ankles, penguins do in fact have knees. Their legs are made of the same four bones that human legs are, but penguins' legs are mostly covered by feathers so you can't really tell.

If you arrange them in the right way at the right time – it helps if they're positioned pole to pole (planets tend to bulge at the equator, making them wider) and if you do it when the moon is at it's furthest point from Earth (called apogee). You can check our maths here.

That feeling you get when something is so cute you want to squeeze it is called "cute aggression". A paper exploring the feeling was presented at a conference and later published in the journal *Psychological Science*.

Some people see sloths swimming and think they are drowning, so try to "rescue" them and put them back on dry land. But sloths are very adept swimmers, and if you see one in the water, you should leave it alone.

The radius of the sun is 695,700 km, so that's how far the photon (a particle of light, essentially) has to travel. The inside of the sun is a dense plasma, and the average distance a photon travels before bumping into something is estimated in one paper at 0.09cm which gives the total time to get to the sun's surface at 170,000 years.

Each penis is technically called a hemipenis, and is associated with one testis. They only use one hemipenis at a time, though. It turns out snakes probably have hemipenes because their genitals develop from cells located near the legs, or where the legs would have been, according to a *Nature* paper published in 2014.

Channel catfish, known scientifically as *Ictalurus punctatus*, have taste buds on their outer layer of skin all over their body, but they’re most concentrated around their whiskers (officially called barbels). The taste buds help catfish hunt down their prey in murky waters.

So this sounds crazy, but bear with me. A piece of paper is about 0.01cm in thickness, and the moon is 384,000 km away. If you fold a piece of paper in half, it’s now twice as thick as it started off. And if you then fold that piece of paper in half again, it’s thickness doubles again, so it’s four times the thickness of one sheet of paper. Every time you fold the paper, it’s thickness doubles – a fancy way of saying this is that the thickness of the folded sheets grows exponentially. When you do the maths, you can work out that this means you only need to fold the paper 42 times to make it thick enough to reach the moon, as Ethan Seigel explains at his blog.

To work out the volume of a cylinder you need to find the area of it's circle and them multiply by the height. The area of a circle is pi multiplied by the radius squared, which can be written as Pi x z² or expanded out to Pi x z x z. Multiply that by the height of the pizza and you get pi x z x z x a!