March 22nd, 2017

Our universe is composed of Dark Energy, Relativistic Particles, and Matter. Within these, 'matter' can be further broken down into two types: Baryons and Dark Matter. Baryons are 'normal' matter, making up everything we see on earth, our bodies, and all the elements on the periodic table. Dark matter is a form of 'invisible' matter. We see its effects in space, where it pulls on baryons through gravity, but we have not yet been able to directly study it, and therefore do not understand its nature. Even if we cannot directly study dark matter, we can measure how much of it there is through observing the strength with which it pulls on normal matter. In our entire universe, we have about 17% normal matter, and the rest is dark matter. Interestingly, however, there seems to be a higher ratio of dark matter in galaxy clusters. This hint may hold a key to understanding dark matter, which remains one of the biggest mysteries in physics.

Bonus:
Because of French Guyana, France's longest land border is surprisingly with Brazil. This is 3 km longer than its border with Spain.

Bonus 2:
A neat website lets you see how the Mercator map projection distorts countries.

-E