Age of the universe
The age of the universe is around 13.7 billion years.
Age of the earth
The age of the earth is around 4.5 billion years.
Atom
An atom contains a nucleus at its center and electrons that "rotate" around the nucleus. The nucleus contains nucleons, that is, protons and neutrons. The electrons have a negative electrical charge. The protons have a positive electrical charge, of the same value as that of the electron.
Billion in million
A billion (1 000 000 000) = a thousand million.
Life
At the chemistry level life is surprisingly commonplace: carbon, hydrogen, oxygen and nitrogen, a little calcium, a drop of sulfur and a light dust of other very ordinary elements.
Life on Earth is not only brief but terribly tenuous. We come from a planet that is very good at promoting life, but far better at annihilating it. The average species on Earth only lasts about 4 million years.
Sea salt
Sea water is salty due to the intense volcanic activity of the early ages of the Earth. A large amount of volcanic gas was then released into the hot atmosphere of the earth. Later, when the earth cooled, all this water vapor and these gases precipitated in acid rain, eroding the rocks for millennia. This water loaded with ions, minerals and alluvial deposits poured into the oceans, gradually stabilizing at the present salinity by the play of the dissolution of the salts and the evaporation of water.
Speed of light
By rounding off:
186 000 mi / second
300 000 km / second
Very large numbers
10 E9 = 1 000 000 000 = 1 Billion short scale (anglophones) = 1 Milliard long scale (others)
10 E12 = 1 000 000 000 000 = 1 Trillion short scale (anglophones) = 1 Billion long scale (others)
10 E15 = 1 000 000 000 000 000 = 1 Quadrillion short scale (anglophones) = 1 Billiard long scale (others)
10 E18 = 1 000 000 000 000 000 000 = 1 Quintillion short scale (anglophones) = 1 Trillion long scale (others)