The 100

One hundred degrees — where water boils Physics

The most familiar 100 in all of science is the boiling point of water. When Anders Celsius laid out his temperature scale in 1742, he pinned it to water itself: 0 degrees where it freezes, 100 degrees where it boils (at sea level), and a hundred even steps in between — which is why the scale was long called “centigrade,” the hundred-step measure. That single choice makes 100 °C one of the most-used reference points on Earth, the temperature every kettle and cook and chemist reaches for.

The number is a human convenience laid onto a real fact — water's boiling is a fixed physical point — and it made the whole metric world's thermometer a scale of 100. Freeze to boil, nothing to everything, in a clean 100 degrees.

Fermium, element 100 — born in a hydrogen bomb ChemistryPhysics

Fermium sits at atomic number 100, and it entered the world in fire. It was first detected in 1952 in the radioactive debris of “Ivy Mike,” the first hydrogen-bomb test — the intense burst of neutrons had slammed into uranium and, in a fraction of a second, built atoms all the way up to element 100. Named for the physicist Enrico Fermi, fermium is intensely radioactive and cannot be gathered in any weighable amount; it exists only as a handful of atoms at a time in laboratories.

It marks a kind of frontier: 100 is near the practical ceiling of what can be made by piling neutrons onto a nucleus, so everything heavier has to be built atom-by-atom in accelerators. Element 100 is the last outpost of the “ordinary” route to new elements — the round number where the familiar way of making matter runs out.

Per centum — the hundred that measures everything MathematicsCulture

Nearly every proportion we quote is a percentage — a part of 100. “Per cent” is Latin for “per hundred,” and the sign % is a worn-down way of writing “/100.” We reach for 100 as the whole because it is 10², the square of our counting base: any fraction becomes easy to grasp when scaled to a hundred. A battery is “100% charged,” a test is out of 100, a discount is a percentage off. The number is so bound up with wholeness that “giving 100 per cent” simply means holding nothing back.

A hundred built from smaller numbers Mathematics

100 is a small treasury of number-patterns. It is the sum of the first four cubes: 1³ + 2³ + 3³ + 4³ = 1 + 8 + 27 + 64 = 100 — which is also (1 + 2 + 3 + 4)², the square of their sum, a case of the same law that made 36 so tidy. It is the sum of the first nine primes (2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 = 100). And, like every square, it is a run of odd numbers: 1 + 3 + 5 + … + 19 = 100 = 10². Three different roads through the numbers all arrive at the round hundred.

The century — a hundred years, a hundred men Culture

100 is the human measure of a long time and a full company. A century is a hundred years, and one who reaches it is a centenarian; a centurion commanded a “century” of Roman soldiers. In cricket a batter's hundred runs is a century, the great personal landmark of an innings. From the Roman legion to the scoreboard, 100 is the round total that marks a genuine achievement — enough of anything to feel like a whole.

Dante's hundred cantos — a poem built to complete Literature

The Divine Comedy is exactly 100 cantos long — and not by accident. Dante gave each of its three realms 33 cantos, and added a single opening canto, so that 33 × 3 + 1 makes the perfect 100: 3 for the Trinity, 100 for wholeness. The greatest poem of the Middle Ages is a cathedral of number, and its outer wall is 100 — the round completeness toward which the whole journey, from Hell to the vision of God, is built.