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The ideas the rest of science is built on, from atoms and evolution to relativity and the quantum world. Each note explains one idea, what the evidence for it is, and where it leads next.
20 notes from Graphite. Free to read, with no account. Nothing here is for sale.
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The note that answers the topic’s biggest question, then the two it leads to most directly.
Start here
Science is a way of building reliable knowledge by testing ideas against evidence. How the scientific method works, step by step, and why science keeps correcting itself.
Graphite6 min read
Then
Albert Einstein (1879–1955) was the physicist who showed that light comes in packets, that mass is energy, and that gravity is curved space and time. His life and ideas, without the equations.
Graphite7 min read
And then
The periodic table lists every known chemical element in order of atomic number, arranged so elements with similar behavior line up in columns. How to read it, and why it works.
Graphite6 min read
Every note
The three above, then the rest. Each answers one question and links to the notes it leads to.
Pi is the ratio of any circle's circumference to its diameter, about 3.14159. Why it never ends or repeats, how people from Archimedes to supercomputers have pinned it down, and where it appears.
Graphite6 min read
No single person invented zero. Babylonian and Maya scribes used it as a placeholder; Indian mathematicians, Brahmagupta in 628 above all, made it a number you can calculate with.
Graphite7 min read
The Fibonacci sequence is 0, 1, 1, 2, 3, 5, 8, 13…, where each number is the sum of the two before it. Where it came from, why it leads to the golden ratio, and where it really appears.
Graphite7 min read
Time zones divide the Earth into regions that share one clock time, set as an offset from UTC. They follow the Earth's turn of 15 degrees an hour, bent by history and law.
Graphite7 min read
Schrödinger's cat is a 1935 thought experiment about a cat in a box whose fate hangs on one atom. Schrödinger meant it as a criticism, to show how strange quantum theory gets at everyday scale.
Graphite7 min read
A tardigrade, or water bear, is an eight-legged animal about half a millimeter long. Dried out into a dormant tun, it survives cold, vacuum and radiation, but active ones die easily.
Graphite7 min read
The speed of light in a vacuum is exactly 299,792,458 meters per second, about 300,000 km a second. Relativity makes it the top speed for anything that carries mass, energy or information.
Graphite7 min read
Quantum mechanics is the physics of atoms, light and particles, where energy comes in steps and outcomes are probabilities. Its core ideas, worked through, and the everyday technology built on it.
Graphite7 min read
An asteroid about 10 km wide hit what is now Mexico 66 million years ago and killed the dinosaurs, except birds. The evidence, step by step, and the debate over India's volcanoes.
Graphite6 min read
A nuclear bomb releases energy from the nuclei of atoms, by splitting heavy ones (fission) or fusing light ones (fusion), millions of times more per kilogram than any chemical explosive.
Graphite7 min read
DNA is the molecule that stores the instructions for building and running living things, written in four chemical letters along a double helix. How it is read, copied and tested.
Graphite7 min read
Entropy measures how many ways the parts of a system can be arranged and still look the same from outside. It tends to grow, which is why heat flows, ice melts and time has a direction.
Graphite7 min read
Newton's three laws say that objects keep moving unless a force acts, that force equals mass times acceleration, and that every push gets an equal push back.
Graphite7 min read
Bacteria are living single cells that can grow and divide on their own. Viruses are far smaller packets of genes that can only copy themselves inside another cell.
Graphite6 min read
The theory of relativity is Einstein's account of space, time and gravity: time and length depend on motion, and gravity is the curving of spacetime by mass.
Graphite7 min read
Evolution works through variation, inheritance and unequal survival: traits that help living things leave more offspring grow more common over generations.
Graphite6 min read
The sky is blue because the molecules in air scatter short, blue wavelengths of sunlight far more than long, red ones, sending blue light at you from every direction.
Graphite6 min read
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