After a
collapse of civilization, what knowledge would be most important to convey in order to quickly bring civilization back to its current level of development? Can that be conveyed in a short amount of written text and illustrations?
Single-Page Science
Scientific method - The universe operates in certain predicable ways, and some can be described as mathematical laws. The only reliable way to gain information about how the universe works is through empirical testing. Form a hypothesis, design an experiment to confirm or disprove that hypothesis, and publish the result.
Peer review of reports is important to ensure reliable methods were used. Over time, a consensus should emerge.
Physics
Atomic theory - Matter is composed of huge numbers of invisibly small particles known as atoms. Each atom is composed of
protons (positive electrical charge) and neutrons (neutral electrical charge) in the central nucleus, surrounded by
electrons (negative electrical charge, of negligible weight) which interact between atoms to make more complicated matter. Multiple atoms bound together form a
molecule.
Matter can exist in the
phases of solid (atoms/molecules in a fixed arrangement), liquid (atoms/molecules slipping past each other), gas (atoms/molecules bouncing around at high speed and widely spaced, filling their container), or plasma (a gas where electrons have been stripped off nuclei), depending on temperature and pressure.
The temperature, pressure, and volume of a gas are approximately related by the
ideal gas law.
Atomic nuclei can be combined (
atomic fusion) or split (
atomic fission) which can require or release extremely large amounts of energy and dangerous radiation (electromagnetic and high-speed particles). Some nuclei are unstable and undergo fission spontaneously (
radioactive decay).
Electric charge can be positive or negative. Like charges repel; opposite charges attract. Charge can be produced by rubbing certain materials together, such as amber, fabrics, fur, or hair, in dry air.
Electricity (including
lightning) is the flow of electric charge carried by moving electrons.
Magnetic fields are generated by certain materials like
iron, and the Earth has a natural one. Magnetic poles can be "north" (attracted to the Earth's northern magnetic pole, which emits a "south" field) or "south" (attracted to the Earth's southern magnetic pole, which emits a "north" field). Opposite poles attract, same poles repel.
Electricity and magnetism are two aspects of
electromagnetism. A changing magnetic field creates an electric field, and a changing electric field creates a magnetic field. The interactions are described by
Maxwell's equations.
Gravity is created by all matter and is always attractive.
The
weak interaction is responsible for radioactive decay. It can be described by
electroweak theory, which describes the weak interaction and electromagnetism as different aspects of the same force.
Light is a type of
electromagnetic radiation or wave. Some lower frequencies are useful for heating matter (
infrared,
microwaves) and communications (
radio waves). Some higher frequencies (
X-rays) have more energy and are useful for seeing inside objects and living things, but are dangerous and can cause
cancer or immediate death if over-exposed.
The matter of everyday objects at everyday speeds are quantified by
classical mechanics which assumes:
Conservation of matter - matter is neither created nor destroyed, except when it is converted to or from energy following the rule
E=mc2
The wave aspect is not apparent for everyday objects, but is important for atom-sized particles. The wave can be interpreted as the probability that the particle will be found in that location.
The particle aspect of light waves are called
photons, and these explain
black body radiation, the
photoelectric effect, and why the energy imparted to an atom depends on the frequency but not intensity of light.
The
speed of light in a
vacuum is constant no matter the velocity of the (non-rotating) observer, as are the laws of physics (
special relativity). To prove this, perform the
Michelson–Morley experiment. This is possible because time passes at a different rate for observers at different velocities, and it is not possible to have a velocity faster than the speed of light. The equations of
general relativity describe gravity as a phenomenon of unified
spacetime and it is possible to produce
gravity waves which are very difficult to detect. The difference between relativistic and classical equations of motion are important for large or fast-moving objects, and noticeably affects the orbit of the planet closest to the Sun (
perihelion precession of Mercury) and bending of light around large astronomical objects. General relativity has not been reconciled with quantum mechanics to produce a set of equations that accurately describe motion at all scales.
The Earth is approximately spherical, and its size can be calculated by observing stars from distant locations (
Spherical Earth). Everyday objects are pulled toward the center of the Earth due to the gravity produced by its large mass. Gravity holds the gases we breathe (the
atmosphere) around the Earth in a relatively thin layer compared to the diameter of the Earth. Beyond that is mostly
vacuum.
The
Sun is a ball of plasma about 109 times the diameter of the Earth. Under the extreme pressure caused by its own gravity, it produces enormous amounts of heat and light by the atomic fusion of
hydrogen ions (one proton) into
helium-4 ions (two protons, two neutrons). It is over 20,000 earth diameters or 8.3 light-minutes away. The Sun produces a
solar wind which can cause electromagnetic fields on Earth and lights the skies in the far north and south with mostly green
aurora.
The
fixed stars are similar to the Sun, but much farther away. The closest is 4.2 light-years. They are clumped by gravity into
star clusters and
galaxies. The Sun is one star in the disc-like
Milky Way Galaxy, which is seen edge-on from the Earth as a concentrated of band of stars in the night sky.
Slow-moving stars that move noticeably against the fixed stars over successive nights, are actually
planets which are spherical like the Earth, some smaller and rocky, some larger and made mostly of gas.
The planets, including the Earth, move around the Sun in
orbits that are approximately ellipses. Two planets are closer to the Sun than the Earth. There are also many small rocks orbiting the sun called
asteroids.
Fast-moving stars are either asteroids that have fallen into the atmosphere and burn up (called
meteors), or
artificial satellites launched into Earth orbit on
rockets for the purposes of over-the-horizon communication or Earth observation.
For unclear reasons, all the matter in the universe exploded from a single point 13.8 billions years ago (the
Big Bang). The echo of this explosion is observable as the
cosmic microwave background radiation. Space itself is expanding, causing galaxies to accelerate away from each other, observable as
red shift.
Chemistry
Benzene
Chemical elements are matter composed of a single type of atom. When arranged according to the number of protons, they form the
periodic table which shows a repeating pattern of properties caused by
electron shells filling up.
The structure of the DNA
double helix. The
atoms in the structure are colour-coded by
element and the detailed structures of two
base pairs are shown in the bottom right.
Science work in progress
BIOLOGY
Cell theory
Central dogma of molecular biology, Medelian inheritance