Atlas / Physics
Domain · 6 threads · 30 fields
Physics
How motion, light and gravity were rebuilt around the speed of light, how heat became the statistics of atoms, and how energy turned out to come in lumps. How starlight revealed what stars are made of, how crystals explained metals and magnets, how a fogged photographic plate led to the nucleus, and what is still dark.
Thread 01 · 5 fields
The Relativity Thread
From Galileo's falling bodies and Maxwell's light to curved spacetime and the expanding universe. Newton's mechanics and Maxwell's electromagnetism both looked finished, yet they disagreed about one number, the speed of light. Settling that disagreement rebuilt space, time and gravity. The map still runs into fog where gravity meets the quantum, and where most of the universe turns out to be dark.
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- Charted: settled results
- Contested: sources disagree on priority or causation
- Unmapped: open problems
Fields in this thread
- 1600s – 1687Classical MechanicsWhat laws govern how things move, from a falling stone to an orbiting planet?One of the thread's roots
- 1820 – 1865ElectromagnetismHow are electricity, magnetism and light connected?One of the thread's roots
- 1905Special RelativityHow can light have the same speed for every observer, and what does that do to space and time?Branched from Classical Mechanics + Electromagnetism
- 1907 – 1915General RelativityWhat is gravity, if it is not a force?Branched from Special Relativity + Classical Mechanics
- 1917 – 1965Physical CosmologyWhat is the history and fate of the universe as a whole?Branched from General Relativity
Thread 02 · 5 fields
The Entropy Thread
From the steam engine to the statistics of atoms. Engineers trying to get more work out of coal found a law that no machine can break: heat flows downhill, and something they called entropy always grows. Explaining that law from the motion of invisible molecules forced physicists to accept that atoms are real, and to reason with probability instead of certainty. The same statistics then explained why water boils at a sharp temperature and why erasing information costs energy. The fog here is the arrow of time itself, and the physics of systems far from equilibrium, which includes every living thing.
Scroll the map sideways →
- Charted: settled results
- Contested: sources disagree on priority or causation
- Unmapped: open problems
Fields in this thread
- 1824 – 1906ThermodynamicsHow much work can be got out of heat, and why does heat only ever flow from hot to cold?Root of the thread
- 1738 – 1908Kinetic Theory of GasesCan pressure, temperature and heat be explained as the motion of countless invisible molecules?Branched from Thermodynamics + Classical Mechanics (The Relativity Thread)
- 1877 – 1926Statistical MechanicsHow do the laws of heat emerge from the statistics of vast numbers of particles?Branched from Kinetic Theory of Gases
- 1867 – 1999Non-Equilibrium PhysicsWhat laws govern systems that are driven, flowing and never at rest, and what does information cost?Branched from Statistical Mechanics
- 1869 – 1973Phase TransitionsWhy does matter change its form abruptly, and why do utterly different substances behave identically at the brink of change?Branched from Statistical Mechanics
Thread 03 · 5 fields
The Quantum Thread
From a stubborn problem about glowing ovens to the particles of the Standard Model. In 1900 the statistics of heat and the theory of light gave an answer that was plainly wrong, and the only fix was to suppose that energy comes in lumps. Twenty-five years of patched-together rules followed, until a new mechanics replaced certainty with probability. Joined to relativity, it became quantum field theory, the most precisely tested theory in science, and it catalogued the particles from which everything is built. Its strangest feature, entanglement, is now an engineering resource. The fog here is what a measurement really is, why the constants of nature have the values they do, and why the universe is made of matter at all.
Scroll the map sideways →
- Charted: settled results
- Contested: sources disagree on priority or causation
- Unmapped: open problems
Fields in this thread
- 1900 – 1924Old Quantum TheoryWhy does energy come in lumps, and how can light be both a wave and a stream of particles?Branched from Statistical Mechanics (The Entropy Thread) + Electromagnetism (The Relativity Thread)
- 1924 – 1932Quantum MechanicsWhat are the laws of motion for atoms and electrons, and what do they say about reality?Branched from Old Quantum Theory
- 1935 – 1996Quantum InformationWhat can be computed and communicated using superposition and entanglement that cannot be done classically?Branched from Quantum Mechanics
- 1927 – 1954Quantum Field TheoryHow can quantum mechanics be made consistent with relativity, when particles can be created and destroyed?Branched from Quantum Mechanics + Special Relativity (The Relativity Thread)
- 1930 – 1983Particle PhysicsWhat are the smallest building blocks of matter, and what forces act between them?Branched from Quantum Field Theory
Thread 04 · 5 fields
The Stars Thread
From dark lines in sunlight to planets around other suns. In 1835 a philosopher declared that the chemistry of the stars could never be known. Within thirty years spectroscopy was reading it from starlight, and the colours of stars became a code for their temperature, composition and motion. Physics then explained what makes stars shine and how they forge the elements, what is left when they die, and how they gather into galaxies around black holes. The fog here is the interior of neutron stars, the Sun's own composition, and whether any of the thousands of known planets carries life.
Scroll the map sideways →
- Charted: settled results
- Contested: sources disagree on priority or causation
- Unmapped: open problems
Fields in this thread
- 1814 – 1925Astronomical SpectroscopyWhat can the light of a star, spread into its colours, reveal about what the star is made of?Branched from Electromagnetism (The Relativity Thread) + Old Quantum Theory (The Quantum Thread)
- 1785 – 1927Galactic AstronomyWhat is the shape of the Milky Way, where are we in it, and what are the other galaxies?Branched from Astronomical Spectroscopy
- 1920 – 1957Stellar AstrophysicsWhat makes the stars shine, and where do the chemical elements come from?Branched from Astronomical Spectroscopy + Quantum Mechanics (The Quantum Thread)
- 1992 – 2009Exoplanetary ScienceAre there planets around other stars, what are they like, and could any of them host life?Branched from Astronomical Spectroscopy + Stellar Astrophysics
- 1915 – 1974Compact ObjectsWhat is left when a star dies, and how dense can matter become?Branched from Stellar Astrophysics + General Relativity (The Relativity Thread)
Thread 05 · 5 fields
The Matter Thread
From the shapes of crystals to phases defined by topology. For a century the regular faces of crystals hinted at an inner order no one could see, until in 1912 X-rays revealed the rows of atoms directly. Quantum mechanics then explained why electrons race through some of those lattices and are trapped in others, and control of the difference produced the transistor. Cooled far enough, some metals lose all resistance, iron's magnetism turned out to be an electric effect of the exclusion principle, and a strip of electrons in a magnetic field gave a resistance fixed by constants of nature, because its quantum states have a shape that cannot be smoothly undone. The fog here is how the copper oxides superconduct, whether anything can superconduct at room temperature, and whether the exotic particles of topological matter can be tamed for computing.
Scroll the map sideways →
- Charted: settled results
- Contested: sources disagree on priority or causation
- Unmapped: open problems
Fields in this thread
- 1784 – 1913CrystallographyHow are atoms arranged inside a solid, and how can we see an arrangement far too small for any microscope?Branched from Electromagnetism (The Relativity Thread)
- 1900 – 1947Solid-State PhysicsWhy do some solids carry electricity easily, others not at all, and a few only when coaxed?Branched from Quantum Mechanics (The Quantum Thread) + Crystallography
- 1911 – 1957SuperconductivityWhy do some materials lose all electrical resistance when cooled, and how warm can that state survive?Branched from Solid-State Physics + Phase Transitions (The Entropy Thread)
- 1980 – 2007Topological MatterCan the shape of electrons' quantum states, rather than the arrangement of their atoms, define a phase of matter?Branched from Solid-State Physics + Phase Transitions (The Entropy Thread)
- 1895 – 1949MagnetismWhy are a few materials, such as iron, permanently magnetic, and what holds their tiny atomic magnets in line?Branched from Solid-State Physics + Statistical Mechanics (The Entropy Thread)
Thread 06 · 5 fields
The Nuclear Thread
From a fogged photographic plate to the fuel of the stars. In 1896 Becquerel found that uranium gives off rays with no visible source of energy, and within a decade radioactivity had shown that atoms can change into other elements. Alpha particles revealed a tiny, dense nucleus, and precise weighing showed that it weighs less than its parts. The missing mass is energy on a scale no chemistry can match. Splitting heavy nuclei, discovered in 1938, released it, and within seven years it had run a reactor and destroyed two cities. Joining light nuclei, as the Sun does, has proved far harder to tame. The same steady decay became a clock that gave the Earth its age of 4.55 billion years. The fog here is how long a free neutron lives, where the chart of nuclei ends, and whether fusion will ever light a city.
Scroll the map sideways →
- Charted: settled results
- Contested: sources disagree on priority or causation
- Unmapped: open problems
Fields in this thread
- 1896 – 1911RadioactivityWhy do some atoms give off energy on their own, and what happens to them when they do?Branched from Electromagnetism (The Relativity Thread)
- 1904 – 1956Radiometric DatingHow can the steady decay of atoms tell us the age of rocks, bones and the Earth itself?Branched from Radioactivity
- 1913 – 1949Nuclear StructureWhat is the atomic nucleus made of, and what holds it together?Branched from Radioactivity + Quantum Mechanics (The Quantum Thread)
- 1934 – 1942Nuclear FissionHow can a nucleus be split, and how can splitting one make others split in turn?Branched from Nuclear Structure
- 1934 – 1969Fusion EnergyCan we release the energy that powers the stars in a controlled way on Earth?Branched from Nuclear Structure + Stellar Astrophysics (The Stars Thread)