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Mechanics

The slope, and the two directions that make it easy
The hill that gives it back, and the forces that do not
Turning is an acceleration, and constant speed does not help
The period that depends on the swing, computed exactly
Collisions are easier than forces, and momentum is the reason
The same push, further out, and why that is a different quantity
The force that takes what it needs
Every minimum is a parabola
The forces that are not there
The point that keeps moving as if nothing had happened
The two pendulums that will not stop swapping
The axis that will not hold
The three ways of coming to rest
The chatter a stiffer holder removes
The energy that depends on the observer
The length nobody has to measure
The push that needs nothing to push against
The error that doubles on a schedule
The last curve to go
The pile that lands heavier than it weighs
The angle that drag moves
Least action, except that it is not least
The conservation law a symmetry hands over
The fold that has to be there
The curve that does not ask where it started
The force a coordinate cannot see
Everywhere a throw can reach
Held up by a force that averages to nothing
Slide or topple
The angle that throws furthest, and why nobody notices
The grip that is not a coefficient
The pendulum, and the small lie that makes it simple
The table statics cannot settle
The mass, and where it sits, which is what decides the race
The push that comes out sideways
The quantity that survives a change of shape
The top that nods before it settles
Five balls, and the law that does not choose
The part of the wrap that is actually gripping
The principle that fixes the energy instead of the clock
The map a dripping tap turns out to be
The oscillator that answers at three times the question
The grip that needs a little slipping
The axis a leak of energy chooses
The deflection that closes on itself
The ratio that decides whether the planet is turning
One curve answers every slope
The best throw is a tangency
The speed at which grip hands over to power
The calm that is the ghost of a cycle
The load nobody applied
A state no load could reach
The one number the tolerances cannot touch
The floor that does no work
The wall that moves while the ball is in flight
The throw most likely to go in
The action that knows where every path ends
The bounces that add up to a stop
The ellipse a pendulum turns by itself
The quarter cycle a turning point costs
The point that takes the blow without a jolt
The wave that can only travel west
The wrong orbit beside a right one
The spectrum that weighs a bond
The bounce an elastic plate cannot give back
The wobble that is slow because the Earth gives
The contact that slips before it slides
The molecule that lives outside its own well
The push that pays only for the hill
The compass that finds the axis the Earth turns about
The ball a turntable will not throw off
The ball thrown up that lands to the west
The third of itself a spring carries
The push a millimetre ahead of the axle
The raindrop that falls at a seventh of g
The jump that does not get higher with size
The spin that sorts by a difference of mass
The vibration that turns part of the way
The weight a frequency can find
The third law that falls out of a change of scale
The parabola that is the top of an ellipse
The spring that swings when it was only bounced
The swing that dies in a straight line
The governor that needed friction to work
The collisions that count the digits of π
The disk that spins faster as it stops
The spool that rolls towards the hand pulling it
The ladder that lets go of the wall
The spring whose bottom does not know it has been dropped
The rod that friction cannot decide about
The kick that does not change the beat
The stack that leans past its own table
The chimney that breaks a third of the way up
The crack at the end of a whip
The swing that turns a step at a time
The pendulum that must not grow when it warms
The egg that keeps turning after it is stopped
The friction an action can hold only by changing its clock
The loop that is not a circle
The toss that is random without chaos
The throw a spinning station bends
The bicycle that steers itself upright
The weights that stop a spinning satellite
The chain that climbs out of the jar

Waves

When two waves meet, they simply add
Only some notes fit, and that is where discreteness comes from
The note that changes on approach, and the two ways of getting it
The frequency that gets an answer, and the quarter cycle nobody mentions
A wave is a shape that travels, and nothing else does
The medium decides the speed, and the source only decides the note
Every front is a source
What happens where the medium changes
The equation that lets a shape travel
The drum that has no harmonics
The swing that is pumped, not pushed
The correction that took a century
The packet that will not keep its shape
The speed that carries no signal
The pipe that will not carry a low note
The gap a repeat opens
The channel with no walls
The mode that lives in the mistake
The distance that takes the treble out
The cone the source leaves behind
The taper that matches every note
The width that is a lifetime
The answer that cannot come first
The arrival that keeps arriving
How many ways there are to vibrate
The front that steepens until it cannot
The pulse two failures keep alive
The wave that comes from the rim
The wave a surface is enough to hold
The count that cannot be cheated
The shift a mirror gives twice
Swap the ends and nothing changes
How a wave thins out
The layer that makes a reflection vanish
The mass that makes another stand still
The packet that moves at another speed than its own crests
The spiral that says how much light arrives
What adding does to the energy
The resonance with a zero in it
The backward wave Huygens had to remove
The frequency a lattice cannot carry
The node that is not standing still
The mode that will not turn a corner
The dent that raises the note
Where the loudness goes
The steps in an absorption curve
The end that knows how the middle was cut
The mirror that works from every direction
The resonance that refuses to leak
The mismatch no network can remove
The fan of plane waves inside every beam
The one medium that was supposed to add exactly
Two tails that swap everything
The ripple that counts the neighbours
Below the gap, where there is nothing to absorb
The solitons a hump already contains
The coupler that does not care about the colour
The phases that turn a glow into pulses
The lattice no phase can bend
The wiggle faster than any wave in it
The absorber whose bandwidth is its thickness
The string whose end will not keep still
The field that turns with nothing turning
The layer too thin to see
The even wave train that cannot stay even
The clock that is pulled into step
The sandbars that reflect the sea
The loss that falls as the frequency rises
The pigment that absorbs less for being packed
The lever that lets air speak to water
The light that spreads in two beams
The mirror that sends a wave back to where it began
The packet that bends with nothing pushing it
The note a bottle sings whatever its shape
The Doppler shift with nothing coming closer
The wave that arrives first by going the long way
The depth an ultrasound image pays for its sharpness
The photograph that keeps the spectrum
The tone the whole Earth rings at
The tide a lake makes by itself
The wall that stops sound by its weight
The pile of glass that stops every colour
The speed below which nothing on water leaves a wake
The silence that fits in a tenth of a wavelength
The noise that helps a weak signal through
The shadow that shows the core is liquid
The tube that sings when heated low down
The chain that swings in Bessel's notes
The speeds a pulsed radar folds into one
The long pulse that arrives as a spike
The pattern two gratings make that neither contains
The ripples that answer at half the shaking
The wall made heavy only at one note
The noise that warns a tube is about to sing
The thunder that passes over the listener's head
The shaking a uniform Earth could not carry
The plate that carries two kinds of sound
The chirp a staircase sings back
The loudspeaker that goes round
The echo hidden in random noise
The fork inside a watch
The oven that cooks in spots
The waves that always arrive square to the beach

Optics

What a lens is doing, and why three rays are enough
The angle past which light cannot leave
The angle the rainbow has to be, and why nobody chose it
The mirror that cannot focus, and the shape that can
Where rays stop being enough, and a shadow acquires a bright centre
The path that does not change
How far apart two things have to be
Why two lamps never interfere
What a thousand slits buy that two cannot
The angle at which reflection picks a side
The ray that bends without a surface
The brightness no lens can increase
The rotation a return trip doubles
The grating that photographs itself
The image that is a diffraction pattern twice
Why a litre of water is not blue for the reason the sky is
The wavelength a fibre does not smear
The condition a lens must meet
The fringe that measures a star
The fringes below the rainbow
The grain that is in the light
The retarder with no crystal in it
The lens that is a set of rings
The correlation that survives what the phase does not
The law that only asks about one component
How far a wave can remember
The bend at the boundary, and what it is really about
The ring at twenty-two degrees
The path that takes the longest time
The crystal that answers twice
The direction of the shaking, and the filter that only asks about it
The phase that is only a shape
The reflection that happens where the glass is not
Two glasses that cancel a derivative
When the particle is the size of the wave
Why the sky is blue and the sunset is not, from one exponent
The cone a fibre will accept
The focus that is a slab, not a plane
The light with no direction of shaking
Everything a scatterer removes, from one direction
The surface that images one point exactly
The fringe and the spectrum are one measurement
The flat scene that comes back curved
The pattern the sky is written in
The angle that is two angles
The ray on the wrong side of the normal
The cone light has to find to get out
The delay that is a random variable
The cloud light has to walk through
The reflection that needs no surface
The invariant that is a count
The work a diluted beam will not do
The same cone, and a different arrival
The rings that belong to the edge
How accurate a mirror has to be
The crystal made of moments
The walk that interference can stop
The medium that images every point
The lens with no axis
The angle at which total reflection stops being total
The corner that sends light home
The colour fringe no aperture can close
The window a diamond is cut inside
The faint light a bright one makes measurable
The hole that makes the sharpest picture
The full moon that is too bright
The dispersion made of angles
The mirror that lights a tenth of a micrometre
The index that falls below one
The beams that add only if they differ
The sand that darkens when it is wet
The depth a broad spectrum can see
The stress that polarised light can see
The nebula no telescope can brighten
The four cosines at the edge of a photograph
The surface that cancels whatever skims it
The plane of focus a tilted lens tilts
The colour at which glass disappears
The rough surface that is a mirror at a glance
The dark lines a wave cannot avoid
The surface every ray is normal to
The drop that cannot hold the light it lets in
The half cycle a focus adds
The beam that focuses itself
The two mirrors that hold a beam
The lens with its glass taken out
The focus that is two lines
The spikes a bright star wears
The hooks that weigh an absorption line
The roof that splits a binocular's image
The twist that carries light round a corner
The light that comes back bluer when it is warm
The specimen that is invisible until its light is delayed
The beam that does not spread and the price it pays
How far the air lets a mountain be seen
The cell weighed by the light it delays
The delay a flat lens has no room for
The width a perfect laser still has
The grid that stops the light along its wires
The windscreen that feels the rain
The eye that loses its lens in water
The rings no ray can reach
The eye a fly cannot afford
The absorption measured with a stopwatch

Relativity

Now is a choice of slicing
Two axes, one speed, and a diagram that does the arguing
The length that depends on when, and is not really about length
Speeds that refuse to add, and the quantity that does
The quantity nobody argues about
Magnetism is electricity seen sideways
The pole that fits and does not fit
The invariant that survives a boost
The sky that crowds into a cone
The push that does not point where the body goes
The field nobody can transform away
The string that breaks between two rockets
The box of light that weighs something
The ring where the two beams disagree
The wall of silence behind a rocket that never stops
The two clocks that flew in opposite directions
The ship that never arrives at c
The temperature of an acceleration
The speed that cannot be measured one way
The motion that measures faster than light
The brightness that is not the same for everyone
The disc that cannot be spun
Everything from an exchange of pulses
The clock that does not feel the turn
The clock that has to slow, and why no clock can refuse
The collision that wastes most of the energy
Mass is a form of energy, which is not the same as a source of it
The clock that is wrong in two directions
The contraction no photograph shows
The mass that is missing
The turn that two pushes leave behind
Which came first, and who decides
The diagram a ruler cannot read
The centre that is not a place
The one quantity a boost leaves alone
The space that speeds live in
The longest way round is the shortest clock
The drag that was only an addition
The cone a decay cannot leave
The transformation that never mentions light
Six numbers, one object
Nothing is allowed to be rigid
The fuel a starship needs
What the light cones alone can decide
The five places infinity turns out to be
The slope a spin leaves in a spectrum
The plane in which three bodies are flat
The rocket that leaves its fuel at home
How big now is
The body that has no temperature when it moves
The count that no observer can disagree about
The bath that pushes back
The orbit that ages less than a throw
The column that is hotter at the bottom
The right angle a fast collision closes
The spring that becomes a light-clock
The clock that runs slow because it is warm
The charge that passes as a flash of light
The heat that turns into matter
The twin who never turns round
The beam that stops pushing itself apart
The wave an electron rides to a gigaelectronvolt
Charge and current are one thing
The river that sound cannot swim up
The contraction the forces work out for themselves
The heat that arrives before it could
The heat hidden in a Doppler shift
The light that pulls twice as hard as its mass
The binary star that would be seen twice
The sound speed a neutron star needs
The spin that runs ahead of its own motion
The magnet period that comes out as an X-ray
The neutrino energy an angle fixes
The gas law relativity leaves exact
The gamma ray its own kind cannot absorb
The speed that stops while the energy keeps coming
The turns a muon makes at any energy
The shift that survives at right angles
The twin who comes back younger
The rod that is level for only one observer
The rocket in which light travels on circles
The spot that outruns light and carries nothing
The wheel whose top cannot go twice as fast
The kick a fast particle can give an electron
The gyroscope a spinning Earth turns
The photon a fast electron throws back
The light that moves an electron and pays it nothing
The lever that is twisted and does not turn
The now a travelling twin can measure
The light that takes back an electron's energy
The angle a collider counts in logarithms
The satellites launched into the wrong orbit
The temperature a gas takes from the light around it
The mass weighed without one of its pieces
The throw a uniform field bends into a chain
The orbit that opens when E reaches cB
The universe one explosion makes in empty space
The wave a row of moving clocks leaves on an instant
The parabola that decides which way a nucleus decays
The energy above which faster arrives later
The test of mass and energy that needs a ruler
The flat spectrum a fast pion must paint
The partner that sets the price of a pair

Thermodynamics

The speeds in a still room
Entropy is a count, and the arrow of time is arithmetic
The ceiling on every engine, set before it was designed
The equation that only runs forwards, and the walk underneath it
How far a molecule gets
The entropy that lives on a surface
Half a kT for every way of moving
The exponential that decides everything
What a system actually minimises
The viscosity that does not care how much gas there is
Why heating a perfect spring changes nothing
The point at which the two become one
The bit that has to be paid for
The glow that says nothing about the surface
The share that is not half a kT
The staircase that never reaches the floor
The entropy that is still there at zero
The gas that leaves is not the gas inside
The barrier a new phase has to climb
Hotter than any temperature there is
The gas that cools by being let go
The gas that nobody counted
The second experiment that cannot disagree
The summer that reaches the cellar in December
Why the triple point is a point
A boiling point is a pressure, not a temperature
Pressure is a rate of arrival, and the gas law falls out of counting
The jiggle that proved atoms
The transition with nothing to order
The walk that comes home
The engine that has to finish
Mixing what is already mixed
The engine that pays back more than it takes
The heat that changes no temperature, and where it actually goes
The part of the curve no fluid follows
Why the air thins with height, and why that is the same law as the speeds
The temperature a molecule does not have
The melting curve that leans the wrong way
The gradient that drives the other thing
The second law, with a probability attached
The first correction to the gas law
The engine a fluctuation cannot run
The energy that refuses to be shared
The height a planet is seen from
The entropy that depends on how fast it was cooled
A law about spectra, not about heat
The temperature an engine really takes its heat at
The work left in two buckets of water
The count that decides which entropy is right
The gas that flows towards more of itself
The condition three modes never meet
Half a kT in a piece of wire
Weighing what cannot be put on a scale
A fridge with no work going into it
An engine with one number in it
The reaction that cannot go all the way
The glow that carries a voltage
The site that fills like an electron level
The product doping cannot move
The voltage that is a chemical potential
The precision a clock pays for in heat
The electron that leaves because there is room
The melting curve that has to arrive flat
The speed limit that does not care how big the molecules are
The noise a high Q moves out of the way
The pressure that ionises
The protons a star cannot afford
The two laws absolute zero will not allow
The diffusion that slows the longer it is watched
The melting line that turns round
The boiling curve that turns back
The hotter start that cools first
The ice that grows more slowly the thicker it gets
The gas of sound that carries a diamond's heat
The degree a spoonful of solute buys
The ice that grows by stealing from the droplets
The note too high for thin air
The frost that lifts by drinking
The puddle that could dry in a second
The entropy every liquid gains on boiling
The cluster that grows where the walkers arrive
The heat capacity that goes up and comes down
The metal that feels colder than the wood
The cold reservoir overhead
The supercooled water that only partly freezes
The insulation that makes a wire lose more heat
The thin foils that stop radiant heat
The heap that sets itself alight
The ball that weighs how a gas stores heat
The squeeze a petrol engine is not allowed
The ring that forgets and then remembers
The salt that dissolves in the air's own water
The rings a reaction lays down in a gel
The column that boils from the middle
The note that fixed the kelvin
The engine that expands further than it compresses
The geyser that remembers one eruption
The attraction that is the small ones' room
The mixture that stays mixed at absolute zero
The markers that move because atoms are unequal
The cylinder that must not be cooled
The pipe that carries heat as vapour
The age a cooling Earth gives

Electromagnetism

The shape decides the falloff, and the force law never changes
The inside of a conductor, where the field is exactly nothing
The field that makes the other, and only while it is changing
The term that made light
Where the energy of a field actually is
The charge that has to be somewhere else
The magnet that has to fight its own field
The field that points where the charge is now
The angular momentum that is in nothing at all
The constant that depends on how fast it is asked
The field outside the solenoid, which is not zero
The potentials that are not unique
The law that is always true and rarely useful
A refraction with no wave in it
The two in the flux quantum
The two equations that are not laws of motion
The pressure a charge puts on its own metal
Counting what comes out, and never looking inside
Field lines are a choice, not a discovery
Nothing can be held still by a static field
One number for every point, and nothing at all is lost
The attraction that needs no charge
The coupling that is the same both ways
The field before the lines were drawn on it
The field that wraps a current
The field the matter takes away
The field with no ends, and the force that does no work
The force that does no work
The force that lives where the model is not
The loop that behaves like a needle
The magnetism classical physics forbids
How much charge a shape will hold, before anything is charged
The magnet that falls slowly
The rule that is two laws wearing one coat
The circuit that fights its own change
The resistance that is a length
The symmetry one missing charge would complete
Two lengths, and which one is longer
The momentum of something that is not moving
The curve that is really a staircase
The force read off a surface that touches nothing
The drift that does not care what the charge is
The distance where a field changes its mind
When the source is not heard all at once
The solution that is thrown away
The field that is pushed out
The pull that grows on the way down
The voltage that is a frequency
The potential is where the wanderers stop
What holds a magnet together is not magnetism
The first length that belongs to the substance
Nothing keeps a magnetisation for ever
The field that points against the magnet it is in
A potential that does not come back to itself
The field outside that cannot find the core
The current no particle carries
The circuit that forgets its charge
The force whose sign a frequency chooses
The momentum light carries into glass
The mass a charge's field gets wrong by a third
The shape that takes five numbers
The number of dimensions a planet can orbit in
The field that keeps Greenwich time
The liquid a field turns solid
The drag that falls as the magnet speeds up
How far a field gets into metal
The attraction that weakens when light is too slow
The zeros a handful of charges can make
The handedness a mirror cannot keep
The force between pieces of a current
The sheet resistance that forgets the shape
The field a spinning superconductor makes of itself
The mass that would make Gauss's law leak
The force that forgets Planck's constant
The current that squeezes what carries it
The voltage that bends an electron like glass
The coupling a resonance rescues
The push at the end of a pair of rails
The spark that needs room to start
The window a spinning magnet floats in
The field a ring of wires lets through
The field a superconductor keeps after all
The field a changing field does not make
The two coils one radius apart
The water drops that charge themselves to a spark
The ring that jumps because its current is late
The current a superconductor stops with its own field
The field at which no electron reaches the anode
The island that takes electrons one at a time
The magnet that reverses where its crystal is weakest
The magnets that put their whole field on one side
The half a wire always takes
The glow a thin wire wears before it sparks
The atom whose nucleus is a reflection
The static field a metal may or may not reflect
The path a charge takes is not its field line
The stripes a superconductor makes of a field
The voltage a moving magnet adds to an insulator
The imbalance of charge that would outweigh gravity
The charge that follows no local rule
The hum at twice the mains
The pan a better conductor will not heat
Two dipoles that agree everywhere but inside
The current a vacuum will not carry

Quantum

The curve that would not come down
Light arrives in lumps, and brightness only changes how many
A photon with a momentum, and a collision that proves it
Everything has a wavelength, and almost nothing shows it
The box that allows only some energies
The spectrum is a subtraction, not a list of values
Where the electron probably is
Sharpness has to be paid for
The wall that is not quite a wall
The answer that was not there before
No two in the same state, and why matter has volume
What happens when the wells get close
A nucleus with no clock
Where the quantum picture hands back the old one
The correlation no instructions can produce
A wall that a factor of two makes impassable
The angular momentum that is not a rotation
The measurement that never touched it
The disagreement that one run settles
The line that is really two
The exponential that is only true in the middle
Four states, and one of them is odd
The order the shells fill
Where the interference goes
The experiment a wave cannot pass
The crossing that never happens
The force with no force in it
The last atom does all the seeing
The state that cannot be copied
The average that obeys Newton
Two walls that let more through than one
One level, and the field that bends the bands
One arrival at a time, and the pattern still appears
The liquid that will not slow down
The mass a curve decides
The motion that cannot be stopped
The pressure that is not a temperature
The questions that can be asked together
The phase a magnet leaves on a path it never touched
The state that swings like a pendulum
How long the crossing takes
What two have they cannot give a third
Why an atom is the size it is
The turn that has to be made twice
The energy that did not all arrive
The chain that runs at its slowest member's rate
The half-life that chemistry can change
The return a classical cloud never makes
The probability that goes below zero
The field an atom calls strong
The fastest a state can stop being itself
A link between two that never met
The corner of Hilbert space that is ever visited
Two states where the counting says three
The experiment that defines spin and cannot be done on it
The outcomes identical photons refuse
The noise pushed below the floor
The fall that leaves the mass in the phase
The metal that is yellow because it is heavy
The speed below which nothing can be made
The line that takes eleven million years
The atom the size of a bacterium
The spin a photon has to carry away
The circuit that goes through a wall
The collisions the exclusion principle forbids
The spectrum that is a thermometer at every height
The barrier the metal cannot choose
The angle the uncertainty principle cannot be written for
The value a gentle measurement returns
The label three identical quarks forced
The ion that exists because its electrons keep apart
The grating made of light
The heat that crosses a gap too narrow for light
The light a full sea will not scatter
The bounce that comes in fixed heights
The image made of frequencies
The clock read by counting atoms
The electrons a field pulls from cold metal
The film whose thinnest point sets the flow
The lines a warm vapour hides
The qubit that carries two bits
The wait that sets the precision
The hydrogen atom inside a crystal
The atom with no nucleus
The electrons that pay in fixed amounts
The X-ray line that counts the protons
The resistance counted in whole numbers
The condensate a trap makes
The noise every amplifier must add
The flicker that is half wave and half particle
The scattering quantum mechanics returns unchanged
The nucleus that would make positrons from nothing
The atom a light wave opens like a wall
The echo that gives back everything but the wandering
The atoms that measure better together
The entangled pair a list of answers can imitate
The molecule that interferes until it glows
The rod that turns when its magnetism flips
The sharpness a variance cannot see
The heating a quantum rotor refuses
The cloud that stops shrinking
The push that makes an electron swing
The lifetime that depends on where the mirror is
The third process equilibrium demands

Fluids

The pressure that only knows depth
The weight of the water that is not there
How high water will climb
The angle a liquid makes with what it sits on
The surface a spin decides
The block the water does not lift
The silo that does not weigh what it holds
The pressure that comes from counting
The column that is pulled, not pushed
The layer a parcel cannot leave
The wave that picks an angle
The angle that does not know the size of the heap
What it costs to take the salt out
The angles a film has no choice about
The big one comes to the top
The skin that is not a skin
Force multiplied, and nothing gained
Momentum going sideways
The fluid that answers back
The fountain a lamp can drive
The fourth power in a pipe
The heap that becomes a solid
The heat that arrives as a wave
The liquid that climbs the rod
The liquid that remembers
The paste that holds up its own hill
The small bubble blows up the big one
The speed that depends on the length
The thickness that goes both ways
The thread that cannot stay a thread
The whirlpool that comes in one size
Why a ship comes back upright
The depth past which it must sink
The height a siphon cannot pass
The ring the drop leaves behind
The surface that pulls toward the stronger side
The shear that only reaches so far
The push that has no direction
The hourglass that keeps time
The membrane that almost holds
The corner a liquid never stops climbing
The swelling a membrane cannot stop
The film that goes black before it bursts
The pile that is never finished settling
The wave that is required to stand still
The reflection that changes the wavelength
The pore that fills from dry air
The angle a voltage can set
The stretch a chain cannot outrun
The counterions that never leave the chain
The latitude past which a tide cannot split
The body that displaces two things
The drift a sound leaves behind
The oil that is a glass for a quarter of a millisecond
Whether a fluid can be made arbitrarily thin
The wave that holds a ship back
The like charges that pull together
The balloon that leans the wrong way
The gas that cools itself into clumps
The sea that stands lower because water gives
The pore that lifts highest fills slowest
The salt that sinks through a stable sea
The drag a distant wall decides
The sand that chooses a side
The suspension that seizes when pushed hard
The water that warms on the way down
The pressure that stops counting molecules
The walls a rinse pulls together
The paste that forgets it was stirred
The viscosity that belongs to the tube
The log that floats on its corner
The mixture heavier than either water
The cereal that gathers at the edge of the bowl
The balloon that floats at a density
The rise a joule of heat buys
The cell that bursts by geometry
The cloud that cools more slowly than the air
The sound sand carries faster the deeper it goes
The water the dent displaces
The bubble that grows by counting its sides
The tension that vanishes where the phases meet
The rod that tumbles for ever in a stream
The drop that runs to the narrow end
The waterfall at every river mouth
The pond that is hottest at the bottom
The floating ice that still raises the sea
The wet plates that hold on when pulled
The floodgate that opens at a chosen depth
The sand that lets a body in and will not let it out
The sand whose friction depends on how fast it flows
The bottle that pours at one rate however full it is
The grounding line with nowhere to stop
The outlet that jams by chance
The drop that takes a decade
The vessel whose level falls evenly
The building that breathes through its doors
The surface whose thickness depends on the view
The plume that stops below the surface
The balloon a cold morning lifts
The drop that will not merge
The stem that stands by pressure
The sandcastle a spoonful of water holds
The lake that holds its gas until it does not

Astrophysics

The floor that cannot be told from gravity
The clock that runs slow lower down
Light has a pressure
The field that cannot get out
The size at which a body becomes round
A charge that turns must glow
Where every model runs out at once
The orbit that cannot be made smaller
The orbit that has to shrink
The ball of gas that heats up as it cools
The lens with no focal length
The knot the field cannot untie
The parallelogram that will not close
The force a charge exerts on itself
The mass no cold matter can hold up
The brightness a mass cannot exceed
The disturbance that grows instead of travelling
The distance that forgets the moon
The circle light cannot leave
The wall a plasma builds against itself
The light that pulls rather than pushes
The frequency below which nothing gets in
The light that takes a hundred thousand years to leave
The long-range force that does not reach
The wave that dies with nothing to rub against
The whistle that arrives sorted
Two clocks that disagree about the fall
How far a neutrino gets
The bend Newton got half right
The delay that is not a bend
The horizon that nothing marks
The orbit that does not come back to itself
The size the light cannot blow away
The surface that only lets things in
The term free fall cannot remove
The wave that stretches one way and squeezes the other
The arrow that says which way the orbit points
What the instrument actually hears
The hole that outlives everything and then does not
Whether a charge on a table glows
The length no experiment can resolve
The area that is not allowed to shrink
The clock that measures a height
The fall that does not depend on what is falling
The same force whichever way the surface faces
The wave that does not know what the gas is made of
The limit that belonged to a simpler atom
The friction made of light
The bill that arrives when the pushing stops
The binding energy that has to fall too
The bias no battery supplies
The estimate that misses by a hundred and twenty
The scale that may not be where it looks
A few cycles that are only mass and spin
The ring that does not come back
The twist that outlives the turbulence
The clocks that must all slow together
The half of the bend a slow body never feels
The orbit special relativity cannot close
The cross-section that forgets the colour
The radiation a difference in falling would make
The flash a circling charge sends once a turn
The hilltop that holds the Trojans
The moon kept molten by its neighbours
The fifth image a galaxy hides
The bias a waveform can choose
The photons that raced for seven billion years
The mountain a spinning star is allowed
The radius a mass adds that no circumference shows
The pull that has to equal the pull back
The pressure that weighs down what it holds up
The target that grows as the traveller slows
The wobble that radiating makes larger
Why the glow of a fast charge is blue
The frequency the sky returns only at a slant
The light a charge makes by changing medium
The antiatom that had to be weighed anyway
The circling that comes in quanta
The redshift that weighs a dead star
The clock that cannot be both light and good
The four shapes a wave of gravity leaves out
The field no symmetric flow can keep
The star whose far side can be seen
The gas a hole catches from far away
The velocity that always lies on a circle
The spinning fluid that becomes a cigar
The sound a plasma carries on its electrons' heat
The rainbow a passing electron leaves on a grating
The light that climbs out of a cluster of galaxies
The atoms the light stops touching
The radio that only heavier electrons can make
The two beams that unravel each other
The dynamo that reverses with nothing pushing it
The light that makes a cold cloud repel itself
The mirror held on a spring of light
The lens a long wave walks round
The nineteen decades a slow coupling buys
The bar a wave of gravity barely touches
The dust a plasma freezes into a crystal
The redshift the Sun's boiling hides
The bend a moving planet gives
The product a fusion plasma has to beat
The twist a bottle of plasma has to have
The fuel held together only by its inertia

Illustrated Physics

An illustrated collection of essays about the physics that is best understood by looking at it — every figure generated from the equations it describes.

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Themes

What stays the same
The same equation again
Approximations that lie
Fields, not forces
The arrow of time

Every figure here is drawn from scratch, in code, and rendered as SVG at build time.