Introduction
You live surrounded by walls, floors, appliances, and vehicles that seem completely ordinary. You flip a switch, flush a toilet, or walk across a wooden floor without wondering about the invisible forces holding your world together. You take these technological marvels for granted because they function reliably right beneath your senses.
Chris Woodford explores the hidden physics and chemistry embedded in everyday objects and spaces in Atoms Under the Floorboards. The central idea is that ordinary domestic environments are complex battlegrounds of thermodynamics, mechanics, and electromagnetism. You will discover how profound scientific laws govern everything from the roof over your head to the smartphone in your pocket.
The book takes you on a journey starting from structural foundations, moving through energy and heat, and ending with light, telecommunications, and advanced materials.
- How do towering skyscrapers stay upright against violent winds?
- Why does a refrigerator consume energy to remove heat?
- How does light travel across the globe to illuminate your screen?
1. Foundations and Forces
Buildings stand still because gravity pulls them down while the ground pushes up with equal force. This dynamic equilibrium keeps your home firmly planted instead of sinking into the dirt.
Buildings stand in static equilibrium through atomic repulsion and gravity, while tall skyscrapers sway flexibly in the wind.
A typical house with its contents weighs about 200 tonnes, generating a total force of 2 million newtons. The pressure exerted by this weight is roughly twice normal atmospheric pressure. Your human ankles withstand about half as much pressure as the load-bearing walls of a home.
Dynamic Equilibrium
Atoms prevent structural collapse because their negatively charged electron clouds repel each other when forced too close together. Materials compress slightly under weight until this atomic repulsion exactly balances the downward force. Skyscrapers even shrink microscopically when filled with people during the day.
- A 400-meter skyscraper shrinks by 1.5 mm when occupied by 50,000 people.
- Atoms use electron clouds surrounding the nucleus to resist compression.
- Buildings experience both compression and tension across their structural elements.
Skyscraper Wobble
Higher altitudes experience faster wind speeds that create a horizontal force on tall buildings. Instead of remaining completely rigid and snapping in a storm, skyscrapers act like pendulums and sway slowly. The maximum typical height-to-width ratio for skyscrapers is 7:1, though extreme designs push these boundaries.
The Highcliff residential block in Hong Kong reaches an astonishing height-to-width ratio of 20:1. The Twin Towers swayed by 1 meter at the top during heavy gales.
The Taipei 101 skyscraper uses a 660-tonne ball as a tuned mass damper near its top to resist wind wobbles. This heavy pendulum absorbs dangerous oscillations and reduces motion sickness for occupants through hydraulic rams.
2. Energy and Motion
Energy drives all mechanical actions, governed by conservation laws, thermal limits, and simple machine trade-offs.
Energy credits and debits always balance out.
Measuring Energy
Scientists measure energy in joules. One joule equals the energy required to lift a 100 g orange by one meter.
Boiling a mug of water takes 120,000 joules, equivalent to lifting 120,000 oranges a meter into the air.
Heavier bodies expend significantly more energy than lighter ones to move the same vertical distance against gravity.
Engineers Andy (95 kg) and Bob (65 kg) climb the stairs of the Empire State Building, 380 m high, requiring Andy to expend an extra 120 kilojoules.
Power measures the rate of using or making energy, expressed in watts as joules per second.
While energy measures the total work done, power dictates how fast that work is executed. Climbing the Empire State Building in half an hour requires an energy use rate of about 200 watts.
A 100-watt lamp uses 100 joules per second. A large wind turbine produces about 2 megawatts, and a large coal or nuclear power plant produces 2 gigawatts.
Simple Machines
Levers can be used to multiply either force or speed, but not both simultaneously.
A long lever multiplies the force applied at the cost of speed. Applying force closer to the pivot point can generate high speed at the working end, such as when swinging an axe. Archimedes stated he could lift the Earth with a lever 80 million trillion kilometers long.
Ramps and screws allow you to exert less force over a greater distance, keeping total energy expenditure constant.
Loading 200 kg of rubble into a truck 1 meter high requires 2,000 joules of energy. This can be delivered via a ramp at a lower wattage over a longer time.
Wool naturally generates heat when absorbing moisture due to chemical bonding, phase changes, and the prevention of evaporative cooling.
Merino wool is highly hygroscopic and exothermic when meeting water. Water molecules form hydrogen bonds with the wool cortex releasing stability energy, moisture condensation transfers latent heat back to the fabric, and because the wool absorbs sweat entirely rather than leaving it on the skin, it prevents cold evaporative cooling.
- Drape yesterday’s woollen jumper on a radiator first to dry it out completely before stepping out into damp air so it can soak up moisture and generate heat.
3. Thermodynamics and Heat
Thermodynamics dictates that heat flows naturally from hot to cold, making cooling far harder than heating and driving metabolism.
The laws of thermodynamics are absolute physical rules that govern all energy exchange. They explain why heat flows only from hot to cold and why perpetual motion is impossible. The First Law of Thermodynamics states that energy is conserved and cannot be created or destroyed. The Second Law states that heat always flows naturally from hot to cold, and the universe moves toward increasing disorder or maximum entropy. Absolute zero temperature sits at -273 °C (-459 °F), while the peak internal temperature reached inside the Large Hadron Collider is 5 trillion degrees.
Laws of Heat
Cooling a home or object is fundamentally harder and more complex than heating it. Cooling works against the universe's natural tendency toward chaos. While heating increases disorder and matches natural heat dissipation, cooling removes heat and introduces order. It requires external machinery and power inputs such as refrigerators and air conditioners to pump heat from cold to hot.
In the mid-19th century, Carlo Gatti shipped up to 400 tonnes of ice blocks at a time from Norway across the North Sea to supply sweltering Londoners before mechanical refrigeration. Making ice cream by removing heat from milky mush typically takes 3 hours.
Home Heating and Cooling
Ground-source heat pumps extract warmth from underground and transfer it into buildings. They achieve greater than 100 percent efficiency by moving existing heat rather than creating it. Because the earth a few metres underground is warmer than the winter air above, a heat pump uses a small amount of electricity to drive a fluid loop. This loop extracts geothermal warmth and deposits it indoors, making them more efficient than direct electric heating.
A heat pump matching four storage heaters pulls up the equivalent of 14 kilowatts of heat. The typical payback period for the installation cost of heat pumps spans 10 to 15 years.
Effective insulation dramatically reduces heat loss by slowing conduction, convection, and radiation. This allows advanced buildings to be heated with minimal energy. Traditional insulation traps air in materials like stone wool. High-tech solutions like aerogel or Passivhaus standards tightly control airflow and thermal bridging to slash heating costs by up to tenfold.
NASA aerogel expert Dr Peter Tsou noted that if a two- or three-bedroom house were insulated with aerogel, it could be heated entirely with a single candle, though the house would eventually become too hot. A typical family home built to the German Passivhaus Standard incurs an annual heating bill of just £25 (around $38). The Passivhaus approach achieves a 5 to 10 times reduction in home heating costs.
Human metabolism operates as a food-burning engine governed by thermodynamic laws. It converts chemical energy from food into mechanical work, heat, and body fat. The human body achieves a mechanical efficiency of 20 to 25 percent. The majority of digested energy maintains basal metabolic functions and body temperature rather than powering movement.
The brain represents 2 per cent of body weight, yet it consumes almost a fifth of resting energy. The basal metabolic rate (BMR) of a resting human burning about 80 joules per second is 80 watts.
4. Light and Telecommunications
Visible light sits at the center of the electromagnetic spectrum. All forms of light share the same underlying electromagnetic nature and speed, differing only in wavelength and energy carried. You encounter waves ranging from radio and microwaves to infrared, ultraviolet, X-rays, and gamma rays.
Electromagnetic waves and light enable instantaneous global communication and artificial illumination across vast frequency spectrums.
Light travels at 300,000 km per second. Typical light waves feature a wavelength of 550 nanometres.
Light is generated when atoms absorb energy. An electron moves to an outer shell when an atom receives energy from heat, electricity, or atomic collisions. Because this excited state is unstable, the atom drops back within a nanosecond, ejecting a photon of light in a process called spontaneous emission.
The Nature of Light
Sound travels at about 1,200 km/h, making long-distance real-time communication impossible. Electromagnetic radiation travels at the speed of light, shrinking the Earth to a pinpoint and enabling instantaneous data transmission across continents.
Laying an undersea cable cut transatlantic message times from 12 days to 16.5 hours. A beam of light makes the same journey in just two-hundredths of a second.
Radio and Satellites
Radio transmitters and receivers use antennas sized to match the wavelength of the electromagnetic waves they emit or capture. An antenna must be about half the wavelength of the waves it transmits or receives. Vibrating electric charges along a straight metal rod generate undulating electric and magnetic fields that ripple outwards at the speed of light.
Mobile phones operating on a 2 GHz frequency band use microwaves about 15 cm long, requiring an antenna the length of a little finger. FM transistor radios use longer wavelengths and pull-out telescopic antennas measuring 1 to 1.5 m.
Radio waves can bend around the curved Earth and travel long distances because they interact with the Earth's conductive ionosphere. Oliver Heaviside predicted that the ionosphere acts as a reflective mirror in the upper atmosphere, bouncing radio waves back down to the planet's surface at night when lower absorption layers recede. The ionosphere sits at a height of 60 to 500 km above the Earth.
Guglielmo Marconi fired radio waves 3,200 km from Cornwall to Newfoundland in 1901. This proved long-distance radio transmission is enabled by atmospheric reflection.
Communications satellites act as artificial space mirrors that reliably relay signals across the globe without relying on the variable ionosphere. Arthur C. Clarke proposed placing three stationary spacecraft in geostationary orbits 36,000 kilometres above the Earth. This theoretical idea was realized through early experimental satellites like the inflatable balloon Echo and later INTELSAT geostationary craft.
The United States launched Echo as the world's first communications satellite to bounce radio waves back to Earth. The craft was a giant inflatable Mylar plastic balloon 30 metres in diameter.
5. Materials and Structure
Everyday objects and spaces are shaped by profound physical, chemical, and thermodynamic laws operating right beneath your senses. Metals like iron can be made significantly stronger or rust-resistant by mixing in other elements that alter their atomic arrangement. Adding carbon to iron creates steel by filling gaps between larger iron atoms to prevent them from shuffling. Adding chromium creates stainless steel by forming a protective oxide coating.
Stainless steel cutlery resists corrosion even when exposed to salty food. Up to 90 per cent of stainless steel cutlery consists of iron.
Plastics survive in the environment for centuries because their giant chain-like polymer structures are highly resistant to degradation by natural elements and microbes.
Unlike paper or wood, plastics feature strong internal bonds and long chains that few bacteria have learned to digest, leading to long-term accumulation. Plastic refuse washes up on beaches and survives in the environment for up to 500 years.
Glass and Polymers
Glass is an amorphous solid or frozen liquid whose atoms are arranged in a random, ad-hoc structure rather than a neat crystalline grid. When sand is heated into a liquid and cooled quickly, atoms move apart and jiggle around, but they do not settle into a regular crystalline pattern. This random intermediate structure gives glass its unique properties, preventing atoms from easily rearranging to absorb energy.
On July 16, 1945, J. Robert Oppenheimer and his colleagues turned a 3/4-km wide circle of desert sand into radioactive green glass when testing the first atomic bomb in New Mexico.
Glass is transparent because its electrons are fully occupied holding its amorphous structure together and lack the low energy needed to capture visible light photons. Metals have free electrons that absorb incoming light photons and spew them back out, making them opaque or reflective. In glass, electrons require much more energy to become excited, allowing ordinary visible light photons to pass straight through without being noticed.
Materials subjected to repeated stress or pushed past their elastic limit undergo permanent plastic deformation, leading to structural fatigue and failure. When stretched or flexed beyond its elastic limit, a material no longer returns to its original shape. Repeated back-and-forth stress creates atomic-scale failures in crystalline or molecular structures that grow into fatal cracks, known as metal fatigue or material sag.
In the early 1950s, seven catastrophic crashes of de Havilland Comet commercial jet airliners were traced to metal fatigue and stress concentration around cabin windows at a cruising altitude of 10,000 m. Steel is 200,000 times less stretchy compared to rubber, while hydrogels can stretch 20 times their original length.
Adhesion and Friction
When two materials stick together, three distinct forces are actually at work: the glue must stick to the first surface, the other side of the glue must stick to the second surface, and the glue must also stick to itself.
If a glue fails, it is often because its internal cohesive forces are weaker than its adhesive forces. When you pull apart a jam sandwich, the jam splits because it cannot stick to itself with as much force as it sticks to the bread. Peeling wallpaper provides another clear example of this daily experience.
Glues bond materials together through four main processes:
- Physical: The glue seeps into gaps to make a mechanical lock.
- Chemical: The glue creates chemical bonds spanning the joint.
- Electrostatic: Atoms pull electrons to create tiny clinging forces.
- Diffusion: The glue and the material swap and mingle their molecules.
Cobblers use tough glue as an intermediary bridge to attach rubber soles to shoes.
10 Key Ideas
- Atoms prevent structural collapse because their negatively charged electron clouds repel each other when forced too close together.
- The Taipei 101 skyscraper uses a 660-tonne ball as a tuned mass damper near its top to resist wind wobbles.
- Wool naturally generates heat when absorbing moisture due to chemical bonding, phase changes, and the prevention of evaporative cooling.
- Cooling a home or object is fundamentally harder and more complex than heating it because cooling works against the universe's natural tendency toward chaos.
- Ground-source heat pumps extract warmth from underground and transfer it into buildings, achieving greater than 100 percent efficiency by moving existing heat rather than creating it.
- The human body achieves a mechanical efficiency of 20 to 25 percent, with the majority of digested energy maintaining basal metabolic functions and body temperature rather than powering movement.
- Electromagnetic radiation travels at the speed of light, shrinking the Earth to a pinpoint and enabling instantaneous data transmission across continents.
- Communications satellites act as artificial space mirrors that reliably relay signals across the globe without relying on the variable ionosphere.
- Plastics survive in the environment for centuries because their giant chain-like polymer structures are highly resistant to degradation by natural elements and microbes.
- When stretched or flexed beyond its elastic limit, a material undergoes permanent plastic deformation, where repeated back-and-forth stress creates atomic-scale failures leading to structural fatigue and failure.