Book summary “How Long is Now?”: summary

Introduction

You often wonder about the strange physics of everyday objects and the bizarre behaviors of living creatures. Science answers these questions, but the explanations remain scattered across complex academic journals and specialized textbooks. You miss out on the sheer joy of discovering how the universe actually operates in its most mundane and magnificent details.

Curiosity drives science forward by applying rigorous investigation to everything from everyday domestic mysteries to the outer limits of physics and biology.

This book collects the best inquiries from inquisitive minds to demystify the natural world. The journey begins with the strange evolutionary traits found in the animal kingdom and human biology. You then move into domestic mysteries and everyday physics, before expanding your view to planetary mechanics and space. Finally, you explore the engineering marvels behind modern technology and transport.

Consider these questions as you read:

• Why do cats always land on their feet?
• How does time change at high speeds?
• What keeps airplanes in the sky?

1. Animal Kingdom and Human Biology

Evolutionary pressures shape the bizarre physical adaptations, senses, and survival strategies of animals and humans alike.

Animal Adaptations

Zebra stripes primarily serve to repel biting horseflies rather than providing thermal regulation or camouflage. Susanne Akesson and her team discovered that uniformly colored animals reflect linearly polarised light, which attracts horseflies. Zebra stripes disrupt this polarized light reflection, preventing insects from targeting them.

Researchers tested models of zebras, horses, and asses covered in glue in a field, and found that the striped zebra models attracted the fewest flies.

Aquatic mammals and fish overcome the loss of a refractive cornea underwater by using spherical, marble-shaped lenses. In air, the curved cornea refracts light significantly, but underwater its refractive index is too close to water, causing severe blurriness in human eyes. Aquatic species compensate with powerful spherical lenses capable of handling the focus.

Recreating dinosaurs from ancient DNA extracted from biting insects preserved in amber is biologically impossible. DNA degrades with a half-life of approximately 500 years, becoming completely uninformative after about 1.5 million years, long before the 64 million years or more since dinosaurs went extinct. Alena Pance noted that while the Jurassic Park movies feature dinosaur recreation from fossilized mosquito blood, real fossilization and digestion would destroy any intact genetic material.

Human Body Limits

A single central heart outperforms a distributed network of smaller pumps in power-to-weight ratio for large animals. Bigger creatures require a dense surface for gas exchange, a vascular network, and a high-pressure pump. While distributed hearts sound appealing, coordinating them and managing valve functions during failure would introduce massive complexity compared to a single heartbeat.

Subconscious body perception, known as proprioception, can lag behind physical changes caused by growth, ageing, or pregnancy. Proprioception relies on the vestibular system in the inner ear and nerves in muscles and joints. Because it is learned through experience, sudden changes in body structure or long-standing habits can create conflicts between the brain's internal map and physical reality.

A pregnant woman noted that even while feeling kicks and seeing her large belly, her closed-eyes internal sense still felt her abdomen was flat and in its previous place. You can manage these shifts by using specific physical exercises:

• Practice movement and awareness exercises like t’ai chi or yoga to improve proprioception and reduce the risk of falls.

Tooth enamel cannot regenerate once formed, making structural tooth preservation dependent on natural resting gaps and soft diets. Enamel formation ceases when a tooth erupts because the ameloblast cells are destroyed. Loss occurs via attrition, abrasion, and erosion. However, minimal wear occurs during normal life because a resting gap exists between the jaws, and food reduces tooth-to-tooth contact during chewing. The outer enamel layer consists of 96 per cent hydroxyapatite crystals by weight, and the jaw leaves a freeway space gap of 2 to 3 millimetres when resting. You can protect your teeth with a simple clinical step:

• Apply surface fluoride to strengthen enamel and make it more resistant to wear.

Humans primarily depend on sunlight exposure to ultraviolet B radiation to synthesize vitamin D, a process blocked by ordinary window glass. Only a narrow band of ultraviolet B light between 290 and 320 nanometres enables skin synthesis of vitamin D, which cannot pass through ordinary glass. Latitude, season, and skin pigmentation heavily dictate synthesis rates. Adults who cannot get enough sunlight face a recommended daily UK and US guideline of 10 micrograms, while the average poor daily dietary intake of vitamin D in the UK sits at 2 to 3.5 micrograms. You can check your status and get enough nutrient intake by following specific guidelines:

• Check your shadow on the ground; if it is longer than you are tall, your body cannot synthesize vitamin D from sunlight.
• Expose your face to the sun for about twenty to thirty minutes as a young fair-skinned adult to synthesize enough vitamin D.

2. Domestic Mysteries and Everyday Physics

Familiar household phenomena operate through precise chemical reactions and mechanical laws. You encounter these daily forces in the kitchen and across the physical world.

Adding damp terracotta to different types of sugar yields opposite results because brown sugar relies on moisture to remain soft, whereas icing sugar contains anti-caking agents that trigger crystallization when moistened.

Brown sugar contains up to 10 per cent molasses whose hygroscopic properties keep it moist. Highly refined granulated sugars contain around 0.05 per cent water content. Icing sugar uses agents like calcium phosphate that cause fine particles to clump and crystallize when damp.

Microwaves can superheat liquids above their boiling point without visible boiling if nucleation sites are absent. This leads to violent bubbling when disturbed by cold water or dissolved air. You handle water heated in dishwashers at 70° to 75°C or hand-wash water at 40° to 45°C.

Reheating cooked rice improperly can lead to food poisoning due to heat-resistant bacterial spores. Bacillus cereus spores survive the boiling process and produce toxins upon cooling unless you manage temperatures carefully.

You can prevent illness by following specific kitchen safety rules:

• Cook your rice until it is hot and eat it soon.
• Keep the rice too hot to touch at 60°C or higher, or cool it to fridge temperature at about 4°C or lower as fast as possible.

Atomic and Material Bonds

Post-it notes stick using a pressure-sensitive adhesive that balances flow and resistance. The adhesive flows just enough to fill tiny surface crevices while maintaining enough resistance to stay put.

On a molecular level, van der Waals' forces created by temporary electron imbalances that form tiny dipoles contribute most to bond strength.

Spencer Silver discovered the incredibly weak adhesive by accident in 1968 while trying to produce an exceptionally strong one. The polymer structure links large lumps together like a tennis net with sticky balls. Cohesive forces exceed adhesive ones so peeling pulls only one ball at a time like a zipper.

Polarising filters reduce reflections from glass and water at Brewster's angle, but fail to do so on metals. Transparent materials like water, glass, and transparent plastics have a refractive index range from 1.33 to 1.6, giving a Brewster's angle range of 50 to 60 degrees. Metals have a complex refractive index with a massive imaginary absorption part, pushing Brewster's angle up to around 85 degrees and keeping reflectivity high with a minimum parallel polarisation reflection dip of 74 per cent.

Photographers notice that light reflecting off water, foliage, and glass is effectively modified by polarising filters, whereas light reflecting off metal surfaces is unaffected.

Vortex shedding occurs when fluid flows past a vertical obstruction, creating alternating pressure changes that can induce destructive structural vibrations. As air or water passes a vertical structure like a lamp post or chimney, vortices form and break away alternately on downstream sides at regular intervals.

A 30-metre steel incinerator chimney at Saltend swayed alarmingly in 35-kilometre-per-hour winds until the National Physical Laboratory solved it by fitting helical strakes. Installing these helical fins disrupts the flow by shedding eddies at different times along the height.

Iron filings form distinct visible lines in a magnetic field because they become temporary mini-magnets that mutually repel. While a magnetic field is continuous and three-dimensional, scattering iron filings creates temporary mini-magnets whose induced fields oppose the main magnet.

You can observe this force using simple workshop items:

• Attach two 5-centimetre nails pointy ends up to the bottom of a bar magnet held vertically.
• Gently move the magnet to try to get the nails to touch.

Vibrations from transport or motors can create standing capillary wave patterns in cups of liquid known as Faraday waves. Ferry passengers observe a fixed interference pattern forming quickly on the surface of a cup of coffee due to the ship's engine vibrations. Michael Faraday first described Faraday waves in 1831.

You can replicate the effect with a few small parts:

• Find a variable DC power supply, a toy motor, and a wheel that fits the motor's axle.
• Glue a weight such as a small nut to the wheel so that it spins off-balance.
• Tape the motor to the side of the cup to produce the standing wave patterns.

3. The World at Large and Space

Planetary mechanics, atmospheric conditions, and cosmic forces govern our physical environment on Earth and beyond.

You inhabit a world shaped by extreme pressures and vast spatial dimensions. Gravity pulls matter together, but material composition sets strict limits on celestial shapes.

Rocky objects over 700 kilometres in diameter develop an orb-like shape. Bodies made of water ice become spherical at around 320 kilometres due to being less rigid.

Ceres, the largest object in the asteroid belt, has a diameter of approximately 945 kilometres and is nearly spherical. Mars features Olympus Mons, which is more than twice the height of Everest.

Earth and Atmosphere

Ultraviolet radiation and sunburn risks can be paradoxically enhanced by broken or hazy clouds through reflection and refraction, rather than being blocked entirely on dull days. High-altitude cirrus clouds refract UV light, which is then reflected by low-altitude cumulus clouds and amplified by ground-level reflectors like sand, snow, and sea.

A researcher experienced severe sunburn on a beach in Wales on a dull misty day, and another suffered sunburn at Jungfraujoch in the Swiss Alps from light reflected off snow.

Flat map projections inherently distort geographical reality because a sphere's surface cannot be flattened without sacrificing area, distance, or direction. On a standard Mercator map, Africa looks smaller than Greenland when it is actually fourteen times larger, and India looks tiny.

High pressure at Earth's center exists despite gravitational forces canceling out at the exact core, because pressure accumulates from the weight of thousands of kilometers of overlying material. The pressure at the bottom of the Mariana Trench exceeds one thousand atmospheres, while at Earth's core it reaches 3.6 million atmospheres.

Earth's magnetic poles undergo periodic reversals driven by convective currents in the liquid outer core, a process taking thousands of years without the magnetic field dropping to zero. David Gubbins analyzed ships' logs kept by early ocean-going explorers recording magnetic declination, showing Earth's field is about 10 per cent weaker than in 1860.

Celestial Mechanics

Exoplanets can be detected indirectly by measuring the slight dimming of their host star when the planet passes in front of it. Transit photometry and the radial velocity method account for approximately 90 per cent of nearly 2,000 discovered exoplanets by observing stellar brightness dips or Doppler shifts.

4. Technology and Transport

Modern engineering solves complex problems of transport, communication, and power generation through applied physics.

Transport and Aviation

High and low pressure fields meet at wing tips, creating a tip vortex that drags airflow downwards and generates induced drag. Winglets act as barriers to minimize this effect, though they add mass and friction. Consequently, very long and thin blades, such as those on wind turbines, do not benefit from winglets because the structural disadvantage outweighs drag reduction.

While modern airliners can cruise and land using instruments, forward-facing windows remain vital for manual takeoffs, taxiing, and collision avoidance. Takeoffs and taxiing are conducted visually to monitor track and counteract lateral engine-failure swings. External vision also aids in spotting weather phenomena, unauthorized obstacles, or other aircraft outside controlled airspace when automated systems reach their limits.

US Airways Flight 1549 safely ditched in the Hudson River using flexible human response, demonstrating the limits of automated systems. Aircraft speed during takeoff tracking reaches 260 kilometres per hour, while minimum horizontal visibility requires 125 metres for visual takeoff and 75 metres for automatic landing.

Modern Technology

Wind turbines rotate at a constant speed in varying winds because internal electrical braking adjusts the load to generate more power. To keep the alternating current in sync with the national grid, turbines rotate at a fixed speed. Stronger winds increase the electrical braking resistance rather than accelerating the blades, analogous to pushing harder on bicycle pedals when going uphill.

Glyn Hicks asked about community turbines rotating at a constant speed of 39 revolutions per minute.

Cotton is preferred for clothing over synthetics due to its high moisture regain and cross-sectional ribbon shape, which provide superior comfort and cleanability. Cotton has a moisture regain of 7 to 7.5 per cent, absorbing body moisture to keep the wearer cool, whereas polyester only has 0.4 per cent. Cotton's ribbon-like cross section bends easily for softness, and its alkali resistance allows it to withstand washing without absorbing body oils that cause stains.

Jean Esnault and Brian Bennett discussed why consumers prefer cotton over synthetic fibers despite environmental and drying trade-offs.

Power companies bring extra generators online during demand surges because alternating current cannot be efficiently stored in large quantities. Electricity cannot be stored easily in batteries without conversion between alternating and direct current. Central stations monitor demand minute by minute using prediction software and high-voltage links between countries to share power during peaks.

Simon Scarle and Paul Keddie discussed whether UK power stations start up during popular TV ad breaks, utilizing a 2,000-megawatt high-voltage link between the UK and France installed in 1986.

Pilling in wool garments occurs when short fibers migrate to the fabric surface and lock together through friction. Short fleece fibers between 4 and 6 centimetres long work their way to the surface much easier than long ones. Carding short fibers into rolags creates a woollen style with randomly arranged fibers full of air, whereas combing long fibers and spinning them in a worsted style keeps them parallel. Loose, light twists and loose fabric density also facilitate pilling.

Sheep breeds like Southdown have short fibers prone to pilling, while Wensleydale has long wool up to 30 centimetres, and Ryeland fleece has a staple length of 5 to 6 centimetres.

• Examine the fabric density to see how tightly the yarn is twisted.
• Check if the garment is loose, which makes it more likely to pill.

10 Key Ideas

1. Zebra stripes primarily serve to repel biting horseflies rather than providing thermal regulation or camouflage by disrupting linear polarised light reflection.
2. Recreating dinosaurs from ancient DNA extracted from biting insects preserved in amber is biologically impossible because DNA degrades with a half-life of approximately 500 years and becomes completely uninformative after about 1.5 million years.
3. Subconscious body perception, known as proprioception, can lag behind physical changes caused by growth, ageing, or pregnancy because it relies on the vestibular system and nerves in muscles and joints learned through experience.
4. Humans primarily depend on sunlight exposure to ultraviolet B radiation to synthesize vitamin D, a process blocked by ordinary window glass and heavily dictated by latitude, season, and skin pigmentation.
5. Microwaves can superheat liquids above their boiling point without visible boiling if nucleation sites are absent, leading to violent bubbling when disturbed by cold water or dissolved air.
6. Reheating cooked rice improperly can lead to food poisoning due to heat-resistant Bacillus cereus spores surviving the boiling process and producing toxins upon cooling unless temperatures are managed carefully.
7. Post-it notes stick using a pressure-sensitive adhesive where cohesive forces exceed adhesive ones so that peeling pulls only one polymer loop at a time like a zipper.
8. Flat map projections inherently distort geographical reality because a sphere's surface cannot be flattened without sacrificing area, distance, or direction.
9. Wind turbines rotate at a constant speed in varying winds because internal electrical braking adjusts the load to keep the alternating current in sync with the national grid.
10. Central power companies bring extra generators online during demand surges because alternating current cannot be efficiently stored in large quantities.