Ikigai DailyExhibition 02 / Science beyond everyday sight
What the eye cannot see
Explore the human body, signals between plants and experiments that reveal quantum behaviour.
About this exhibition
02 / 03Some discoveries need more than eyesight. Instruments and experiments help us understand what we cannot observe directly.
- Cards
- 7
- Chapters
- 3
- Languages
- EN · TR
Inside the body
Start with cells, sleep and the heart: things that happen inside us while we go about the day.
01.1Neuroplasticity is the brain's ability to change its connections, and even its structure, in response to experience. It is strongest in childhood but continues through adult life, which is why adults can still learn a language, an instrument or a new skill, even if it often takes them longer.
For much of the 20th century scientists believed the adult brain was more or less fixed. Brain scans changed that view. In 2004 researchers in Germany taught adults to juggle three balls over three months; scans showed extra grey matter, the tissue packed with nerve cells, in areas that track moving objects, and it shrank back once they stopped practising. A follow-up in 2008 found the same kind of change in volunteers around 60 years old, although they learned less well than 20-year-olds. The best-known example comes from London, where Katherine Woollett and Eleanor Maguire followed trainee taxi drivers for four years as they memorised the city's 25,000 streets. Those who passed the exam gained grey matter at the back of the hippocampus, a region involved in finding our way; those who failed, and people who never trained, showed no such change.
Read the full cardA 2013 study in mice found that the brain cleared amyloid-beta, a protein that builds up in Alzheimer's disease, faster during sleep. A 2024 mouse study, which used a small fluorescent dye and different methods, found clearance was slower during sleep. Scientists are still debating how sleep affects the brain's waste removal.
The 2013 study came from Maiken Nedergaard's laboratory at the University of Rochester, which in 2012 had described what it called the glymphatic system: cerebrospinal fluid, the clear liquid around the brain, flows in along channels around blood vessels and washes through the tissue. Her team reported that the space between brain cells widened by about 60% during sleep, letting fluid flow more freely. In 2024 Nick Franks and William Wisden at Imperial College London measured the movement of dyes directly and found clearance markedly reduced in sleeping and anaesthetised mice. In 2025 Nedergaard's group reported that during non-REM sleep, the stages without the rapid eye movements of dreaming sleep, which fill most of the night, slow waves of the chemical messenger noradrenaline make blood vessels tighten and relax, pumping fluid into the brain. The methods differ, and none of these studies was in humans.
Read the full cardThe adult heart beats roughly 100,000 times a day at a resting rate of about 70 beats a minute. Each beat pushes out around 70 millilitres of blood, which adds up to about 7,000 litres a day at rest, and more during exercise.
The heart is a muscle about the size of a fist, weighing 250 to 350 grams, with four chambers: two atria that receive blood and two ventricles that pump it out. The right side sends blood to the lungs to collect oxygen; the left side sends it round the rest of the body. Each beat is started by the sinoatrial node, a small cluster of cells that acts as the heart's natural pacemaker. It fires an electrical signal that spreads through the heart muscle and makes it contract. The rate changes all day: it falls during sleep and rises with exercise, stress, fever and illness. Over an 80-year life, 100,000 beats a day adds up to nearly three billion heartbeats.
Read the full cardPlants and long lives
Read about airborne signals between plants and how scientists estimate the age of Greenland sharks.
02.1When caterpillars or other insects chew a plant, it can release airborne chemicals, including the ones that give cut grass its smell. Nearby plants that sense them can strengthen their own chemical defences before they are attacked.
The effect was first reported in 1983. Ian Baldwin and Jack Schultz found that young poplar and sugar maple trees sharing air with damaged plants raised their levels of defensive compounds, such as tannins, within about two days, an idea soon nicknamed “talking trees”. It was met with scepticism for years, but many later studies confirmed that such airborne signals exist, although how strongly plants respond varies with species and conditions. In 2023 Masatsugu Toyota's team at Saitama University in Japan filmed the process as it happened. When thale cress, a small plant widely used in laboratories, was exposed to air from injured plants, calcium signals spread through its leaves almost at once; plant cells use such signals to raise the alarm. Two of the cut-grass compounds were enough to trigger them. The chemicals enter through stomata, the tiny pores in leaves.
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02.2The Greenland shark is the longest-living vertebrate known. Radiocarbon dating of one large individual put its age at about 392 years, though the method's own uncertainty range spans roughly 270 to over 500 years.
A Danish-led team reported the result in the journal Science in 2016, after studying 28 Greenland sharks collected in Greenland waters. They radiocarbon-dated the core of each shark's eye lens, which forms before birth and never changes afterwards; radiocarbon dating measures how much of a slowly decaying form of carbon remains. The largest shark, about 5 metres long, came out at 392 years, with a range of roughly 272 to 512 years, so the study cannot say for sure whether it was alive in 1564, when Shakespeare was born. Greenland sharks live in the cold, deep waters of the North Atlantic and Arctic, grow about a centimetre a year or less and may not breed until around 150.
Read the full cardQuantum experiments
Explore the double-slit experiment and electrical circuits that behave as quantum objects.
03.1In the double-slit experiment, light or particles such as electrons pass through two narrow slits and leave bright and dark bands on a screen, the mark of overlapping waves. If a detector records which slit each particle went through, the bands disappear.
In the early 1800s, Thomas Young shone light through two narrow openings to argue that light is a wave. Where two waves meet crest to crest they reinforce each other, and where a crest meets a trough they cancel out; physicists call this interference. The real surprise came with matter. Claus Jönsson repeated the experiment with electrons in 1961, and in 1974 Italian physicists sent electrons through a similar set-up one at a time. Each landed as a single dot, yet thousands of dots built up the striped pattern. Similar interference has since been seen with molecules of up to 2,000 atoms and, in 2026, with clusters of more than 7,000 sodium atoms. The pattern does not vanish because a person is watching: any physical interaction that records the path, even with no one looking, disturbs the delicate quantum state that produces the interference.
Read the full card03.2In 1984 and 1985, John Clarke, Michel Devoret and John Martinis showed that a whole electrical circuit on a chip, cooled almost to absolute zero, can behave as a single quantum object, just like an atom. The discovery earned them the 2025 Nobel Prize in Physics.
The experiments were done at the University of California, Berkeley, in Clarke's group; Martinis was his doctoral student and Devoret a postdoctoral researcher. Absolute zero, −273.15 °C, is the lowest temperature possible. At the heart of the circuit was a Josephson junction: two superconductors, metals that carry current with no resistance when very cold, separated by an insulating layer only a few atoms thick. Vast numbers of electrons moved together as if they were one particle. The team saw two signs of quantum behaviour: the circuit escaped from a trapped state by tunnelling, slipping through an energy barrier it could not climb over, and it absorbed microwave energy only in fixed steps, or quanta, as an atom does. Circuits of this kind are now the qubits, the basic units of information, in the superconducting quantum computers built by companies such as Google and IBM.
Read the full cardA surprising fact is more interesting when you can see how researchers reached it.Next exhibitionThe past is still here