Ikigai Daily
Menu
WonderFact

Bright white LED lighting became possible only after efficient blue LEDs were made, a problem that had defeated researchers for decades. Isamu Akasaki, Hiroshi Amano and Shuji Nakamura solved it in Japan in the late 1980s and early 1990s with a material called gallium nitride, and shared the 2014 Nobel Prize in Physics.

Isamu Akasaki, Hiroshi Amano, Shuji Nakamura; 2014 Nobel Prize in Physics

TechnologyScience

The story behind the card

An LED, or light-emitting diode, is a tiny piece of semiconductor that glows when electric current flows through it. Red LEDs appeared in the early 1960s, but white light also needs blue, and blue needs a material that is very hard to grow as clean crystals: gallium nitride. At Nagoya University, Akasaki and Amano grew high-quality gallium nitride in 1986 and by 1989 had made it carry current in the way an LED needs. Shuji Nakamura, working at the Japanese chemical company Nichia, developed his own methods and produced bright blue LEDs in 1993. Coating a blue LED with a yellow-glowing layer called a phosphor gives white light, which uses far less electricity than an old filament bulb.

Türkçe oku
Parlak beyaz LED aydınlatma, ancak verimli mavi LED'ler yapılabildikten sonra mümkün oldu; bu sorun araştırmacıları onlarca yıl uğraştırmıştı. Isamu Akasaki, Hiroshi Amano ve Shuji Nakamura, 1980'lerin sonu ile 1990'ların başında Japonya'da galyum nitrür adlı bir malzemeyle sorunu çözdü ve 2014 Nobel Fizik Ödülü'nü paylaştı.

LED, yani ışık yayan diyot, içinden elektrik akımı geçtiğinde parlayan küçücük bir yarı iletken parçasıdır. Kırmızı LED'ler 1960'ların başında ortaya çıktı; ama beyaz ışık için maviye de ihtiyaç vardı. Mavi ışık için gereken galyum nitrürün temiz kristaller hâlinde büyütülmesi ise çok zordu. Nagoya Üniversitesi'nden Akasaki ile Amano 1986'da yüksek kaliteli galyum nitrür elde etti; 1989'a gelindiğinde de malzemenin akımı bir LED'in gerektirdiği gibi iletmesini sağladı. Japon kimya şirketi Nichia'da çalışan Shuji Nakamura kendi yöntemlerini geliştirdi ve 1993'te parlak mavi LED'ler üretti. Mavi bir LED, fosfor denen ve sarı ışık veren bir katmanla kaplanınca beyaz ışık verir. Bu ışık, eski telli ampullere göre çok daha az elektrik harcar.

Sources and further reading

Background reading: Light-emitting diode
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderHistory

When Neil Armstrong radioed “Houston, Tranquility Base here. The Eagle has landed” on 20 July 1969, his words reached Earth about 1.3 seconds later. Radio waves travel at the speed of light, and the Moon is about 384,000 km (239,000 miles) away.

Eagle was the lunar module that carried Armstrong and Buzz Aldrin down to the surface. Light, and so radio, travels at almost 300,000 km per second. At the Moon's average distance of about 384,400 km, a signal takes roughly 1.28 seconds each way, so every exchange with Mission Control in Houston had a built-in pause of about 2.6 seconds before an answer could arrive. Large dish antennas at Goldstone in California and at Honeysuckle Creek and Parkes in Australia picked up the signals; the clearest pictures of the first steps came through Australia and were watched live by an estimated 600 million people. Before leaving, the crew set up a panel of reflectors on the surface. Scientists still fire lasers at it and time the light's return, which is how we know the Moon is drifting away from Earth by about 3.8 cm a year.

Ikigai DailyRead card
WonderTechnology

Telomeres are stretches of repeated DNA that cap the ends of chromosomes, a little like the plastic tips on shoelaces. They get shorter as many of our cells divide, but their length cannot predict how long a particular person will live.

In the mid-1970s the Australian-born biologist Elizabeth Blackburn, working at Yale, found that chromosome ends carry a short DNA “word” repeated many times; in humans it is TTAGGG. She shared the 2009 Nobel Prize in Physiology or Medicine with Carol Greider and Jack Szostak for showing how telomeres, and an enzyme called telomerase that rebuilds them, protect chromosomes. Each time most body cells divide, the copying machinery cannot quite reach the very end, so a little telomere is lost; when it gets too short, the cell stops dividing, which is why telomeres are often called a clock. But it is a poor clock for comparing people or species: mice have much longer telomeres than humans yet live only two or three years, and telomere length varies widely between people from birth. Many scientists therefore doubt commercial tests that claim to read your “biological age” from them.

Ikigai DailyRead card
WonderTechnology

The atomic clocks on GPS satellites run about 38 millionths of a second a day faster than clocks on the ground, an effect predicted by Einstein's theories of relativity. Left uncorrected, the drift would put your position out by about 11 km within a single day.

A GPS receiver, such as the one in your phone, works out where it is by timing signals from several satellites orbiting about 20,200 km up. Radio signals travel about 300 metres in a microsecond, a millionth of a second, so even tiny clock errors matter. Relativity pulls the clocks apart in two ways. Special relativity says moving clocks run slow: travelling at almost 4 km a second, the satellite clocks lose about 7 microseconds a day. General relativity says clocks in weaker gravity run fast: high above Earth they gain about 46. The net gain is about 38 microseconds a day. So before launch, each satellite clock is set to run slightly slow, at 10.22999999543 million cycles a second instead of 10.23 million, and in orbit it keeps step with clocks on the ground.

Ikigai DailyRead card
WonderTechnology

The Apollo Guidance Computer that steered astronauts to the Moon had about 4 kilobytes of rewritable memory and 72 kilobytes of permanent memory. Its programs were woven by hand into “rope memory”: a wire threaded through a tiny magnetic ring stored a 1, and a wire passing it by stored a 0.

Designed at the MIT Instrumentation Laboratory and built by Raytheon, the computer was one of the first to use silicon chips (integrated circuits) and fitted into about 28 litres. Its memory was counted in “words” of 16 bits, or binary digits: 2,048 rewritable and 36,864 permanent. During Apollo 11's descent on 20 July 1969 it flashed 1202 and 1201 alarms: a radar left on in case the landing had to be abandoned was stealing processing time and overloading it. Its operating system, designed by J. Halcombe Laning, dropped less urgent jobs and restarted in a moment while the landing programs kept running, so Mission Control told the crew to carry on. The flight software was written by a team led by Margaret Hamilton, who received the Presidential Medal of Freedom in 2016. Its power was similar to that of the first home computers of the late 1970s.

Ikigai DailyRead card
WonderTechnology

In 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.

Ikigai DailyRead card
Next card in the archiveSome crystals, such as quartz, produce an electric charge when squeezed. This is the piezoelectric effect, discovered in 1880 by the brothers Pierre and Jacques Curie, years before Pierre's research on radioactivity with Marie Curie. It makes the spark when you press the button of a gas lighter.Read next →