Among the measures approved at the 68th session of the United Nations General Assembly in December 2013 were resolutions to develop “a world against violence and violent extremism” and “measures to eliminate international terrorism”. Against such targets, the goal of UN resolution A/RES/68/221, passed in the same session, might seem unambitious: to recognize the importance of light in the lives of the citizens of the world.

Some 42 days into that effort — officially called the International Year of Light and Light-based Technologies 2015 — Nature is doing its bit. In this special issue, we offer a series of articles that explore how researchers are pushing the properties of light to new extremes, and the impact that these studies are already having and could have in future. The print-journal package begins on page 153 and there is more available online at

Light and science have been entwined for more than a thousand years; light and life for much longer. This is reflected in the goals of the UN celebration, from discussions of solar energy and its crucial potential in tackling energy and climate problems to the societal impact of artificial light in our cities and homes, and how it guides develop­ment. According to the UN, “the 21st century will depend as much on photonics as the 20th century depended on electronics”. If so, then more of the work that researchers are engaged in to understand and harness light — to make light work — will need to move out of the laboratory.

Light inspires, too. The organizers of the UN year of light are seeking people to follow in the (chunky) footsteps of writers such as Fyodor Dostoyevsky and Johann Wolfgang von Goethe, who wrote about optics. They invite those who feel that they have something to say about light and any phenomena or feeling connected to it to enter a literary competition. Poems, short stories, essays and plays are welcome, but must be submitted by the end of next month (see for details). Winning entries will appear in a special anthology — published a thousand years after Ibn al-Haytham’s classic treatise, Book of Optics (see page 164).

Light in 2015 may be all about applications and technology, but it retains a powerful theoretical pull on the scientific mind. Countless children in night-time gardens have been astonished and intrigued by the news that the light arriving from distant stars is a historical record — the stars themselves could be long gone even as the light carries their image on its journey. Generations of students have tried to decipher whether light is a wave or a particle, and in doing so have come to accept that scientific reality demands a greater tolerance of uncertainty than the textbooks suggest. Albert Einstein’s general theory of relativity — the centenary of which is recognized as part of the UN’s celebration — has come to represent an intuition warped just as much as the light in the gravitational field that it describes.

Light has outgrown its metaphorical role as an answer to questions; light itself remains a puzzle. To solve that puzzle is an ambition that deserves the recognition that the coming months will shine on it. As the biochemist and author Isaac Asimov put it: “There is a single light of science, and to brighten it anywhere is to brighten it everywhere.”