SCIENCE sciencemag.org 23 DECEMBER 2016 • VOL 354 ISSUE 6319 1523
Scorecard for 2016
Last year, Science’s writers and editors
picked three areas we considered ripe
for new discoveries. How prescient
were we? Our self-evaluations (the box
scores) are mixed. Predictions for 2017
are on p. 1524.
WHO LET THE DOGS IN?
Last year, we predicted that 2016 might
finally be the year we figure out where dogs
came from. Scientists have fiercely debated
whether our canine pals evolved from wolves
in Europe or in Asia, and a new international
collaboration of researchers promised to
solve the mystery once and for all. We don’t
have an answer yet, but a study published
this year suggests both sides of the debate
might be right: Dogs may have been
domesticated twice, once in Asia and once in
Europe or the Near East.
We recommended keeping an eye on a
satellite called MicroSCOPE, which is testing
whether two free-falling objects made of
different materials accelerate at the same
rate under Earth’s gravity. Galileo supposedly tested that equivalence by dropping
balls from the Leaning Tower of Pisa in Italy,
and it is a cornerstone of Einstein’s theory of
gravity, general relativity. MicroSCOPE was
launched successfully on 25 April, testing was
completed this month, and researchers have
begun an 18-month data run. Keep watching.
It was a fairly safe bet a year ago when
we made gravitational waves an area to
watch for 2016. The Laser Interferometer
Gravitational-Wave Observatory (LIGO) had
recently undergone a major upgrade, physicists were sifting through early data, and
rumors were swirling that they had detected
ripples in spacetime: gravitational waves.
Indeed, they had. LIGO has spotted two
events so far, and many more are expected
from LIGO and other planned detectors.
These achievements earned our pick as
Science’s Breakthrough of the Year.
Glass lenses were one of humanity’s earliest high-tech innovations. They enabled
Galileo to see Jupiter’s moons, Antonie van Leeuwenhoek to spy microbes, and millions of people to just plain see clearly. But lenses are still made roughly the same
way as they were centuries ago—by grinding and polishing glass and other transparent materials so that they focus light without aberration. Now, lens technology is
poised to take a major leap. This year, researchers used computer chip–patterning
techniques to create the first metamaterial lens, or metalens, that can focus the full
spectrum of visible light. Because metalenses are cheap to produce, thinner than a
sheet of paper, and far lighter than glass, they could revolutionize everything from
microscopes to virtual reality displays to cameras—including the ones in
Metamaterials are composed of arrays of tiny pillars, rings, and other arrangements of materials, which work together to manipulate light waves as they pass
by. In recent years, researchers have designed metamaterial-based “invisibility
shields” that steer light around objects, as well as light filters and antennas. But
previous efforts to make metalenses succeeded only with infrared and other long
wavelengths of light; the patterning techniques didn’t work as well with materials
transparent to visible light.
This year, researchers figured out how to use a conventional chip-patterning
technique, known as atomic layer deposition, to precisely pattern arrays of pillars
of titanium dioxide. Just 600 nanometers high, the pillars are transparent to visible
light, and they can focus it to produce a magnification of up to 170 times—as good
as state-of-the-art-glass optics. The team tested its metalens techniques by using
them to make holograms and carry out detailed spectroscopy, opening the way for
other potential applications. Watch for the high-tech optics to make cellphones even
sleeker, lead to new scientific instruments, and transform virtual reality headsets.
—Robert F. Service
Light passing upward through a metalens is focused by nanoscale fins.
BREAKTHROUGH OF THE YEAR | RUNNERS-UP 2016