The increasing pace of modern life — and how we can adapt | Kathryn Bouskill
Why Rembrandt and da Vinci may have painted themselves with skewed eyes
A strongly dominant eye, not
an eye disorder, may explain why Leonardo da Vinci and Rembrandt van Rijn painted
themselves with misaligned eyes.
Previous research suggested
that the famous artists may have had a literal artist’s eye —
an eye disorder called exotropia in which one eye turns outward. Exotropia
makes it harder for the brain to use input from both eyes to see in 3-D, so it
must rely on 2-D cues to see depth. This gives people with the disorder a
“flattened” view of the world, which could give artists who work on flat
surfaces like canvas an advantage.
But using trigonometry and
photographs of people looking into a mirror, David Guyton, an ophthalmologist
at Johns Hopkins University, and his colleague Ahmed Shakarchi, conclude that the artists could have had eyes that faced straight ahead
after all. The researchers published
their analysis November 27 in JAMA
Ophthalmology.
The brains of people who have
a strongly dominant eye will favor whatever that eye sees. So when people with
a strongly dominant eye look closely in a mirror — like, say, artists leaning in to get details needed
to paint a self-portrait —
they could perceive that they have exotropia even if that’s not true, Guyton
says.
For instance, a person with
a strongly dominant eye and eyes six centimeters apart who was sitting 16.5
centimeters from a mirror would wrongly perceive that the weaker eye is turned
outward at a 10.3-degree angle, the researchers found. That angle is consistent
with the eye angle portrayed in some artworks painted by or modeled after da Vinci.
“It is a clever idea,” says
Christopher Tyler, a visual neuroscientist at the City University of London
whose previous analysis of six pieces of art — some by da Vinci himself and some for which it’s
suspected he was the model —
suggested that da Vinci had exotropia (SN: 10/22/18).
In many of those works, the eyes appear misaligned.
For the geometry of the
strong eye explanation to work, Tyler says, the artist would have to sit
“unrealistically close” to the mirror, especially for some of Rembrandt’s half-length,
self-portraits or for the painting Salvator
Mundi, which da Vinci may have partially modeled after himself. And it
doesn’t fully explain why statues that were sculpted in da Vinci’s likeness by
other artists also show apparent exotropia, Tyler says.
Bevil Conway, a
neurobiologist at the National Institutes of Health in Bethesda, Md., says both
explanations are plausible. A common trick among artists is to shut one eye and
hold out a thumb to get a sense of how a three-dimensional world looks in 2-D. Both
exotropia and a strongly dominant eye could have a similar “flattening” effect,
which could have helped da Vinci and Rembrandt bring a 3-D world to life on flat
canvases.
“The debate is still open,
and the answer is that we can never know,” Conway says.
Stealthy robots with microphones could improve maps of ocean noise
Moving
slowly and stealthily through the Pacific Ocean, a robotic glider with a
microphone captured a cacophony of sounds from ships, whales and underwater
explosions.
The
glider’s journey, across 458 kilometers off the Washington and Oregon coast and
down to 650 meters, demonstrates that gliders could be effective tools to help map ocean noise levels, researchers report November 20 in PLOS ONE. Separate audio recordings from
nearby microphones dangled from the water’s surface confirmed the accuracy of
the glider’s 18 days of recordings in July and August 2012.
Stationary microphones can’t catch the full array of sounds throughout large swathes of sea or at various depths in the water column the way a glider can, though, the researchers say. Ocean noise is “something we need to measure and try to better understand why that’s happening, where it’s happening, and what the impacts are” to wildlife and marine ecosystems, says oceanographer Joe Haxel, at Oregon State University’s coastal campus in Newport. For example, previous research has shown that Navy sonar (SN: 3/25/11) and passing ships can create noise pollution that harms marine animals (SN: 2/13/18), impacting social behaviors and foraging habits.
Typically,
scientists eavesdrop underwater with hydrophones, waterproof microphones that
are moored or dangled from the surface, or mounted on large ships that can drown
out other sounds and scare away marine life.
The
glider’s slow speed —
just over 1 kilometer per hour —
and quiet movement allow it to sneak through the water picking up ambient
noises. A pump moves oil in and out of the glider’s bladder, affecting its buoyancy
and causing it to float up or sink down in the water column. Those depth
changes propelled the glider forward on a slow, meandering path.
“The
glider is good because it’s noninvasive,” says Haxel. “It’s coming in on
stealth mode.”
Electric charges on dust grains may help explain how planets are born
Growing up is hard to do, especially for
baby planets. Now, scientists may have uncovered the solution to one puzzle
about protoplanetary growing pains.
An obstacle to planetary formation,
known as the bouncing barrier, hinders the clumping of dust particles that
eventually form planets. But electric charge can provide extra stickiness that those
cosmic motes need for clumps to keep
growing, scientists report December 9 in Nature
Physics. Testing that explanation required vigorously shaking thousands of
small glass beads and catapulting them more than 100 meters skyward in an
attempt to mimic planets’ birthplaces, protoplanetary disks.
In the pancakes of dust and gas known as
protoplanetary disks, the seeds of planets collide and stick, forming larger and
larger clumps. But, according to experiments and simulations, once particles are
a millimeter or so in size, their growth stalls as they bounce off one another,
rather than sticking. It’s a quandary that has stymied attempts to simulate how
planets form.
Somehow, the dust particles overcome the
bouncing barrier, resulting in a cosmos peppered with a wide variety of worlds (SN: 1/8/19).
“We see exoplanets, so there must be a way to get bigger particles,” says
experimental astrophysicist Tobias Steinpilz of the University of
Duisburg-Essen in Germany.
So Steinpilz and colleagues set out to
form analogs of planetary seeds. Instead of protoplanetary dust grains, the
researchers used glass beads, each a bit less than half a millimeter in
diameter. Collisions between those beads would mimic colliding dust particles
in the protoplanetary disk. But there was one catch: Earth’s gravity. “That
overpowers everything we want to see,” Steinpilz says.
So the researchers launched their experiment
with a catapult inside the 120-meter-tall Bremen Drop Tower in Germany, letting the apparatus containing the beads, a camera and
other measurement equipment, fly upward and back down. During its approximately
nine-second flight, the device was effectively weightless.
Prior to the launch, the researchers
shook the beads, mimicking the collisions that particles in a protoplanetary
disk would experience over time. That movement caused the beads to build up electric
charges, some negative and some positive. When the beads went weightless, they formed
clumps — some consisting of over a thousand beads — thanks to electric forces
between the charged beads, the researchers determined.
The results “clearly show that electrostatic
forces help grow beyond the bouncing barrier in lab conditions,” says
astronomer Richard Booth of the University of Cambridge. But, he notes, “there
is a question of trying to extrapolate these lab conditions to what we see in
protoplanetary disks.” In particular, protoplanetary disks consist of dust
grains made of natural materials rather than glass.
Steinpilz’s team also performed shaking
experiments with basalt spheres, which are more similar to the particles in a
real protoplanetary disk. Basalt particles charged up even more than the glass
beads, the team found, suggesting that the effect might be even stronger in
protoplanetary disks.
Other barriers remain for developing planets,
though. High-speed particles, for example, can collide and break larger clumps apart,
so growing up still takes grit.