Scientific American Space & Physics 2021 01.pdf

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DECEMBER 2020/JANUARY 2021 | SCIENTIFICAMERICAN.COM
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Space
&
Physics
LIFE ON
VENUS?
BLACK HOLE
SCIENTISTS
SNAG NOBEL
ROGUE PLANET IN
THE MILKY WAY
DO WE LIVE IN A HIGHER BEING’S COMPUTER?
ADVANCED RESEARCH MAY TELL US
WITH COVERAGE FROM
A Simulated
Universe
FROM
THE
EDITOR
&PHYSICS
Your Opinion
Matters!
Help shape the future
of this digital magazine.
Let us know what you
think of the stories within
these pages by emailing us:
editors@sciam.com.
SPACE
Are We Real? And Other Questions of Physics
What if this life is just a computer simulation running on some intellectually superior alien’s console? Something about
this idea is tantalizing to people (evidenced by the success of
The Matrix
films) and has special appeal for our readers.
It’s hooked physicists, philosophers, computer scientists and engineers, too, as author Anil Ananthaswamy writes in this
edition’s cover feature [“Do We Live in a Simulation? Chances Are about 50–50”]. What is it, exactly, that is so enticing
about this possibility? The fear that we are mere puppets of a more advanced species? Or perhaps it’s the calm that
comes from the idea that none of this is real anyway. Examining the nature of our own reality, indeed whether we have a
reality, is the most “meta” branch of physics.
In more satisfying endeavors, journalist Daniel Garisto reviews the long history of the search for black holes, whose
champions were awarded this year’s Nobel Prize in Physics [“Nobel Prize Work Took Black Holes from Fantasy to
Fact”]. One recipient, physicist Andrea Ghez, pushed her fellow astronomers and technicians tirelessly, despite doubt
from the field, as her colleague Hilton Lewis describes in this issue’s opinion section [“How Andrea Ghez Won the No-
bel for an Experiment Nobody Thought Would Work”]. Sometimes we have to fight for the realities we believe in.
LIZ TORMES
On the Cover
Andrea Gawrylewski
Senior Editor, Collections
editors@sciam.com
GETTY IMAGES
Do we live in a higher being’s computer?
Advanced research may tell us
2
WHAT’S
INSIDE
ALAMY
December 2020–
January 2021
Volume 3
•
No. 6
OPINION
29.
How Andrea Ghez
Won the Nobel for an
Experiment Nobody
Thought Would Work
She insisted on doing it
anyway—and ultimately
provided conclusive
evidence for a super-
massive black hole at the
core of the Milky Way
31.
The Quantum
Butterfly Noneffect
A familiar concept from
chaos theory turns out
to work differently in
the quantum world
34.
In Memoriam:
John D. Barrow
Remembering the
maverick physicist who
pioneered an “anthropic”
approach to cosmology
NEWS
4.
First Room-
Temperature
Superconductor
Excites and Baffles
Scientists
A compound of
hydrogen, carbon and
sulfur has broken a
symbolic barrier—but
its high-pressure
conditions make it
difficult to analyze
6.
Rogue Rocky
Planet Found Adrift
in the Milky Way
The diminutive world
and others like it could
help astronomers
probe the mysteries
of planet formation
8.
Google’s Quantum
Computer Achieves
Chemistry Milestone
A downsized version of
the company’s Sycamore
chip performed a record-
breaking simulation
of a chemical reaction
OU DONGQU
ALAMY
10.
Want to Talk
to Aliens?
Try Changing
the Technological
Channel
beyond Radio
Finding cosmic
civilizations might
require a more
innovative approach
than listening for
radio transmissions
13.
Water on Mars:
Discovery of Three
Buried Lakes
Intrigues Scientists
Researchers say they
have detected a group of
lakes hidden under the
Red Planet’s icy surface
15.
Identical Quantum
Particles Pass
Practicality Test
A new study proves
that far from being mere
mathematical artifacts,
particles that are
indistinguishable from
one another can be
a potent resource in
real-world experiments
GETTY IMAGES
FEATURES
18.
Do We Live in a Simulation?
Chances Are about 50–50
Gauging whether or not we dwell inside someone
else’s computer may come down to advanced
AI research—or measurements at the frontiers
of cosmology
22.
Venus Might Host Life,
New Discovery Suggests
The unexpected atmospheric detection of
phosphine, a smelly gas made by microbes on Earth,
could spark a revolution in astrobiology
26.
Nobel Prize Work Took Black Holes
from Fantasy to Fact
Over the past century the existence of these
invisible cosmic bodies has become unmistakable
3
NEWS
An artist’s concept
of a magnet levitating
over a cryogenically
cooled superconductor.
Scientists have created a mystery
material that seems to conduct
First Room-
electricity without any resistance at
Temperature
temperatures of up to about 15 de-
Superconductor
grees Celsius. That’s a new record
Excites and Baffles
for superconductivity, a phenomenon
usually associated with very cold
Scientists
temperatures. The material itself is
A compound of hydrogen, carbon
poorly understood, but it shows the
and sulfur has broken a symbolic
potential of a class of superconduc-
barrier—but its high-pressure
conditions make it difficult to analyze
tors discovered in 2015.
The superconductor has one
serious limitation, however: it
survives only under extremely high
pressures, approaching those at the
center of Earth, meaning that it will
not have any immediate practical
applications. Still, physicists hope it
could pave the way for the develop-
ment of zero-resistance materials
that can function at lower pressures.
Superconductors have a number
of technological applications, from
magnetic resonance imaging
machines to mobile-phone towers,
and researchers are beginning to
experiment with them in high-perfor-
mance generators for wind turbines.
But their usefulness is still limited
by the need for bulky cryogenics.
Common superconductors work at
atmospheric pressures, but only if
they are kept very cold. Even the
most sophisticated ones—copper
oxide–based ceramic materials—
work only below 133 kelvins (–140
ALAMY
4
NEWS
degrees Celsius). Superconductors
that work at room temperature could
have a big technological impact, for
example, in electronics that run faster
without overheating.
The latest study, published in
Nature
on October 14, seems to
provide convincing evidence of
high-temperature conductivity, says
physicist Mikhail Eremets of the Max
Planck Institute for Chemistry in
Mainz, Germany—although he adds
that he would like to see more raw
data from the experiment. He says
that it vindicates a line of work that
he started in 2015, when his group
reported the first high-pressure,
high-temperature superconductor—
a compound of hydrogen and sulfur
that had zero resistance up to –70
degrees C.
In 2018 a high-pressure com-
pound of hydrogen and lanthanum
was shown to be superconductive at
–13 degrees C. But the latest result
marks the first time this kind of
superconductivity has been seen in
a compound of three elements rather
than two—the material is made of
carbon, sulfur and hydrogen. Adding
a third element greatly broadens the
combinations that can be included
in future experiments searching for
new superconductors, says study
co-author Ashkan Salamat, a physi-
cist at the University of Nevada, Las
Vegas. “We’ve opened a whole new
region” of exploration, he notes.
Materials that superconduct at
high but not extreme pressures
could already be put to use, says
Maddury Somayazulu, a high-pres-
sure materials scientist at Argonne
National Laboratory. The study
shows that by “judiciously choosing
the third and fourth element” in a
superconductor, he says, you could
in principle bring down its operation-
al pressure.
The work also validates de-
cades-old predictions by theoretical
physicist Neil Ashcroft of Cornell
University that hydrogen-rich
materials might superconduct at
temperatures much higher than was
thought possible. “I think there were
very few people outside of the
high-pressure community who took
him seriously,” Somayazulu says.
MYSTERY MATERIAL
“I am sure,
after this
manuscript
is published, many
theoretical and
experimental groups
will jump on
this problem.”
—Eva Zurek
Physicist Ranga Dias of the Uni-
versity of Rochester, along with
Salamat and other collaborators,
placed a mixture of carbon, hydro-
gen and sulfur in a microscopic
niche they had carved between the
tips of two diamonds. They then
triggered chemical reactions in the
sample with laser light and watched
as a crystal formed. As they lowered
the experimental temperature,
resistance to a current passed
through the material dropped to
zero, indicating that the sample had
become superconductive. Then they
increased the pressure and found
that this transition occurred at
higher and higher temperatures.
Their best result was a transition
temperature of 287.7 kelvins at
267 gigapascals—2.6 million times
atmospheric pressure at sea level.
The researchers also found some
evidence that the crystal expelled its
magnetic field at the transition
temperature, a crucial test of
superconductivity. But much about
the material remains unknown,
researchers warn. “There are a lot of
things to do,” Eremets says. Even
the crystal’s exact structure and
chemical formula are not yet under-
stood. “As you go to higher pres-
sures, the sample size gets smaller,”
Salamat says. “That’s what makes
these types of measurements
really challenging.”
High-pressure superconductors
made of hydrogen and one other
element are well understood. And
researchers have made computer
simulations of high-pressure mix-
tures of carbon, hydrogen and sulfur,
says Eva Zurek, a computational
chemist at the State University of
New York at Buffalo. But she adds
those studies cannot explain the
exceptionally high superconducting
temperatures seen by Dias’s group.
“I am sure, after this manuscript is
published, many theoretical and
experimental groups will jump on
this problem,” she says.
—Davide Castelvecchi
This article is reproduced with
permission and was first published
in
Nature
on October 14, 2020.
5

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