4 Scientific American, April 2022 Illustration by Nick HigginsFROM
THE EDITOR Laura Helmuth is editor in chief of Scientific American.
Follow her on Twitter @laurahelmuthBOARD OF ADVISERS
Robin E. Bell
Research Professor, Lamont-Doherty Earth Observatory,
Columbia University
Emery N. Brown
Edward Hood Taplin Professor of Medical Engineering
and of Computational Neuro science, M.I.T.,
and Warren M. Zapol Prof essor of Anesthesia, Harvard Medical School
Vinton G. Cerf
Chief Internet Evangelist, Google
Emmanuelle Charpentier
Scientific Director, Max Planck Institute for Infection Biology,
and Founding and Acting Director, Max Planck Unit for the
Science of Pathogens
Rita Colwell
Distinguished University Professor, University of Maryland College Park
and Johns Hopkins Bloomberg School of Public Health
Kate Crawford
Director of Research and Co-founder, AI Now Institute,
and Distinguished Research Professor, New York University,
and Principal Researcher, Microsoft Research New York City
Nita A. Farahany
Professor of Law and Philosophy, Director,
Duke Initiative for Science & Society, Duke UniversityJonathan Foley
Executive Director, Project Drawdown
Jennifer A. Francis
Senior Scientist and Acting Deputy Director,
Woodwell Climate Research Center
Carlos Gershenson
Research Professor, National Autonomous University of Mexico
Alison Gopnik
Professor of Psychology and Affiliate Professor
of Philosophy, University of California, Berkeley
Lene Vestergaard Hau
Mallinckrodt Professor of Physics and of Applied Physics,
Harvard University
Hopi E. Hoekstra
Alexander Agassiz Professor of Zoology, Harvard University
Ayana Elizabeth Johnson
Co-founder, Urban Ocean Lab, and
Co-founder, The All We Can Save Project
Christof Koch
Chief Scientist, MindScope Program, Allen Institute for Brain Science
Meg Lowman
Director and Founder, TREE Foundation, Rachel Carson Fellow,
Ludwig Maximilian University Munich, and Research Professor,
University of Science MalaysiaJohn Maeda
Global Head, Computational Design + Inclusion, Automattic, Inc.
Satyajit Mayor
Senior Professor, National Center for Biological Sciences,
Tata Institute of Fundamental Research
John P. Moore
Professor of Microbiology and Immunology,
Weill Medical College of Cornell University
Priyamvada Natarajan
Professor of Astronomy and Physics, Yale University
Donna J. Nelson
Professor of Chemistry, University of Oklahoma
Lisa Randall
Professor of Physics, Harvard University
Martin Rees
Astronomer Royal and Professor of Cosmology and Astrophysics,
Institute of Astronomy, University of Cambridge
Daniela Rus
Andrew (1956) and Erna Viterbi Professor of Electrical Engineering
and Computer Science and Director, CSAIL, M.I.T.
Meg Urry
Israel Munson Professor of Physics and Astronomy, Yale University
Amie Wilkinson
Professor of Mathematics, University of ChicagoMagnetic Vision
While we sleep this spring, billions of birds will be flying through
the night from their wintering grounds to their breeding territo-
ries. Bird migration is a mind-bendingly astonishing phenome-
non: these tiny creatures fly thousands of kilometers with enough
precision to return to the same nesting site year after year. They
use three types of compass, guided by the stars, sun and, most
mysteriously, Earth’s magnetic field. In this issue’s cover story on
page 26, scientists Peter J. Hore and Henrik Mouritsen explain
how some birds are able to “see” Earth’s magnetic field using quan-
tum effects in exquisitely photosensitive molecules in their eyes.
We hope this article will add to the enjoyment of seeing migrato-
ry birds return to your neighborhoods after a long winter.
I’ve been looking at streams with more appreciation after read-
ing about their “hyporheic zone,” the area of streambed extend-
ing below the water and to the sides of a waterway. This hidden
layer of sand and gravel, where the groundwater and stream mix,
is home to small animals and larvae and microbes. As author Eri-
ca Gies describes on page 40, it’s known as the “liver of the river”
because of how it keeps a waterway healthy. People who are restor-
ing drained or dying streams are using new knowledge about the
hyporheic zone to bring back thriving habitats.
Looking up from streams and beyond the birds, astronomers
are planning ambitious projects to seek the source of dark mat-
ter, the invisible stuff in the universe that moves stars and galax-
ies ( page 58 ). Theoretical physicist Chanda Prescod-Weinstein
presents the best ideas for how to look for dark matter, some of
which could get a boost this year if physicists involved in a once-
a-decade planning project endorse dark matter probes as a top
scientific priority. (We hope they do.)
The culture of astronomy has been transformed by a wave of
women entering the field (including Scientific American adviso-
ry board member Meg Urry), as writer Ann Finkbeiner o b serves
on page 32. She is admired in science writing circles for inspiring
the “Finkbeiner test,” a guide to avoiding sexist clichés when talk-
ing about women in science. Now she realizes we are in a new era,
when women are proudly themselves and determined to make
science more welcoming to all.
Biblical archaeology is another field being transformed, albe-
it fitfully. Researchers using modern analytical methods are trying
to add some rigor to excavations in Jerusalem, which have been
guided by scripture rather than science. On page 66, author Andrew
Lawler shows how religious and international conflicts add to phys-
ical constraints (the land is very crumbly) to make this one of the
most challenging places in the world to unearth true history.
Modern neuroscience began with Santiago Ramón y Cajal’s
careful observations of neurons and how they interact. Author
Benjamin Ehrlich, on page 50, details how revolutionary Cajal’s
ideas were and how they changed the way we think about the brain.
The painstakingly drawn illustrations are indeed wondrous.
In 1889 Scientific American shared some of Thomas Edison’s
thoughts on sleep. He was against it. But he did appreciate nap-
ping—or at least the half-asleep state that led to many of his inspi-
rations. Starting on page 74, you can learn how to follow his advice
to extract creativity from a snooze. Writer Bret Stetka tells the tale.
We’re introducing a print column this month called Mind Mat-
ters ( page 78 ), in which experts will share recent interesting insights
from social science. Enjoy, and let us know what you think.