926 27 MAY 2022 • VOL 376 ISSUE 6596 science.org SCIENCEPHOTO: NASABy Catherine HeymansO
ne hundred years ago in May 1922,
the Dutch astronomer Jacobus
Kapteyn published a study of the
motion of stars in the Milky Way
that led to a visionary conclusion:
The existence of any invisible “dark
matter” in the Universe can be detected
through its gravitational effect ( 1 ). A new
era of research was born—one that is cel-
ebrated by Dutch science journalist Govert
Schilling in his new book, The Elephant in
the Universe.
It takes a village to raise a child, and sci-
entific theories likewise require the efforts
of many to reach maturity. Schilling takes
readers on a journey through the stories of
a veritable army of physicists from around
the globe as they have sought to understand
the dark matter and dark energy that ap-
pear to make up 95% of our Universe.
Many readers will be familiar with the
story of pioneering astronomer Vera Rubin.
Harnessing the power of Kent Ford’s revo-
lutionary image-intensifying technology,
Rubin put Kapteyn’s theory to the test, mea-
suring the gravity-induced motion of hot
gas clouds in distant galaxies.
In Schilling’s retelling, Ford happily
reminisces about his colleague, who died in- A photo displayed in his living room
shows Rubin, clad in a thick winter coat
and gloves, painstakingly collecting light on
a frozen mountaintop during each 3-hour-
long exposure. (Rubin and Ford’s work
started at a time when telescopes were still
hand-driven.)
Throughout the 1970s, the pair studied 21
galaxies, all exhibiting unexpected behav-
ior that could only be explained by the ex-
istence of dark matter. This work is widely
recognized as the first conclusive evidence
for dark matter, and with the construction
of the Vera C. Rubin Observatory in Chile,
which Schilling visits, we will soon be able
ASTRONOMYImplied
but unseen
to confront theories that seek to explain the
Universe’s dark side.
Schilling delves behind this well-known
narrative, introducing readers to the lesser-
known “Westerbork cowboys,” the Dutch
radio astronomers who, in fact, beat Rubin
and Ford to their conclusive measurement
by several years in work that Rubin herself
cited. Has science forgotten about their work,
published in Albert Bosma’s doctoral thesis,
because radio astronomy was not fully estab-
lished at the time? Or was it because of the
cowboys’ “tacky” behavior, which prompted
the director of the competing Mullard Radio
Astronomy Observatory to write a formal
letter of complaint to their boss? We will
never know for sure, but Schilling is keen
to correct the history books on this matter.
Schilling does not shy away
from complex experiments and
theories that have led to an as-
yet-undetected cold dark matter
particle becoming the corner-
stone of modern physics. He
dives headfirst into such top-
ics as CP violation and Bose-
Einstein condensates as well as
other graduate-level theoretical
particle physics that underpins
the alternative axion theory for
dark matter.
There is a joy to finding these
challenging yet clearly explained
concepts interspersed between charming
stories of the scientists responsible for
discovering them. Schilling relates, for ex-
ample, how Samuel Ting once received a
speeding ticket on the way to the launch
of his own particle detector on the last
space shuttle Endeavour mission and how
Martin Rees and Joel Primack, killing time
together while colleagues skied at a con-ference, discovered that a cold dark matter
particle could explain the observed pattern
of large-scale structures in the Universe.
He writes of the chance Scandinavian ferry
meeting between Marc Davis and George
Efstathiou that led to the birth of compu-
tational simulations of the whole Universe
and even joins the story himself, describ-
ing how he has followed his subjects over
the lifetimes of both his and their careers.
As the decades pass, the nature of re-
search shifts from a moment when aca-
demics had the freedom and time to pursue
interdisciplinary research to today’s era
of fast-paced competition. Mistakes are
made, and individuals who should know
better intimidate and bully. Robert Kirsh-
ner, a key player in the discovery of dark
energy, laments, “What’s the
strongest force in the Universe?
It’s not gravity, it’s jealousy.” And
while the decade-long search
for the weakly interacting mas-
sive particle (WIMP) dark mat-
ter candidate continues to come
up empty-handed, fear is in the
air as we move from the era of
the “WIMP miracle” into a fast-
approaching “dark crisis.”
Will dark matter and dark en-
ergy become the ether of the 21st
century? Schilling introduces
readers to an array of alternative
theories, including those that question the
likes of Einstein and Newton. One thing is
for certain, as Schilling’s book makes clear:
There are thousands of researchers eager
to find out. jREFERENCES AND NOTES- J. C. Kapteyn, Astrophys. J. 55 , 302 (1922).
10.1126/science.abq1661The Alpha Magnetic Spectrometer on the International Space Station measures antimatter.A journalist probes
dark matter and those
who study it
The reviewer is Astronomer Royal for Scotland and is
at the Institute for Astronomy, University of Edinburgh,
Edinburgh, UK, and the German Centre for Cosmological
Lensing, Ruhr-University Bochum, Bochum, Germany.
Email: [email protected]The Elephant
in the Universe:
Our Hundred-Year
Search for Dark Matter
Govert Schilling
Belknap Press, 2022.
376 pp.INSIGHTS | BOOKS