74 Science & technology The EconomistNovember 28th 2020
2 space in a vehicle that could otherwise be
occupied by a child.
And space in the vehicle is the crucial
factor. In pre-safety-seat days, squeezing
three young children into the back of a
family saloon was a perfectly feasible pro-
position. Most such cars, though, can com-
fortably accommodate only two safety
seats. So, the older a child must be before
no safety seat is required, the longer a fam-
ily must wait before a third child will fit in
the car. Sometimes, that wait will mean no
third child is ever conceived and born.
Unless, of course, the family concerned
buys a bigger car. And here things get yet
more interesting, for the obvious reasons
not to do so—big cars cost more, and are
more costly to run—may not be the only
disincentive to changing. Dr Nickerson
and Dr Solomon found, in fact, that the
third-child deterrent appears stronger
among wealthier families. As they observe,
“large cars like minivans also have class
and aesthetic connotations that may make
people reluctant to switch even when they
can afford to.”Back-seat driver
Oddly, though, the authors do not leave it at
that. Instead, they point to previous stud-
ies which suggest that, for children over
two, safety seats are no better than seat
belts at protecting against death or serious
injury in a crash. They estimate that laws
requiring children to sit in special seats un-
til they are eight years old saved about 57
lives in 2017 and contrast that number with
the 8,000 children who might have been
conceived and born in the absence of such
rules. There is, they conclude, no “compel-
ling social interest” in requiring child seats
for children over four.
This seems weird. Comparing putative
lives forgone to actual lives saved is, to put
it politely, a strange moral calculation. And
the empirical basis for it is, in any case,
doubtful. Alisa Baer, a paediatrician in New
York who specialises in car-seat safety and
who says she has installed at least 15,000
such seats over the years (she is known as
“The Car Seat Lady”), says that this part of
the paper is “completely preposterous”.
Children’s car seats, she says, “save the
quality of life” of children who would suf-
fer higher rates of injury compared with
simply belting up—including massive ab-
dominal trauma and paralysis. A recent
study by Mark Anderson at the University
of Washington and Sina Sandholt at Co-
lumbia University bears this point out.
That does not, though, detract from the
wider observation Dr Nickerson and Dr Sol-
omon make that well-intentioned actions
can have surprising knock-on effects. And
one such, it seems, is that the back seats of
American cars, once renowned as places
where children were conceived, may now,
themselves, be acting as contraceptives. 7A
recibo observatorywas conceived in
an era of space-age monumentalism,
an imposition of geometry onto geology as
striking in its simplicity and scale as the
greatest brutalist architecture. When the
James Bond franchise, in its pomp a show-
case for iconic 1960s design, eventually got
around to using the 306-metre dish as a lo-
cation in the 1990s, the only surprise was
that it had taken so long.
The observatory was not new to spy-
craft. It was created as a tool for using radar
to study the ionosphere, an electrically
charged upper layer of the atmosphere.
America’s defence department had an in-
terest in such work, which might lead to
new ways of characterising incoming mis-
siles or of snooping on enemy transmis-
sions, so it stumped up some cash.
A free-standing dish big enough for the
job would have been impractical. The de-
signers therefore looked for a hole in the
ground to repurpose. They found it in
north-western Puerto Rico, a sinkhole
where the limestone landscape had col-
lapsed in just the right way. They built three
towers on the sinkhole’s rim and hoisted
the electronic heart of the instrument—the
bit which emits and receives radio waves—
into the empty space between them. Sig-
nals travelling to or from this equipment
would bounce off eight hectares of wire
mesh stretched out beneath it.
As a radar, Arecibo used the world’s big-
gest dish to study not just the ionospherebut also the surfaces of nearby planets and
passing asteroids. But it was as a radio tele-
scope that it truly excelled, making some
crucial discoveries during the 1960s and
1970s, radio astronomy’s golden age. The
most famous was a pair of pulsars—spin-
ning neutron stars—orbiting each other in
a way which was shown to prove Einstein’s
general theory of relativity. Later data re-
vealed planets around another pulsar. This
was the first definitive detection of planets
beyond the solar system.
Arecibo was also used for radio astrono-
my’s wayward offshoot, the search for ex-
traterrestrial intelligence. Since 1960 radio
astronomers have occasionally employed
their instruments to look for artificial sig-
nals from the stars. In 1974, after an up-
grade that saw the original mesh replaced
by a dish made up of 38,778 aluminium
panels, Arecibo was used to go a step fur-
ther. It transmitted a 1,679-bit message to-
wards a star cluster 25,000 light-years
away. Encoded in this message were graph-
ical representations of basic biochemistry
and astronomy, and of the technology with
which it had been sent.
Over time, technological advance erod-
ed the advantages of Arecibo’s sheer size,
and its funding dwindled. The engineering
began to show its age. In August one of the
cables supporting the instrument platform
snapped, damaging the dish. The snapping
of a second, in early November, seemed to
presage imminent collapse. And so it is to
be closed.
But as the vegetation beneath the dish
rises through its remains, and the site falls
into picturesque ruin, the sketch of its
cross-section encoded in that message
from the 1970s will continue on its way. It is
already 46 light-years from Earth. Its pixels
now constitute the farthest-flung memori-
al to a human achievement anywhere in
the universe. And they always will. 7An era ends for radio astronomyThe death of AreciboSi monumentum
requiris respicite
Farewell, my lovely