The EconomistFebruary 3rd 2018 Science and technology 6912 at a comparatively stately three metres a
second. This is slow enough, he reckons, to
permit fish to swim through easily.
There could be financial benefits, too.
Existing tidal-power schemes, such as the
one on the Rance estuary in France, funnel
their water through tapered concrete chan-
nels, because the turbines used in them
work best when water is flowing fast. Wa-
ter wheels are quite happy with slower
currents, eliminating the need to build ex-
pensive channels. Also, steel is cheaper
than the concrete used in other schemes.
Comparing the amount of steel in his wa-
ter wheels with the amount used in off-
shore wind turbines (for which it is a signif-
icant cost) has convinced Mr Rainey that
his scheme could be competitive. One of
his wheels would contain about half as
much steel again as does a modern wind
turbine, but it would produce five times
more power.
So far, so hard-headed. The final advan-
tage of Mr Rainey’s scheme, though, is pure
poetry. Water wheels powered the early
stages of the Industrial Revolution, but
were eventually replaced by coal. There is
a pleasing symmetry to the idea of fighting
the planet-heating side-effects of fossil fu-
els with the help of an energy source they
had supposedlymade obsolete. 7
The genetics of divorceFamily values
T
HAT the children of divorced parents
are more likely, when they grow up, to
get divorced themselves is well known.
What is not known is how much this
tendency is the result of nurture (with
children manifesting, in later life, behav-
iours learned from theirparents), and
how much it is caused by nature (with
children inheriting from divorced parents
the sorts of genes that lead to marriage-
breaking behaviour). That genes are
importanthas, though, now been con-
firmed by a study published in Psycholog-
ical Scienceby Jessica Salvatore and
Kenneth Kendler of the Virginia Institute
for Psychiatric and Behavioural Genetics.
To explore the role of genes Dr Salva-
tore and Dr Kendler turned to the Swed-
ish national registries. These databases
store, for all residents of Sweden, infor-
mation on sex, year of birth, year of
death, marital status, criminal activity,
education and alcohol abuse. They also
contain details of both the biological and
the adoptive parents ofadopted children.
Using these data, the researchers set
about the daunting task of analysing the
marriages of19,715 adopted children, to
see how often these ended in divorce and
whether that divorce rate bore any rela-tionship to divorces amongtheiradop-
tive and biological parents. This analysis
showed that such children were 20%
more likely to divorce if their biological
parents had divorced than if those par-
ents had stayed together, but no more
(and no less) likely to do so iftheir adop-
tive parents had split up.
With this result under their belt, Dr
Salvatore and Dr Kendler then looked at
adopted and biological siblings brought
up in the same households. As expected,
they found that individuals showed a
similar tendency to divorce to that of
their biological siblings but not to that of
theiradopted siblings. They also discov-
ered thatif one biological sibling di-
vorces, the others are 20% more likely to
do so than would otherwise be the case.
This is not true foradoptive siblings.
All of these results stronglysuggest, Dr
Salvatore and Dr Kendler argue, that
genetic factors play an important part in
the “transmission” of divorce across
generations—and that this needs to be
taken into consideration when offering
psychological support and relationship
counselling to people whose parents
have split up, even if those people never
knew the parents in question.A study of adopted children shows that genes play a role in divorceE
XPECTATIONS are high, among those
boosting the idea of self-driving cars,
that people will be able to do otherthings,
such as reading, working on a laptop or
having a nap, when riding in such a vehi-
cle. But for many that is an unlikely pros-
pect. Apart from those who have no inten-
tion of even getting into an autonomous
car, which currently amounts to some 23%
of Americans, another 36% would be will-
ing to ride but would not take their eyes off
the road, according to a studypublished in
2014 by the University of Michigan. Some
of those people will be looking out of the
window because it helps to avoid nausea,
dizziness and vomiting, particularly if they
are among the 5-10% of the population
who regularly experience the unpleasant
symptoms of motion sickness.
Help, though, is at hand. The selfsame
authors of the Michigan study, Michael Si-
vak and Brandon Schoettle, who both
work for the university’s Transportation
Research Institute, have justbeen awarded
a patent for a device that could act as a
countermeasure against the malady.Motion sickness is caused by a conflict
between signals arriving in the brain from
the inner ear (which forms the base of the
vestibular system, the sensory apparatus
that deals with movement and balance,
and which detects motion mechanically),
and from the eyes, which detect motion
optically. If someone is looking at a station-
ary objectwithin a vehicle, such as a maga-
zine, his eyes will inform his brain that
what he is viewing is not moving. His innerears, however, will contradict this by sens-
ing the motion of the vehicle. The resulting
confusion, at least according to one theory,
leads his brain to conclude that he is hallu-
cinating because he has ingested poison.
Hence the need to throw up, to rid the
stomach of any toxins.
The idea that Dr Sivak and Mr Schoettle
have come up with is to arrange for an ar-
ray of small lights to appear in the periph-
ery of a potential sufferer’s field of view,Motion sicknessThe upchuck
wagon
How not to feel queasy in a self-driving
motor car