3 October 2020 | New Scientist | 55Tom Gauld
for New Scientist
Answers
Iain Brassington
University of Manchester, UK
I am in no position to say whether
an infectious cure for a disease
would be a practical possibility,
but let’s assume that it would be.
There would, however, be a serious
ethical and legal concern about
any such intervention because it
would amount to unconsented
medical treatment.
It is a widely accepted principle
that people should be able to
refuse medical treatment, even
if it would be irrational to do so
and even if there’s a public good
to be served by giving it. But with
a contagious cure, these people
wouldn’t even get the chance
to refuse, since they would be
exposed to the “treatment” simply
by standing next to the wrong
person at the supermarket.
We do sometimes intervene
medically without consent – we
vaccinate babies, for example.
However, even in that case,
there is someone who could
refuse on their behalf. There
would be no such possibility
with infectious cures.
Doubly dark
What would it look like if
dark matter fell into a black
hole? What might you see
while it was happening?Mike Follows
Sutton Coldfield, West Midlands, UK
There would be no discernible
difference to the appearance
of a black hole. Besides, a small
amount of dark matter probably
already falls into black holes.
Dark matter doesn’t interact
electromagnetically – so cannot
emit, absorb or scatter light – but
it does respond to the force of
gravity, so would fall into a black
hole in the same way that ordinary
matter does. However, while
ordinary matter collapses to
form a galactic disc, emittingelectromagnetic radiation in the
process, dark matter stays in the
form of a spherical halo around
the visible component. This
means that it is mainly ordinary
matter that falls into a black hole.
Dark matter probably paved
the way for black holes to exist
by creating the texture of the
universe, as well as the location
of galaxies. Until the universe
was about 300,000 years old,
it was too hot for neutral atoms
to form. The early universe was
composed of plasma (protons and
electrons). These charged particles
were scattered by photons and
this prevented ordinary matter
clumping together gravitationally.
Meanwhile, any fluctuations
in the density of dark matter were
accentuated by gravity, whose
fingerprint can be seen today as
ripples in the cosmic microwave
background radiation. As soon
as neutral atoms formed, they
could gravitate towards areas
where clumps of dark matter
built up, leading to the creation
of galaxies and the spawning
of stars, including black holes. ❚Quick quiz #71
Answers
1 Bellerophon, after a hero from
Greek mythology known for
capturing winged horse Pegasus2 Carl Friedrich Gauss3 Mistletoe. It is more commonly
known as the mistletoebird or
the mistletoe flowerpecker4 18045 Rock flour, or glacial flour. This
finely ground rock is produced by
erosion. When particles of it are
suspended in water, they reflect
more blue and green lightQuick Crossword
#67 Answers
ACROSS 1/4 Planet Earth,
8 Blossom, 9 Camphor,
11 Hydrophobia, 14 Piece,
15 Orbiting, 17 All clear, 19 Ebb,
20 Answerphone, 24 Eurasia,
25 Nitrile, 26 Latex, 27 EdisonDOWN 1 Paley, 2 Absorbency,
3 Ecosphere, 5 Atari, 6 Tape,
7 Cocooned, 10/18 Tomorrow’s
World, 13 Star charts, 14/12
Pale blue dot, 16 Bowerbird,
21 Noise, 22 Nylon, 23 Gaia#78 Farewell My
Blubbery^
SolutionThe book has 153 pages. You
can discover this by trial and error,
but algebra offers a shortcut.
The number of digits N needed to
number a book with 100 pages
is 192; with 101 pages it is- So, in general, if a book has
ABC pages, N = 3(ABC) – 108.
Try A = 1, which is the shortest
possible book: 3 × (1BC) – 108 =
CB1. If 3 × 1BC – 108 ends in 1,
then 3 × 1BC ends in 9, so C must
be 3. That means ABC = 1B3.
The only value of B that works is 5,
so there are 153 pages and these
will take (as you may easily check)
351 digits to number.
“ People would be
exposed to the
‘treatment’ simply
by standing next
to the wrong person
at the supermarket”