54 | New Scientist | 8 January 2022The back pages Almost the last word
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Full terms and conditions at newscientist.com/lw-termsSpider survival
I often catch house spiders and
release them some distance away.
Can they navigate back? If not,
what are their chances of survival?Brian Reffin Smith
Berlin, Germany
The only place to release a
house spider is a house. That’s
their habitat.Matt Bertone
North Carolina State University, US
First, it depends on the type of
spider. If it is one of the more
active ground spiders, like a wolf
or sac spider, it would appreciate
being released outdoors. This
is because these spiders often
accidentally come into homes,
where there isn’t a lot of prey
for them. If they become trapped
for too long, they can perish, so
letting them go live back outside
can be a huge favour for them.
Other spiders, like cobweb
spiders and cellar spiders, tend
to do well in our homes for their
entire life. In this case, they canbe left alone, but if removed from
the house, they will often find
the nearest area that is suitable
and do their best to survive.
Such spiders don’t have good
ways to find their way back to your
house, and it would require a lot of
energy and drive to do so. I would
also caution that removing spiders
from a home, with a specific
temperature and humidity, into
an environment that may be
drastically different could harm
the spider. For instance, if the
temperature outside is too cold or
hot, it may have negative effects.
However, spiders are pretty hardy
animals, so moving them usually
doesn’t cause problems.
All said, spiders are fairlyDASR
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/GETTY^ IMAGESadaptable to local habitats, and
most don’t require special spaces,
except places to build webs or
areas to hunt for food.Me and my brain
If I could somehow replace
every atom in my brain one at
a time with the same elements,
am I mentally still me?Eric Kvaalen
Les Essarts-le-Roi, France
Yes, you would still mentally
be you. In fact, the replacement
of brain atoms does happen
at a certain rate. Besides which,
from the point of view of
quantum mechanics, identical
atoms are like dollars in a bank
account – they don’t have
individual identities.Garry Trethewey
Cherryville, South Australia
That is pretty much what actually
happens: your brain and body
have very few, if any, of their
original atoms. In fact, we
probably all contain atoms that
once were part of Adolf Hitler,
Albert Einstein or a dinosaur. Even
without the replacement issue, are
you mentally the same person you
were when you were 2 years old?Nick Canning
Coleraine, County Londonderry, UK
The problem of personal identity
is an ancient one, analogous to a
wooden ship undergoing repairs
until eventually every plank has
been replaced. Is it still the same
ship? If all the discarded planks
were themselves reassembled,
would we have one or two ships?And are you mentally the same
person you were as a child,
when you were a tenth the
mass of your adult self?
If your sense of self at any
moment is a product of your
material body, associated with the
workings of your brain – which
depends on all the neurons and
their exact location, function
and connections established
over time – then if you could
build an exact replica, it would
also feel that it was mentally
still you. The content of its
self-consciousness would be
indistinguishable from yours.Arnold Taylor
Isle of Wight, UK
It is a fundamental tenet of
quantum theory that all atomic
particles of the same kind are
indistinguishable. Therefore, if all
the atoms in a brain were replaced
by identical atoms, the person
would remain mentally the same,
although the states all the atoms
were in would probably need to
be unchanged as well.
While such a replacement is
hypothetical, the same brain
pattern could, in principle, recur
on another planet in the universe
if our evolutionary process were
repeated. This is, however,
exceedingly improbable. In
addition, the vast number of
atoms in the brain, or the part of
it that determines an individual
consciousness, also means that
such a recurrence is unlikely to
happen anywhere in the universe.
But there are cosmological
theories that propose that our
universe could be one of infinitely
many having the same physical
laws. If so, the recurrence of a
person’s brain pattern becomes
almost certain to occur among
them, albeit with unimaginable
separations in time and space.
This would be physical
reincarnation, although the
individuals would be totally
unaware it had happened.This week’s new questions
UV glow Why do only some materials glow under UV light?
For instance, when I shine my UV torch at a packet, only
the price ticket glows bright blue. John Cooper, London, UKPong problem How is it that one’s own farts smell tolerable,
but other people’s smell awful? How does the brain
differentiate between the two? Tim Hale, Sheffield, UKWhat causes some materials
to glow under ultraviolet light,
but not others?“ Spiders don’t have
good ways to find
their way back to your
house, so they find the
nearest suitable area
and try to survive”