54 | New Scientist | 15 January 2022The back pages Almost the last word
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Full terms and conditions at newscientist.com/lw-termsIn hot water
I am right-handed and I find
it difficult to accurately judge
the temperature of bathwater
with my left hand. Why?Jacky Pett
Hampshire, UK
If you have used your right hand
to test the temperature of the
bathwater all your life, then it
has been trained to know what
the “right” temperature is to
within a fine tolerance, whereas
your left hand only knows
roughly within a broad tolerance.
I am a right-hander and
use my right hand to test the
bathwater. However, I find that
the temperature that is right for
this hand is often wrong for the
rest of me. My right hand is less
sensitive to hot or cold on the
skin than my left hand, wrists
or elbows, which are all better
places for testing bathwater.
This means that water I can
put my right hand into may be
uncomfortably hot or cold for
other parts of my body. I suspectthis is related to the ability
of many cooks to easily hold
dishes that others find too hot.
This hypothesis is complicated
by me being left-handed for some
things and not others, partly
due to being told to write with
my right hand at school. So
my right-handedness may
not be a valid comparison.Selina Dussaye
Perth, Western Australia
Repeated use of a dominant
hand for tasks like checking the
bathwater may mean that there
are more neural pathways in
the brain dedicated to analysing
information received through
the sensory receptors in that hand.SHUTTE
RS
TOCK
/BACHKO
VA
NATA
LIADaniel Casasanto
Department of Psychology,
Cornell University, Ithaca,
New York, US
This is the first time I have
heard of someone being able
to discriminate temperature
better with their right hand
than with their left.
Whether this pattern
is found in people more
generally is an open question.
If so, here is a possible reason
why it could happen. People
use their dominant and non-
dominant hands differently.
The dominant hand is used
for more “approach-related”
actions, in which you engage
with the world around you
in an intentional way.
The non-dominant hand
more often performs “avoidance-
related” actions, in which you areresponding reflexively to prevent
something bad from happening.
I call this the sword and shield
pattern of hand use.
The person asking this question
is reporting less temperature
sensitivity in their non-dominant
“shield hand”. It would make
sense, evolutionarily, for the
shield hand to have reduced
sensitivity given that it is more
likely to be injured in the service
of classic avoidance actions,
such as fending off attack.
This is just a hypothesis.
An easy way to test it would
be to find out whether, on
average, right-handed people
have less sensitivity to
temperature (and presumably
also to pain) in their shielding
left hand, whereas left-handed
individuals have less sensitivity
in their right hand.Into the void
The universe is expanding, but
what exactly is it expanding into?Andrew Taubman
Queens Park, New South Wales,
Australia
By definition, the universe is
everything, so there is nothing
external to it for it to expand
into. It is not expanding into
anything as such – everything
is expanding.Richard Swifte
Darmstadt, Germany
It is all too easy to think of the
big bang and the resulting
expanding universe as being
like an ordinary explosion,
with everything expanding
out from a central point.
A better analogy is to consider
the surface of an inflating balloon
where the surface is a two-
dimensional equivalent of our
three-dimensional universe.
The balloon fabric is space; dots
marked on this surface (equivalent
to galaxies) will move apart as
the balloon expands, but only
because the fabric (space itself)
is expanding, and without any
central point for the expansion.
The balloon is expanding into
the third dimension, but here
the analogy is more problematic.
Is our universe also expanding
into a higher dimension?
If the universe is all there
is, and isn’t part of a larger
multiverse, then there is nothing
outside it (not even a vacuum,
which is still space), so it probably
makes no sense to ask what
it is expanding into.Nick Canning
Coleraine, County Londonderry, UK
A two-dimensional being on the
surface of an expanding balloon
can observe all distances in its
surface world getting larger. It
can’t see the third dimension into
which the balloon is expanding.This week’s new questions
Wakeful winter Why are there no birds that hibernate?
Jim Stone, Great Hucklow, Derbyshire, UKFace up to it On a cold night, why does our body require
clothing or bedding yet our face remains warm without
covering? Bonita Ely, Marrickville, New South Wales, AustraliaBears, bats and many other
creatures hibernate in winter,
so why not birds too?“ Your non-dominant
hand is often used
reflexively like a
shield to prevent
something bad
from happening”