28 | New Scientist | 11 June 2022
Views Columnist
I
RECENTLY posted an article
to Twitter about a question
that completely caught me
off guard: do we understand
why planes stay aloft? It turns out
that the answer to that depends
on who you ask.
To allay any anxiety you might
suddenly be feeling, the first
thing to say is that we know which
equations to solve and which
solutions give us a plane that stays
up in the air. The challenge is that
we don’t know how to interpret
those solutions to offer an
intuitive explanation, something
we can all immediately grasp,
rooted in physical principles.
I grew up hearing that it is all
explained by Bernoulli’s principle,
with lift resulting from air flowing
faster over the top of the wing and
slower underneath. But I learned
recently that this can’t explain
why planes can fly inverted.
Whether this is a problem or
not depends on what you think
counts as a good understanding
of physics. The mathematically
inclined may be happy with the
solutions alone. But as physicists,
we are trained to expect that once
an equation has been solved, we
should be able to reverse-engineer
an explanation for why the
solution is physically sensible.
Sure, physicists often work with
complex equations. But we should
be able to give everyone a feel for
what we have learned, right?
Well, sort of. In my book The
Disordered Cosmos, I write about
the time when British-Iraqi drag
performer, writer and film-maker
Amrou Al-Kadhi told a Channel 4
News presenter in the UK that
subatomic particles are non-
binary, so of course it follows
that gender can naturally be non-
binary too. I loved this comment
from Al-Kadhi for reasons that
perhaps they themselves would
find surprising: to me, it suggestedthat all of the physicists who
were shocked to discover that
these fundamental objects can
be particles and waves at the same
time were too stuck in old ideas
about gender to have an intuition
for it. Perhaps if we all grew up
without the gender binary, then
wave-particle duality, as this
quantum phenomenon is called,
would feel as intuitive as gravity
does, at least in terms of how it
behaves in and around Earth.
That is the thing about
intuition. It is a feeling. The fifth
definition of “intuition” in the
Oxford English Dictionary comes
from philosophy and is articulatedas follows: “The immediate
apprehension of an object by the
mind without the intervention of
any reasoning process; a particular
act of such apprehension.” That
is to say, intuition is immediately
understanding something
without really having to think
about it. In that sense, I am not
sure intuition is possible in
physics. We always have to think
deeply about the subject at hand
to understand what is going on.
But it is certainly the case that
such thinking becomes faster as
we get more used to certain ideas.
Importantly, even if we
understand something, that
doesn’t necessarily mean we know
how to describe it in words. Alexis
Shotwell writes about this in her
book of philosophy, Knowing
Otherwise: Race, gender, and
implicit understanding. Shotwell
describes the phenomenon of
“implicit understanding” –knowledge that we hold but can’t
put into words. Take riding a
bicycle. As I wrote this paragraph,
I thought about how to describe
the mechanism of riding a bike
and realised it would probably be
a good writing exercise because
the words didn’t come naturally
to me. So, while I disagree with
some applications of the idea
in Shotwell’s book, I think her
concept of implicit understanding
can help us to better understand
our own perceptions and
expectations of what physicists do.
Does it matter if we can’t put
into words why planes fly, as long
as we keep them aloft? This is,
on some level, a philosophical
question. Calling it philosophy
doesn’t mean I am not responsible
as a physicist for sorting out an
answer, just that I understand
I am choosing a position that
reflects my own personal view,
not something that is rooted
in definitive empirical data. As
it happens, the way I think about
this question has implications for
questions that are more relevant
to my research than planes are.
A reader of this column wrote
to me some months back, for
example, asking what it meant
that space-time is expanding:
where was all of the extra
space-time coming from? As I
considered how to answer this
question, I read other people’s
explanations and realised that it
might seem as if I were cheating if
I gave similar explanations. None
of them is intuitive and some of
them boil down to “the equations
imply this”, which would hardly
be satisfying. In the end, the
answer is that space-time isn’t an
object but a phenomenon. What
does that mean? It may not be
immediately obvious, but in my
next column I will try to explain,
to make sense of it in the most
intuitive way I can. Stay tuned. ❚“ Perhaps if we all
grew up without
the gender binary,
wave-particle
duality would
feel intuitive”Why planes fly We physicists want to give everyone a feel for
what we are learning, but the truth is that physics and intuition
don’t always mix, writes Chanda Prescod-WeinsteinField notes from space-time
This column appears
monthly. Up next week:
Graham LawtonWhat I’m reading
Audre Lorde’s poetry
has been helping me deal
with the mass shootings
here in the US.What I’m watching
Women’s basketball
is back here in the US.
Go Connecticut Sun!What I’m working on
I am part of a national
planning process to help
determine what particle
physics research we will
do in the next decade.Chanda’s week
Chanda Prescod-Weinstein
is an assistant professor
of physics and astronomy,
and a core faculty member
in women’s studies at the
University of New Hampshire.
Her research in theoretical
physics focuses on cosmology,
neutron stars and particles
beyond the standard model