December 2, 2021 • 39 mins
Once more, Robert and Joe consult the winners of the Ig-Nobel Prizes for a few examples of the hilarious and the weird from the world of legitimate scientific research.
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Speaker 1 (00:03):
Welcome to Stuff to Blow Your Mind, the production of
My Heart Radio. Hey you welcome to Stuff to Blow
your Mind. My name is Robert Lamb and I'm Joe McCormick.
And today we're finally getting around to it. We wanted
to talk about a few of the ig Nobel Prize
(00:24):
winners from this year. Yes, we're a little late. The
awards ceremony was in September of this year and we're
just now getting to it. But you know, a lot
of things are happening around the September October. It's a
busy time for us. Yeah. I think we've covered the
ig Nobels every year since we started covering them, and
I'm not sure when that year was. Maybe it was
like two thousand seven, two eight or something. I don't know,
(00:46):
it's pretty early on. Um, we almost never cover them
right away because, like you said, there's there's generally a
lot going on. The awards usually come out during September
or very early October, and so we're either wrapped up
in Halloween stuff I then, or we're getting ready to
do Halloween stuff or something like that. Uh, So we
generally come in like late November or part of sometime
(01:09):
in November or in this case, very early December. But
I guess it's better late than never. And uh, I
guess one of the cool things about this is is
we kind of come in after the initial coverage and
chew on them a bit more. So, if you're waiting
on these episodes and you and you're inclined to complain,
just don't stop. But if you're not familiar, the ig
(01:30):
no Bells are a series of awards given out once
a year by a scientific humor journal called the Annals
of Improbable Research that's been edited for many years now
by somebody named Mark Abraham's and the stated purpose of
this of these awards is to quote honor achievements that
first make people laugh and then make them think. So
(01:52):
to give you an idea if if you haven't heard
one of these episodes before and you've never read about
the ig Nobels. Among the awards we covered last or
there was a prize in the material science category for
research into whether you could make a knife blade out
of frozen feces. What was the verdict on that? I
think it was no right that no matter how hard
(02:13):
you freeze them, they just don't really cut. I believe
so um, you know, it reminds me of Yeah. I
think they think that the research ended up saying, yeah,
like you, no matter how hard it gets, uh, you're
still gonna have a certain amount of melting that's going
to take place, right because the friction on the sharp
end will will pretty quickly wear it away and then
it's then it's blunt. Yeah, better to make it like
(02:34):
a frozen poop warhammer, I think, so that could shatter.
I don't know, we'll look into that in the future. Um,
but then let's see what was One of the other
ones we did last year was there was a prize
in the acoustics category for a study that made alligators
huff helium to see if it made their voices higher pitched.
(02:54):
I remember that. Yeah. So occasionally the papers that get
selected for these prizes are I think originally themselves intended
to be satirical or funny. One example like that that
comes to mind is, uh, there was a rayology study
one year about whether cats should be considered a solid
or a liquid. That that was a good one, but
(03:15):
clearly there was a good bit of jokiness about the
paper itself most of the time. Actually, this the research
covered in in these prizes, is it's just straightforward research.
They're they're straightforward experiments published in real scientific journals that
happened to have some weirdly hilarious methodology or finding. Yeah.
(03:35):
Either you know, it varies, but you know, sometimes it's
it's just a particular experiment that is hilarious or giggle inducing. Um.
Other times it's just the minutia of it, you know,
one of those kind of a shrimp on a treadmill
situation where it may it's still important work. It's all
part of the general um, you know, expansion of scientific
(03:57):
knowledge of of the universe, but it just in an
area that we might not think about. Or sometimes it's
just an important study that involves like pooper vomit or something,
and therefore just by ver orteese or something, you know,
just by virtue of the subject, kissing, yeah, is inherently funny. Now,
in these episodes we're doing on on the Igno Bells,
(04:18):
we're just going to pick out a few of the
prizes to highlight because there was something about them that
we wanted to talk about. We're not gonna have a
chance to cover all of the winners, but if you
want to read about those. You can go to the
Annals of Improbable Research website at Improbable dot com and
you can see the full list of the awards and
click on links to to read about them. I mean,
(04:39):
and not only the most recent awards, but you can
go back through the entire history of the Igno Bells
and just and explore them all. It's a very simple,
easy to use website. Well, I am ready to get
started if you are, Uh, let's do it, okay, Well,
the first area I wanted to get into was actually
this will be a pair of thematically linked prizes from this.
(05:00):
The first is the Physics Prize, which went to Alessandro Corbetta,
Jasper Mayu, Sen Chung Min Lee, Roberto Benzi, and Federico
Tashi quote for conducting experiments to learn why pedestrians do
not constantly collide with other pedestrians. And then the second
here is the Kinetics Prize, which went to his Sashimurakami,
(05:25):
Claudio Feliciani, Utah Nishi Yama, and katsu Hero Nishi Nari.
And this is quote for conducting experiments to learn why
pedestrians do sometimes collide with other pedestrians. Uh, Rob, have
you ever had a really memorable, just bodily head on
with somebody. I was trying to remember if I had,
and I could not bring any instances to mind. Though
(05:47):
I have run into plenty of things in my life.
I run into tree branches and sliding glass doors, but
I can't really think of any head ons with humans
except maybe while playing soccer. Yeah, thinking back, yes, certainly,
I there have been more than a few low hanging
branches that have have clipped the top of my head
or tried to stab me in the eye, that sort
(06:09):
of thing. But in terms of of running into people,
um even in crowded cities, and like I was just
in um in New Orleans, and you know, those are
some crowded streets at times, and those are also some
drunken streets at times. You know they're folks wandering around
in various states of inebriation, and yet you don't see
people just colliding with each other. I feel like I've
(06:32):
had I can think maybe to some close calls in
the past where you have that moment where you almost
run into somebody and you both kind of acknowledge it
and it's a little bit awkward, but still it's not
like you see. I guess in a lot of like
comedy films where people just plow into each other, knock
their groceries down, and then they have a romantic moment
as they pick up each other's groceries, that sort of thing. Yes,
(06:53):
why is it romantic comedies where people plow into each other?
I guess there's something metaphorical about that, about you know,
the oh you came into my life like a like
a large, massive meat slamming me in the face. Yeah.
Because Yeah, in general, you don't see like fights breaking
out because people ran into each other, or at least
I don't think I've ever seen that occur. I mean
(07:15):
it probably has occurred, but not with the regularity you
might expect, given just how intense uh streets and sidewalks
are at times. Yeah, and I think this is something
we should keep in mind as we discussed this research.
It's interesting how rare collisions are given how often huge
masses of people are just criss crossing with each other
all day. So to actually reference the two papers here,
(07:38):
the first one was Corbetta at all. This was in
Physical Review E in eighteen and it was called Physics
based Modeling and Data Representation of pair wise interactions among pedestrians.
And then the second paper the Kinetics Prize was called
Mutual anticipation can contribute to self organization and human crowds.
This was by more commy at all in one in
(08:00):
Science Advances. Now, I was interested in this pair of
findings not only because I was obviously amused by the
image of people just absolutely eating each other's teeth in
in high speed sidewalk collisions, but because this is one
of those ignoble subjects where once you get beyond the
mildly funny image it conjures, it actually raises quite i think,
(08:23):
quite deep, mysterious, fascinating questions about the emergent mathematical properties
of human behavior in groups. And it's also a subject
that goes way beyond mere curiosity. Understanding the flow of
crowds is a matter of life and death. It is
a vitally important subject for all kinds of reasons. So
(08:44):
this involves questions like how do masses of people move
through space on foot? What rules govern their behavior both
as individuals and as as a group, How can that
behavior be influenced, and especially how does the built environment
shape that behavior? Uh, you know, as you were alluding
to a minute ago. I think it's actually kind of
(09:05):
amazing how pedestrians can navigate through crowds without running into
each other. It's one of those, you know, thousand little
miracles of human human brain capacity that we don't usually
notice or appreciate. But you can have huge crowds moving
quickly and bi directionally mean running at cross directions, past
(09:25):
each other, straight through each other, and uh and most
of the time people are able to avoid human crashes. Yeah,
and it it seems to be the case no matter
where you go, even though I will say, and this
is just uh my my observation. I don't know to
what extent this this holds up to research, but it
feels like in in some parts of the world, the
(09:47):
the energy of love, say, the movement of crowds on
a sidewalk can feel different, can a little bit different,
you know, but it's still maintaining, you know, the same
collision free experience. You know, like like maybe there's there's
something slightly different going on there, there's some sort of
there are different cultural norms in place regarding say, like
(10:08):
what side of the sidewalk people moving this way should
be on, or or so or so forth, or or
even maybe you know how much space is permittable between
you and the next person, but still people are managing
not to blow into each other. Yeah. So to discuss
a few of the details of these two studies, regarding
the first one, Corbetta at all from from eighteen. I
(10:29):
was reading about this uh in an article that had
a few interview clips um from in l Times, and
this was looking at Technical University Eindhoven researchers Federico Tashi
and Alessandro Corbetta and uh so their study in particular
was looking at the question of how pedestrians avoid running
(10:51):
into each other when moving through the Eindhoven train station,
and they did this by installing sensors under the plow
forms of the train station which they used to track
the movements of pedestrians across the platform. So this was
an area of like twenty seven square meters and they
tracked pedestrian movement within it for six months. This came
(11:13):
out to measuring the movements about five million pedestrians total,
and they found a few measurable quantities. So first of all,
they said that people keep an average distance of about
seventy five centimeters away from other people while moving through crowds,
so that's about two and a half feet. And they
said that about one out of every thousand people quote
(11:34):
will turn around and go back the way they came
to avoid bumping into somebody else. According to Alessandro Corbetta, quote,
about eighty of the pedestrians actually collided with each other.
The other pedestrians adjusted their walking route when they were
at least a hundred and forty centimeters which is about
four ft and seven inches apart, and thus managed to
(11:55):
avoid a collision. And though I was wondering about that,
so he gives the number eighty eight pedestrians collided. Does
that mean eighty pedestrians total, meaning roughly forty collisions or
is that like, uh, there were eighty collisions, which would
make you think they'd be like at least a hundred
and sixty people involved. I'm not sure. Well, it raises
the question how many people are necessary to create a collision?
(12:18):
Is it one? Or is it too it's at least two,
I mean you could have more, I guess, But is
it I guess it depends on like is it is
it negligence on one person's part that leads to collision?
Or negligence or distraction whatever on two people's parts. You know, Ah,
well that will I will actually come up in the
other study, I think. But what this study found is that, yeah,
(12:40):
people are constantly monitoring for upcoming collisions and then adjusting
their walking trajectories accordingly several meters in advance. So ultimately,
the question here is it's not really relevant exactly how
many people slammed faces, but how on average pedestrians adjust
their courses to avoid collisions. What rules do they use
(13:01):
to make those those evasions? And this just apparently happens constantly.
We're usually not even aware of it. But you know,
I can recall, like moving through an airport or something,
you are just doing a delicate dance for for several
minutes of a time at a time, often you know,
just dodging dodging, dodging, dodging, and you don't even really
think about it. It's a process that can be be
(13:23):
oddly captivating, I find, you know, especially if I'm on
my own, I don't have to worry about anyone else,
you know, traveling with me. Uh, you know, cutting a
swath for them to travel through, you know, checking back
on how they're doing it. It's just me cutting through, um,
like a reasonable sized crowd or a reasonable flow of
pedestrian traffic. Uh, it feels kind of empowering. Well, yeah
(13:47):
it is, and I think that highlights one of the
interesting features there, which is that, um, so when you're
moving through a crowd, you are making individual decisions, like
and those decisions are being driven by different things. Like,
on one hand, you've got your basic propulsive drive, like
you have where you need to be and the course
you think you need to take to get there. And
(14:08):
then probably the second main thing governing your movement is
what these researchers would refer to as social forces, which
would be things like the taboo against touching other people
while you're walking, or basically the force that keeps you
separate from other people and makes you want to avoid
running into them or touching them in some other way. Yeah,
(14:28):
because there's a physical risk to actually running into somebody,
and there is like a social risk to not only
running into somebody, but even almost running into somebody, yeah,
even getting too close exactly. But so while those forces
are are guiding your decision making as an individual, you
are a thinking person and you you know there are
cognitive inputs, like you are moving through this crowd as
(14:51):
an individual. It's strange that take thousands of people and
they're all making these individual decisions based on these types
of forces, you know, their drive forces, and their and
their restrictive social forces. And yet when you look at
them as a group, they seem to behave in ways
that are predictable. Even though they're making in these individual decisions,
(15:12):
they behave in ways that can quite well be modeled
and predicted and understood by things that are that are
like physics models the way the same way that you
would model, say, the movements of a fluid, you know,
a gas or a liquid through a container than and
(15:34):
so the authors of this first study you're saying, well,
by studying the natural movement patterns of pedestrians and trying
to model them in in terms of the language of
physics on a large scale, Uh, this can be useful
in terms of things like architecture and design. You know,
you can design better spaces for people to walk, both
in terms of efficiency the throughput how many people can
(15:54):
move through them quickly, but also in terms of safety
because as we know, and as I'll talk about in
a bit, UH, crowds can become quite dangerous when when
density gets too high. Now, I was also reading an
article that that had a few uh quotes from these researchers,
And this was an article for Physics, the magazine of
the American Physical Society by Michael scherber Uh. And this
(16:18):
one also discussed the second winner, the winner of the
Kinetics Prize, the paper that was by Murakami at all.
And this study was interesting too. So it instead of measuring,
you know, putting sensors under a floor and measuring natural movement,
it's staged experiments. So this study asked volunteers to walk
by directionally, so imagine people crossing each other, walking in
(16:43):
opposite directions the way they would say, like a crowded
crosswalk in the street. And then it tried to see
what happens when when people walk by directionally under normal circumstances,
and then what happens when some of those people are distracted, specifically,
what happens when they're trying to do calculations on their phones.
(17:03):
And the purpose of this experiment was to interfere with
people's ability to see collisions coming and avoid them. Now,
it probably won't come as a big surprise that pedestrians
who were distracted by phones made more navigation mistakes, leading
to a number of near collisions. But even when not distracted,
people sometimes had difficulty and uh. One of the implications
(17:26):
of this experiment is that avoiding collisions is a collaborative effort.
It requires awareness and coordination of multiple parties, both looking
at each other and trying to assess what paths they're
about to take, and then adjusting their own paths in accordingly.
(17:48):
And this becomes difficult when even just one of these
parties is distracted, especially if multiple parties are distracted. I
was also reading an interview with one of the researchers
from the second study, the coninectics ees UM. This was
on a Swiss news site swiss Info dot c H
and it was an interview by Zeno Soccatelli with a
researcher named Claudio Feliciani who works at the University of
(18:11):
Tokyo but who originally hails from Switzerland. And so Feliciani
mentioned a few interesting things in this interview. One is that, okay,
so when you when you have people not distracted, UM,
how do they tend to move in groups when they're
moving by directionally, like you imagine people crossing each two
crowds at at a busy crosswalk trying to go past
(18:31):
each other. How do they normally move? And Feliciani says
that what tends to happen is people automatically self organize
into lines. People tend to naturally follow the person directly
in front of them, and simply by obeying this rule,
the moving crowd naturally forms into lanes or lines of people.
(18:53):
And so they were trying to understand the mechanisms that
make these lines form and how they work. Of course,
you know one way understand how something works is to
see if you can break it. Um So, Feliciani says,
quote specifically, we caused some of the pedestrians to be distracted,
asking them to walk while solving simple calculations on their phones.
With just three out of fifty four people focused on
(19:16):
something else, rows formed much less quickly, especially if the
distracted people were at the front of the group, and
the increased attention of the non distractors is not enough
to make up for the lack of attention of the
three who are distracted. And then on this website there
is actually video I could watch maybe you want to
(19:36):
take a look, rob But there's video that shows how
people move in these lines under normal conditions, and then
what it looks like when just a few of them
are distracted. So not everybody is trying to do math
on their phone. Just a few people, just a few
people out of the fifty four completely screw things up
and everybody gets jammed up. The lanes stone form naturally.
(19:56):
Uh So it seems like its navigating through crowds by directionally.
It has this tendency to for you know, self organizing
emergent structures to form, but that requires everybody to be
paying attention and monitoring each other and sort of communicating
nonverbally about where they're headed. This is interesting. I mean,
(20:18):
of course, this has huge ramifications on a are already
you know, near ubiquitous use of smartphones and the fact
that people will have them out while they're walking around.
But it also makes me wonder about, you know, the
more we push into this idea of augmented reality, of
of having some sort of you know, a metaverse that
is digitally imposed on the world around us. Uh, you know,
(20:40):
what's what's that going to do? Or does it make
it easier? I don't know like I can. Maybe you
imagine the case being made that like, well, you're not
looking at your screen, You're looking at the world around
you for this information, which you were probably already doing
and potentially distracted by, just as a normal pedestrian pre smartphone. Well,
I mean it is yet another one of those things
are we have surprisingly powerful capacities, you know, like we
(21:05):
can do things that are kind of amazing if you
sit and think about them, like walking through crowds without
collisions or driving a car, but we also fail to
have the metacognitive recognition of how much attention it takes
to do that correctly. So you have people not realizing
how impaired they are when they're texting while driving, or uh,
(21:26):
not quite appreciating how quickly this entire crosswalk will get
jammed up if just a couple of people are distracted
while they're walking. But anyway, I just got really interested
in the subject of the the modeling of the flow
of human crowds. Um uh. Like one idea that that
I found very sticky is I was looking at a
paper from two thousand three in the Annual Review of
(21:49):
Fluid Mechanics by Roger L. Hughes, who is who worked
in the Department of Civil and Environmental Engineering at the
University of Melbourne, and the paper is called the Flow
of Human Crowds, and he was discussing the idea that
human movements could be modeled like like the flow of
of non human substances, you know, just like molasses flowing
(22:10):
out of a jar, or like the way particles of
gas move around in a container. But of course it's
complicated by the fact that there are social inputs on
the movement, even if the movement can be modeled like
the movement of a physical substance at the large scale. Uh.
And he ended up characterizing crowds as the field of
(22:30):
quote thinking fluids, which is just wonderful. Uh. And so
this isn't related to either of the prize winners I
was just talking about, but I was also I ended
up reading another really interesting article on the subject of
physical and mathematical modeling of crowdflow. And this was an
article in Smithsonian Magazine from January by Evelyn Lamb. It
(22:52):
was called how fluid dynamics can help You Navigate crowds
And so the premise of this article is that because
the of human crowds can be modeled like the flow
of physical substances. Physics modeling can also offer suggestions to
individual members of crowds for how to move through them
in the safest and best way, at least potentially. I mean,
(23:14):
there's a lot of uncertainty. Uh this, I guess it's
kind of a young scientific field right now, but um
that it could potentially offer individual advice in addition to
the stuff we already talked about, like informing how to
better design spaces for people to walk through and uh so,
of course, this article mentioned some of the same research
we already talked about, such as the the idea that
(23:36):
moving crowds tend to form the self organizing natural lanes
or lines, often just by a rule as simple as
you directly follow the person ahead of you. But then
this article goes on to side a few researchers offering
some other observations. So one thing is that it cites
a researcher named Dirk Helping, who is at the Swiss
Federal Institute of Technology and Zurich and who studies computation
(24:00):
all social science. Um, I just noticed, I wonder if
there's like a big center of crowdflow study in Switzerland,
because several of these uh of these papers have had
Swiss connections of one kind or another, so springing off
of some stuff that that helping says here, Lamb actually
highlights a couple of the main governing forces that appear
(24:22):
to drive the individual behaviors of people within crowds, and
I think they actually they sort of line up with
what we're talking about a minute ago. So on one hand,
you've got a force that propels the person towards their goal.
They're they're trying to get somewhere, and then second you've
got the social forces that prevent them from doing something,
mostly prevent them from colliding with with other people in
(24:43):
the crowd. And regarding that second force, the social force,
I thought this was really interesting. The article makes the
case that it is similar to the repulsive force that
keeps particles from colliding, like physical particles, and in the
case of physic goal like atoms and molecules, this would
be the electromagnetic force. Electrons of course repel one another.
(25:06):
They've got like charges, they push back against each other,
and in the case of particles, you can actually calculate
the strength of the repulsive force via what's known as
the inverse square law. So the inverse square law is
a very important mathematical principle that applies throughout physics. Basically,
it applies to any quantity of energy or force propagating
(25:28):
out from a central source in three dimensions, and it
says that the that quantity will decrease, not just in
a linear way as you move away from the source,
but it will decrease according to the square of the
distance between you and the source. So a simpler way
to conceptualize this is that when you're thinking about light intensity,
(25:48):
or gravity or electromagnetic repulsive forces between particles, proximity really matters,
and a force that is almost undetectable at a distance
can become very strong as you can close. So this
is true of particles avoiding collisions in flowing masses of
liquid or gas. But it's also true of humans moving
(26:08):
in a crowd, uh, though in a slightly different way.
And then the article calls attention to a paper that
made a really interesting discovery back in so this paper
was by Johannis Karamutzas, Brian Skinner, and Stephen Jay Guy
and Physical Review letters called universal power law governing pedestrian interactions,
(26:30):
and the author summarize their findings like this, They say, quote,
here we introduce a novel statistical mechanical approach to directly
measure the interaction energy between pedestrians. This analysis, when applied
to a large collection of human motion data, reveals a
simple power law interaction that is based not on the
physical separation between pedestrians, but on their projected time to
(26:55):
a future collision, and it's therefore fundamentally anticipatory in nature.
So this really got me. So so there is a
rule in operation just automatically in moving human crowds that
works somewhat like the inverse square law for the repulsion
between particles in a fluid, but it's a repulsion based
(27:17):
not just on physical proximity. It's based on the anticipation
of movement pathways. So you can think about it this way.
If you're in a big crowd of people and you're
moving along on the sidewalk, you can actually be very
close to another person. So you can be walking beside
somebody parallel, side by side, or you can even be
(27:38):
pretty close to the person ahead of you or behind
you walking in the same direction, where you have to
adjust your path to avoid a collision is when you
notice that your path is about to cross somebody else's.
And we calculate these adjustments not purely in terms of distance,
but in terms of time. That like, the variable is
time to collision based on the current speed of your movement,
(28:02):
and people are typically anticipating about one to three seconds
into the future, depending on the characteristics of the crowd.
Thank so, people use these rules pretty reliably to move
in crowds, and as we've said already, they can usually
avoid collisions. But there are some situations where the rules
(28:25):
stop working, particularly as the density of the crowd increases.
The higher the density, the more your collision avoidance skills
are overwhelmed and different principles take over. And sometimes, unfortunately,
these situations can turn very dangerous. Uh. You know, people
are killed in crowds all the time, at everything from
(28:47):
music festivals to religious events. And I think a lot
of times when people read reporting about about deaths through
through crowd crush and crowd dynamics, I think a lot
of times people fail to understand exactly what's happening in
these situations, Like they sometimes seem to imagine that this
must result from the crowds being somehow evil like violent
(29:11):
or malicious or chaotic, or at least the news reporting
on these events sometimes has that kind of tone, and
this is not necessarily the case at all. People in
large crowds can easily be injured or killed simply by
the uncontrollable flow of human bodies through space. Like you
don't have to imagine people in the crowd wanting to
(29:31):
trample each other. There there are irresistible physical forces at work,
like you could you could essentially have a large mass
of people attending a rally about the importance of crowd
safety and if we're not managed properly, it could result
in injury. Right. Yeah, So say maybe you're trying to
quickly move a huge, massive people and they're moving through
(29:51):
a corridor that's originally a hundred meters wide and then
suddenly it narrows to five ms wide. Uh, this could
this could spell disaster. And you can also imagine scenarios where,
you know, especially at events that are attracting big crowds,
non crowdflow dynamics can can have exactly the wrong incentives
(30:13):
for how to shape those spaces, right, Like maybe at
a big music festival or something, you want to have
choke points that control access to spaces, maybe so that
you can check for tickets or who knows what UM.
But but it's exactly at areas where there are there
are things like bottlenecks where suddenly the density of the
crowd increases dramatically and unexpectedly, that things can really get dangerous.
(30:37):
And researchers in this field studying crowdflow have actually uh
looked at a lot of video documentation to come up
with models to try to understand what happens when crowdflow
becomes deadly. And the article here discusses a few observations
in this area. Though it's quick to caveat and I
guess we should too, that we we we we can't
give you, you know, the hard and fast rules to
(31:00):
follow that will always keep you safe, because there's still
a lot that's not known about exactly how this happens.
But there are a few things that seem probably true.
One of them, again, obviously, is that density seems to
be a major contributor to when when crowds get dangerous.
That you know, if a pathway suddenly narrows at a
tunnel or a bridge or something um and the article
(31:22):
describes how increasing density and these types of areas can
lead to something called stop and go waves, where people
can no longer keep moving continuously forward. They're moving, they're
used to walking, and then they eventually reach a point
where the crowd is so dense that even at low speeds,
they can't keep moving forward, so they stop. And then
(31:45):
once they're stopped, they move forward, but of course people
are still trying to move in behind them. Uh, so
they're stopped, people are advancing behind them, and they tend
to move forward into any gaps as soon as they appear. Uh.
Stop and go waves are not always necessarily dangerous, but
they can be an indication that crowd density is getting
too high. And then, to read from Lamb's description of
(32:07):
what happens after this here quote, things get really dangerous
if the crowd continues to get denser or people make
unexpected movements. At that point, the crowd can become turbulent
and chaotic, with people being pushed randomly in different directions.
Disasters can break out when say, one person stumbles, causing
someone else to be pushed into their place and either
(32:29):
trampling them or stumbling themselves, and this whole can have
a kind of gravitational effect pulling in more and more people,
which in terms of the physical dynamics, this is similar
to how the flow of physical substances like water behave
when they're funneled into narrower and narrower places. Like I
think about how some of the world's most dangerous whirlpools
(32:51):
seem to occur in bottlenecks for the flow of water,
where for example, the tide is pushing a huge amount
of water through a narrow, straight or your This can
lead to rushing and turbulence. It's chaotic flow and unpredictable
directions which can sometimes create these whirlpools. Anyway, back to
the article, it mentions a couple of other UH seeming
(33:13):
risk factors for for when this happens UH. In addition
to the high density another one is bidirectional or multidirectional flow.
So things can get more dangerous if you have high
density and people trying to move in different directions UM.
And then finally, lambsites The researcher Juannas Kara Mutzis, who
was one of the authors on that paper from feen
(33:34):
I mentioned a minute ago saying that in large enclosed spaces.
For some reason, the sides of the space seemed possibly
to be more dangerous than the middle, though there isn't
enough research to be sure of that or to explain
why it happens. So obviously, understanding the flow of crowds
goes way beyond just just being a kind of interesting
(33:55):
little curiosity and like looking at how people move. It
is something that is of critical importance in managing, you know,
large masses of people, and in designing spaces for them
to move through, and in planning events and all kinds
of things like that. I mean, this is like one
of those things that starts off being really funny but
is in fact a critically important subject. Yeah, I mean absolutely,
(34:18):
they're they're just going to be more and more office
and these uh, these large events of of you know,
varying genres are going to continue to be a part
of our lives. This actually got me wondering about something,
which is um why doesn't anything like like uncontrollable crowdflow
with with actual like pressing against one another happen with cars.
(34:41):
You can see some of the characteristics happen with cars
because you can get traffic back up when there's a
bottleneck in the highway, maybe seven lanes suddenly go down
to one, and this will cause a huge traffic jam.
But you don't usually have the problem with like cars
pushing each other and and pressing against one another and
leading to this bill up of uncontrollable forces. I was
(35:02):
wondering why that is. Maybe it's because I'm just guessing.
I wonder if it's because it's never considered acceptable for
cars to touch each other at all. Uh. And people,
of course mostly avoid try to avoid touching one another
in crowds, but in some situations, maybe it just seems
like there's no avoiding it, so you just sort of
(35:23):
resign yourself to touching and then that and then that
can build up. Maybe I'm not sure, you know, that's
a good point. Yeah, because even though some drivers do
like to come as close as possible to touching your car, uh,
which is something I've never been able to understand, just
given how dangerous it actually is to you know, to
(35:44):
to you know, to pull up right behind somebody will
at high speeds on the interstate. Uh. Yeah, yeah, to
your point, they you're not actually supposed to ram into
them even a little bit. And and while you know,
certainly pile ups do occur. You do have acts density,
do have cars crashing into one another and then multiple
car pile ups occurring. Um, yeah, I wonder if this
(36:07):
stricter no touch policy with cars has some sort of
influence on us. Well yeah, maybe another thing is I'm
not conceptualizing it right, And maybe the crowd dynamics I
was talking about are more analogous to just actual like
pile up crashes, I guess, which I wasn't thinking about
in a similar way because those happen at higher speeds.
I wonder what would we would see in something that's
(36:28):
halfway between if what would be between a car and
a person if we were to say, look at a
bicycle traffic in very congested bicycle situations, say a city
where there's a high number of bicycle riders or something,
or bicycle races. Because I feel like one of the
things with people is that yeah, it's like, yeah, maybe segways,
(36:49):
but I feel like one of the things with people,
like you've already mentioned, is when you're pushed forward, you
may be pushed into that hole that you could not
otherwise occupy or wouldn't occupy socially. But now you know,
if you're being pushed. I guess that's where I'm going. Um,
so there's just more nooks and crannies for for human beings.
Um and then with with cars less so. But perhaps
(37:09):
if you're looking at bicycles, like maybe maybe we see
something that's more like the human scenario. It'd be interested
to hear from some of our bicyclists out there, like
what are the social laws of crowded bicycle scenarios? How
close can you get to another bicyclist while moving while
stationary while sort of you know, uh, tiptoeing along. I'd
be interested a year, Yeah, totally, I mean especially yeah,
(37:33):
like it seems a key difference is is the the
the balancing act that's necessary on a bicycle? Yeah? Well, anyway,
I want to say about these two subjects, the physics
and kinetics price this year. This definitely did, uh did
achieve the desired intent. It made me laugh a little
bit and then did make me think it was not
I will I will grant it did not make me
(37:54):
laugh hilariously, so it was a mild chuckle, but then
it got really interesting to me. Yes, all right, we're
gonna go and close this episode out, but we will
be back. Um, I'm going to talk about the Biology Prize.
We're gonna get into some other prizes from the Igno
Bells this year, so just tune into that in the
(38:16):
next Core episode of Stuff to Blow Your Mind. To
remind everybody, Stuff to Blow Your Mind. The podcast feed
can be found wherever you get your podcasts. Core episodes
come out on Tuesdays and Thursday's Monday is listener Mail,
Wednesday is a short form artifact episode, and on Friday's
we do Weird House Cinema. That's our time to set
aside most serious concerns and just focus on a weird film.
(38:38):
Huge thanks as always to our excellent audio producer Seth
Nicholas Johnson. If you would like to get in touch
with us with feedback on this episode or any other,
to suggest topic for the future, or just to say hello,
you can email us at contact at stuff to Blow
your Mind dot com. Stuff to Blow Your Mind is
(39:01):
production of I Heart Radio. For more podcasts for My
Heart Radio, visit the I Heart Radio app, Apple Podcasts,
or wherever you listening to your favorite shows
Welcome to Stuff to Blow Your Mind, the production of
My Heart Radio. Hey you welcome to Stuff to Blow
your Mind. My name is Robert Lamb and I'm Joe McCormick.
And today we're finally getting around to it. We wanted
to talk about a few of the ig Nobel Prize
(00:24):
winners from this year. Yes, we're a little late. The
awards ceremony was in September of this year and we're
just now getting to it. But you know, a lot
of things are happening around the September October. It's a
busy time for us. Yeah. I think we've covered the
ig Nobels every year since we started covering them, and
I'm not sure when that year was. Maybe it was
like two thousand seven, two eight or something. I don't know,
(00:46):
it's pretty early on. Um, we almost never cover them
right away because, like you said, there's there's generally a
lot going on. The awards usually come out during September
or very early October, and so we're either wrapped up
in Halloween stuff I then, or we're getting ready to
do Halloween stuff or something like that. Uh, So we
generally come in like late November or part of sometime
(01:09):
in November or in this case, very early December. But
I guess it's better late than never. And uh, I
guess one of the cool things about this is is
we kind of come in after the initial coverage and
chew on them a bit more. So, if you're waiting
on these episodes and you and you're inclined to complain,
just don't stop. But if you're not familiar, the ig
(01:30):
no Bells are a series of awards given out once
a year by a scientific humor journal called the Annals
of Improbable Research that's been edited for many years now
by somebody named Mark Abraham's and the stated purpose of
this of these awards is to quote honor achievements that
first make people laugh and then make them think. So
(01:52):
to give you an idea if if you haven't heard
one of these episodes before and you've never read about
the ig Nobels. Among the awards we covered last or
there was a prize in the material science category for
research into whether you could make a knife blade out
of frozen feces. What was the verdict on that? I
think it was no right that no matter how hard
(02:13):
you freeze them, they just don't really cut. I believe
so um, you know, it reminds me of Yeah. I
think they think that the research ended up saying, yeah,
like you, no matter how hard it gets, uh, you're
still gonna have a certain amount of melting that's going
to take place, right because the friction on the sharp
end will will pretty quickly wear it away and then
it's then it's blunt. Yeah, better to make it like
(02:34):
a frozen poop warhammer, I think, so that could shatter.
I don't know, we'll look into that in the future. Um,
but then let's see what was One of the other
ones we did last year was there was a prize
in the acoustics category for a study that made alligators
huff helium to see if it made their voices higher pitched.
(02:54):
I remember that. Yeah. So occasionally the papers that get
selected for these prizes are I think originally themselves intended
to be satirical or funny. One example like that that
comes to mind is, uh, there was a rayology study
one year about whether cats should be considered a solid
or a liquid. That that was a good one, but
(03:15):
clearly there was a good bit of jokiness about the
paper itself most of the time. Actually, this the research
covered in in these prizes, is it's just straightforward research.
They're they're straightforward experiments published in real scientific journals that
happened to have some weirdly hilarious methodology or finding. Yeah.
(03:35):
Either you know, it varies, but you know, sometimes it's
it's just a particular experiment that is hilarious or giggle inducing. Um.
Other times it's just the minutia of it, you know,
one of those kind of a shrimp on a treadmill
situation where it may it's still important work. It's all
part of the general um, you know, expansion of scientific
(03:57):
knowledge of of the universe, but it just in an
area that we might not think about. Or sometimes it's
just an important study that involves like pooper vomit or something,
and therefore just by ver orteese or something, you know,
just by virtue of the subject, kissing, yeah, is inherently funny. Now,
in these episodes we're doing on on the Igno Bells,
(04:18):
we're just going to pick out a few of the
prizes to highlight because there was something about them that
we wanted to talk about. We're not gonna have a
chance to cover all of the winners, but if you
want to read about those. You can go to the
Annals of Improbable Research website at Improbable dot com and
you can see the full list of the awards and
click on links to to read about them. I mean,
(04:39):
and not only the most recent awards, but you can
go back through the entire history of the Igno Bells
and just and explore them all. It's a very simple,
easy to use website. Well, I am ready to get
started if you are, Uh, let's do it, okay, Well,
the first area I wanted to get into was actually
this will be a pair of thematically linked prizes from this.
(05:00):
The first is the Physics Prize, which went to Alessandro Corbetta,
Jasper Mayu, Sen Chung Min Lee, Roberto Benzi, and Federico
Tashi quote for conducting experiments to learn why pedestrians do
not constantly collide with other pedestrians. And then the second
here is the Kinetics Prize, which went to his Sashimurakami,
(05:25):
Claudio Feliciani, Utah Nishi Yama, and katsu Hero Nishi Nari.
And this is quote for conducting experiments to learn why
pedestrians do sometimes collide with other pedestrians. Uh, Rob, have
you ever had a really memorable, just bodily head on
with somebody. I was trying to remember if I had,
and I could not bring any instances to mind. Though
(05:47):
I have run into plenty of things in my life.
I run into tree branches and sliding glass doors, but
I can't really think of any head ons with humans
except maybe while playing soccer. Yeah, thinking back, yes, certainly,
I there have been more than a few low hanging
branches that have have clipped the top of my head
or tried to stab me in the eye, that sort
(06:09):
of thing. But in terms of of running into people,
um even in crowded cities, and like I was just
in um in New Orleans, and you know, those are
some crowded streets at times, and those are also some
drunken streets at times. You know they're folks wandering around
in various states of inebriation, and yet you don't see
people just colliding with each other. I feel like I've
(06:32):
had I can think maybe to some close calls in
the past where you have that moment where you almost
run into somebody and you both kind of acknowledge it
and it's a little bit awkward, but still it's not
like you see. I guess in a lot of like
comedy films where people just plow into each other, knock
their groceries down, and then they have a romantic moment
as they pick up each other's groceries, that sort of thing. Yes,
(06:53):
why is it romantic comedies where people plow into each other?
I guess there's something metaphorical about that, about you know,
the oh you came into my life like a like
a large, massive meat slamming me in the face. Yeah.
Because Yeah, in general, you don't see like fights breaking
out because people ran into each other, or at least
I don't think I've ever seen that occur. I mean
(07:15):
it probably has occurred, but not with the regularity you
might expect, given just how intense uh streets and sidewalks
are at times. Yeah, and I think this is something
we should keep in mind as we discussed this research.
It's interesting how rare collisions are given how often huge
masses of people are just criss crossing with each other
all day. So to actually reference the two papers here,
(07:38):
the first one was Corbetta at all. This was in
Physical Review E in eighteen and it was called Physics
based Modeling and Data Representation of pair wise interactions among pedestrians.
And then the second paper the Kinetics Prize was called
Mutual anticipation can contribute to self organization and human crowds.
This was by more commy at all in one in
(08:00):
Science Advances. Now, I was interested in this pair of
findings not only because I was obviously amused by the
image of people just absolutely eating each other's teeth in
in high speed sidewalk collisions, but because this is one
of those ignoble subjects where once you get beyond the
mildly funny image it conjures, it actually raises quite i think,
(08:23):
quite deep, mysterious, fascinating questions about the emergent mathematical properties
of human behavior in groups. And it's also a subject
that goes way beyond mere curiosity. Understanding the flow of
crowds is a matter of life and death. It is
a vitally important subject for all kinds of reasons. So
(08:44):
this involves questions like how do masses of people move
through space on foot? What rules govern their behavior both
as individuals and as as a group, How can that
behavior be influenced, and especially how does the built environment
shape that behavior? Uh, you know, as you were alluding
to a minute ago. I think it's actually kind of
(09:05):
amazing how pedestrians can navigate through crowds without running into
each other. It's one of those, you know, thousand little
miracles of human human brain capacity that we don't usually
notice or appreciate. But you can have huge crowds moving
quickly and bi directionally mean running at cross directions, past
(09:25):
each other, straight through each other, and uh and most
of the time people are able to avoid human crashes. Yeah,
and it it seems to be the case no matter
where you go, even though I will say, and this
is just uh my my observation. I don't know to
what extent this this holds up to research, but it
feels like in in some parts of the world, the
(09:47):
the energy of love, say, the movement of crowds on
a sidewalk can feel different, can a little bit different,
you know, but it's still maintaining, you know, the same
collision free experience. You know, like like maybe there's there's
something slightly different going on there, there's some sort of
there are different cultural norms in place regarding say, like
(10:08):
what side of the sidewalk people moving this way should
be on, or or so or so forth, or or
even maybe you know how much space is permittable between
you and the next person, but still people are managing
not to blow into each other. Yeah. So to discuss
a few of the details of these two studies, regarding
the first one, Corbetta at all from from eighteen. I
(10:29):
was reading about this uh in an article that had
a few interview clips um from in l Times, and
this was looking at Technical University Eindhoven researchers Federico Tashi
and Alessandro Corbetta and uh so their study in particular
was looking at the question of how pedestrians avoid running
(10:51):
into each other when moving through the Eindhoven train station,
and they did this by installing sensors under the plow
forms of the train station which they used to track
the movements of pedestrians across the platform. So this was
an area of like twenty seven square meters and they
tracked pedestrian movement within it for six months. This came
(11:13):
out to measuring the movements about five million pedestrians total,
and they found a few measurable quantities. So first of all,
they said that people keep an average distance of about
seventy five centimeters away from other people while moving through crowds,
so that's about two and a half feet. And they
said that about one out of every thousand people quote
(11:34):
will turn around and go back the way they came
to avoid bumping into somebody else. According to Alessandro Corbetta, quote,
about eighty of the pedestrians actually collided with each other.
The other pedestrians adjusted their walking route when they were
at least a hundred and forty centimeters which is about
four ft and seven inches apart, and thus managed to
(11:55):
avoid a collision. And though I was wondering about that,
so he gives the number eighty eight pedestrians collided. Does
that mean eighty pedestrians total, meaning roughly forty collisions or
is that like, uh, there were eighty collisions, which would
make you think they'd be like at least a hundred
and sixty people involved. I'm not sure. Well, it raises
the question how many people are necessary to create a collision?
(12:18):
Is it one? Or is it too it's at least two,
I mean you could have more, I guess, But is
it I guess it depends on like is it is
it negligence on one person's part that leads to collision?
Or negligence or distraction whatever on two people's parts. You know, Ah,
well that will I will actually come up in the
other study, I think. But what this study found is that, yeah,
(12:40):
people are constantly monitoring for upcoming collisions and then adjusting
their walking trajectories accordingly several meters in advance. So ultimately,
the question here is it's not really relevant exactly how
many people slammed faces, but how on average pedestrians adjust
their courses to avoid collisions. What rules do they use
(13:01):
to make those those evasions? And this just apparently happens constantly.
We're usually not even aware of it. But you know,
I can recall, like moving through an airport or something,
you are just doing a delicate dance for for several
minutes of a time at a time, often you know,
just dodging dodging, dodging, dodging, and you don't even really
think about it. It's a process that can be be
(13:23):
oddly captivating, I find, you know, especially if I'm on
my own, I don't have to worry about anyone else,
you know, traveling with me. Uh, you know, cutting a
swath for them to travel through, you know, checking back
on how they're doing it. It's just me cutting through, um,
like a reasonable sized crowd or a reasonable flow of
pedestrian traffic. Uh, it feels kind of empowering. Well, yeah
(13:47):
it is, and I think that highlights one of the
interesting features there, which is that, um, so when you're
moving through a crowd, you are making individual decisions, like
and those decisions are being driven by different things. Like,
on one hand, you've got your basic propulsive drive, like
you have where you need to be and the course
you think you need to take to get there. And
(14:08):
then probably the second main thing governing your movement is
what these researchers would refer to as social forces, which
would be things like the taboo against touching other people
while you're walking, or basically the force that keeps you
separate from other people and makes you want to avoid
running into them or touching them in some other way. Yeah,
(14:28):
because there's a physical risk to actually running into somebody,
and there is like a social risk to not only
running into somebody, but even almost running into somebody, yeah,
even getting too close exactly. But so while those forces
are are guiding your decision making as an individual, you
are a thinking person and you you know there are
cognitive inputs, like you are moving through this crowd as
(14:51):
an individual. It's strange that take thousands of people and
they're all making these individual decisions based on these types
of forces, you know, their drive forces, and their and
their restrictive social forces. And yet when you look at
them as a group, they seem to behave in ways
that are predictable. Even though they're making in these individual decisions,
(15:12):
they behave in ways that can quite well be modeled
and predicted and understood by things that are that are
like physics models the way the same way that you
would model, say, the movements of a fluid, you know,
a gas or a liquid through a container than and
(15:34):
so the authors of this first study you're saying, well,
by studying the natural movement patterns of pedestrians and trying
to model them in in terms of the language of
physics on a large scale, Uh, this can be useful
in terms of things like architecture and design. You know,
you can design better spaces for people to walk, both
in terms of efficiency the throughput how many people can
(15:54):
move through them quickly, but also in terms of safety
because as we know, and as I'll talk about in
a bit, UH, crowds can become quite dangerous when when
density gets too high. Now, I was also reading an
article that that had a few uh quotes from these researchers,
And this was an article for Physics, the magazine of
the American Physical Society by Michael scherber Uh. And this
(16:18):
one also discussed the second winner, the winner of the
Kinetics Prize, the paper that was by Murakami at all.
And this study was interesting too. So it instead of measuring,
you know, putting sensors under a floor and measuring natural movement,
it's staged experiments. So this study asked volunteers to walk
by directionally, so imagine people crossing each other, walking in
(16:43):
opposite directions the way they would say, like a crowded
crosswalk in the street. And then it tried to see
what happens when when people walk by directionally under normal circumstances,
and then what happens when some of those people are distracted, specifically,
what happens when they're trying to do calculations on their phones.
(17:03):
And the purpose of this experiment was to interfere with
people's ability to see collisions coming and avoid them. Now,
it probably won't come as a big surprise that pedestrians
who were distracted by phones made more navigation mistakes, leading
to a number of near collisions. But even when not distracted,
people sometimes had difficulty and uh. One of the implications
(17:26):
of this experiment is that avoiding collisions is a collaborative effort.
It requires awareness and coordination of multiple parties, both looking
at each other and trying to assess what paths they're
about to take, and then adjusting their own paths in accordingly.
(17:48):
And this becomes difficult when even just one of these
parties is distracted, especially if multiple parties are distracted. I
was also reading an interview with one of the researchers
from the second study, the coninectics ees UM. This was
on a Swiss news site swiss Info dot c H
and it was an interview by Zeno Soccatelli with a
researcher named Claudio Feliciani who works at the University of
(18:11):
Tokyo but who originally hails from Switzerland. And so Feliciani
mentioned a few interesting things in this interview. One is that, okay,
so when you when you have people not distracted, UM,
how do they tend to move in groups when they're
moving by directionally, like you imagine people crossing each two
crowds at at a busy crosswalk trying to go past
(18:31):
each other. How do they normally move? And Feliciani says
that what tends to happen is people automatically self organize
into lines. People tend to naturally follow the person directly
in front of them, and simply by obeying this rule,
the moving crowd naturally forms into lanes or lines of people.
(18:53):
And so they were trying to understand the mechanisms that
make these lines form and how they work. Of course,
you know one way understand how something works is to
see if you can break it. Um So, Feliciani says,
quote specifically, we caused some of the pedestrians to be distracted,
asking them to walk while solving simple calculations on their phones.
With just three out of fifty four people focused on
(19:16):
something else, rows formed much less quickly, especially if the
distracted people were at the front of the group, and
the increased attention of the non distractors is not enough
to make up for the lack of attention of the
three who are distracted. And then on this website there
is actually video I could watch maybe you want to
(19:36):
take a look, rob But there's video that shows how
people move in these lines under normal conditions, and then
what it looks like when just a few of them
are distracted. So not everybody is trying to do math
on their phone. Just a few people, just a few
people out of the fifty four completely screw things up
and everybody gets jammed up. The lanes stone form naturally.
(19:56):
Uh So it seems like its navigating through crowds by directionally.
It has this tendency to for you know, self organizing
emergent structures to form, but that requires everybody to be
paying attention and monitoring each other and sort of communicating
nonverbally about where they're headed. This is interesting. I mean,
(20:18):
of course, this has huge ramifications on a are already
you know, near ubiquitous use of smartphones and the fact
that people will have them out while they're walking around.
But it also makes me wonder about, you know, the
more we push into this idea of augmented reality, of
of having some sort of you know, a metaverse that
is digitally imposed on the world around us. Uh, you know,
(20:40):
what's what's that going to do? Or does it make
it easier? I don't know like I can. Maybe you
imagine the case being made that like, well, you're not
looking at your screen, You're looking at the world around
you for this information, which you were probably already doing
and potentially distracted by, just as a normal pedestrian pre smartphone. Well,
I mean it is yet another one of those things
are we have surprisingly powerful capacities, you know, like we
(21:05):
can do things that are kind of amazing if you
sit and think about them, like walking through crowds without
collisions or driving a car, but we also fail to
have the metacognitive recognition of how much attention it takes
to do that correctly. So you have people not realizing
how impaired they are when they're texting while driving, or uh,
(21:26):
not quite appreciating how quickly this entire crosswalk will get
jammed up if just a couple of people are distracted
while they're walking. But anyway, I just got really interested
in the subject of the the modeling of the flow
of human crowds. Um uh. Like one idea that that
I found very sticky is I was looking at a
paper from two thousand three in the Annual Review of
(21:49):
Fluid Mechanics by Roger L. Hughes, who is who worked
in the Department of Civil and Environmental Engineering at the
University of Melbourne, and the paper is called the Flow
of Human Crowds, and he was discussing the idea that
human movements could be modeled like like the flow of
of non human substances, you know, just like molasses flowing
(22:10):
out of a jar, or like the way particles of
gas move around in a container. But of course it's
complicated by the fact that there are social inputs on
the movement, even if the movement can be modeled like
the movement of a physical substance at the large scale. Uh.
And he ended up characterizing crowds as the field of
(22:30):
quote thinking fluids, which is just wonderful. Uh. And so
this isn't related to either of the prize winners I
was just talking about, but I was also I ended
up reading another really interesting article on the subject of
physical and mathematical modeling of crowdflow. And this was an
article in Smithsonian Magazine from January by Evelyn Lamb. It
(22:52):
was called how fluid dynamics can help You Navigate crowds
And so the premise of this article is that because
the of human crowds can be modeled like the flow
of physical substances. Physics modeling can also offer suggestions to
individual members of crowds for how to move through them
in the safest and best way, at least potentially. I mean,
(23:14):
there's a lot of uncertainty. Uh this, I guess it's
kind of a young scientific field right now, but um
that it could potentially offer individual advice in addition to
the stuff we already talked about, like informing how to
better design spaces for people to walk through and uh so,
of course, this article mentioned some of the same research
we already talked about, such as the the idea that
(23:36):
moving crowds tend to form the self organizing natural lanes
or lines, often just by a rule as simple as
you directly follow the person ahead of you. But then
this article goes on to side a few researchers offering
some other observations. So one thing is that it cites
a researcher named Dirk Helping, who is at the Swiss
Federal Institute of Technology and Zurich and who studies computation
(24:00):
all social science. Um, I just noticed, I wonder if
there's like a big center of crowdflow study in Switzerland,
because several of these uh of these papers have had
Swiss connections of one kind or another, so springing off
of some stuff that that helping says here, Lamb actually
highlights a couple of the main governing forces that appear
(24:22):
to drive the individual behaviors of people within crowds, and
I think they actually they sort of line up with
what we're talking about a minute ago. So on one hand,
you've got a force that propels the person towards their goal.
They're they're trying to get somewhere, and then second you've
got the social forces that prevent them from doing something,
mostly prevent them from colliding with with other people in
(24:43):
the crowd. And regarding that second force, the social force,
I thought this was really interesting. The article makes the
case that it is similar to the repulsive force that
keeps particles from colliding, like physical particles, and in the
case of physic goal like atoms and molecules, this would
be the electromagnetic force. Electrons of course repel one another.
(25:06):
They've got like charges, they push back against each other,
and in the case of particles, you can actually calculate
the strength of the repulsive force via what's known as
the inverse square law. So the inverse square law is
a very important mathematical principle that applies throughout physics. Basically,
it applies to any quantity of energy or force propagating
(25:28):
out from a central source in three dimensions, and it
says that the that quantity will decrease, not just in
a linear way as you move away from the source,
but it will decrease according to the square of the
distance between you and the source. So a simpler way
to conceptualize this is that when you're thinking about light intensity,
(25:48):
or gravity or electromagnetic repulsive forces between particles, proximity really matters,
and a force that is almost undetectable at a distance
can become very strong as you can close. So this
is true of particles avoiding collisions in flowing masses of
liquid or gas. But it's also true of humans moving
(26:08):
in a crowd, uh, though in a slightly different way.
And then the article calls attention to a paper that
made a really interesting discovery back in so this paper
was by Johannis Karamutzas, Brian Skinner, and Stephen Jay Guy
and Physical Review letters called universal power law governing pedestrian interactions,
(26:30):
and the author summarize their findings like this, They say, quote,
here we introduce a novel statistical mechanical approach to directly
measure the interaction energy between pedestrians. This analysis, when applied
to a large collection of human motion data, reveals a
simple power law interaction that is based not on the
physical separation between pedestrians, but on their projected time to
(26:55):
a future collision, and it's therefore fundamentally anticipatory in nature.
So this really got me. So so there is a
rule in operation just automatically in moving human crowds that
works somewhat like the inverse square law for the repulsion
between particles in a fluid, but it's a repulsion based
(27:17):
not just on physical proximity. It's based on the anticipation
of movement pathways. So you can think about it this way.
If you're in a big crowd of people and you're
moving along on the sidewalk, you can actually be very
close to another person. So you can be walking beside
somebody parallel, side by side, or you can even be
(27:38):
pretty close to the person ahead of you or behind
you walking in the same direction, where you have to
adjust your path to avoid a collision is when you
notice that your path is about to cross somebody else's.
And we calculate these adjustments not purely in terms of distance,
but in terms of time. That like, the variable is
time to collision based on the current speed of your movement,
(28:02):
and people are typically anticipating about one to three seconds
into the future, depending on the characteristics of the crowd.
Thank so, people use these rules pretty reliably to move
in crowds, and as we've said already, they can usually
avoid collisions. But there are some situations where the rules
(28:25):
stop working, particularly as the density of the crowd increases.
The higher the density, the more your collision avoidance skills
are overwhelmed and different principles take over. And sometimes, unfortunately,
these situations can turn very dangerous. Uh. You know, people
are killed in crowds all the time, at everything from
(28:47):
music festivals to religious events. And I think a lot
of times when people read reporting about about deaths through
through crowd crush and crowd dynamics, I think a lot
of times people fail to understand exactly what's happening in
these situations, Like they sometimes seem to imagine that this
must result from the crowds being somehow evil like violent
(29:11):
or malicious or chaotic, or at least the news reporting
on these events sometimes has that kind of tone, and
this is not necessarily the case at all. People in
large crowds can easily be injured or killed simply by
the uncontrollable flow of human bodies through space. Like you
don't have to imagine people in the crowd wanting to
(29:31):
trample each other. There there are irresistible physical forces at work,
like you could you could essentially have a large mass
of people attending a rally about the importance of crowd
safety and if we're not managed properly, it could result
in injury. Right. Yeah, So say maybe you're trying to
quickly move a huge, massive people and they're moving through
(29:51):
a corridor that's originally a hundred meters wide and then
suddenly it narrows to five ms wide. Uh, this could
this could spell disaster. And you can also imagine scenarios where,
you know, especially at events that are attracting big crowds,
non crowdflow dynamics can can have exactly the wrong incentives
(30:13):
for how to shape those spaces, right, Like maybe at
a big music festival or something, you want to have
choke points that control access to spaces, maybe so that
you can check for tickets or who knows what UM.
But but it's exactly at areas where there are there
are things like bottlenecks where suddenly the density of the
crowd increases dramatically and unexpectedly, that things can really get dangerous.
(30:37):
And researchers in this field studying crowdflow have actually uh
looked at a lot of video documentation to come up
with models to try to understand what happens when crowdflow
becomes deadly. And the article here discusses a few observations
in this area. Though it's quick to caveat and I
guess we should too, that we we we we can't
give you, you know, the hard and fast rules to
(31:00):
follow that will always keep you safe, because there's still
a lot that's not known about exactly how this happens.
But there are a few things that seem probably true.
One of them, again, obviously, is that density seems to
be a major contributor to when when crowds get dangerous.
That you know, if a pathway suddenly narrows at a
tunnel or a bridge or something um and the article
(31:22):
describes how increasing density and these types of areas can
lead to something called stop and go waves, where people
can no longer keep moving continuously forward. They're moving, they're
used to walking, and then they eventually reach a point
where the crowd is so dense that even at low speeds,
they can't keep moving forward, so they stop. And then
(31:45):
once they're stopped, they move forward, but of course people
are still trying to move in behind them. Uh, so
they're stopped, people are advancing behind them, and they tend
to move forward into any gaps as soon as they appear. Uh.
Stop and go waves are not always necessarily dangerous, but
they can be an indication that crowd density is getting
too high. And then, to read from Lamb's description of
(32:07):
what happens after this here quote, things get really dangerous
if the crowd continues to get denser or people make
unexpected movements. At that point, the crowd can become turbulent
and chaotic, with people being pushed randomly in different directions.
Disasters can break out when say, one person stumbles, causing
someone else to be pushed into their place and either
(32:29):
trampling them or stumbling themselves, and this whole can have
a kind of gravitational effect pulling in more and more people,
which in terms of the physical dynamics, this is similar
to how the flow of physical substances like water behave
when they're funneled into narrower and narrower places. Like I
think about how some of the world's most dangerous whirlpools
(32:51):
seem to occur in bottlenecks for the flow of water,
where for example, the tide is pushing a huge amount
of water through a narrow, straight or your This can
lead to rushing and turbulence. It's chaotic flow and unpredictable
directions which can sometimes create these whirlpools. Anyway, back to
the article, it mentions a couple of other UH seeming
(33:13):
risk factors for for when this happens UH. In addition
to the high density another one is bidirectional or multidirectional flow.
So things can get more dangerous if you have high
density and people trying to move in different directions UM.
And then finally, lambsites The researcher Juannas Kara Mutzis, who
was one of the authors on that paper from feen
(33:34):
I mentioned a minute ago saying that in large enclosed spaces.
For some reason, the sides of the space seemed possibly
to be more dangerous than the middle, though there isn't
enough research to be sure of that or to explain
why it happens. So obviously, understanding the flow of crowds
goes way beyond just just being a kind of interesting
(33:55):
little curiosity and like looking at how people move. It
is something that is of critical importance in managing, you know,
large masses of people, and in designing spaces for them
to move through, and in planning events and all kinds
of things like that. I mean, this is like one
of those things that starts off being really funny but
is in fact a critically important subject. Yeah, I mean absolutely,
(34:18):
they're they're just going to be more and more office
and these uh, these large events of of you know,
varying genres are going to continue to be a part
of our lives. This actually got me wondering about something,
which is um why doesn't anything like like uncontrollable crowdflow
with with actual like pressing against one another happen with cars.
(34:41):
You can see some of the characteristics happen with cars
because you can get traffic back up when there's a
bottleneck in the highway, maybe seven lanes suddenly go down
to one, and this will cause a huge traffic jam.
But you don't usually have the problem with like cars
pushing each other and and pressing against one another and
leading to this bill up of uncontrollable forces. I was
(35:02):
wondering why that is. Maybe it's because I'm just guessing.
I wonder if it's because it's never considered acceptable for
cars to touch each other at all. Uh. And people,
of course mostly avoid try to avoid touching one another
in crowds, but in some situations, maybe it just seems
like there's no avoiding it, so you just sort of
(35:23):
resign yourself to touching and then that and then that
can build up. Maybe I'm not sure, you know, that's
a good point. Yeah, because even though some drivers do
like to come as close as possible to touching your car, uh,
which is something I've never been able to understand, just
given how dangerous it actually is to you know, to
(35:44):
to you know, to pull up right behind somebody will
at high speeds on the interstate. Uh. Yeah, yeah, to
your point, they you're not actually supposed to ram into
them even a little bit. And and while you know,
certainly pile ups do occur. You do have acts density,
do have cars crashing into one another and then multiple
car pile ups occurring. Um, yeah, I wonder if this
(36:07):
stricter no touch policy with cars has some sort of
influence on us. Well yeah, maybe another thing is I'm
not conceptualizing it right, And maybe the crowd dynamics I
was talking about are more analogous to just actual like
pile up crashes, I guess, which I wasn't thinking about
in a similar way because those happen at higher speeds.
I wonder what would we would see in something that's
(36:28):
halfway between if what would be between a car and
a person if we were to say, look at a
bicycle traffic in very congested bicycle situations, say a city
where there's a high number of bicycle riders or something,
or bicycle races. Because I feel like one of the
things with people is that yeah, it's like, yeah, maybe segways,
(36:49):
but I feel like one of the things with people,
like you've already mentioned, is when you're pushed forward, you
may be pushed into that hole that you could not
otherwise occupy or wouldn't occupy socially. But now you know,
if you're being pushed. I guess that's where I'm going. Um,
so there's just more nooks and crannies for for human beings.
Um and then with with cars less so. But perhaps
(37:09):
if you're looking at bicycles, like maybe maybe we see
something that's more like the human scenario. It'd be interested
to hear from some of our bicyclists out there, like
what are the social laws of crowded bicycle scenarios? How
close can you get to another bicyclist while moving while
stationary while sort of you know, uh, tiptoeing along. I'd
be interested a year, Yeah, totally, I mean especially yeah,
(37:33):
like it seems a key difference is is the the
the balancing act that's necessary on a bicycle? Yeah? Well, anyway,
I want to say about these two subjects, the physics
and kinetics price this year. This definitely did, uh did
achieve the desired intent. It made me laugh a little
bit and then did make me think it was not
I will I will grant it did not make me
(37:54):
laugh hilariously, so it was a mild chuckle, but then
it got really interesting to me. Yes, all right, we're
gonna go and close this episode out, but we will
be back. Um, I'm going to talk about the Biology Prize.
We're gonna get into some other prizes from the Igno
Bells this year, so just tune into that in the
(38:16):
next Core episode of Stuff to Blow Your Mind. To
remind everybody, Stuff to Blow Your Mind. The podcast feed
can be found wherever you get your podcasts. Core episodes
come out on Tuesdays and Thursday's Monday is listener Mail,
Wednesday is a short form artifact episode, and on Friday's
we do Weird House Cinema. That's our time to set
aside most serious concerns and just focus on a weird film.
(38:38):
Huge thanks as always to our excellent audio producer Seth
Nicholas Johnson. If you would like to get in touch
with us with feedback on this episode or any other,
to suggest topic for the future, or just to say hello,
you can email us at contact at stuff to Blow
your Mind dot com. Stuff to Blow Your Mind is
(39:01):
production of I Heart Radio. For more podcasts for My
Heart Radio, visit the I Heart Radio app, Apple Podcasts,
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