- This episode of Because Science
is brought to you by Destiny 2: Forsaken.
I have a confession to make,
I've been trying to science Spiderman for years now
and every time I have been asked to look into
the so called Spidey-sense,
I've dismissed it out of hand without ever
really looking into it.
And now that I have, I have to apologize.
I was so wrong.
Spiders have tarsal claws down
some of the most amazing senses of any organisms
on this planet.
If Peter Parker had spider senses,
they would definitely make him amazing.
Ooooohhhhh.
Spiderman's Spidey-sense has been a part of
Peter Parker's webatoir since the hero first
swung into the pages of Marvel Comics
all the way back in 1963.
Since then, comics, movies and video games
have depicted spider-sense as a feeling or premonition
that something is about to happen
or that something, somewhere is going wrong.
It's an almost magical sixth sense without
a solid biological backing.
Like I said, you don't have to look any further
than real spider senses to make Spidey-sense
make sense, sense.
So let's ignore the weird precognitive stuff
in the name of science
and give this power that biological backing.
Spiders and many other terrestrial arthropods
like crickets, have three main sensory systems
that could add up to theoretically give a spiderperson
a spectacular sense of their surroundings.
Two of these systems use tiny hairs
to detect touch and motion,
tactile hairs and trichobothria.
The third uses a fascinating little organ
called slit sensilla.
Let's start with the tactile hairs,
as they are the closest thing to a sense
that we are familiar with.
Oh you're a big boy.
The most common sensory structures in the animal kingdom
aren't eyes or ears, they are hairs.
Most of the human body is covered in hair of some type
and all of those hairs add up
along with other receptors in your skin
to give us an exquisite sense of touch.
We can feel if even a single hair is disturbed.
Ooh, excelsior.
We mostly hairless apes have about
60 hairs per square centimeter of surface area of skin.
Which makes our sensitivity to physical disturbance,
our mechanoreception, pretty good.
Spiders though, are on another level.
They have around 40,000 hairs in the same amount
of surface area and they have up to three nerves
per hair for sensation, whereas we only have one.
Wow.
Hey if you were that big,
how are you even breathing right now,
cause I'm pretty sure if you scaled up your volume
based on your...
These thousands of spider tactile hairs,
like human tactile hairs,
will trigger a sensation in the animal
if they are deflected a certain amount.
Like pushing or pulling a simple lever.
The threshold of force though that will trigger a response
from a spider is unbelievably small.
A spider's tactile hairs will respond to a force
less than half a micronewton.
This is only five times more force
than a hydrogen atom's nucleus puts on it's electron.
It's hard to even conceptualize how gentle that is.
So if Peter Parker's hairs somehow mutated
along with the rest of his body to become
as numerous as a spider's hairs
and acquired this kind of extreme sensitivity,
it would be the first part of an impressive spider-sense.
Sorry.
From our perspective it would be like he's able
to feel touches before they even happen.
Sorry.
Spider-like tactile hairs would make Spiderman
intensely attentive to touch,
which would be a good place to start for a real spider-sense
especially considering that in the movies,
we've seen Peter Parker grow spider-like hairs.
But spiders other senses are even more impressive.
They can feel things that aren't even touching them.
The second spider sensing system is trichobothria
or hairs that feel for fluid flow, like moving air.
These hairs look like the spiders tactile hairs
and they're even located in the same place,
but these are evolved to feel for even
the slightest breeze
and I do mean slightest.
For example, trichobothria are so sensitive,
they can pick up the minute atmospheric disturbances
that a flies wings produce from up to a
few body lengths away from a spider.
This would be like you being able to feel your friend
wave at you from across the room.
Oh he is friendly, that's nice.
This air-hair isn't just really responsive spider stubble,
it is, as one review by Freidrich G. Barth put it,
one of the most finely tuned biological sensors
in all of nature.
Modeling trichobothria as simple levers,
scientists have estimated that
the amount of energy it would take to elicit
a response from these hairs is on the order
of 10 zeptojoules.
I've never even said that prefix out loud before.
This is in theory so little energy
that a spider's trichobothria would respond
to a laser pointer.
It would respond to the pressure of light.
Less friendly, ahh!
One day, all the way back in 1827, Scottish botanist
and smart boy Robert Brown, was looking through
a microscope at pollen particles suspended in water.
What he saw was something like this.
The pollen particles were moving around randomly
when he assumed they should be still.
Cut to 78 years later and the smart boy, Albert Einstein,
publishing a paper that described this motion.
Einstein argued that the pollen particles were being
batted around randomly by physical atoms and molecules
in the water, moving around randomly.
At that time, in 1905, the physical existence
of atoms and molecules had not yet been proven.
Einstein's findings were eventually confirmed
and accepted and this was one of Einstein's
first great contributions to science.
Today the random motion of atoms and molecules
in a fluid is called Brownian Motion,
in honor of Robert Brown.
And I told you that story to tell you this,
spider trichobothria are, in theory,
sensitive enough to feel Brownian Motion.
To feel, against their hairs, the individual impacts
of atoms and molecules.
This represents a spider-sense that is an almost perfectly
evolved material interaction at the very edge of physics.
Real trichobothria could plausibly play a huge part
of a real spider-sense.
Being able to feel your enemies move through the atmosphere
at a distance would be a huge advantage
but the last arachnoid sense would take all of this biology
from spider to super.
The final component of a spider's sensory system
are the slit sensilla,
which are mechanoreceptory organs
in the spider's exoskeleton that are unlike anything
that we humans feel with.
These organs sound fancy but they actually are rather simple
In the spiders legs, near the joints,
there are rows of parallel channels
where the exoskeleton has been thinned out.
If the spider's leg moves or bends
in response to some vibration or force
in the substrate or ground that the spider is standing on
or touching, these slit sensilla
will deform like accordions.
By now, it should not surprise you
that the amount of vibration it takes to alert a spider is
astonishingly small.
Scientists have found that these sensilla can alert spiders
to forces near them that are as small as
point zero one micronewtons.
This is less than half a percent the body weight
of a single cockroach.
That means, that if I were to just take a single step
I would...oh, I guess I'm...ahhhhh!
Basically if a nearby force or vibration
moves a spider's legs at all, it's going to feel it.
If I was moving around next to it,
a spider about that size would be able to feel
if I caused it's legs to bend just a billionth of a meter
but that's so small it's hard to visualize
so let's increase the spider size.
Bigger.
Keep going!
If that spider got big enough that it was
over 100 kilometers across,
that it could reach up with one of it's legs
and touch space,
it would still be able to feel if any one of it's legs
deformed, literally that much.
Just a single millimeter
or a millimeter Parker.
Argh.
If whatever mutations Peter Parker got
from that radioactive spider indeed
enabled him to do whatever a spider could do,
then I think that using an array of arachnid sense systems
web-head could absolutely approximate a sixth sense,
at least as sensitive as human eyesight or hearing.
Slit sensilla scaled up to human size
might be able to pick up an approaching bad guy
or at least a rampaging rhino.
Trichobothria on Spiderman might be able to pick up
the minute atmospheric disturbances
from an incoming projectile
or even the pressure from the light
of a gunman's laser site, which is ridiculous.
Real spider senses operate at the limits
of the physically possible
and if that doesn't sound like super powers,
I don't know what does.
So, how does spider-sense really work?
Well I don't think you have to look any further
than the arachnids themselves.
Spiders have some of the most delicate senses
in all of biology
and if Peter Parker had them,
I think he could approximate something like we see
in the comic books and the movies.
Of course, he would have to find a way
to make those tiny hairs work underneath his suit
and sure, slit sensilla are only in exoskeltons
and not endoskeletons like we have,
but being the science wiz that he is,
I bet that Parker could find a work around,
because if he was truly a spider man,
he would feel so good, Mr. Stark.
Because science.
Everyone gets one right, yeah!
Oh, oh why is it hot?
Oh it's like al dente spaghetti.
(techno music)
So let's say that you were a more realistic version
of Spiderman and let's say you were, I don't know,
in New York and a giant spaceship appeared over New York,
which would feasibly cause a giant atmospheric disturbance,
perhaps if your hairs were like spider hairs
they'd stand up on end like trichobothria.
Oh wait, does that happen?
Confirmed.
Thank you again to Destiny 2: Forsaken
for sponsoring this episode of Because Science.
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Thank you so much for watching, Celia.
Thank you so much to Phil Torres
for his help on this episode.
He discovers new species of spiders in the Amazon
and I'm totally jealous.
If you want more of me,
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Whaaaaa!