We should use this amazing mechanism that's inside a grasshopper leg

this is the mechanism inside a

grasshopper's leg that enables it to

jump so high and it's really clever

because it solves a fundamental

limitation of animal muscles humans come

up against the same limitation but we

get around it with tools and actually

it's kind of two limitations I'm going

to show you how humans deal with the

problem first because it's quite

instructive and then we'll see how the

same mechanical principles are found

inside the grasshopper's body and a few

different variations in other animal so

here's a problem that a human might face

there's an object in the distance that I

would like to puncture a hole in and

I've got this little steel ball here so

I think if I can get the ball going fast

enough by the time it reaches that thing

maybe it'll puncture a hole in it and I

think well how can I do that I'm going

to throw it with my

arm the problem is the steel ball is

quite light which means it's not

offering much inertial resistance to my

muscles so my hand ends up traveling

really quickly and actually it takes

muscles a little bit of time to build up

to their maximum force and by the time

the ball has left my arm I'm nowhere

near my maximum Force that's the first

limitation of muscles and it's quite

easy to overcome actually in quite a

counterintuitive way and that is to just

make the ball heavier so this ball has

much more inertia so my arm is is going

to move more slowly when I throw it but

at least it's going to give my muscles a

chance to get up to maximum force and

because it's heavier it's going to have

more kinetic energy meaning when it hits

the target it's going to have more

puncturing ability but this is where we

come up against the big limitation of

muscles you can either apply a large

Force slowly or a small Force at high

speed and it's something you've

experienced like if you've ever lifted

weight if it feels heavy to you you have

to lift it slowly so that makes

intuitive sense but it also makes

mathematical sense because what you're

experiencing is your muscle maximum

power output like you know that power is

a measure of how quickly you can deliver

energy in other words energy divided by

time but maybe you also know that energy

is force times distance moved in

direction of force and if we slide

things around to get the force term on

its own you can now see that power is

also force times speed so given that

your muscles have a maximum power output

that explains why you can either have a

small force moving quickly or a large

force moving slowly but if I want either

of these balls to leave my hand with

enough speed to puncture the target when

it arrives I need to be applying a large

Force at high speed but with my muscles

I can't do both and that's where the use

of tools comes in the tool in this case

is a slingshot here in the UK we call it

a caterp but that's a bit confusing cuz

other things are called catapults so

I'll keep calling it a slingshot

probably the elastic of this thing is

really strong so to pull it back I have

to use a large Force which means I have

to move my muscle slowly but that's fine

because what I'm doing is I'm storing

all that energy as elastic potential

energy in the slingshot and the

slingshot doesn't have the same

limitations as my muscles it can move

with a large Force quickly

so a slingshot is an example of a

mechanical Power amplification device

and humans have invented loads of those

things another obvious example is a bow

and arrow I use a large Force traveling

slowly to flex the bow and that stores

energy again as elastic potential energy

and all that energy can be delivered by

the bow with a large Force quickly one

of my favorite examples is a barbecue

lighter inside there is a quartz crystal

and if you hit it really hard it'll

generate an electric spark these two

wires carry that electric spark up to

the tip where it can ignite a flame but

you would never be able to hit it hard

enough just like with moving your finger

that short distance so instead you apply

a large Force slowly right and that

compresses a spring so all that energy

is being stored in the spring and at

some point you get far enough down that

um catch is released and all the energy

that's stored in the spring is released

with a large Force

quickly and that's enough of a force

hitting the crystal to generate the

spark the hammer on a pistol works in

the same way as a barbecue lighter and

by the way in all these examples we're

never using an external source of energy

all the energy comes from your body it's

just stored slowly and released quickly

even the electrical energy in the spark

ultimately comes from your muscles so

that's what humans have figured out but

what about the gra Hopper is there

something like a slingshot or an archery

bow inside the grasshopper's body so

here's a diagram of the back leg of a

grasshopper and there are two tendons

the one shown in red extends the leg so

that's called the extensor tendon and

the blue one flexes the leg so that's

called the flexer tendon and of course

each tendon is pulled by a muscle and in

my model that's just these two ropes

here the flexer tendon in blue the

extensor tendon in red and you can see

it's just a lever that pivots around

this point this is the knee joint that

extensor muscle is big like amazingly in

a large grasshopper like a locust that

extensive muscle can produce almost 15

Newtons of force which means with both

back legs at the same time a grasshopper

could lift these three bags of sugar so

the peak force is huge but unfortunately

it takes a little while to reach Peak

Force about 300 millisecond which

doesn't sound like a lot but it only

takes 30 milliseconds for the

grasshopper to leave the ground once the

jump has started so by the time the peak

Force has reached there's nothing to

push against that's a bit like the issue

that I had with my tricep muscle and

then there's the big limitation of

maximum power that we talked about

earlier like a locust could bench press

3 Kg but it could only do it very very

slowly and that's no use for the jump so

the grasshopper needs something like a

bow something that can store energy and

release it quickly and this is actually

something that you can see from the

outside compare this jumping leg on the

left with this middle leg on the right

everything you can see here is

exoskeleton but the darker region is a

different type of exoskeleton it's much

stiffer much better for storing lots of

elastic energy and you can see in this

video how it bends before the kick a lot

of these videos and animations come from

Dr Bill heer's website by the way which

has been an amazing resource for this

video linking the description for that

so in our model we've added a spring to

represent that specialized exoskeleton I

also added this lever here that's not

part of the grasshopper's body that's

just there to give my puny muscles

enough mechanical advantage to be able

to represent the immense strength of the

grasshopper's extensor muscle so here's

the sequence first the flex attendant

pulls the leg up and it holds it there

so then when the extensor muscle

contracts it's not going to cause the

leg to kick out because it's being held

in place by the flexor muscle in instead

it's going to cause that spring to

contract which remember in the case of

the grasshopper is actually a super

stiff specialized bit of exoskeleton

that's going to bend like an Archer bow

and because it's so stiff the extensor

muscle has to apply a large Force which

means it has to move slowly and that's

absolutely fine because what it's doing

is storing up all that energy in the

spring then all the grasshopper has to

do is release the flexor muscle and all

that gets delivered with a large Force

quickly like that but that's not the

whole story because the flexor muscle is

much weaker than the extensor muscle

like the extensor muscle can produce up

to 15 Newtons of force but the flexor

muscle can produce up to like 0.7

Newtons of force so how is it that the

flexa muscle is able to hold the leg in

place against the much Superior force of

the extensor muscle that's acting to

oppose it well there's two things the

first is mechanical advantage you'll

notice that um the position of this

tendon is much further away from the

Pivot Point than this tendon here so

this has mechanical advantage over this

one but even that isn't enough there's

actually a little bump inside the knee

joint of the grasshopper and the flex

attendant goes around that bump so I've

put a rod here for the flex attendant to

go around so when the flexor tendon is

pulled and the leg reaches this position

you see how the tendon is leaving the

leg almost perpendicular so almost all

the force from the tendon is acting to

turn the leg around the pivot whereas if

you look at the angle of the extensor

tendon where it meets the leg it's a

shallower angle so it's only the

perpendicular component of that force

that acts to rotate the leg in the

opposite direction around the pivot

point and it's the combination of those

two factors that means the much weaker

flexer muscle is able to hold the leg in

place against a much stronger extensor

muscle there are loads of different

mechanical Power amplification

mechanisms found in nature and it's

really interesting to look at the

different types for example the frog

hopper it has one of the largest

accelerations in the animal kingdom

clocking in 500 G's it does that by

first pulling its leg up against its

chest right so imagine like the Frog

Hopper's body is up here this is the

chest and this is the leg that's coming

up and they stick together by something

akin to Velcro so I've put some velcro

there and then a muscle tries to pull

the leg free but it does it via some

kind of elastic thing like this so again

it's a large Force applied slowly energy

is being stored in that elastic medium

until eventually the dark C gives way

and all that energy is released with a

large Force quickly the human equivalent

might be something like a spud gun where

you build up energy until something

gives way in this case you're building

up pressure until the potato seal gives

way what about catch mechanisms do you

find those anywhere in nature like

humans use catches a lot to hold back a

large force with a catch that only

requires a small Force to release and it

turns out that the Trap jaw ant uses a

catch mechanism to to hold its jaw open

it then uses a large Force to slowly

build up energy behind the jaw and then

it uses a small Force to release the

catch so that the jaw snap shut on the

ant's prey this footage is from the ant

lab by the way link to their brilliant

video in the card and description so the

Trap jaw ant mechanism is not quite the

same as a crossbow in the sense that the

energy buildup stage happens after the

catch has been put in place it's a bit

like if the string of my crossbow was

slack when I locked it in place and only

then did I tighten up the string right

this is where I get distracted by a

massive side quest and I hope you'll

come with me cuz it's really interesting

so thinking about all these different

Power amplification mechanisms I thought

of one I was like I'm sure I've seen

this in a device before but I wonder if

it's ever happened in nature so I

printed this thing out to demonstrate it

gets harder and harder to open this

thing up as the elastic becomes more and

more stretched but actually Beyond a

certain point it gets easier again and

that's because of the shallow angle of

the elastic like only a small component

of the force from that elastic is

perpendicular to the arm so it gets

easier and easier and easier until look

when it passes the pivot point there

it's actually slightly holding it open

now and you only need a really small

Force to close it again I was sure that

I'd seen a mechanism like this in a

device but I just couldn't think where

it was which is very frustrating I even

built an alternative representation of

the thing so look this is a compliant

mechanism it's a by stable switch I

didn't Design This by the way and look

it switches between these two

configurations and you need a lot of

force to switch between the two stable

States but look if I get it just like

halfway between the two stable States

just as you're getting over that energy

hump you hardly need any Force at all to

move it around you know it's just as you

get over the hump and then it races away

to the other stable configuration but

what if you put a little nub in there

right so just as you're getting over the

energy hump the nub in's in the way so

you hardly need any Force at all to get

it back to that first stable

configuration and I'm pretty sure it's

the same kind of thing as this right you

get just past the energy hump you know

it gets easier and easier and easier you

get just past the hump and then it's

like on a a hair trigger but I still

couldn't think of any device that

employs this mechanism and then I spoke

to some people if you've got any ideas

please tell me because this video goes

out in two days uh lots of people had

ideas by the way tickets go on sale for

our end of year show in a few days I'll

link to that in the description a few

people said what about a mouse trap but

that's not quite the same mechanism like

when you're priming a mouse trap and

you're pulling that thing back it gets

harder and harder and harder harder and

harder all the way and then you apply a

catch to

it so it's not the same as this right

where it starts to get easier just at

the end there David didn't actually

suggested the lever Arch file just like

the thing that I demonstrated it's hard

to move at the beginning but look

eventually this is mostly moving side to

side so at that point you don't need

much force to move but you're not

working against this spring and it would

be easy to pop up if it wasn't for all

that

friction and it's easy to pop up Step

Smith mentioned these boom cards look

they pop up into a cube inside there's

an elastic band and when you get towards

flat there's pretty much no resistance

at all because the elastic band at that

point isn't really changing length but

there's enough bounce in the card to get

it started my favorite suggestion comes

from Matt barington the compound bow

actually gets easier to pull back Beyond

a certain point so it's easier to hold

in that drawn position compare that

experience to a normal bow where your

arm is quivering with the strain of

holding it at full draw that's a clever

idea isn't it so it turns out that

humans have used that mechanism a number

of times but I don't have an example of

it in nature if you can think of one let

me know you know it seems to me any way

you try to categorize the natural world

you'll always be able to find some

exception that defies your categorical

rule like the rule that mammals don't

lay eggs or fish don't fly or whatever

so I need to be careful because I've

kind of implied that humans always do

their power amplification through the

use of tools and animals always use

their bodies but actually I can think of

an exception to both of those rules like

take clicking your fingers for example

try and do that directly without par

amplification

it's a pretty weak sound what we

actually do is we press our thumb and

finger together and slowly build up

elastic energy in the muscles tendons

and joints and then we release it

quickly and you get that snapping of the

fingers there's only one known example

of an animal using something external to

its own body for mechanical Power

amplification and that's the slingshot

spider it stores elastic potential

energy in its web then transfer all that

energy suddenly into the web and its own

body as a means of catching prey how

cool is that it's interesting to see how

new business models are born like during

the California Gold Rush Savvy people

started new businesses selling shovels

but these days a lot of obscure

intangible things have value so it's not

always easy to spot the businesses that

pop up around them take personal data

for example we live in a world where

that has value now so of course

companies have popped up to make money

off it companies called Data Brokers

that gather information about you and

sell it to other companies I'll get to

how the sponsor of this video incognit

can help with the problem in a minute

but first why should you be concerned

about data Brokers well it's not just

about you receiving targeted ads and

Robo calls and marketing text messages

data Brokers are also selling your

health data to insurance companies for

example some data Brokers have been

charged with supplying lists of elderly

and vulnerable people to scammers even

collecting data on successful scams to

refine their algorithms but perhaps the

biggest problem is data breaches when a

data broker experiences a breach that's

your personal information that is now in

the hands of a criminal now you can tell

these data Brokers to delete your data

and legally they have to the problem is

there are hundreds of them so it's

almost impossible to do on your own so

here's a new interesting business model

that's actually useful incog have

figured out how to contact all these

different companies and request data

removal and they've automated the

process so you sign up you give them

permission to act on your behalf and

they just take care of it all look these

are all the companies that no longer

have my data you know I used to get

these phone calls from companies that

seem to know a lot about me and from

what they were saying in the words they

were using I say oh this is my insurance

company I guess and then I find out it

isn't and they're trying to sell me

something since signing up to incognit I

don't get those phone calls anymore the

promo on this one is really good if you

go to incognit do.com science you'll get

60% off the annual plan the link is also

in the description so check out incog

today I hope you enjoyed this video if

you did don't forget to hit subscribe

and the algorithm thinks you'll enjoy

this video next

[Music]