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This video is sponsored by The Great Courses Plus
I'll sometimes get an idea for a video and I really
like it but it's too short for its own
video so i've collected a few of them together
into one video so this
is five interesting things. I guess it's
a new format, potentially so if you like it,
i'll make more of them. If you don't,
maybe i'll try it one more time because you know, you gotta give these
things more than one go. Anyway, here you go
five interesting things, here's interesting thing number one: Image Stabilisation.
So if you record a video on your phone or on your camera,
and it comes out shaky, you can take the footage and load it into video editing software
or you can upload it to YouTube and there'll be options to stabilise the footage
and the way the software does it, the way YouTube does it is to analyse
the footage frame by frame to work out how the camera must have been moving to create that shot
and then it tries to figures out how we can soften that movement. So there's artificial intelligence involved with that.
The interesting thing is that I got this phone recently.
It's a (Google) Pixel 2 - It has image stabilisation built in.
but the way that the phone does it is different, I believe to the way software does it, to way it's done on YouTube.
I don't think the phone analyses the footage as it comes in to work out what's going on.
Instead, I think it uses the sensors inside of the phone.
So the phone has a gyroscope inside
and it has an accelerometer inside.
Those sensors tell the phone about its orientation in space
and how the phone is moving so the
camera should already know how it's moving, it shouldn't have to try and work it out by analysing the footage
and I think I can prove that this is happening.
So by attaching my phone to the outside of a box with the camera looking through a hole
I'm fixing the cameras position, relative to the box, relative to the picture of the cat there
so no matter how I move the box around
the picture of the cat and the camera will
remain fixed relative to each other.
So when I hit record on this camera phone
the image going into the lens
will be completely stable.
It won't move even when I move the box
but if the camera attempts to stabilise the image based on
the internal sensors telling it how the camera is moving then we will see some erroneous
stabilisation. The stable image will actually become unstable
So let's let's give that a whirl. You'll notice as I rotate the box like this,
the picture
suddenly moves to one side then when I stop it kind of slowly settles back down to the middle
and you can kind of see how that would stabilise an image if
the phone wasn't attached to a box and
look, it works going up and down as well
like that so the image kind of snaps to the top and the bottom to try and compensate
for the motion. Something I wasn't expecting to see when I put this experiment together
Was that the camera also seems to compensate for rolling shutter?
I've talked about rolling shutter in other videos, but basically
the sensor in a camera doesn't take an instantaneous picture.
Instead it scans down the sensor like that so if you've got an object
that's moving across your frame, and the sensor is scanning down like that
you can see how the object would become slanted that's called rolling shutter and
pretty much all digital cameras have it. It's very rare to have a sensor that doesn't do that
And so look if I spin round really quickly like this
The the picture of the cat becomes slanted... Goodness, wait, get your balance.
*Laughs*
So the camera is compensating for that sideways motion that normally
produces rolling shutter
that slants the image, it's trying to understand the image
But because the image is not moving it ends up slanting the image the other way interesting thing number two fig
Interesting thing number 2: Fig Pollination
So a fig is a syconium meaning its flowers are all pointing inwards
so you've got this outer shell and then all the flowers are pointing inwards hidden inside there.
So if all the flowers are hidden away, how were they pollinated?
They're pollinated by a wasp a particular kind of wasp called a fig wasp
creatively and
Here's how it goes down, so you've actually got two types of fig: male figs and female figs. What the
wasp wants to do, "wants to do"
(asterisk on screen referencing info in video description) is get inside a male fig because
that's a nice place to lay your eggs. It's safe in there, so
the crazy thing is that
you've got this tiny hole, and that's what the pregnant female fig wasp climbs through
but it's so small that the wasp loses bits of its body as it kind of shimmies through there.
So some of its wings go, its antennae.
Once it's inside, it lays its eggs, and then it's trapped. It can't get out again
so it dies in there, and then the eggs hatch, so you've got a whole lot of male and female wasps
inside the fig, the first thing they do is mate with each other so
the female fig was are pregnant before they've even left the fig that they were born in
the male wasps then dig a hole out of the fig for the females to get out of.
The males are blind and flightless so once they've done that they die their work is done. They've already mated
They've dug a hole out for the females and then they're done
The pregnant females now covered in pollen from inside the male fig fly off to find another fig.
But here's the thing, if the pregnant female wasp, that has just left the male fig
flies off and then burrows into another male fig, that's no good for the fig tree. What the fig tree wants
"wants" is for the
female pollen carrying pregnant wasp
to burrow into a female fig where it will deposit its pollen and pollinate the flowers inside the female fig
but that's not good for the wasp because when
a wasp burrows into a
female fig, it can't lay eggs, it just dies in there,
it's the end of the line. So the fig tree has evolved for the male and female
Figs at that stage in their lives to look identical
it's potluck which one the
wasp will burrow into. It's the female ones that we eat the male ones aren't tasty
So you might be thinking "Ah, so when I eat a fig, that crunchiness is because I'm crunching on dead wasps"
It's actually not, the crunchiness is the seeds and in fact when a wasp
dies inside a female fig, and actually that can happen several times, so you might have several wasps climb in there and die
the fig releases an enzyme
that breaks down the body of the wasp to release those nutrients the nutrients are then absorbed
into the flesh of the fig so in that sense, I guess you are eating dead wasps,
but I mean
by that definition whenever you eat vegetables you're eating dead animals because when an animal dies it
fertilizes the ground
But I suppose with a fig, it's a bit more direct.
Interesting thing number three. Outside my window just over the River Thames
there's the Tate & Lyle Sugar Factory
and it's got these two chimneys with
spiral fins around the outside and you may have seen that on chimneys before there's a good reason for them to be there, so
when air passes over a cylinder it sets up this?
oscillation in the air
downwind. It's called vortex shedding because it produces these
Alternating vortices that are spinning one way and then the other
And the reason you get this is because of fluid dynamics, fluid dynamics is complicated, so
You get vortex shedding for complicated reasons, but but there it is. It's it's fluid dynamics
But the important thing is if you've got this
oscillation in the air, this backwards and forwards motion well
every action has an equal and opposite reaction: Newton's third law
so the chimney must be feeling a side-to-side force as well opposite to the force that the air is feeling
And that's okay just make sure your chimney is sturdy enough to resist that side-to-side force
except that the frequency of
vortex shedding, like how quickly does it go back and forth is?
related to the wind speed, if you increase the wind speed, you increase the frequency of vortex shedding what that means is if
by some bad luck the wind speed is just right you'll get the resonating frequency of your chimney.
I've talked about resonating frequency before but the important thing is
if you hit the resonating frequency of the system, the energy that you put in adds to the energy that's already there and
The amplitude goes up dramatically, so suddenly your chimneys doing this which is bad news
and I can illustrate this effect actually with an elastic band and a hairdryer
*Hair Dryer On Low*
*Hair Dryer On High*
It's similar to when you put a blade of grass between your thumbs and blow through
*Blowing and High Pitched Noise*
You don't want that to happen to your chimney because it will fall over so you put these fins around it and they
direct the air downwards on one side. upwards on the other side
and that's enough to disrupt the flow of air to the point where you don't get vortex shedding.
Interesting thing number four: Lima beans.
Lima bean plants have evolved this amazing defence against caterpillars.
Basically they call in the meta predator, like if you can find a way to summon the predator of your predator
you might be able to survive an attack and the meta predator in this case is a wasp.
Different wasps to the other one we talked about, this one is a caterpillar wasp obviously and this one injects its eggs into caterpillars
So typically when you think of wasp you think about it's an insect that stings you
But I mean that's a type of wasp, another type is a wasp that uses its
stinger to
inject eggs into things in this case
caterpillars, so the egg hatches inside the caterpillar.
The newly hatched wasp eats the caterpillar from the inside out and the caterpillar dies of that obviously.
So what the lima bean plant does is when a caterpillar comes along and bites into a leaf
that's detected chemically by the plant and it reacts by releasing a scent and
this scent is like an advert. It's like the signs outside a Krispy Kreme.
You know they light up when there are fresh donuts. It's like this scent is saying hey
"We've got fresh caterpillars, come and get them"
So the wasps fly on over and inject their eggs, the caterpillars die and the lima bean survives
it's amazing and it's a coordinated thing as well like one caterpillar takes a bite and the whole plant releases a scent and
neighboring plants release the scent as well. It's really amazing interesting think number five Tower of string
Interesting Thing Number Five: Tower of String.
I've got this tower of string sort of sculpture
So it's slightly mind-bending because you know, string isn't rigid,
it's flexible so it should fall over and while this tower thing has
rigid parts these plastic bits are rigid. They're not attached to each other directly
they're attached via bits of string and string is flexible
I mean think about it for a bit, you can see how it works like the
bits of plastic are under tension, and they're holding the string in tension as well
String is strong under tension and that's what makes the tower stand but still
it's a little bit mind-bending when you first look at it which is fun
Thanks to Austin Engle for bringing that to my attention he sent me a picture of one that he'd seen on Twitter
which inspired me to build my own. So there you go five interesting things one more bonus
detail at the end of the video
but before that I just want to say we have covered a few different topics in this video biology, engineering, technology.
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Here's the bonus fact, it's about the fig wasps.
A female fig can be pollinated by many
female fig wasps so you might have a few crawling in there with their pollen covered heads and
if you're a fig farmer
that's a problem because if too many of those internal flowers there get pollinated then
the fig bursts open and
the figs are harder to sell I guess when they're burst open so
the farmers keep the male fig trees and the female fig trees completely separates. There'll be two completely separate
plantations or orchards maybe
and the distance is too great for the wasps to just kind of find themselves
crossing between the two and so what the farmers then do is they they collect the wasps from the male
orchard and carry them over and just release exactly the right number that they want to perfectly
fertilise the fig without it bursting.
That's it. I hope you enjoyed the video if you did don't forget to hit subscribe and i'll see you next time.
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