Bang Goes The Theory (2009) s03e04 Episode Script
Season 3, Episode 4
Tonight on Bang Goes The Theory Jem investigates the latest in wave technology.
' Hey! l'm getting light! l'm getting light from waves! 'Yan is larking about with ping pong balls.
' lt's like something is holding it back.
'And l demonstrate the theory of evolution using an eye 'and a very brainy man.
' Reason tells me it would be easy for it to evolve by natural selection.
'That's Bang Goes The Theory, putting science to the test.
' Welcome to the show.
First, something as British as queuing at Wimbledon or the Queen's Speech.
That is talking about the weather.
l'm going back in time to find out where our weather came from.
Here we are on the south coast and it's early September.
lt's warm-ish, but in a couple of months we'll be wondering if it will be a white Ohristmas.
What causes the seasons? How come we get warm weather in summer and cold weather in winter? Well, the answer to that question is 4.
6 billion years old.
So come with me to the very dawn of the solar system.
We're going to travel back to when the Sun was a few million years old and the planets were being formed from a cloud of protoplanetary dust.
This is the new young Sun.
Over there is the brand new Earth.
You wouldn't want to hang out on it.
There's no atmosphere, no land masses, no oceans.
lt's a big lump of hot soft rock.
The planets are forming from this rubble orbiting around our brand new Sun.
Huge asteroids hitting the Earth are a rare phenomenon today.
Back then, it was happening all the time.
The effect was that the Earth was knocked this way and that on its axis.
Rather than it being a nice stable spinning top like this .
.
the Earth's axis would have been wobbling like this.
What's that got to do with the seasons? The seasons are determined by the angle at which the Earth is facing the Sun.
The Earth's orbit is elliptical - it's closest to the Sun in January and furthest away in July.
That makes little difference to the amount of solar energy we receive.
To show how the Earth's tilt affects seasons, let's do an experiment.
lmagine that the Earth's axis is flat on, parallel with the Sun's as it orbits round.
All the Sun's energy is hitting the same bits of the Earth all the time throughout the year, therefore you don't have seasons.
The northern and southern bits are dark and cold.
The equator is incredibly hot all the time.
But the Earth is not at 90 degrees to the Sun.
lt's at an angle, and that's thanks to one massive collision.
About 4.
6 billion years ago, we had a next-door neighbour, a still-forming planet called Theia, just a bit smaller than the planet Mars.
Unfortunately, its orbit became unstable and, one fateful day .
.
it collided with the Earth.
This was no ordinary collision like the one that famously wiped out the dinosaurs.
The energy from this was so huge that it blew out a portion of the Earth's crust into space and helped form our very large moon.
lt's this 4.
5 billion-year-old rock that seems to hold the key to making our planet such a nice place to live.
A large moon keeps the Earth very stable on its axis, tilted towards the Sun at a perfect 23.
5 degrees.
So, thanks to our moon, the Earth hardly wobbles at all.
Over eons, the seasons have remained stable, the distribution of the Sun's energy moving slightly north or south over a six-monthly cycle.
Here we are, late summer, early autumn.
Most of the heat of the Sun is aimed at the northern hemisphere.
We're nice and warm-ish.
They're freezing cold down here.
Out to six months later, the tilt remains exactly the same.
Now, the southern hemisphere is basking in the Sun's warmth.
We're freezing cold, wishing we were there, throwing prawns on the barbie.
Basically, all you need to know, Liz, is that size does matter.
We've got this abnormally large moon, and its motion around the Earth, its gravitational influence, means we're not wobbling.
lf we were tilting on a wobbly axis, we'd have extremes of weather.
We'd go from hot dessert to Arctic conditions in a short space of time, which would pose serious problems for all life on Earth.
Booking a summer holiday would be practically impossible! We wouldn't be here to book one! Even with relatively benign weather, it's our biggest source of renewable energy.
We've pretty much got solar power.
We've got wind power.
We have not cracked wave power.
l've been to Scotland to see what the latest scheme is.
As an island, the UK has an awful lot of coastline.
Waves are usually here in abundance, and waves contain a surprising amount of power.
Tiny waves like these would easily lift a boat that it would normally take a forklift truck to move! Where does this power come from? You can think of waves as solar power third hand.
The Sun heats the Earth, making winds, and winds create the waves.
lt may sound inefficient but the process effectively concentrates the energy.
These boats weigh a few hundred tonnes each and are thrown around like match sticks.
This makes me wonder how much power is in a wave.
The best way to find out is to get stuck in.
MUSlO: ''Surfin' USA'' by The Beach Boys Although there's obviously not enough force in these waves for a bloke to surf, how much power lS there? There's a rule of thumb for calculating it.
Half the height of the wave squared, multiplied by the time between waves.
So even little tiddlers like this have about 300 watts per metre.
Every metre of this coastline could be running your fridge.
On our Atlantic coast, where the waves are generally bigger, each metre of coastline is, on average, buffeted by 40,000 watts of power.
The difficult thing is how to extract that power.
The basic principle of most wave power systems is very simple - use the motion of the wave to spin a turbine, which spins a dynamo, creating electricity.
This is a neat way of getting electrical power out of waves.
lt's an oscillating water column, or a dustbin with a fan on it! What happens is, as the wave comes in, it rushes up the inside of the dustbin, squashing the air inside, forcing it through this fan.
The fan spins round very quickly.
lt creates electricity with a dynamo.
The electricity should light these bulbs.
Let's see.
Whoa! That worked! That didn't.
l'm getting light! l'm getting light from waves! Yes! Electrical power from waves! Not much electrical power, but it's definitely there.
Oan we ever get more than a tiny flash from wave power? Yes.
l want to show you something that extracts millions of watts out of waves up in Scotland.
The real obstacle to commercial wave power is designing a system to withstand massive waves that smash into our coast.
Ships have a hard enough time on top of them, but to extract power, wave power machines have to absorb that energy.
And that usually destroys them.
Built in Edinburgh, the Pelamis system might just have solved that problem.
With wave power, survivability is everything.
A vessel like that side on to a big wave will get smashed to pieces.
Pelamis does what a ship does in a heavy sea.
lt turns nose-on to the waves to give it the minimum impact.
The whole purpose of it is to collect wave energy.
How does it do that? Pelamis is made up of five huge floating sections.
lmagine these are two.
They rock up and rock back down.
lt's that movement that power generation comes from.
Here between the sections are these huge pistons.
They get squeezed in and out.
How that generates electricity, though, is all in here.
- Hi, Ross.
- Hi, Jem.
This is the back end of one of those big pistons.
lt's where the energy comes into the machine so we can make use of it.
These are like giant bicycle pumps.
They suck in low pressure fluid and push it out at high pressure into storage accumulators.
Those accumulators smooth it out.
- Otherwise it's squirt, squirt, squirt.
- Exactly.
Waves deliver energy in bursts.
We're collecting those spurts of energy and smoothing it out.
- Oan we look at the accumulators? - Sure.
So these are the accumulators.
Yeah.
Where we store energy between waves.
- Do you mind if l pull a gun? - Go on! lt strikes me that pretty much what you've got is like a water pistol, squeezing fluid out as each wave comes in.
What you want is a smooth, constant flow.
Hm.
That's right.
lt's the same problem l had with my little wave machine on the beach.
The energy came in bursts, so what Pelamis does is store that energy from each wave as high-pressure fluid, then releases it slowly, to give a constant drive to its turbines.
These accumulators are like a large bucket.
lt doesn't matter how spurty the incoming power is, as long as we can tap it out smoothly from the bottom.
Got it.
l guess this is where it all ends up? That's right.
The fluid from the accumulators spins this generator to produce electricity.
The power is fed along under-sea cables to the shore station five miles away.
The cleverest thing about Pelamis is that it can tune itself to the resonant frequency of the wave.
Sophisticated computers adjust the angle between sections to a slight zig-zag, so it gets as much movement - hence as much energy - from the wave as it can.
How much electricity do you produce? The whole machine is rated at 750 kilowatts.
An average over the year, we provide enough power for 500 homes.
This big snake can run a village! On average, over the year, yeah.
Oool.
Ourrently, Pelamis is a prototype under test.
There are other wave power systems being tested, too.
One day, the most effective way of getting energy from the Sun might be through the waves it generates.
ls this technology the future of wave power? Wave power is a difficult nut to crack.
lmagine the difference between a little wave and a huge wave.
Nothing really survives out there.
The great thing about Pelamis is its survivability.
lt can produce power day in, day out, in any conditions.
lnteresting.
Actually, the Queen, on a visit to Oanada, charged her iPod on wave power alone.
l'm sorry.
Ooming up, it's Dr Yan.
This week, he's playing with ping-pong balls.
Say nothing, Jem.
How high can you blow this ping-pong ball out of the top of this tube? l've lost it already! Yeah.
About that much.
We'll pick it up later! Oh, not bad! - How do you think you'd do with that? - Better.
- lt's weird.
- Yeah.
Just blow it up? You expect that a stream of air from your mouth would blow it out, like the tube.
l can't! lt's impossible.
Because the air isn't as concentrated in one area? lnteresting.
lt's a bit like that.
lt's actually to do with air pressure, a misunderstood idea, by the name of Bernoulli's principle.
Bernoulli's principle says that the acceleration of air is always accompanied by a drop in pressure.
l'll show you with this funnel.
To make it clearer, without me having to blow, so l can talk, l'll use an air pump.
lt goes up a bit at first, but then all of the air starts rushing round the sides.
There's a lot of air coming out of my lungs or out of this tube.
To get all that air-flow through that tiny gap between the ball and the funnel at the same rate as it's coming out of my lungs it has to go faster in that spot.
That means that this bit here has low air pressure.
Because of the funnel, that low pressure bit is at the bottom.
The bottom of the ball is being hit with much less force than you think.
Enough for the air pressure out here to hit the top of the ball and hold it in place.
You can even use it against gravity.
(BLOWS) - You're doing really well.
- Thank you.
A nice constant air flow.
That's going to keep the boys entertained for years to come! l tell you what, that's your Ohristmas present sorted.
- lf you send me one of those, l swear.
- lt'll be a nice one.
Next up, in 1859 my hero, Oharles Darwin, published his theory of evolution by natural selection.
Even to this day, some people contest that theory, often giving the eye as an example of something too complex and perfect to have evolved from scratch.
l'm on a mission to prove Darwin right.
Eons ago, animals had to bump into things to know what they were.
lmagine the benefits if they could develop an awareness of food before stumbling upon it, or of predators nearby.
Lucky for us, evolution has given us the perfect tool for this, the eye.
How on Earth does something so incredibly complex actually evolve? 'Before l answer that, l've come to the Oxford Eye Hospital, 'to find out how my own eye works.
' The eye is very much like a camera.
Light rays come in, focused by the lens, like the lens of a camera, they go through to the back, focused onto the retina lined by photoreceptor cells, like the film of the camera.
The photoreceptor cells generate an electrical signal from the light energy.
This is sent through the optic nerve into the brain.
And that's translated into the image that we actually see.
The eye is extraordinary.
Oan something so complex evolve in gradual stages? 'To find the answer, l've come to meet world renowned evolutionary biologist Richard Dawkins.
' Richard, the eye is such a complex structure.
l can understand why some people find it hard to believe it evolved out of nothing.
Even Darwin commented on its complexity.
Darwin said it was impossible to imagine that it evolved by gradual degrees, but reason tells me that if there were a series of gradual improvements it would be easy for it to have evolved by natural selection.
You find over the animal kingdom eyes in various stages of what look like stages of evolution.
The great thing is that we've got examples of intermediate stages of this evolution in modern-day animals.
So, what would the first step be? Here, for example is euglena, a single-celled organism.
lt has a little eye spot at the head end of the cell that is just sensitive to light.
lt can't form an image, see anything.
lt can tell whether it's light or dark.
That could be a first step.
lmagine you had a sheet of cells, each of which is sensitive to light.
This is a substance that glows in ultraviolet.
This is an ultraviolet light.
lf we hold it over, you can see it's sort of glowing.
Ok, so this demonstrates cells that are reacting to light.
Yes.
That's a flat sheet of cells.
You can't tell the direction that the light's coming from.
But if you gradually evolve a slight curve, turn it into a cup, light from that direction hits this side of a bent sheet.
lf the light's from over here, the other side lights up.
You can tell what direction the light's from.
Perhaps you could tell the direction a predator's shadow is passing over.
Animals with cup eyes, like these planarian worms, have a huge evolutionary advantage over animals with a flat eye.
How do we progress from something that tells the direction of light, to something that can form an image? lf you imagine that the cup gradually evolves to get deeper - Yeah.
- and close up the hole at the top, then you get a pinhole camera.
Now, a pinhole camera is a pretty poor piece of work.
lt doesn't show you much of an image but it does show you a crude image.
This is a pinhole camera.
There's a hole.
There's a screen inside.
Have a look.
lf l hold this in front of the pinhole Wow.
l can see the A.
lt's blurry and upside down but, yeah, l can see it.
'And a perfect example of this next stage 'in the evolution of the eye can be seen in many aquariums.
' This is the mollusc nautilus, a relative of the extinct ammonite, with an eye that acts like a pinhole camera.
These little fellas can see blurred images.
This might be good enough for a nautilus, but what if you wanted a bit more detail? The solution, as anybody will tell you, is a lens.
A proper man made lens is exactly shaped.
lt's glass, refracts light.
How does that come about in nature? To get a really good image you do need a decently curved lens, but any old bit of gunge which is transparent will do if it's just approximately curved.
A polythene bag of water just naturally falls into a curved shape.
Now, if l stick this bag of water Bring the bag forward.
There.
Perfect.
That's a real lens.
Think of that as a blob of gunge in the cup eye.
lf this gunge or jelly hardened, it would form a proper lens and transmit a clearer image.
We can see an example of this back at the aquarium.
Sea snails have a blob of jelly that acts like a simple lens.
They can focus on an object even if that image is a bit blurry.
lt does mean they can make out food and predators.
Once you've got that, because it works a bit better than nothing, you've got the raw material for natural selection to go to work.
Generation after generation, each stage a slight improvement in the curvature, in the transparency.
A steady ramp of improvement all the way up to a proper lens such as you'd get in the vertebrate eye.
Really, the eye is an example of how complex structures and simpler ones can evolve quickly and easily.
The eye is legendarily complicated.
lf you can show that it evolved easily and quickly, then all the more easy it will have been to evolve something simple.
What's incredible is that, as the eye evolved over millions of years, wildly differing species like monkeys and molluscs, seem to have developed the same solutions.
At the top of the mollusc evolutionary ladder is the octopus eye.
lt's got a proper lens.
lt can adjust its own exposure.
lts eye is pretty much like our own, except that it comes from a completely different evolutionary line.
- Wow! You met Richard Dawkins.
- And he signed my Selfish Gene.
Nice.
How long does it take to get from nothing to a working eye? Scientists reckon it only took about 400,000 generations to get from the simplest light sensitive cell to a fully functioning eye.
So, given that this all started in simple aquatic organisms with short life cycles, so the eye would have evolved in less than half a million years, which may sound like a lot, but in evolutionary terms, it's the blink of an eye.
- Do you like that? - l like what you did there.
Well that's it for this week, but we will see you next week.
- Say goodbye boys.
- Bye.
' Hey! l'm getting light! l'm getting light from waves! 'Yan is larking about with ping pong balls.
' lt's like something is holding it back.
'And l demonstrate the theory of evolution using an eye 'and a very brainy man.
' Reason tells me it would be easy for it to evolve by natural selection.
'That's Bang Goes The Theory, putting science to the test.
' Welcome to the show.
First, something as British as queuing at Wimbledon or the Queen's Speech.
That is talking about the weather.
l'm going back in time to find out where our weather came from.
Here we are on the south coast and it's early September.
lt's warm-ish, but in a couple of months we'll be wondering if it will be a white Ohristmas.
What causes the seasons? How come we get warm weather in summer and cold weather in winter? Well, the answer to that question is 4.
6 billion years old.
So come with me to the very dawn of the solar system.
We're going to travel back to when the Sun was a few million years old and the planets were being formed from a cloud of protoplanetary dust.
This is the new young Sun.
Over there is the brand new Earth.
You wouldn't want to hang out on it.
There's no atmosphere, no land masses, no oceans.
lt's a big lump of hot soft rock.
The planets are forming from this rubble orbiting around our brand new Sun.
Huge asteroids hitting the Earth are a rare phenomenon today.
Back then, it was happening all the time.
The effect was that the Earth was knocked this way and that on its axis.
Rather than it being a nice stable spinning top like this .
.
the Earth's axis would have been wobbling like this.
What's that got to do with the seasons? The seasons are determined by the angle at which the Earth is facing the Sun.
The Earth's orbit is elliptical - it's closest to the Sun in January and furthest away in July.
That makes little difference to the amount of solar energy we receive.
To show how the Earth's tilt affects seasons, let's do an experiment.
lmagine that the Earth's axis is flat on, parallel with the Sun's as it orbits round.
All the Sun's energy is hitting the same bits of the Earth all the time throughout the year, therefore you don't have seasons.
The northern and southern bits are dark and cold.
The equator is incredibly hot all the time.
But the Earth is not at 90 degrees to the Sun.
lt's at an angle, and that's thanks to one massive collision.
About 4.
6 billion years ago, we had a next-door neighbour, a still-forming planet called Theia, just a bit smaller than the planet Mars.
Unfortunately, its orbit became unstable and, one fateful day .
.
it collided with the Earth.
This was no ordinary collision like the one that famously wiped out the dinosaurs.
The energy from this was so huge that it blew out a portion of the Earth's crust into space and helped form our very large moon.
lt's this 4.
5 billion-year-old rock that seems to hold the key to making our planet such a nice place to live.
A large moon keeps the Earth very stable on its axis, tilted towards the Sun at a perfect 23.
5 degrees.
So, thanks to our moon, the Earth hardly wobbles at all.
Over eons, the seasons have remained stable, the distribution of the Sun's energy moving slightly north or south over a six-monthly cycle.
Here we are, late summer, early autumn.
Most of the heat of the Sun is aimed at the northern hemisphere.
We're nice and warm-ish.
They're freezing cold down here.
Out to six months later, the tilt remains exactly the same.
Now, the southern hemisphere is basking in the Sun's warmth.
We're freezing cold, wishing we were there, throwing prawns on the barbie.
Basically, all you need to know, Liz, is that size does matter.
We've got this abnormally large moon, and its motion around the Earth, its gravitational influence, means we're not wobbling.
lf we were tilting on a wobbly axis, we'd have extremes of weather.
We'd go from hot dessert to Arctic conditions in a short space of time, which would pose serious problems for all life on Earth.
Booking a summer holiday would be practically impossible! We wouldn't be here to book one! Even with relatively benign weather, it's our biggest source of renewable energy.
We've pretty much got solar power.
We've got wind power.
We have not cracked wave power.
l've been to Scotland to see what the latest scheme is.
As an island, the UK has an awful lot of coastline.
Waves are usually here in abundance, and waves contain a surprising amount of power.
Tiny waves like these would easily lift a boat that it would normally take a forklift truck to move! Where does this power come from? You can think of waves as solar power third hand.
The Sun heats the Earth, making winds, and winds create the waves.
lt may sound inefficient but the process effectively concentrates the energy.
These boats weigh a few hundred tonnes each and are thrown around like match sticks.
This makes me wonder how much power is in a wave.
The best way to find out is to get stuck in.
MUSlO: ''Surfin' USA'' by The Beach Boys Although there's obviously not enough force in these waves for a bloke to surf, how much power lS there? There's a rule of thumb for calculating it.
Half the height of the wave squared, multiplied by the time between waves.
So even little tiddlers like this have about 300 watts per metre.
Every metre of this coastline could be running your fridge.
On our Atlantic coast, where the waves are generally bigger, each metre of coastline is, on average, buffeted by 40,000 watts of power.
The difficult thing is how to extract that power.
The basic principle of most wave power systems is very simple - use the motion of the wave to spin a turbine, which spins a dynamo, creating electricity.
This is a neat way of getting electrical power out of waves.
lt's an oscillating water column, or a dustbin with a fan on it! What happens is, as the wave comes in, it rushes up the inside of the dustbin, squashing the air inside, forcing it through this fan.
The fan spins round very quickly.
lt creates electricity with a dynamo.
The electricity should light these bulbs.
Let's see.
Whoa! That worked! That didn't.
l'm getting light! l'm getting light from waves! Yes! Electrical power from waves! Not much electrical power, but it's definitely there.
Oan we ever get more than a tiny flash from wave power? Yes.
l want to show you something that extracts millions of watts out of waves up in Scotland.
The real obstacle to commercial wave power is designing a system to withstand massive waves that smash into our coast.
Ships have a hard enough time on top of them, but to extract power, wave power machines have to absorb that energy.
And that usually destroys them.
Built in Edinburgh, the Pelamis system might just have solved that problem.
With wave power, survivability is everything.
A vessel like that side on to a big wave will get smashed to pieces.
Pelamis does what a ship does in a heavy sea.
lt turns nose-on to the waves to give it the minimum impact.
The whole purpose of it is to collect wave energy.
How does it do that? Pelamis is made up of five huge floating sections.
lmagine these are two.
They rock up and rock back down.
lt's that movement that power generation comes from.
Here between the sections are these huge pistons.
They get squeezed in and out.
How that generates electricity, though, is all in here.
- Hi, Ross.
- Hi, Jem.
This is the back end of one of those big pistons.
lt's where the energy comes into the machine so we can make use of it.
These are like giant bicycle pumps.
They suck in low pressure fluid and push it out at high pressure into storage accumulators.
Those accumulators smooth it out.
- Otherwise it's squirt, squirt, squirt.
- Exactly.
Waves deliver energy in bursts.
We're collecting those spurts of energy and smoothing it out.
- Oan we look at the accumulators? - Sure.
So these are the accumulators.
Yeah.
Where we store energy between waves.
- Do you mind if l pull a gun? - Go on! lt strikes me that pretty much what you've got is like a water pistol, squeezing fluid out as each wave comes in.
What you want is a smooth, constant flow.
Hm.
That's right.
lt's the same problem l had with my little wave machine on the beach.
The energy came in bursts, so what Pelamis does is store that energy from each wave as high-pressure fluid, then releases it slowly, to give a constant drive to its turbines.
These accumulators are like a large bucket.
lt doesn't matter how spurty the incoming power is, as long as we can tap it out smoothly from the bottom.
Got it.
l guess this is where it all ends up? That's right.
The fluid from the accumulators spins this generator to produce electricity.
The power is fed along under-sea cables to the shore station five miles away.
The cleverest thing about Pelamis is that it can tune itself to the resonant frequency of the wave.
Sophisticated computers adjust the angle between sections to a slight zig-zag, so it gets as much movement - hence as much energy - from the wave as it can.
How much electricity do you produce? The whole machine is rated at 750 kilowatts.
An average over the year, we provide enough power for 500 homes.
This big snake can run a village! On average, over the year, yeah.
Oool.
Ourrently, Pelamis is a prototype under test.
There are other wave power systems being tested, too.
One day, the most effective way of getting energy from the Sun might be through the waves it generates.
ls this technology the future of wave power? Wave power is a difficult nut to crack.
lmagine the difference between a little wave and a huge wave.
Nothing really survives out there.
The great thing about Pelamis is its survivability.
lt can produce power day in, day out, in any conditions.
lnteresting.
Actually, the Queen, on a visit to Oanada, charged her iPod on wave power alone.
l'm sorry.
Ooming up, it's Dr Yan.
This week, he's playing with ping-pong balls.
Say nothing, Jem.
How high can you blow this ping-pong ball out of the top of this tube? l've lost it already! Yeah.
About that much.
We'll pick it up later! Oh, not bad! - How do you think you'd do with that? - Better.
- lt's weird.
- Yeah.
Just blow it up? You expect that a stream of air from your mouth would blow it out, like the tube.
l can't! lt's impossible.
Because the air isn't as concentrated in one area? lnteresting.
lt's a bit like that.
lt's actually to do with air pressure, a misunderstood idea, by the name of Bernoulli's principle.
Bernoulli's principle says that the acceleration of air is always accompanied by a drop in pressure.
l'll show you with this funnel.
To make it clearer, without me having to blow, so l can talk, l'll use an air pump.
lt goes up a bit at first, but then all of the air starts rushing round the sides.
There's a lot of air coming out of my lungs or out of this tube.
To get all that air-flow through that tiny gap between the ball and the funnel at the same rate as it's coming out of my lungs it has to go faster in that spot.
That means that this bit here has low air pressure.
Because of the funnel, that low pressure bit is at the bottom.
The bottom of the ball is being hit with much less force than you think.
Enough for the air pressure out here to hit the top of the ball and hold it in place.
You can even use it against gravity.
(BLOWS) - You're doing really well.
- Thank you.
A nice constant air flow.
That's going to keep the boys entertained for years to come! l tell you what, that's your Ohristmas present sorted.
- lf you send me one of those, l swear.
- lt'll be a nice one.
Next up, in 1859 my hero, Oharles Darwin, published his theory of evolution by natural selection.
Even to this day, some people contest that theory, often giving the eye as an example of something too complex and perfect to have evolved from scratch.
l'm on a mission to prove Darwin right.
Eons ago, animals had to bump into things to know what they were.
lmagine the benefits if they could develop an awareness of food before stumbling upon it, or of predators nearby.
Lucky for us, evolution has given us the perfect tool for this, the eye.
How on Earth does something so incredibly complex actually evolve? 'Before l answer that, l've come to the Oxford Eye Hospital, 'to find out how my own eye works.
' The eye is very much like a camera.
Light rays come in, focused by the lens, like the lens of a camera, they go through to the back, focused onto the retina lined by photoreceptor cells, like the film of the camera.
The photoreceptor cells generate an electrical signal from the light energy.
This is sent through the optic nerve into the brain.
And that's translated into the image that we actually see.
The eye is extraordinary.
Oan something so complex evolve in gradual stages? 'To find the answer, l've come to meet world renowned evolutionary biologist Richard Dawkins.
' Richard, the eye is such a complex structure.
l can understand why some people find it hard to believe it evolved out of nothing.
Even Darwin commented on its complexity.
Darwin said it was impossible to imagine that it evolved by gradual degrees, but reason tells me that if there were a series of gradual improvements it would be easy for it to have evolved by natural selection.
You find over the animal kingdom eyes in various stages of what look like stages of evolution.
The great thing is that we've got examples of intermediate stages of this evolution in modern-day animals.
So, what would the first step be? Here, for example is euglena, a single-celled organism.
lt has a little eye spot at the head end of the cell that is just sensitive to light.
lt can't form an image, see anything.
lt can tell whether it's light or dark.
That could be a first step.
lmagine you had a sheet of cells, each of which is sensitive to light.
This is a substance that glows in ultraviolet.
This is an ultraviolet light.
lf we hold it over, you can see it's sort of glowing.
Ok, so this demonstrates cells that are reacting to light.
Yes.
That's a flat sheet of cells.
You can't tell the direction that the light's coming from.
But if you gradually evolve a slight curve, turn it into a cup, light from that direction hits this side of a bent sheet.
lf the light's from over here, the other side lights up.
You can tell what direction the light's from.
Perhaps you could tell the direction a predator's shadow is passing over.
Animals with cup eyes, like these planarian worms, have a huge evolutionary advantage over animals with a flat eye.
How do we progress from something that tells the direction of light, to something that can form an image? lf you imagine that the cup gradually evolves to get deeper - Yeah.
- and close up the hole at the top, then you get a pinhole camera.
Now, a pinhole camera is a pretty poor piece of work.
lt doesn't show you much of an image but it does show you a crude image.
This is a pinhole camera.
There's a hole.
There's a screen inside.
Have a look.
lf l hold this in front of the pinhole Wow.
l can see the A.
lt's blurry and upside down but, yeah, l can see it.
'And a perfect example of this next stage 'in the evolution of the eye can be seen in many aquariums.
' This is the mollusc nautilus, a relative of the extinct ammonite, with an eye that acts like a pinhole camera.
These little fellas can see blurred images.
This might be good enough for a nautilus, but what if you wanted a bit more detail? The solution, as anybody will tell you, is a lens.
A proper man made lens is exactly shaped.
lt's glass, refracts light.
How does that come about in nature? To get a really good image you do need a decently curved lens, but any old bit of gunge which is transparent will do if it's just approximately curved.
A polythene bag of water just naturally falls into a curved shape.
Now, if l stick this bag of water Bring the bag forward.
There.
Perfect.
That's a real lens.
Think of that as a blob of gunge in the cup eye.
lf this gunge or jelly hardened, it would form a proper lens and transmit a clearer image.
We can see an example of this back at the aquarium.
Sea snails have a blob of jelly that acts like a simple lens.
They can focus on an object even if that image is a bit blurry.
lt does mean they can make out food and predators.
Once you've got that, because it works a bit better than nothing, you've got the raw material for natural selection to go to work.
Generation after generation, each stage a slight improvement in the curvature, in the transparency.
A steady ramp of improvement all the way up to a proper lens such as you'd get in the vertebrate eye.
Really, the eye is an example of how complex structures and simpler ones can evolve quickly and easily.
The eye is legendarily complicated.
lf you can show that it evolved easily and quickly, then all the more easy it will have been to evolve something simple.
What's incredible is that, as the eye evolved over millions of years, wildly differing species like monkeys and molluscs, seem to have developed the same solutions.
At the top of the mollusc evolutionary ladder is the octopus eye.
lt's got a proper lens.
lt can adjust its own exposure.
lts eye is pretty much like our own, except that it comes from a completely different evolutionary line.
- Wow! You met Richard Dawkins.
- And he signed my Selfish Gene.
Nice.
How long does it take to get from nothing to a working eye? Scientists reckon it only took about 400,000 generations to get from the simplest light sensitive cell to a fully functioning eye.
So, given that this all started in simple aquatic organisms with short life cycles, so the eye would have evolved in less than half a million years, which may sound like a lot, but in evolutionary terms, it's the blink of an eye.
- Do you like that? - l like what you did there.
Well that's it for this week, but we will see you next week.
- Say goodbye boys.
- Bye.