i-Science

This is a human trial for a sunscreen made using nanotechnology.

Nanotechnology is the art of manipulating matter on an atomic or molecular scale.

That's 100,000 times smaller than the width of a human hair.

This team of scientists in Nottingham have devised a material

that can help protect us from the sun.

We use nanotechnology in sunscreens to replace the conventional UV filters.

Conventional filters work by absorbing ultraviolet light.

But titanium dioxide reflects it, rather than absorbing.

Now, we got the idea from the paint industry,

because in the paint industry,

titanium dioxide reflects visible light. Which is why paint is white.

But we got on the idea that if you were to make the particle sizes smaller,

then they would reflect ultraviolet light and you would have a sunscreen.

Most sunscreens rely on chemicals within the lotion to absorb the sun's radiation.

However, traditional chemical absorbers only work efficiently

on a limited number of wavelengths.

The titanium dioxide reflectors work more consistently across a wider range.

We can also look on a microscope screen at the sun product

to see the titanium dioxide crystals within the product.

Little tiny dots of ovoid crystals.

Ideally, they would be as spherical as possible but titanium dioxide crystals aren't spherical.

They're slightly ovoid, but they're the nearest thing to spherical.

That's why we use titanium dioxide.

Size is absolutely critical to whether or not they reflect ultraviolet light.

So that's where the nanotechnology comes in.

We have to engineer these crystals

to be exactly the right size to reflect ultraviolet light.

And then we take them to another lab where we test them

to make sure that they work.

The scientists are testing to assess how much extra protection this sunscreen gives the volunteer.

We try to simulate exactly what happens on the beach.

So we use human volunteers. We put the sun cream on their back

and then we expose it to artificial sunlight,

which comes from an instrument called a solar simulator.

We actually only expose little one centimetre squares of their back.

We're looking to see how much the sun cream protects them from burning from the artificial sunlight.

When the sunscreen is proved safe and effective in human trials,

the ingredients are sent to the factory for mass production.

The sun's ultraviolet rays are a form of high energy electromagnetic radiation,

that can penetrate our skin and make its way right into our cells.

Too much exposure will damage our DNA, causing mutations that can lead to cancer.

When skin is exposed to sunlight,

it tries to protect itself from UV radiation

by producing melanin.

Melanin is a brown pigment that absorbs ultraviolet light and makes skin appear tanned.

Because dark-skinned people have more melanin, they are less likely to suffer sunburn

than those who are fair.

Not all contact with sunlight is dangerous, however.

As well as making us feel happier, it's our main source of vitamin D.

Vitamin D performs many useful functions,

including regulating the amount of calcium and phosphate in the body,

which is especially important for our bones.

As well as that, many people think they look healthier and more attractive when they're tanned.

ENGINE STARTS

The chemicals we release into our atmosphere have a wide-ranging effect on the natural world.

Rivers like this one, in the Peak District, can be devastated by contamination.

Chris Curtis of University College London

has been monitoring pollution and its effects on the countryside.

I'm gonna test the pH of this drinking water.

Good old London tap water.

For comparison with acid river water sample.

As you can see, when I put the probe in the tap water,

the pH goes up to about 7, which is circum neutral.

So that's neutral tap water.

But if I then put the probe in the stream...

..the pH value goes down to about 5.2.

Now because that's a difference of two pH units,

but because pH is a logarithmic scale

that actually means it's not ten times,

it's 100 times more acid in the stream,

than it is in the tap water.

We're trying to collect insects and other invertebrate animals that live under the rocks and in the gravel,

to see which species are present and see if there are any acid-sensitive species present,

which might indicate that this system is recovering from acidification.

Now what we can see is that there's actually not very much here.

That may seem like a bad thing,

but it tells us a lot about the stream,

and it tells us that the water quality isn't very good.

In other words, it's very acid.

If we went to a very healthy lowland stream with a high pH,

we might expect to find a very diverse community of invertebrates

living in the sediments and under the rocks in the stream.

If invertebrates are missing, it tells us they could have been killed by acid episodes in the stream.

Rob Mills from Bangor University uses a different technique to test acidity in the environment.

He is trying to assess the impact of acid rain by isolating small plots of land

away from the influence of people and cars.

In this first section of test plots,

the soil is open to the elements as normal.

But in the second block,

a plastic cover shields the plants when it rains.

Instead of rain water,

these sheltered plants receive the same quantity of distilled water.

However, not all the moisture in soil comes from rainfall.

Some of it comes from the dense fog that regularly covers this area.

This water can also be tested using an ingenious collection method.

OK, what this is - we call it the cloud collector.

And essentially what it does, is it collects clouds.

So as the clouds move across the hillside,

they come across this fishing line wire,

and small droplets from the cloud condense,

run down into the funnel and we collect it at the bottom.

And this is another way of us getting an idea of how much acid material is coming into the system.

We can have a quick look at this.

And what we can find in here

is that this will be full with a range of particles.

And these particles are what the water droplets condense around.

So this could be particles of dust from car vehicle emissions,

from fossil fuel power plant emissions,

and each one of these tiny little specks of black dust

could represent a single droplet.

But, of course, this material then eventually enters the ecosystem.

The consequences of which, we're trying to find out.

Another of Rob's tests assesses the effects of global warming.

He covers some plots at night, in order to raise their temperature.

Over several years, Rob wants to see how the effect of temperature alone

affects the plants' growth.

Global warming is a product of a natural phenomenon,

naturally we have greenhouse gases which exist in the atmosphere allowing life on Earth to exist.

But global warming is a function of "anthropogenic activities". That's all human activity.

And over the past few hundred years we've been contributing a lot more greenhouse gases to the atmosphere.

Essentially, what we're seeing is the climate is changing. Not necessarily always getting warmer everywhere.

But generally, the climate is changing. You can term that "global warming" or "global climate change".

A lot of pollution is caused by traffic.

Exhaust fumes contain tiny particles of solid carbon, which is why it looks black.

These can give you health problems like asthma when you breathe them in.

There are also gases you can't see, including sulphur dioxide,

carbon monoxide, carbon dioxide and nitrogen oxide.

Even just a short five-mile trip from school

produces about 500g of CO2.

CO2 makes up a small proportion of our atmosphere,

but it is a powerful greenhouse gas.

-Bye!

-Bye!

This means it traps heat in the Earth's atmosphere.

London has a 184,000 vehicles entering its congestion zone every day.

Even if they only travel five miles each, they will produce over 90 million grams of polluting CO2.

With so much pollution entering the atmosphere, many think we should find ways to discourage driving.

By introducing congestion zones, for example,

or raising the taxes on petrol and diesel.

Another approach to reduce pollution is to use cleaner fuels.

One such fuel is hydrogen,

created here by the reaction of metal in acid.

We know that hydrogen burns explosively in air,

but there are other ways it can be used to release energy.

Companies all over the world are competing to develop a fuel cell

that uses hydrogen to generate electricity.

Automotive manufacturers are investigating alternatives to fossil fuels.

Much like traditional cars today,

you can refuel the fuel cell of a hydrogen tank in a matter of minutes.

A hydrogen fuel cell is very much like an engine

in that it converts a fuel into energy.

But unlike your traditional combustion engine,

there's no burning involved.

In a fuel cell, in an electric chemical reaction, it combines a hydrogen molecule

with an oxygen molecule, producing water, electricity and heat.

A fuel cell uses hydrogen gas to generate electricity.

It splits hydrogen molecules into negatively charged electrons and positively charged protons.

The protons can pass through the membrane in the middle of the cell.

But the electrons are forced to take a different route, creating an electrical current.

Once they reach the other side of the cell,

the protons and electrons combine with oxygen from the air

to form water molecules.

Fossil fuels that we're traditionally using today are running out.

And climate change is dictating we have to start reducing our emissions.

When using a fuel cell in a vehicle, utilising hydrogen as a fuel,

you're using a sustainable fuel and you're producing zero emissions.

Daphne Goodship and Barbara Herbert are identical twins.

But they did not meet until they were 35 years old.

They were separated shortly after they were born and brought up by adoptive parents

in very different environments.

Barbara's adopted father was a gardener

and Daphne's was a scientist.

I didn't really suspect there was a twin but...

My grandma told me when I was about 11 that I had a double.

But I knew then that I was adopted.

We met on King's Cross Station. The thing was, the train was a 125, which was a very long train,

and I opened the door and standing right there was Barbara.

It was like meeting an old friend.

It wasn't difficult at all. It was like we'd always known each other.

The first similarity was we discovered that we both had a miscarriage.

And then it was followed by two boys and a girl in that order.

And our second sons were born within three weeks of one another.

So that was rather strange. Erm, course our crooked fingers.

It was one of the first things we ever said to each other. Look!

-How sweet!

-They're really crooked. And I remember when I was at school, I could do that -

and I thought, that is so original! It's one of the first things we said!

Walking down King's Cross station.

Twins separated at birth are very rare.

Researchers are keen to study them to compare the effects of nature and nurture on their development.

I think a lot of the discoveries were medical to start with. Well, we both had a heart murmur.

-Thyroid, they discovered.

-Yeah, underactive thyroids.

Er, our IQ. We were within about one point of one another, which we thought was odd,

-because we both grew up...different schools.

-You're tested separately, so you go in and the researcher says,

"Write a sentence".

You think, oh gosh, what can I write? Just a short sentence. So I thought, I know - the cat sat on the mat.

So I ended up writing, because I was trying to do it quick, "the caz sat on the mat".

Next day, I thought "the cat sat on the mat". But there it goes, I wrote "the caz sat on the mat".

Daphne and Barbara are so similar because they are clones.

Two people who have exactly the same genetic make-up.

When their mother was pregnant, her fertilised egg split into two,

creating two identical cells, that grew into Daphne and Barbara.

Identical twins are not the only clones in nature.

Many living things like strawberries and aphids reproduce asexually, without a partner.

The offspring are genetically identical to the parents.

Scientists can now clone animals. The first ever cloned animal was produced in Edinburgh.

It was a now famous sheep called Dolly.

In order to clone an animal, scientists use a technique called somatic cell nuclear transfer.

This involves replacing the nucleus of one egg cell with the nucleus from any other somatic cell.

This could be from any part of the body, as long as that cell has a nucleus.

Just like Daphne and Barbara,

the embryos here are genetically identical to one another.

They are clones.

Scientists in Newcastle are developing cloning techniques

that they hope one day will heal currently incurable diseases.

Janice has a neurodegenerative disorder.

That means part of her brain is deteriorating.

I found out in the year 2000 and decided to have the diagnostic test

because my mother has the disorder.

It's been in the family for generations.

Up until the symptoms started in 2005, I never thought about it,

even though I'd had the test.

And...but since the symptoms started, I've had to retire from work,

because it makes one very very tired,

and I haven't a lot of strength.

And, um, most of the problem is with my speech.

Scientists think that replacing the damaged cells with the new ones will cure Janice's condition.

This technique requires special embryonic stem cells.

Unfortunately, the easiest way to get them at the moment is from a controversial source.

Human embryos.

Well, sadly, quite a lot of people have difficulty conceiving a child.

We do a procedure called IVF, whereby we put the egg and the sperm together in the laboratory.

And then two days later, we put that embryo directly back into the womb to help them achieve a pregnancy.

So we give the woman medication to make her grow lots of eggs.

We will often collect maybe 10 eggs

from a woman in the process of one IVF and put the sperm with them all.

And then we put the best one or two embryos back.

So, effectively, a side effect from IVF treatment

is that there'll often be some embryos remaining after treatment.

They're usually very poor quality,

but usually then, they would just have to be discarded.

We can use some of those potentially for research, and create embryonic stem cell lines from those embryos.

Stem cells are originators. They are the beginning of a tissue,

and the special thing about them is they retain the capacity to divide constantly and repair themselves.

Our body's full of them.

They're in skin, which constantly replaces our surface covering.

The most exciting stem cells are the ones with embryonic properties.

Those are the ones that develop a few days

after fertilisation of the egg.

And that little ball of cells will ultimately form the embryo proper.

Scientists have proved that embryonic stem cells can make the majority of other cell types.

Here, stem cells have become heart cells.

You can see that they have contractile properties.

Stem cells of embryonic origin are like apprentices that can do anything.

They haven't yet been specialised into any single function.

And if we can capture them, grow them in a dish and persuade them to develop under direction,

then potentially we could produce any human tissues, and use that to repair any manner of diseases and injuries.

Scientists believe that in the future the damage to Janice's brain could be repaired,

by giving her new cloned brain cells.

The problem is, the brain doesn't have its own stem cells and can't repair itself.

So the idea is, if we could give it some apprentices,

then those apprentices can be placed very precisely into the bit of the brain that's not working

and hopefully will pick up the function of local cells and start to repair damage caused

by the accumulation of iron or other products.

Stem cells offer tremendous hope to medicine because it gives us, for the first time,

the chance to explore treating diseases where the tissues have stopped working,

by producing genetically identical replacement tissue.

Something we've done for a long time in limited areas, like bone marrow transplant,

but now we can begin to think of doing on a much wider basis.

Stem cell research raises ethical issues, which makes some people uncomfortable about it,

in spite of the potential benefits.

There are two major costs to embryonic stem cell research.

One is that it involves the destruction, often,

of large numbers of human embryos.

Some people believe this is either akin to murder of human beings

or it results in the devaluing of human life.

And the second major cost is that we develop technology,

such as cloning technology,

that can be used to produce live-born human clones.

I have no problem at all with stem cell research,

and I hope one day to be the recipient of it.

This is deoxyribonucleic acid. DNA.

It is the most extraordinary molecule on Earth.

It literally encodes the genetic instructions from which you are made.

It has an amazing base pairing structure which can be replicated,

and the information is passed on.

Understanding DNA has given scientists new ways of trying to cure diseases,

previously thought to be incurable.

Like the hereditary respiratory disease, cystic fibrosis.

I take about 20 different types of drugs.

Some of which are here. And I also take some of them intravenously

and most of them are in tablet form.

I take about 250 tablets a week,

which is 1,000 a month and 12,000 in a year.

It mainly affects your lungs,

because the hairs in your lungs don't work properly,

so they can't get rid of the mucus in your lungs and so the tubes get blocked up in your lungs.

I have about 30% lung function now. It means that I can't walk very far.

I can't really do much,

and it affects pretty much everything that I do.

Until I was about 12 I was in the school swimming team, I was in the running team,

I was in doing PE, I won lots of sports awards,

I did pretty much everything that you could do.

It is a genetic disease.

My mum has one gene mutation and my dad has another one.

I just so happened to get both of them at one time, so I got CF.

My brother, who's 17, he doesn't have CF at all,

because he just has two perfectly normal genes.

Gene therapy is when you put in new copies of genes

that are defective within patient cells.

For example, with cystic fibrosis,

both genes have to be abnormal for you to get cystic fibrosis,

so what we're trying to do is reintroduce a new copy of the gene into the cell.

The first scan we're going to do gives us an image of the whole of your chest

so we can plan where we're going to start and stop the actual scans.

Cystic fibrosis is a possible target, because firstly you need to know what the gene is,

and that was identified in 1989.

Secondly, there has to be need for this fancy and probably quite expensive new therapy,

and, sadly, these patients don't have good enough therapy.

Finally, you have to be able to introduce the gene somehow,

and because we can spray things into the lungs of patients, all three come together

to suggest that cystic fibrosis would be a good candidate for gene therapy.

The sensible thing would be to do gene therapy as soon as you know you have a diagnosis of cystic fibrosis,

and there is now a newborn screening happening in the UK.

So you could put the two programmes together, and say "you have been diagnosed with cystic fibrosis.

"Now you need gene therapy to prevent,

"rather than treat". And that's actually what we're very much aiming for.

Gene therapy for CF should be a preventative treatment in the future.

Not trying to stop something that already has deteriorated.

The science of gene therapy provides hope for cystic fibrosis sufferers.

In the future, there might be a cure.

Tragically, this is too late for Lorna and her family,

as she died two weeks after giving this interview.

The discovery of the structure of DNA, in 1953, is accredited to two young scientists in Cambridge,

called Francis Crick and James Watson.

Although many scientists were working on unlocking the secrets of DNA at the same time,

Crick and Watson were the first to publish their results, and receive public recognition.

Understanding DNA has led to a huge increase in our knowledge of how life works.

From the intricate patterns of a butterfly's wing, to the pelican's dive.

DNA provides the blueprint for the development and functioning of all living organisms.

DNA is a molecule made up of four chemical bases. Adenine, guanine, cytosine and thymine.

Or A, G, C and T.

In many ways, all life on Earth can be described with just these four letters.

In 1990, the human genome project began.

Scientists started to work out the DNA code of human life.

It's about three billion bases long.

Many thought it was an impossible task, but it was completed in 2001, four years ahead of schedule,

thanks to computers like these.

One of the most exciting areas of medical research, following the unlocking of the human genome,

is genetic screening, which aims to prevent illnesses before they occur.

Here at University College Hospital, Dr Sandra Anglin is part of an international programme

to screen all patients for sickle-cell thalassemia.

It specifically affects the oxygen-carrying capacity in the blood

and a specific protein called haemoglobin.

Genetic screening, unlike screening for specific illnesses,

is a screening process whereby we want to identify

an unusual gene that you may pass on to your child.

With sickle-cell and thalassemia,

these are specific genes that affect the haemoglobin in the blood.

In terms of antenatal screening, it's offered as part of routine care,

so any pregnant woman that turns up will be offered screening for sickle cell and thalassemia.

The normal type of red blood cells are haemoglobin A,

and if you are a carrier, you have one gene that makes normal red blood cells

and one that makes a more unusual type of red blood cells.

If both parents are carriers of the gene, their baby has a 1 in 4 chance of inheriting a copy

of a sickle cell gene.

Nelly went through the screening process.

I was asked to go in to check whether I was a carrier or not.

And obviously my husband went with me as well, and we went together.

And that's when I discovered I was a carrier of the sickle cell disease, and he was a carrier as well.

The options that were given to us,

one of them was having a termination,

and the other obviously, was having a baby, despite all the risks involved.

We decided to go ahead and have a baby, despite all the risks.

My twin girls do not have sickle cell. Perfectly healthy.

Perfectly normal children.

Genetic screening provides us with uniquely personal data about people

and society needs to decide how to use this information.

People have concerns that this will result in intolerance to people

who choose not to employ the technology,

and so have children with one of these diseases

or Down's syndrome, for example.

And this will result in intolerance to people with diseases.

And further into the future,

the same technology could be used to select out embryos,

or to select for embryos with certain genetic traits

that may predispose them to higher intelligence,

or less prone to addiction, or more prone to addiction,

various personality types, physical abilities as well.

So it opens the door to the selection or the creation of designer children.

Children who have certain valued genetic properties.

So whether genetic technology causes social harms

is really up to us and how we choose to deploy it.

Good morning, Mrs Picking.

We're going to do some measurements and photos on your eye today.

Specialist eye surgeons at the world famous Moorfields Eye Hospital in London,

use some of the most technically advanced equipment to help their patients maintain their sight.

Look down.

OK sir, if you come forward. Pop your chin there, on the rest.

This OCT scanner can see the retina at the very back of the eye and analyse it's health.

Eyes wide open.

The scanner can show structures as small as ten microns.

It gives the surgeon a cross section view of the retina and the blood vessels underneath it.

These images are often used for the early detection of a detached retina.

OK, so I'm just gonna do the same on the other eye.

The retina can become detached from its underlying layer - the choroids,

which contains the many blood vessels that provide the retina with its nourishment.

When this happens, vision in the affected region is lost.

A detached retina is a serious condition that can lead to blindness

if it's not diagnosed and treated quickly.

This patient's retina has started to detach. But he's lucky. It can be fixed.

The retina is the innermost layer at the back of the eye.

It performs much the same function as the sensor chip in a digital camera.

It is made of two types of light-sensitive cells - rods and cones.

Rods work in dim light and cones detect colour.

These cells send electrical impulses to the brain,

which interprets them as a picture.

I'm using a slit lamp to examine Tony's eye.

A slit lamp is a high-powered microscope

that allows us to see the eye up close,

as in this picture on the TV screen here.

And the first thing that we see when we look into the eye is the cornea.

This is a clear window that allows light to get inside the eye.

It does more than that though. It focuses most of the light.

And most of the focusing power of the eye comes from the cornea.

When light enters your eye, it must be focused on the retina.

If it is not then what you see will be blurred.

To focus, the light rays must be refracted,

so that they meet at a single point.

Most of the focusing is done by the curved cornea.

When we move into the anterior chamber,

which is the space between the cornea and the pupil,

we can see the iris.

The iris dilates in the dark.

When I turn on the light, the iris muscles constrict

and the pupil becomes small.

When I turn the light off,

the pupil gets bigger again.

The iris is made from two different types of muscle.

Circular and radial. In dim light the radial muscles contract.

In bright light, the circular muscles contract.

Where we look in very close, through the pupil,

we can see the front surface of the lens.

The lens of the eye is another clear tissue that allows light

through to the retina behind.

The lens can change its shape, so you can see far and near objects.

This is called accommodation.

To focus on distant objects, the lens becomes thin.

To see close objects, the lens becomes more convex.

Here at the very back of the eye,

we see where the optic nerve enters the eye.

The optic nerve carries all of the electrical information,

from all of the rods and cones in the retina,

back to the brain,

where the information is translated into the things that we see.

These eyes are the products of natural selection,

a process whereby genetic variations in things

like size, shape and colour that give individuals the best chance to survive and reproduce,

are passed on to subsequent generations.

All of these eyes have evolved to work best for the animals that use them.

The eye is one of nature's marvels.

But the first living organisms didn't have eyes at all.

So how did something so complex evolve?

Darwin himself said that it made him shudder to think

of how something so complicated could have happened by natural selection.

But it's actually quite easy.

We're going to look at just one way it could have happened.

The simplest eye that you can imagine, is a patch of light-sensitive cells.

And in fact,

many animals like flatworms still have eyes like this today.

Here we have a model of such an eye. These are the light-sensitive cells.

Now, this can be useful in order to tell an animal whether or not it's day or night, for instance.

But it has a drawback. As I move the light around,

it cannot tell where the light is coming from.

As an eye, it's really rather limited.

But we should remember that biological surfaces are often quite flexible,

and so, if some of the offspring of these animals could have had slight indentations.

And when you get an indentation,

then you can start to get a shadow around the rim,

which can tell you where the light is coming from.

And that brings us to the next stage.

So, now our patch of light-sensitive cells is lining

the edge of this shallow bowl

on the surface of an organism. It works pretty well, like before,

but when I start moving the light, you can see a shadow appearing,

and where the shadow is depends on where the light is.

As a result, while this is still not very good, it's not a great eye,

it's a lot better than the one before.

This, for instance, can tell us maybe where a predator's coming from.

And the thing about this kind of eye is that the deeper it gets,

the better the effect.

And so the most obvious thing to do now, is to start bringing the surface in again,

to make a sort of sphere inside the organism.

And the more that happens, the better it gets.

So, now all of our light-sensitive cells are underneath the surface.

They're reached by this small hole.

It's almost completely closed up again.

In order to show you what this does to our ability to tell where light's coming from,

we're going to have to take the camera underneath the table.

Now, as you can see,

where I'm shining the light is very, very clear.

It's very precise at telling us exactly where the torch is coming from.

And when you have a system like this,

where there's a cavity which is reached through a small hole through which you shine light

and something really amazing happens.

We are here at the Royal Observatory in Greenwich,

and this is a camera obscura.

It's a massive pinhole camera.

Up above me, in the roof,

light is being shone through a small hole, up there, reflected from the outside

down onto a white table in front of me.

This white table is just like the patch of light-sensitive cells

we were looking at earlier.

Now, if you look at the table,

you can see objects, like, there's the Queen's house.

And there's the Royal Naval College.

And you can even see things moving, like people or cars.

And remember, all of this is just with a mirror and a hole in the roof.

It's as if we're standing in the middle of a huge eye.

Eyes like this can still be found in the nautilus.

This animal has the most well-developed pinhole camera eye in the natural world,

and it's never had to change it,

because this basic eye gives it all the information it needs.

It hasn't changed because it's got the best eye for the job.

This is really impressive.

Just a hole in the roof has managed to give us an image of the world outside.

But it is a faint image. How can we make it better?

A lens is the obvious answer.

But how could a lens evolve?

We have to remember

that this kind of eye is open to the outside world.

And so a plug of mucus could be formed

in order to protect the interior,

And that plug of mucus, in time, could be selected

to become clearer and thicker and much more like the lens

that we know today.

This is London's Ministry Of Sound.

And DJ Anna Kiss is combining new technology with old.

She's mixing CDs, which are digital recordings, with vinyl records that are analogue.

We can't see sound waves but when a microphone records sound, it generates a changing voltage signal

that can be seen on an oscilloscope.

The wave changes continuously and is called an analogue signal.

This machine etches a version of the original recording onto a master disc.

The groove is a continuous copy of the analogue sound wave.

And these machines press that groove into vinyl records.

Stereo groove is split into two parts. Left and right.

When the stylus vibrates in the groove, it generates an electrical signal in a record player

which recreates the original sound wave.

We've got the high frequency, can be seen as this very sharp line either side.

And we've got left and the right-hand side

of the groove, which is left and right of your stereo music.

And then, as the disc turns round, the very low wobble is the bass,

which causes the needle to vibrate at a much lower frequency.

But vinyl is fragile and easily scratched.

This is a vinyl record magnified many times.

The scratch has cut into the groove and has made the record unplayable.

CDs are more durable

because they store a digital version of the original sound wave.

This digital code is created by taking samples of the analogue wave.

The values of the voltage at these points

are converted into a binary number,

which is made of only zeros and ones.

On a CD this binary code is stored as millions of tiny bumps, arranged in a spiral track.

As the CD rotates, laser light is reflected from the bumps.

These reflected pulses are turned into "on" or "off" electrical signals...

..which are then decoded by the CD player to produce sound.

Digital technology has transformed the way we store and retrieve music.

The digital revolution's changed the way I DJ. It's so much easier and quicker to buy music now.

I haven't bought a record

for about a year, but I still play the older stuff.

I brought a few tonight to play.

Playing with vinyl, there's a real tactile thing about it.

People love the feel of it, the sound of it's good,

but at the end of the day you've gotta move with the times,

and that's...that's what a good DJ should do.

This grey research facility, outside Oxford, might look dull from the outside,

but it holds an incredible secret.

Within these walls lies the hottest place in the solar system.

The temperature at the centre of the sun

is 15 million degrees centigrade.

Scientists here have created their own tiny star,

that is 10 times hotter.

Their goal is to produce a cheap, safe form of energy

that emits no harmful gases or dangerous waste.

The sun releases energy through a reaction called nuclear fusion.

The sun is not a solid, liquid or a gas,

but a fourth state of matter, known as plasma.

The sun's temperature is so high that electrons cannot stay attached to nuclei.

It means atoms cannot exist here.

Instead, the sun consists of electrons, protons and neutrons,

moving around at incredible speed in a plasma.

Normally, protons repel each other because they have the same positive charge.

However, in a plasma,

hydrogen nuclei or protons are able to overcome their mutual repulsion

and combine.

In other words, they fuse,

and as they fuse they create helium nuclei and release huge amounts of energy.

The continuous production of energy helps more protons to fuse and keeps the sun shining.

If we could harness the power of fusion on Earth,

we could generate huge amounts of energy.

But to do this we need to recreate the conditions of the sun in a lab.

JET, at the moment, is the largest fusion reactor in the world.

But JET is an experimental reactor. We don't produce net energy in JET.

But they have proved that fusion power can work.

One of the big technical challenges for the scientist

is working with temperatures hotter than the sun.

How do you heat plasma up to a temperature of 150 million degrees?

Well, the answer is simple. In an oven.

In fact, it's a microwave oven.

So you stick your gas into a microwave oven, you switch on your microwave and it heats up.

After a while you reach temperatures of a few thousand degrees.

But you will never reach 150 million degrees. Why not?

Because the particles hit the wall and they will cool down.

Now you can actually contain charged particles in the magnetic field.

So if in our oven, we switch on the magnetic field,

then these particles will actually be contained by the magnetic field.

That way you can keep them away from the wall.

Because it's so hot inside the reactor,

maintenance is carried out by skilled remote handlers.

Although it looks like a computer game, these engineers have to train for three years

to be able to control the robotic arms that operate inside the core.

Despite the intense heat,

scientists believe that fusion power is far less dangerous than the traditional form

of nuclear power - nuclear fission.

It's very safe and if anything goes wrong,

then the plasma will cool down

and the fusion reaction can't take place anymore.

So you will never have the possibility of a chain reaction.

It can never run out of hand. If anything goes wrong it immediately stops.

Nuclear power, created through a process called nuclear fission,

plays an important role in supplying our energy needs.

This is a nuclear power station. There are more than 400 of them around the world.

And together they produce about 17% of the global electricity supply.

Underneath this floor, a nuclear reaction is taking place.

This reaction is very powerful and potentially dangerous, which is why it has to be safely enclosed

beneath several metres of concrete.

This is what's in the heart of the nuclear reactor.

It's what we call a fuel element

and inside each one of these elements there's 36 fuel pins.

And inside each one of those pins is over 60 of these uranium oxide pellets.

And inside those pellets is where the fission is taking place, generating the heat.

Each one of these elements is part of a stack of seven fuel elements,

which is what we call a stringer.

And there's 408 of those stringers

in each one of the reactor cores at Dungeness B.

As we've seen, the core of a nuclear reactor contains lots of fuel rods.

Inside the rods are thousands of pellets, made of uranium.

Uranium atoms have a special property.

They can be made to split by firing neutrons at them.

When a uranium atom absorbs a neutron, it splits up, releasing more neutrons

and a huge amount of energy.

This is known as nuclear fission.

The neutrons released by the split atom, go on to release more neutrons and more energy.

This is known as a nuclear chain reaction

and could be dangerous if not controlled.

The energy released from the nuclear fission

makes the fuel rods very hot.

The amount of heat released by the uranium pellets can be controlled

by boron control rods in the reactor.

They absorb the neutrons released when the uranium atoms split.

Lowering the control rods into the fuel can slow down

or even stop the nuclear chain reaction.

The heat from the fuel rods is used to turn water into steam...

..which is then used to drive turbines

which generate electricity, just like any other power plant.

People have concerns about nuclear power stations for two reasons.

Firstly, if the reaction is not managed properly, it could get out of control

with potentially catastrophic consequences.

The poor design and management of the Chernobyl nuclear power station caused a steam explosion and fire

that released massive amounts of radiation into the atmosphere,

resulting in the evacuation and resettlement of over 336,000 people.

Secondly, the waste products from nuclear fission are radioactive and can remain dangerous for hundreds,

and in some cases, thousands of years.

Nuclear waste is divided into low, medium and high-level waste,

depending on the amount of radioactivity it produces.

There are low levels of radioactivity in everything around us.

Atoms are radioactive when their nuclei are unstable.

In order to become stable they need to lose energy.

They do this by emitting radiation

in the form of alpha, beta or gamma radiations.

Nuclear radiation can be dangerous because it can damage the DNA in our cells.

Depending on the type and amount of radiation our cells are exposed to,

this can lead to health problems, ranging from nausea to cancer.

This is why great care is taken in storing nuclear waste

and making sure none of it reaches our environment.

Radioactive waste remains lethal for hundreds of thousands of years.

And we have no idea what we're gonna do to deal with it.

At the moment it's stored onsite.

It's cooled, and costs the taxpayer billions of pounds to sort out.

In the long term we have no idea what we're gonna do with it.

People can say, we'll bury it under ground. There's nowhere in the world anyone's ever managed to do this.

So, we're hoping someone might have a brainwave sometime in the future!

There are things that physicists

are working on at the moment.

There are ways of firing protons

into nuclear waste, basically, and making it safe almost immediately.

And that will come in the future. It's not there right now.

But people are working on these things.

As a waste product, nuclear reactors make plutonium, the prime ingredient for making nuclear weapons.

In this age of heightened terrorism and security risks,

the last thing we should do is spreading this material round the world.

This is the reason why things like Sellafield, in the UK,

should not be shut down.

Because we deal with nuclear waste, and we deal with it responsibly,

and there's only a...a small handful of reprocessing plants in the world,

and the UK has two of them, actually.

What does this...

..and this...

..have in common with this?

They're all feeding.

Plants feed using a process called photosynthesis.

Photosynthesis is the chemical reaction through which plants make glucose.

It also produces oxygen.

It is crucial to all life on Earth because it is the source of nearly all the food and oxygen

we need to stay alive.

But what do plants need to photosynthesise?

First, they need water.

Water is as essential to plant life as it is to us.

It is one of the reactants in the photosynthetic reaction.

Plants which have little access to water go to great lengths

to conserve the water they collect.

These desert plants survive by maximising the amount of water they get from their harsh conditions.

The other reactant needed for photosynthesis is carbon dioxide.

Most plants collect this from the air.

To do this they have tiny holes in their leaves, called stomata.

As well as water and carbon dioxide,

plants need one other thing for photosynthesis - light.

This provides the energy for the chemical reaction to take place.

Photosynthesis takes place in the chloroplasts in plant cells.

Chloroplasts contain a green substance called chlorophyll,

which absorbs the light energy needed to make photosynthesis happen.

To summarise, photosynthesis takes the raw ingredients of water and carbon dioxide

and uses light energy to make glucose and oxygen.

This pondweed is called cabomba. Because it lives in water, we can see it releasing bubbles of oxygen

as it photosynthesises.

When we vary the amount of light the plant receives,

we can see it affects the rate of photosynthesis.

This one has full light and we can see it bubbling vigorously.

This one has been shielded from the light and the photosynthesis has stopped.

Our skin is constantly regenerating.

Millions of skin cells die every day.

But they are replaced by a process called cell division.

Mitosis is one form of cell division and it's taking place in your body, thousands of times, every second.

Before a cell divides, it makes a copy of every chromosome's DNA.

The nuclear membrane dissolves and the chromosomes line up in the centre of the cell.

The chromosomes are then separated to opposite sides of the cell.

New nuclear membranes from around the chromosomes

and the cell begins to divide.

The two cells that result are genetically identical and so can replace others that have died.

The only place in the body where mitosis isn't used to make new cells is the production of sex cells.

This process is called meiosis.

Meiosis starts with a normal cell, just like mitosis.

But immediately before a cell divides, the DNA of every chromosome is copied,

leaving the cell with twice its usual number of chromosomes.

In meiosis, two chromosomes mix up their genes.

They do this by a process called recombination.

The cell then divides.

The chromosomes line up in the centre and spindles attach.

As they are pulled apart, the cell starts to divide.

The resultant four cells, known as haploid, have only half the normal genetic material.

This is important, as if they are successful,

they will meet a gamete cell,

which is an egg or a sperm,

and combine to produce a unique diploid cell, which is an embryo.

VOICE CRACKLES OVER RADIO

On July 20th, 1969, humans landed on the moon for the first time.

This huge leap for mankind was made possible by the work of a scientist

who lived more than 300 years earlier.

Isaac Newton revolutionised our understanding of the world.

His work on how things move is at the heart of everything,

from spaceship design...

..to car safety.

We can illustrate the principles of Newton's laws of motion, using a rocket-powered sled on an ice rink.

Of course, these conditions are not perfect, because on Earth

we can never create a completely frictionless environment.

But it should give you an idea of what the laws mean.

Newton's first law states that if something is stationary,

it won't start moving unless something pushes it or pulls it.

It also says that if something is already moving, it will keep moving in the same way

unless another force acts on it.

If this ice was frictionless and there was nothing in the way,

the rocket would slide forever.

These rockets have three different strength engines.

Although they all start from the same place,

they demonstrate Newton's second law,

which says that the acceleration of an object

is proportional to the force acting on it.

It also says that the more mass an object has,

the less it will accelerate for a given force.

The force an object experiences depends on how quickly its momentum changes.

So if something comes to a sudden stop,

it experiences a greater force than if it comes to rest gently.

Newton's third law tells us that forces are always produced in equal but opposite pairs.

It is often simplified to - for every action, there is an equal and opposite reaction.

In this demonstration of Newton's third law, we've fixed a canon to the sledge.

When the canon fires the ball, the ball pushes back on the canon with an equal force.

Subtitles by Emma Johnston, Red Bee Media Ltd

E-mail [email protected]