0:00:13 > 0:00:17This is a human trial for a sunscreen made using nanotechnology.
0:00:24 > 0:00:29Nanotechnology is the art of manipulating matter on an atomic or molecular scale.
0:00:30 > 0:00:34That's 100,000 times smaller than the width of a human hair.
0:00:35 > 0:00:39This team of scientists in Nottingham have devised a material
0:00:39 > 0:00:42that can help protect us from the sun.
0:00:46 > 0:00:50We use nanotechnology in sunscreens to replace the conventional UV filters.
0:00:50 > 0:00:53Conventional filters work by absorbing ultraviolet light.
0:00:53 > 0:00:56But titanium dioxide reflects it, rather than absorbing.
0:00:56 > 0:00:58Now, we got the idea from the paint industry,
0:00:58 > 0:01:00because in the paint industry,
0:01:00 > 0:01:04titanium dioxide reflects visible light. Which is why paint is white.
0:01:04 > 0:01:07But we got on the idea that if you were to make the particle sizes smaller,
0:01:07 > 0:01:12then they would reflect ultraviolet light and you would have a sunscreen.
0:01:12 > 0:01:17Most sunscreens rely on chemicals within the lotion to absorb the sun's radiation.
0:01:18 > 0:01:21However, traditional chemical absorbers only work efficiently
0:01:21 > 0:01:23on a limited number of wavelengths.
0:01:26 > 0:01:30The titanium dioxide reflectors work more consistently across a wider range.
0:01:33 > 0:01:37We can also look on a microscope screen at the sun product
0:01:37 > 0:01:41to see the titanium dioxide crystals within the product.
0:01:42 > 0:01:44Little tiny dots of ovoid crystals.
0:01:45 > 0:01:50Ideally, they would be as spherical as possible but titanium dioxide crystals aren't spherical.
0:01:50 > 0:01:54They're slightly ovoid, but they're the nearest thing to spherical.
0:01:54 > 0:01:56That's why we use titanium dioxide.
0:01:56 > 0:02:00Size is absolutely critical to whether or not they reflect ultraviolet light.
0:02:00 > 0:02:02So that's where the nanotechnology comes in.
0:02:02 > 0:02:04We have to engineer these crystals
0:02:04 > 0:02:07to be exactly the right size to reflect ultraviolet light.
0:02:07 > 0:02:10And then we take them to another lab where we test them
0:02:10 > 0:02:12to make sure that they work.
0:02:17 > 0:02:22The scientists are testing to assess how much extra protection this sunscreen gives the volunteer.
0:02:22 > 0:02:27We try to simulate exactly what happens on the beach.
0:02:27 > 0:02:31So we use human volunteers. We put the sun cream on their back
0:02:31 > 0:02:33and then we expose it to artificial sunlight,
0:02:33 > 0:02:36which comes from an instrument called a solar simulator.
0:02:36 > 0:02:39We actually only expose little one centimetre squares of their back.
0:02:39 > 0:02:45We're looking to see how much the sun cream protects them from burning from the artificial sunlight.
0:02:45 > 0:02:48When the sunscreen is proved safe and effective in human trials,
0:02:48 > 0:02:52the ingredients are sent to the factory for mass production.
0:03:02 > 0:03:07The sun's ultraviolet rays are a form of high energy electromagnetic radiation,
0:03:07 > 0:03:10that can penetrate our skin and make its way right into our cells.
0:03:14 > 0:03:19Too much exposure will damage our DNA, causing mutations that can lead to cancer.
0:03:24 > 0:03:25When skin is exposed to sunlight,
0:03:25 > 0:03:28it tries to protect itself from UV radiation
0:03:28 > 0:03:30by producing melanin.
0:03:32 > 0:03:37Melanin is a brown pigment that absorbs ultraviolet light and makes skin appear tanned.
0:03:38 > 0:03:42Because dark-skinned people have more melanin, they are less likely to suffer sunburn
0:03:42 > 0:03:44than those who are fair.
0:03:44 > 0:03:47Not all contact with sunlight is dangerous, however.
0:03:47 > 0:03:51As well as making us feel happier, it's our main source of vitamin D.
0:03:51 > 0:03:54Vitamin D performs many useful functions,
0:03:54 > 0:03:57including regulating the amount of calcium and phosphate in the body,
0:03:57 > 0:04:00which is especially important for our bones.
0:04:00 > 0:04:05As well as that, many people think they look healthier and more attractive when they're tanned.
0:04:08 > 0:04:10ENGINE STARTS
0:04:12 > 0:04:17The chemicals we release into our atmosphere have a wide-ranging effect on the natural world.
0:04:18 > 0:04:22Rivers like this one, in the Peak District, can be devastated by contamination.
0:04:25 > 0:04:27Chris Curtis of University College London
0:04:27 > 0:04:30has been monitoring pollution and its effects on the countryside.
0:04:32 > 0:04:35I'm gonna test the pH of this drinking water.
0:04:35 > 0:04:36Good old London tap water.
0:04:36 > 0:04:39For comparison with acid river water sample.
0:04:42 > 0:04:46As you can see, when I put the probe in the tap water,
0:04:46 > 0:04:52the pH goes up to about 7, which is circum neutral.
0:04:53 > 0:04:54So that's neutral tap water.
0:04:55 > 0:04:58But if I then put the probe in the stream...
0:05:00 > 0:05:02..the pH value goes down to about 5.2.
0:05:02 > 0:05:05Now because that's a difference of two pH units,
0:05:05 > 0:05:07but because pH is a logarithmic scale
0:05:07 > 0:05:10that actually means it's not ten times,
0:05:10 > 0:05:12it's 100 times more acid in the stream,
0:05:12 > 0:05:14than it is in the tap water.
0:05:26 > 0:05:32We're trying to collect insects and other invertebrate animals that live under the rocks and in the gravel,
0:05:32 > 0:05:36to see which species are present and see if there are any acid-sensitive species present,
0:05:36 > 0:05:40which might indicate that this system is recovering from acidification.
0:05:40 > 0:05:43Now what we can see is that there's actually not very much here.
0:05:43 > 0:05:45That may seem like a bad thing,
0:05:45 > 0:05:47but it tells us a lot about the stream,
0:05:47 > 0:05:50and it tells us that the water quality isn't very good.
0:05:50 > 0:05:51In other words, it's very acid.
0:05:51 > 0:05:55If we went to a very healthy lowland stream with a high pH,
0:05:55 > 0:05:59we might expect to find a very diverse community of invertebrates
0:05:59 > 0:06:02living in the sediments and under the rocks in the stream.
0:06:02 > 0:06:07If invertebrates are missing, it tells us they could have been killed by acid episodes in the stream.
0:06:10 > 0:06:16Rob Mills from Bangor University uses a different technique to test acidity in the environment.
0:06:16 > 0:06:22He is trying to assess the impact of acid rain by isolating small plots of land
0:06:22 > 0:06:24away from the influence of people and cars.
0:06:29 > 0:06:31In this first section of test plots,
0:06:31 > 0:06:34the soil is open to the elements as normal.
0:06:39 > 0:06:40But in the second block,
0:06:40 > 0:06:43a plastic cover shields the plants when it rains.
0:06:43 > 0:06:44Instead of rain water,
0:06:44 > 0:06:49these sheltered plants receive the same quantity of distilled water.
0:06:51 > 0:06:54However, not all the moisture in soil comes from rainfall.
0:06:54 > 0:06:58Some of it comes from the dense fog that regularly covers this area.
0:06:59 > 0:07:03This water can also be tested using an ingenious collection method.
0:07:05 > 0:07:08OK, what this is - we call it the cloud collector.
0:07:08 > 0:07:11And essentially what it does, is it collects clouds.
0:07:11 > 0:07:14So as the clouds move across the hillside,
0:07:14 > 0:07:17they come across this fishing line wire,
0:07:17 > 0:07:20and small droplets from the cloud condense,
0:07:20 > 0:07:23run down into the funnel and we collect it at the bottom.
0:07:23 > 0:07:28And this is another way of us getting an idea of how much acid material is coming into the system.
0:07:28 > 0:07:30We can have a quick look at this.
0:07:32 > 0:07:34And what we can find in here
0:07:34 > 0:07:38is that this will be full with a range of particles.
0:07:38 > 0:07:45And these particles are what the water droplets condense around.
0:07:45 > 0:07:48So this could be particles of dust from car vehicle emissions,
0:07:48 > 0:07:50from fossil fuel power plant emissions,
0:07:50 > 0:07:53and each one of these tiny little specks of black dust
0:07:53 > 0:07:55could represent a single droplet.
0:07:55 > 0:07:59But, of course, this material then eventually enters the ecosystem.
0:07:59 > 0:08:01The consequences of which, we're trying to find out.
0:08:02 > 0:08:06Another of Rob's tests assesses the effects of global warming.
0:08:06 > 0:08:10He covers some plots at night, in order to raise their temperature.
0:08:10 > 0:08:15Over several years, Rob wants to see how the effect of temperature alone
0:08:15 > 0:08:17affects the plants' growth.
0:08:17 > 0:08:20Global warming is a product of a natural phenomenon,
0:08:20 > 0:08:25naturally we have greenhouse gases which exist in the atmosphere allowing life on Earth to exist.
0:08:25 > 0:08:30But global warming is a function of "anthropogenic activities". That's all human activity.
0:08:30 > 0:08:36And over the past few hundred years we've been contributing a lot more greenhouse gases to the atmosphere.
0:08:36 > 0:08:42Essentially, what we're seeing is the climate is changing. Not necessarily always getting warmer everywhere.
0:08:42 > 0:08:47But generally, the climate is changing. You can term that "global warming" or "global climate change".
0:08:51 > 0:08:53A lot of pollution is caused by traffic.
0:08:56 > 0:09:01Exhaust fumes contain tiny particles of solid carbon, which is why it looks black.
0:09:01 > 0:09:05These can give you health problems like asthma when you breathe them in.
0:09:08 > 0:09:11There are also gases you can't see, including sulphur dioxide,
0:09:11 > 0:09:15carbon monoxide, carbon dioxide and nitrogen oxide.
0:09:21 > 0:09:24Even just a short five-mile trip from school
0:09:24 > 0:09:25produces about 500g of CO2.
0:09:30 > 0:09:32CO2 makes up a small proportion of our atmosphere,
0:09:32 > 0:09:35but it is a powerful greenhouse gas.
0:09:35 > 0:09:37- Bye!- Bye!
0:09:38 > 0:09:41This means it traps heat in the Earth's atmosphere.
0:09:44 > 0:09:49London has a 184,000 vehicles entering its congestion zone every day.
0:09:50 > 0:09:58Even if they only travel five miles each, they will produce over 90 million grams of polluting CO2.
0:10:05 > 0:10:11With so much pollution entering the atmosphere, many think we should find ways to discourage driving.
0:10:11 > 0:10:14By introducing congestion zones, for example,
0:10:14 > 0:10:17or raising the taxes on petrol and diesel.
0:10:17 > 0:10:20Another approach to reduce pollution is to use cleaner fuels.
0:10:21 > 0:10:23One such fuel is hydrogen,
0:10:23 > 0:10:27created here by the reaction of metal in acid.
0:10:27 > 0:10:30We know that hydrogen burns explosively in air,
0:10:30 > 0:10:33but there are other ways it can be used to release energy.
0:10:37 > 0:10:40Companies all over the world are competing to develop a fuel cell
0:10:40 > 0:10:43that uses hydrogen to generate electricity.
0:10:45 > 0:10:50Automotive manufacturers are investigating alternatives to fossil fuels.
0:10:50 > 0:10:52Much like traditional cars today,
0:10:52 > 0:10:56you can refuel the fuel cell of a hydrogen tank in a matter of minutes.
0:10:56 > 0:10:59A hydrogen fuel cell is very much like an engine
0:10:59 > 0:11:02in that it converts a fuel into energy.
0:11:02 > 0:11:04But unlike your traditional combustion engine,
0:11:04 > 0:11:06there's no burning involved.
0:11:06 > 0:11:10In a fuel cell, in an electric chemical reaction, it combines a hydrogen molecule
0:11:10 > 0:11:15with an oxygen molecule, producing water, electricity and heat.
0:11:15 > 0:11:19A fuel cell uses hydrogen gas to generate electricity.
0:11:20 > 0:11:26It splits hydrogen molecules into negatively charged electrons and positively charged protons.
0:11:28 > 0:11:31The protons can pass through the membrane in the middle of the cell.
0:11:31 > 0:11:36But the electrons are forced to take a different route, creating an electrical current.
0:11:37 > 0:11:39Once they reach the other side of the cell,
0:11:39 > 0:11:42the protons and electrons combine with oxygen from the air
0:11:42 > 0:11:44to form water molecules.
0:11:48 > 0:11:52Fossil fuels that we're traditionally using today are running out.
0:11:52 > 0:11:56And climate change is dictating we have to start reducing our emissions.
0:11:56 > 0:12:00When using a fuel cell in a vehicle, utilising hydrogen as a fuel,
0:12:00 > 0:12:04you're using a sustainable fuel and you're producing zero emissions.
0:12:10 > 0:12:14Daphne Goodship and Barbara Herbert are identical twins.
0:12:14 > 0:12:18But they did not meet until they were 35 years old.
0:12:18 > 0:12:22They were separated shortly after they were born and brought up by adoptive parents
0:12:22 > 0:12:24in very different environments.
0:12:27 > 0:12:30Barbara's adopted father was a gardener
0:12:30 > 0:12:33and Daphne's was a scientist.
0:12:33 > 0:12:36I didn't really suspect there was a twin but...
0:12:36 > 0:12:40My grandma told me when I was about 11 that I had a double.
0:12:40 > 0:12:44But I knew then that I was adopted.
0:12:44 > 0:12:50We met on King's Cross Station. The thing was, the train was a 125, which was a very long train,
0:12:50 > 0:12:57and I opened the door and standing right there was Barbara.
0:12:57 > 0:12:59It was like meeting an old friend.
0:12:59 > 0:13:02It wasn't difficult at all. It was like we'd always known each other.
0:13:02 > 0:13:07The first similarity was we discovered that we both had a miscarriage.
0:13:07 > 0:13:10And then it was followed by two boys and a girl in that order.
0:13:10 > 0:13:16And our second sons were born within three weeks of one another.
0:13:16 > 0:13:20So that was rather strange. Erm, course our crooked fingers.
0:13:20 > 0:13:23It was one of the first things we ever said to each other. Look!
0:13:23 > 0:13:28- How sweet!- They're really crooked. And I remember when I was at school, I could do that -
0:13:28 > 0:13:33and I thought, that is so original! It's one of the first things we said!
0:13:33 > 0:13:35Walking down King's Cross station.
0:13:37 > 0:13:39Twins separated at birth are very rare.
0:13:39 > 0:13:45Researchers are keen to study them to compare the effects of nature and nurture on their development.
0:13:46 > 0:13:54I think a lot of the discoveries were medical to start with. Well, we both had a heart murmur.
0:13:54 > 0:13:57- Thyroid, they discovered. - Yeah, underactive thyroids.
0:13:57 > 0:14:02Er, our IQ. We were within about one point of one another, which we thought was odd,
0:14:02 > 0:14:08- because we both grew up...different schools.- You're tested separately, so you go in and the researcher says,
0:14:08 > 0:14:10"Write a sentence".
0:14:10 > 0:14:15You think, oh gosh, what can I write? Just a short sentence. So I thought, I know - the cat sat on the mat.
0:14:15 > 0:14:21So I ended up writing, because I was trying to do it quick, "the caz sat on the mat".
0:14:21 > 0:14:29Next day, I thought "the cat sat on the mat". But there it goes, I wrote "the caz sat on the mat".
0:14:29 > 0:14:33Daphne and Barbara are so similar because they are clones.
0:14:33 > 0:14:36Two people who have exactly the same genetic make-up.
0:14:40 > 0:14:43When their mother was pregnant, her fertilised egg split into two,
0:14:43 > 0:14:47creating two identical cells, that grew into Daphne and Barbara.
0:14:49 > 0:14:52Identical twins are not the only clones in nature.
0:14:54 > 0:14:59Many living things like strawberries and aphids reproduce asexually, without a partner.
0:14:59 > 0:15:02The offspring are genetically identical to the parents.
0:15:04 > 0:15:10Scientists can now clone animals. The first ever cloned animal was produced in Edinburgh.
0:15:10 > 0:15:15It was a now famous sheep called Dolly.
0:15:16 > 0:15:21In order to clone an animal, scientists use a technique called somatic cell nuclear transfer.
0:15:22 > 0:15:28This involves replacing the nucleus of one egg cell with the nucleus from any other somatic cell.
0:15:30 > 0:15:33This could be from any part of the body, as long as that cell has a nucleus.
0:15:35 > 0:15:37Just like Daphne and Barbara,
0:15:37 > 0:15:40the embryos here are genetically identical to one another.
0:15:40 > 0:15:43They are clones.
0:15:50 > 0:15:54Scientists in Newcastle are developing cloning techniques
0:15:54 > 0:15:58that they hope one day will heal currently incurable diseases.
0:15:58 > 0:16:02Janice has a neurodegenerative disorder.
0:16:02 > 0:16:04That means part of her brain is deteriorating.
0:16:06 > 0:16:12I found out in the year 2000 and decided to have the diagnostic test
0:16:12 > 0:16:15because my mother has the disorder.
0:16:15 > 0:16:18It's been in the family for generations.
0:16:19 > 0:16:25Up until the symptoms started in 2005, I never thought about it,
0:16:25 > 0:16:27even though I'd had the test.
0:16:27 > 0:16:33And...but since the symptoms started, I've had to retire from work,
0:16:33 > 0:16:36because it makes one very very tired,
0:16:36 > 0:16:39and I haven't a lot of strength.
0:16:39 > 0:16:44And, um, most of the problem is with my speech.
0:16:44 > 0:16:49Scientists think that replacing the damaged cells with the new ones will cure Janice's condition.
0:16:49 > 0:16:53This technique requires special embryonic stem cells.
0:16:53 > 0:16:59Unfortunately, the easiest way to get them at the moment is from a controversial source.
0:16:59 > 0:17:01Human embryos.
0:17:01 > 0:17:05Well, sadly, quite a lot of people have difficulty conceiving a child.
0:17:05 > 0:17:10We do a procedure called IVF, whereby we put the egg and the sperm together in the laboratory.
0:17:10 > 0:17:15And then two days later, we put that embryo directly back into the womb to help them achieve a pregnancy.
0:17:15 > 0:17:19So we give the woman medication to make her grow lots of eggs.
0:17:19 > 0:17:21We will often collect maybe 10 eggs
0:17:21 > 0:17:24from a woman in the process of one IVF and put the sperm with them all.
0:17:24 > 0:17:27And then we put the best one or two embryos back.
0:17:27 > 0:17:30So, effectively, a side effect from IVF treatment
0:17:30 > 0:17:33is that there'll often be some embryos remaining after treatment.
0:17:33 > 0:17:35They're usually very poor quality,
0:17:35 > 0:17:38but usually then, they would just have to be discarded.
0:17:38 > 0:17:44We can use some of those potentially for research, and create embryonic stem cell lines from those embryos.
0:17:44 > 0:17:49Stem cells are originators. They are the beginning of a tissue,
0:17:49 > 0:17:57and the special thing about them is they retain the capacity to divide constantly and repair themselves.
0:17:57 > 0:17:58Our body's full of them.
0:17:58 > 0:18:01They're in skin, which constantly replaces our surface covering.
0:18:01 > 0:18:05The most exciting stem cells are the ones with embryonic properties.
0:18:05 > 0:18:07Those are the ones that develop a few days
0:18:07 > 0:18:09after fertilisation of the egg.
0:18:09 > 0:18:14And that little ball of cells will ultimately form the embryo proper.
0:18:14 > 0:18:20Scientists have proved that embryonic stem cells can make the majority of other cell types.
0:18:20 > 0:18:23Here, stem cells have become heart cells.
0:18:23 > 0:18:26You can see that they have contractile properties.
0:18:28 > 0:18:32Stem cells of embryonic origin are like apprentices that can do anything.
0:18:32 > 0:18:35They haven't yet been specialised into any single function.
0:18:35 > 0:18:41And if we can capture them, grow them in a dish and persuade them to develop under direction,
0:18:41 > 0:18:49then potentially we could produce any human tissues, and use that to repair any manner of diseases and injuries.
0:18:49 > 0:18:54Scientists believe that in the future the damage to Janice's brain could be repaired,
0:18:54 > 0:18:56by giving her new cloned brain cells.
0:18:57 > 0:19:02The problem is, the brain doesn't have its own stem cells and can't repair itself.
0:19:02 > 0:19:05So the idea is, if we could give it some apprentices,
0:19:05 > 0:19:09then those apprentices can be placed very precisely into the bit of the brain that's not working
0:19:09 > 0:19:14and hopefully will pick up the function of local cells and start to repair damage caused
0:19:14 > 0:19:17by the accumulation of iron or other products.
0:19:17 > 0:19:23Stem cells offer tremendous hope to medicine because it gives us, for the first time,
0:19:23 > 0:19:29the chance to explore treating diseases where the tissues have stopped working,
0:19:29 > 0:19:33by producing genetically identical replacement tissue.
0:19:33 > 0:19:37Something we've done for a long time in limited areas, like bone marrow transplant,
0:19:37 > 0:19:40but now we can begin to think of doing on a much wider basis.
0:19:40 > 0:19:45Stem cell research raises ethical issues, which makes some people uncomfortable about it,
0:19:45 > 0:19:48in spite of the potential benefits.
0:19:48 > 0:19:53There are two major costs to embryonic stem cell research.
0:19:53 > 0:19:56One is that it involves the destruction, often,
0:19:56 > 0:19:58of large numbers of human embryos.
0:19:58 > 0:20:03Some people believe this is either akin to murder of human beings
0:20:03 > 0:20:07or it results in the devaluing of human life.
0:20:07 > 0:20:11And the second major cost is that we develop technology,
0:20:11 > 0:20:12such as cloning technology,
0:20:12 > 0:20:16that can be used to produce live-born human clones.
0:20:16 > 0:20:20I have no problem at all with stem cell research,
0:20:20 > 0:20:25and I hope one day to be the recipient of it.
0:20:31 > 0:20:35This is deoxyribonucleic acid. DNA.
0:20:35 > 0:20:40It is the most extraordinary molecule on Earth.
0:20:40 > 0:20:43It literally encodes the genetic instructions from which you are made.
0:20:43 > 0:20:49It has an amazing base pairing structure which can be replicated,
0:20:49 > 0:20:51and the information is passed on.
0:20:51 > 0:20:57Understanding DNA has given scientists new ways of trying to cure diseases,
0:20:57 > 0:20:59previously thought to be incurable.
0:20:59 > 0:21:03Like the hereditary respiratory disease, cystic fibrosis.
0:21:03 > 0:21:07I take about 20 different types of drugs.
0:21:07 > 0:21:12Some of which are here. And I also take some of them intravenously
0:21:12 > 0:21:15and most of them are in tablet form.
0:21:15 > 0:21:17I take about 250 tablets a week,
0:21:17 > 0:21:20which is 1,000 a month and 12,000 in a year.
0:21:22 > 0:21:24It mainly affects your lungs,
0:21:24 > 0:21:29because the hairs in your lungs don't work properly,
0:21:29 > 0:21:35so they can't get rid of the mucus in your lungs and so the tubes get blocked up in your lungs.
0:21:35 > 0:21:41I have about 30% lung function now. It means that I can't walk very far.
0:21:41 > 0:21:43I can't really do much,
0:21:43 > 0:21:46and it affects pretty much everything that I do.
0:21:46 > 0:21:52Until I was about 12 I was in the school swimming team, I was in the running team,
0:21:52 > 0:21:55I was in doing PE, I won lots of sports awards,
0:21:55 > 0:22:00I did pretty much everything that you could do.
0:22:00 > 0:22:02It is a genetic disease.
0:22:02 > 0:22:06My mum has one gene mutation and my dad has another one.
0:22:06 > 0:22:10I just so happened to get both of them at one time, so I got CF.
0:22:10 > 0:22:14My brother, who's 17, he doesn't have CF at all,
0:22:14 > 0:22:18because he just has two perfectly normal genes.
0:22:18 > 0:22:22Gene therapy is when you put in new copies of genes
0:22:22 > 0:22:26that are defective within patient cells.
0:22:26 > 0:22:28For example, with cystic fibrosis,
0:22:28 > 0:22:32both genes have to be abnormal for you to get cystic fibrosis,
0:22:32 > 0:22:38so what we're trying to do is reintroduce a new copy of the gene into the cell.
0:22:38 > 0:22:42The first scan we're going to do gives us an image of the whole of your chest
0:22:42 > 0:22:46so we can plan where we're going to start and stop the actual scans.
0:22:46 > 0:22:50Cystic fibrosis is a possible target, because firstly you need to know what the gene is,
0:22:50 > 0:22:53and that was identified in 1989.
0:22:53 > 0:22:59Secondly, there has to be need for this fancy and probably quite expensive new therapy,
0:22:59 > 0:23:04and, sadly, these patients don't have good enough therapy.
0:23:04 > 0:23:07Finally, you have to be able to introduce the gene somehow,
0:23:07 > 0:23:12and because we can spray things into the lungs of patients, all three come together
0:23:12 > 0:23:16to suggest that cystic fibrosis would be a good candidate for gene therapy.
0:23:16 > 0:23:22The sensible thing would be to do gene therapy as soon as you know you have a diagnosis of cystic fibrosis,
0:23:22 > 0:23:26and there is now a newborn screening happening in the UK.
0:23:26 > 0:23:31So you could put the two programmes together, and say "you have been diagnosed with cystic fibrosis.
0:23:31 > 0:23:34"Now you need gene therapy to prevent,
0:23:34 > 0:23:38"rather than treat". And that's actually what we're very much aiming for.
0:23:38 > 0:23:42Gene therapy for CF should be a preventative treatment in the future.
0:23:42 > 0:23:46Not trying to stop something that already has deteriorated.
0:23:46 > 0:23:50The science of gene therapy provides hope for cystic fibrosis sufferers.
0:23:50 > 0:23:53In the future, there might be a cure.
0:23:53 > 0:23:56Tragically, this is too late for Lorna and her family,
0:23:56 > 0:24:01as she died two weeks after giving this interview.
0:24:07 > 0:24:12The discovery of the structure of DNA, in 1953, is accredited to two young scientists in Cambridge,
0:24:12 > 0:24:15called Francis Crick and James Watson.
0:24:15 > 0:24:20Although many scientists were working on unlocking the secrets of DNA at the same time,
0:24:20 > 0:24:25Crick and Watson were the first to publish their results, and receive public recognition.
0:24:26 > 0:24:32Understanding DNA has led to a huge increase in our knowledge of how life works.
0:24:32 > 0:24:37From the intricate patterns of a butterfly's wing, to the pelican's dive.
0:24:40 > 0:24:46DNA provides the blueprint for the development and functioning of all living organisms.
0:24:48 > 0:24:56DNA is a molecule made up of four chemical bases. Adenine, guanine, cytosine and thymine.
0:24:56 > 0:24:59Or A, G, C and T.
0:25:00 > 0:25:04In many ways, all life on Earth can be described with just these four letters.
0:25:08 > 0:25:11In 1990, the human genome project began.
0:25:11 > 0:25:16Scientists started to work out the DNA code of human life.
0:25:16 > 0:25:19It's about three billion bases long.
0:25:23 > 0:25:28Many thought it was an impossible task, but it was completed in 2001, four years ahead of schedule,
0:25:28 > 0:25:32thanks to computers like these.
0:25:36 > 0:25:41One of the most exciting areas of medical research, following the unlocking of the human genome,
0:25:41 > 0:25:45is genetic screening, which aims to prevent illnesses before they occur.
0:25:52 > 0:25:58Here at University College Hospital, Dr Sandra Anglin is part of an international programme
0:25:58 > 0:26:02to screen all patients for sickle-cell thalassemia.
0:26:07 > 0:26:11It specifically affects the oxygen-carrying capacity in the blood
0:26:11 > 0:26:15and a specific protein called haemoglobin.
0:26:15 > 0:26:19Genetic screening, unlike screening for specific illnesses,
0:26:19 > 0:26:22is a screening process whereby we want to identify
0:26:22 > 0:26:25an unusual gene that you may pass on to your child.
0:26:25 > 0:26:28With sickle-cell and thalassemia,
0:26:28 > 0:26:33these are specific genes that affect the haemoglobin in the blood.
0:26:33 > 0:26:37In terms of antenatal screening, it's offered as part of routine care,
0:26:37 > 0:26:42so any pregnant woman that turns up will be offered screening for sickle cell and thalassemia.
0:26:42 > 0:26:46The normal type of red blood cells are haemoglobin A,
0:26:46 > 0:26:50and if you are a carrier, you have one gene that makes normal red blood cells
0:26:50 > 0:26:53and one that makes a more unusual type of red blood cells.
0:26:53 > 0:26:58If both parents are carriers of the gene, their baby has a 1 in 4 chance of inheriting a copy
0:26:58 > 0:27:01of a sickle cell gene.
0:27:01 > 0:27:04Nelly went through the screening process.
0:27:04 > 0:27:09I was asked to go in to check whether I was a carrier or not.
0:27:09 > 0:27:13And obviously my husband went with me as well, and we went together.
0:27:13 > 0:27:19And that's when I discovered I was a carrier of the sickle cell disease, and he was a carrier as well.
0:27:19 > 0:27:22The options that were given to us,
0:27:22 > 0:27:26one of them was having a termination,
0:27:26 > 0:27:30and the other obviously, was having a baby, despite all the risks involved.
0:27:30 > 0:27:35We decided to go ahead and have a baby, despite all the risks.
0:27:35 > 0:27:40My twin girls do not have sickle cell. Perfectly healthy.
0:27:40 > 0:27:43Perfectly normal children.
0:27:45 > 0:27:48Genetic screening provides us with uniquely personal data about people
0:27:48 > 0:27:51and society needs to decide how to use this information.
0:27:55 > 0:27:58People have concerns that this will result in intolerance to people
0:27:58 > 0:28:00who choose not to employ the technology,
0:28:00 > 0:28:03and so have children with one of these diseases
0:28:03 > 0:28:05or Down's syndrome, for example.
0:28:05 > 0:28:09And this will result in intolerance to people with diseases.
0:28:09 > 0:28:11And further into the future,
0:28:11 > 0:28:15the same technology could be used to select out embryos,
0:28:15 > 0:28:18or to select for embryos with certain genetic traits
0:28:18 > 0:28:21that may predispose them to higher intelligence,
0:28:21 > 0:28:24or less prone to addiction, or more prone to addiction,
0:28:24 > 0:28:27various personality types, physical abilities as well.
0:28:27 > 0:28:33So it opens the door to the selection or the creation of designer children.
0:28:33 > 0:28:36Children who have certain valued genetic properties.
0:28:36 > 0:28:40So whether genetic technology causes social harms
0:28:40 > 0:28:43is really up to us and how we choose to deploy it.
0:28:48 > 0:28:49Good morning, Mrs Picking.
0:28:49 > 0:28:53We're going to do some measurements and photos on your eye today.
0:28:53 > 0:28:57Specialist eye surgeons at the world famous Moorfields Eye Hospital in London,
0:28:57 > 0:29:02use some of the most technically advanced equipment to help their patients maintain their sight.
0:29:02 > 0:29:04Look down.
0:29:04 > 0:29:08OK sir, if you come forward. Pop your chin there, on the rest.
0:29:08 > 0:29:12This OCT scanner can see the retina at the very back of the eye and analyse it's health.
0:29:12 > 0:29:14Eyes wide open.
0:29:14 > 0:29:17The scanner can show structures as small as ten microns.
0:29:18 > 0:29:23It gives the surgeon a cross section view of the retina and the blood vessels underneath it.
0:29:24 > 0:29:28These images are often used for the early detection of a detached retina.
0:29:28 > 0:29:31OK, so I'm just gonna do the same on the other eye.
0:29:31 > 0:29:36The retina can become detached from its underlying layer - the choroids,
0:29:36 > 0:29:41which contains the many blood vessels that provide the retina with its nourishment.
0:29:41 > 0:29:45When this happens, vision in the affected region is lost.
0:29:45 > 0:29:49A detached retina is a serious condition that can lead to blindness
0:29:49 > 0:29:53if it's not diagnosed and treated quickly.
0:29:53 > 0:29:59This patient's retina has started to detach. But he's lucky. It can be fixed.
0:30:00 > 0:30:04The retina is the innermost layer at the back of the eye.
0:30:04 > 0:30:08It performs much the same function as the sensor chip in a digital camera.
0:30:08 > 0:30:13It is made of two types of light-sensitive cells - rods and cones.
0:30:14 > 0:30:17Rods work in dim light and cones detect colour.
0:30:19 > 0:30:22These cells send electrical impulses to the brain,
0:30:22 > 0:30:24which interprets them as a picture.
0:30:24 > 0:30:27I'm using a slit lamp to examine Tony's eye.
0:30:27 > 0:30:29A slit lamp is a high-powered microscope
0:30:29 > 0:30:31that allows us to see the eye up close,
0:30:31 > 0:30:33as in this picture on the TV screen here.
0:30:33 > 0:30:39And the first thing that we see when we look into the eye is the cornea.
0:30:39 > 0:30:43This is a clear window that allows light to get inside the eye.
0:30:43 > 0:30:46It does more than that though. It focuses most of the light.
0:30:46 > 0:30:49And most of the focusing power of the eye comes from the cornea.
0:30:51 > 0:30:54When light enters your eye, it must be focused on the retina.
0:30:54 > 0:30:57If it is not then what you see will be blurred.
0:30:59 > 0:31:02To focus, the light rays must be refracted,
0:31:02 > 0:31:04so that they meet at a single point.
0:31:05 > 0:31:07Most of the focusing is done by the curved cornea.
0:31:09 > 0:31:12When we move into the anterior chamber,
0:31:12 > 0:31:15which is the space between the cornea and the pupil,
0:31:15 > 0:31:17we can see the iris.
0:31:17 > 0:31:22The iris dilates in the dark.
0:31:22 > 0:31:25When I turn on the light, the iris muscles constrict
0:31:25 > 0:31:28and the pupil becomes small.
0:31:28 > 0:31:30When I turn the light off,
0:31:30 > 0:31:32the pupil gets bigger again.
0:31:32 > 0:31:35The iris is made from two different types of muscle.
0:31:37 > 0:31:42Circular and radial. In dim light the radial muscles contract.
0:31:42 > 0:31:45In bright light, the circular muscles contract.
0:31:45 > 0:31:50Where we look in very close, through the pupil,
0:31:50 > 0:31:54we can see the front surface of the lens.
0:31:55 > 0:32:00The lens of the eye is another clear tissue that allows light
0:32:00 > 0:32:02through to the retina behind.
0:32:03 > 0:32:08The lens can change its shape, so you can see far and near objects.
0:32:08 > 0:32:10This is called accommodation.
0:32:13 > 0:32:16To focus on distant objects, the lens becomes thin.
0:32:20 > 0:32:23To see close objects, the lens becomes more convex.
0:32:26 > 0:32:28Here at the very back of the eye,
0:32:28 > 0:32:32we see where the optic nerve enters the eye.
0:32:32 > 0:32:36The optic nerve carries all of the electrical information,
0:32:36 > 0:32:40from all of the rods and cones in the retina,
0:32:40 > 0:32:41back to the brain,
0:32:41 > 0:32:47where the information is translated into the things that we see.
0:32:53 > 0:32:57These eyes are the products of natural selection,
0:32:57 > 0:33:00a process whereby genetic variations in things
0:33:00 > 0:33:06like size, shape and colour that give individuals the best chance to survive and reproduce,
0:33:06 > 0:33:10are passed on to subsequent generations.
0:33:10 > 0:33:14All of these eyes have evolved to work best for the animals that use them.
0:33:18 > 0:33:20The eye is one of nature's marvels.
0:33:20 > 0:33:24But the first living organisms didn't have eyes at all.
0:33:24 > 0:33:27So how did something so complex evolve?
0:33:29 > 0:33:32Darwin himself said that it made him shudder to think
0:33:32 > 0:33:36of how something so complicated could have happened by natural selection.
0:33:36 > 0:33:38But it's actually quite easy.
0:33:38 > 0:33:41We're going to look at just one way it could have happened.
0:33:41 > 0:33:46The simplest eye that you can imagine, is a patch of light-sensitive cells.
0:33:46 > 0:33:47And in fact,
0:33:47 > 0:33:51many animals like flatworms still have eyes like this today.
0:33:51 > 0:33:55Here we have a model of such an eye. These are the light-sensitive cells.
0:33:56 > 0:34:01Now, this can be useful in order to tell an animal whether or not it's day or night, for instance.
0:34:01 > 0:34:06But it has a drawback. As I move the light around,
0:34:06 > 0:34:11it cannot tell where the light is coming from.
0:34:11 > 0:34:14As an eye, it's really rather limited.
0:34:14 > 0:34:18But we should remember that biological surfaces are often quite flexible,
0:34:18 > 0:34:24and so, if some of the offspring of these animals could have had slight indentations.
0:34:24 > 0:34:27And when you get an indentation,
0:34:27 > 0:34:32then you can start to get a shadow around the rim,
0:34:32 > 0:34:37which can tell you where the light is coming from.
0:34:37 > 0:34:41And that brings us to the next stage.
0:34:41 > 0:34:45So, now our patch of light-sensitive cells is lining
0:34:45 > 0:34:48the edge of this shallow bowl
0:34:48 > 0:34:51on the surface of an organism. It works pretty well, like before,
0:34:51 > 0:34:56but when I start moving the light, you can see a shadow appearing,
0:34:56 > 0:34:59and where the shadow is depends on where the light is.
0:35:00 > 0:35:04As a result, while this is still not very good, it's not a great eye,
0:35:04 > 0:35:06it's a lot better than the one before.
0:35:06 > 0:35:10This, for instance, can tell us maybe where a predator's coming from.
0:35:10 > 0:35:14And the thing about this kind of eye is that the deeper it gets,
0:35:14 > 0:35:16the better the effect.
0:35:16 > 0:35:21And so the most obvious thing to do now, is to start bringing the surface in again,
0:35:21 > 0:35:24to make a sort of sphere inside the organism.
0:35:24 > 0:35:27And the more that happens, the better it gets.
0:35:27 > 0:35:32So, now all of our light-sensitive cells are underneath the surface.
0:35:32 > 0:35:35They're reached by this small hole.
0:35:35 > 0:35:37It's almost completely closed up again.
0:35:37 > 0:35:42In order to show you what this does to our ability to tell where light's coming from,
0:35:42 > 0:35:44we're going to have to take the camera underneath the table.
0:35:44 > 0:35:46Now, as you can see,
0:35:46 > 0:35:50where I'm shining the light is very, very clear.
0:35:50 > 0:35:54It's very precise at telling us exactly where the torch is coming from.
0:35:54 > 0:35:56And when you have a system like this,
0:35:56 > 0:36:01where there's a cavity which is reached through a small hole through which you shine light
0:36:01 > 0:36:04and something really amazing happens.
0:36:04 > 0:36:08We are here at the Royal Observatory in Greenwich,
0:36:08 > 0:36:10and this is a camera obscura.
0:36:10 > 0:36:13It's a massive pinhole camera.
0:36:13 > 0:36:16Up above me, in the roof,
0:36:16 > 0:36:21light is being shone through a small hole, up there, reflected from the outside
0:36:21 > 0:36:24down onto a white table in front of me.
0:36:24 > 0:36:28This white table is just like the patch of light-sensitive cells
0:36:28 > 0:36:30we were looking at earlier.
0:36:30 > 0:36:31Now, if you look at the table,
0:36:31 > 0:36:34you can see objects, like, there's the Queen's house.
0:36:34 > 0:36:37And there's the Royal Naval College.
0:36:37 > 0:36:41And you can even see things moving, like people or cars.
0:36:41 > 0:36:49And remember, all of this is just with a mirror and a hole in the roof.
0:36:49 > 0:36:52It's as if we're standing in the middle of a huge eye.
0:36:53 > 0:36:56Eyes like this can still be found in the nautilus.
0:36:58 > 0:37:02This animal has the most well-developed pinhole camera eye in the natural world,
0:37:02 > 0:37:04and it's never had to change it,
0:37:04 > 0:37:08because this basic eye gives it all the information it needs.
0:37:08 > 0:37:13It hasn't changed because it's got the best eye for the job.
0:37:13 > 0:37:15This is really impressive.
0:37:15 > 0:37:20Just a hole in the roof has managed to give us an image of the world outside.
0:37:20 > 0:37:25But it is a faint image. How can we make it better?
0:37:25 > 0:37:27A lens is the obvious answer.
0:37:27 > 0:37:29But how could a lens evolve?
0:37:29 > 0:37:30We have to remember
0:37:30 > 0:37:34that this kind of eye is open to the outside world.
0:37:34 > 0:37:36And so a plug of mucus could be formed
0:37:36 > 0:37:38in order to protect the interior,
0:37:38 > 0:37:41And that plug of mucus, in time, could be selected
0:37:41 > 0:37:46to become clearer and thicker and much more like the lens
0:37:46 > 0:37:48that we know today.
0:37:55 > 0:37:58This is London's Ministry Of Sound.
0:37:58 > 0:38:02And DJ Anna Kiss is combining new technology with old.
0:38:03 > 0:38:08She's mixing CDs, which are digital recordings, with vinyl records that are analogue.
0:38:09 > 0:38:16We can't see sound waves but when a microphone records sound, it generates a changing voltage signal
0:38:16 > 0:38:18that can be seen on an oscilloscope.
0:38:19 > 0:38:22The wave changes continuously and is called an analogue signal.
0:38:25 > 0:38:29This machine etches a version of the original recording onto a master disc.
0:38:29 > 0:38:34The groove is a continuous copy of the analogue sound wave.
0:38:36 > 0:38:39And these machines press that groove into vinyl records.
0:38:42 > 0:38:47Stereo groove is split into two parts. Left and right.
0:38:48 > 0:38:53When the stylus vibrates in the groove, it generates an electrical signal in a record player
0:38:53 > 0:38:56which recreates the original sound wave.
0:38:56 > 0:39:03We've got the high frequency, can be seen as this very sharp line either side.
0:39:03 > 0:39:05And we've got left and the right-hand side
0:39:05 > 0:39:10of the groove, which is left and right of your stereo music.
0:39:10 > 0:39:16And then, as the disc turns round, the very low wobble is the bass,
0:39:16 > 0:39:20which causes the needle to vibrate at a much lower frequency.
0:39:20 > 0:39:24But vinyl is fragile and easily scratched.
0:39:24 > 0:39:28This is a vinyl record magnified many times.
0:39:29 > 0:39:33The scratch has cut into the groove and has made the record unplayable.
0:39:38 > 0:39:39CDs are more durable
0:39:39 > 0:39:43because they store a digital version of the original sound wave.
0:39:43 > 0:39:48This digital code is created by taking samples of the analogue wave.
0:39:51 > 0:39:53The values of the voltage at these points
0:39:53 > 0:39:55are converted into a binary number,
0:39:55 > 0:39:58which is made of only zeros and ones.
0:40:00 > 0:40:08On a CD this binary code is stored as millions of tiny bumps, arranged in a spiral track.
0:40:08 > 0:40:13As the CD rotates, laser light is reflected from the bumps.
0:40:14 > 0:40:19These reflected pulses are turned into "on" or "off" electrical signals...
0:40:21 > 0:40:25..which are then decoded by the CD player to produce sound.
0:40:27 > 0:40:31Digital technology has transformed the way we store and retrieve music.
0:40:31 > 0:40:38The digital revolution's changed the way I DJ. It's so much easier and quicker to buy music now.
0:40:38 > 0:40:40I haven't bought a record
0:40:40 > 0:40:42for about a year, but I still play the older stuff.
0:40:42 > 0:40:44I brought a few tonight to play.
0:40:44 > 0:40:47Playing with vinyl, there's a real tactile thing about it.
0:40:47 > 0:40:50People love the feel of it, the sound of it's good,
0:40:50 > 0:40:52but at the end of the day you've gotta move with the times,
0:40:52 > 0:40:55and that's...that's what a good DJ should do.
0:40:59 > 0:41:04This grey research facility, outside Oxford, might look dull from the outside,
0:41:04 > 0:41:07but it holds an incredible secret.
0:41:08 > 0:41:12Within these walls lies the hottest place in the solar system.
0:41:17 > 0:41:19The temperature at the centre of the sun
0:41:19 > 0:41:21is 15 million degrees centigrade.
0:41:25 > 0:41:29Scientists here have created their own tiny star,
0:41:29 > 0:41:30that is 10 times hotter.
0:41:32 > 0:41:36Their goal is to produce a cheap, safe form of energy
0:41:36 > 0:41:39that emits no harmful gases or dangerous waste.
0:41:44 > 0:41:48The sun releases energy through a reaction called nuclear fusion.
0:41:48 > 0:41:51The sun is not a solid, liquid or a gas,
0:41:51 > 0:41:54but a fourth state of matter, known as plasma.
0:41:56 > 0:42:01The sun's temperature is so high that electrons cannot stay attached to nuclei.
0:42:02 > 0:42:04It means atoms cannot exist here.
0:42:04 > 0:42:09Instead, the sun consists of electrons, protons and neutrons,
0:42:09 > 0:42:12moving around at incredible speed in a plasma.
0:42:12 > 0:42:16Normally, protons repel each other because they have the same positive charge.
0:42:16 > 0:42:18However, in a plasma,
0:42:18 > 0:42:23hydrogen nuclei or protons are able to overcome their mutual repulsion
0:42:23 > 0:42:24and combine.
0:42:24 > 0:42:27In other words, they fuse,
0:42:27 > 0:42:33and as they fuse they create helium nuclei and release huge amounts of energy.
0:42:33 > 0:42:39The continuous production of energy helps more protons to fuse and keeps the sun shining.
0:42:39 > 0:42:41If we could harness the power of fusion on Earth,
0:42:41 > 0:42:44we could generate huge amounts of energy.
0:42:44 > 0:42:49But to do this we need to recreate the conditions of the sun in a lab.
0:42:59 > 0:43:02JET, at the moment, is the largest fusion reactor in the world.
0:43:02 > 0:43:08But JET is an experimental reactor. We don't produce net energy in JET.
0:43:08 > 0:43:10But they have proved that fusion power can work.
0:43:13 > 0:43:17One of the big technical challenges for the scientist
0:43:17 > 0:43:21is working with temperatures hotter than the sun.
0:43:21 > 0:43:25How do you heat plasma up to a temperature of 150 million degrees?
0:43:25 > 0:43:28Well, the answer is simple. In an oven.
0:43:28 > 0:43:29In fact, it's a microwave oven.
0:43:29 > 0:43:35So you stick your gas into a microwave oven, you switch on your microwave and it heats up.
0:43:35 > 0:43:38After a while you reach temperatures of a few thousand degrees.
0:43:38 > 0:43:42But you will never reach 150 million degrees. Why not?
0:43:42 > 0:43:47Because the particles hit the wall and they will cool down.
0:43:47 > 0:43:51Now you can actually contain charged particles in the magnetic field.
0:43:51 > 0:43:54So if in our oven, we switch on the magnetic field,
0:43:54 > 0:43:58then these particles will actually be contained by the magnetic field.
0:43:58 > 0:44:00That way you can keep them away from the wall.
0:44:02 > 0:44:05Because it's so hot inside the reactor,
0:44:05 > 0:44:09maintenance is carried out by skilled remote handlers.
0:44:09 > 0:44:14Although it looks like a computer game, these engineers have to train for three years
0:44:14 > 0:44:17to be able to control the robotic arms that operate inside the core.
0:44:19 > 0:44:20Despite the intense heat,
0:44:20 > 0:44:26scientists believe that fusion power is far less dangerous than the traditional form
0:44:26 > 0:44:29of nuclear power - nuclear fission.
0:44:29 > 0:44:32It's very safe and if anything goes wrong,
0:44:32 > 0:44:34then the plasma will cool down
0:44:34 > 0:44:37and the fusion reaction can't take place anymore.
0:44:37 > 0:44:40So you will never have the possibility of a chain reaction.
0:44:40 > 0:44:43It can never run out of hand. If anything goes wrong it immediately stops.
0:44:51 > 0:44:55Nuclear power, created through a process called nuclear fission,
0:44:55 > 0:44:58plays an important role in supplying our energy needs.
0:44:59 > 0:45:04This is a nuclear power station. There are more than 400 of them around the world.
0:45:04 > 0:45:09And together they produce about 17% of the global electricity supply.
0:45:14 > 0:45:18Underneath this floor, a nuclear reaction is taking place.
0:45:18 > 0:45:24This reaction is very powerful and potentially dangerous, which is why it has to be safely enclosed
0:45:24 > 0:45:26beneath several metres of concrete.
0:45:26 > 0:45:29This is what's in the heart of the nuclear reactor.
0:45:29 > 0:45:31It's what we call a fuel element
0:45:31 > 0:45:35and inside each one of these elements there's 36 fuel pins.
0:45:35 > 0:45:39And inside each one of those pins is over 60 of these uranium oxide pellets.
0:45:39 > 0:45:44And inside those pellets is where the fission is taking place, generating the heat.
0:45:44 > 0:45:48Each one of these elements is part of a stack of seven fuel elements,
0:45:48 > 0:45:50which is what we call a stringer.
0:45:50 > 0:45:52And there's 408 of those stringers
0:45:52 > 0:45:55in each one of the reactor cores at Dungeness B.
0:45:56 > 0:46:00As we've seen, the core of a nuclear reactor contains lots of fuel rods.
0:46:00 > 0:46:05Inside the rods are thousands of pellets, made of uranium.
0:46:05 > 0:46:07Uranium atoms have a special property.
0:46:07 > 0:46:11They can be made to split by firing neutrons at them.
0:46:14 > 0:46:18When a uranium atom absorbs a neutron, it splits up, releasing more neutrons
0:46:18 > 0:46:20and a huge amount of energy.
0:46:20 > 0:46:22This is known as nuclear fission.
0:46:22 > 0:46:28The neutrons released by the split atom, go on to release more neutrons and more energy.
0:46:28 > 0:46:30This is known as a nuclear chain reaction
0:46:30 > 0:46:33and could be dangerous if not controlled.
0:46:33 > 0:46:36The energy released from the nuclear fission
0:46:36 > 0:46:38makes the fuel rods very hot.
0:46:38 > 0:46:42The amount of heat released by the uranium pellets can be controlled
0:46:42 > 0:46:45by boron control rods in the reactor.
0:46:45 > 0:46:49They absorb the neutrons released when the uranium atoms split.
0:46:49 > 0:46:52Lowering the control rods into the fuel can slow down
0:46:52 > 0:46:55or even stop the nuclear chain reaction.
0:46:57 > 0:47:00The heat from the fuel rods is used to turn water into steam...
0:47:01 > 0:47:03..which is then used to drive turbines
0:47:03 > 0:47:07which generate electricity, just like any other power plant.
0:47:07 > 0:47:11People have concerns about nuclear power stations for two reasons.
0:47:11 > 0:47:17Firstly, if the reaction is not managed properly, it could get out of control
0:47:17 > 0:47:20with potentially catastrophic consequences.
0:47:20 > 0:47:26The poor design and management of the Chernobyl nuclear power station caused a steam explosion and fire
0:47:26 > 0:47:30that released massive amounts of radiation into the atmosphere,
0:47:30 > 0:47:35resulting in the evacuation and resettlement of over 336,000 people.
0:47:37 > 0:47:43Secondly, the waste products from nuclear fission are radioactive and can remain dangerous for hundreds,
0:47:43 > 0:47:47and in some cases, thousands of years.
0:47:49 > 0:47:54Nuclear waste is divided into low, medium and high-level waste,
0:47:54 > 0:47:56depending on the amount of radioactivity it produces.
0:48:00 > 0:48:04There are low levels of radioactivity in everything around us.
0:48:04 > 0:48:09Atoms are radioactive when their nuclei are unstable.
0:48:09 > 0:48:12In order to become stable they need to lose energy.
0:48:13 > 0:48:15They do this by emitting radiation
0:48:15 > 0:48:18in the form of alpha, beta or gamma radiations.
0:48:20 > 0:48:25Nuclear radiation can be dangerous because it can damage the DNA in our cells.
0:48:25 > 0:48:29Depending on the type and amount of radiation our cells are exposed to,
0:48:29 > 0:48:33this can lead to health problems, ranging from nausea to cancer.
0:48:37 > 0:48:41This is why great care is taken in storing nuclear waste
0:48:41 > 0:48:44and making sure none of it reaches our environment.
0:48:45 > 0:48:49Radioactive waste remains lethal for hundreds of thousands of years.
0:48:49 > 0:48:52And we have no idea what we're gonna do to deal with it.
0:48:52 > 0:48:54At the moment it's stored onsite.
0:48:54 > 0:48:58It's cooled, and costs the taxpayer billions of pounds to sort out.
0:48:58 > 0:49:01In the long term we have no idea what we're gonna do with it.
0:49:01 > 0:49:06People can say, we'll bury it under ground. There's nowhere in the world anyone's ever managed to do this.
0:49:06 > 0:49:09So, we're hoping someone might have a brainwave sometime in the future!
0:49:09 > 0:49:12There are things that physicists
0:49:12 > 0:49:13are working on at the moment.
0:49:13 > 0:49:16There are ways of firing protons
0:49:16 > 0:49:21into nuclear waste, basically, and making it safe almost immediately.
0:49:21 > 0:49:25And that will come in the future. It's not there right now.
0:49:25 > 0:49:28But people are working on these things.
0:49:28 > 0:49:35As a waste product, nuclear reactors make plutonium, the prime ingredient for making nuclear weapons.
0:49:35 > 0:49:38In this age of heightened terrorism and security risks,
0:49:38 > 0:49:42the last thing we should do is spreading this material round the world.
0:49:42 > 0:49:46This is the reason why things like Sellafield, in the UK,
0:49:46 > 0:49:47should not be shut down.
0:49:47 > 0:49:52Because we deal with nuclear waste, and we deal with it responsibly,
0:49:52 > 0:49:56and there's only a...a small handful of reprocessing plants in the world,
0:49:56 > 0:49:59and the UK has two of them, actually.
0:50:04 > 0:50:06What does this...
0:50:11 > 0:50:13..and this...
0:50:16 > 0:50:18..have in common with this?
0:50:21 > 0:50:22They're all feeding.
0:50:25 > 0:50:28Plants feed using a process called photosynthesis.
0:50:33 > 0:50:38Photosynthesis is the chemical reaction through which plants make glucose.
0:50:38 > 0:50:40It also produces oxygen.
0:50:41 > 0:50:46It is crucial to all life on Earth because it is the source of nearly all the food and oxygen
0:50:46 > 0:50:47we need to stay alive.
0:50:48 > 0:50:52But what do plants need to photosynthesise?
0:50:52 > 0:50:54First, they need water.
0:50:54 > 0:50:58Water is as essential to plant life as it is to us.
0:50:59 > 0:51:02It is one of the reactants in the photosynthetic reaction.
0:51:10 > 0:51:13Plants which have little access to water go to great lengths
0:51:13 > 0:51:15to conserve the water they collect.
0:51:17 > 0:51:23These desert plants survive by maximising the amount of water they get from their harsh conditions.
0:51:27 > 0:51:30The other reactant needed for photosynthesis is carbon dioxide.
0:51:33 > 0:51:35Most plants collect this from the air.
0:51:36 > 0:51:41To do this they have tiny holes in their leaves, called stomata.
0:51:42 > 0:51:44As well as water and carbon dioxide,
0:51:44 > 0:51:48plants need one other thing for photosynthesis - light.
0:51:50 > 0:51:53This provides the energy for the chemical reaction to take place.
0:51:55 > 0:51:59Photosynthesis takes place in the chloroplasts in plant cells.
0:51:59 > 0:52:04Chloroplasts contain a green substance called chlorophyll,
0:52:04 > 0:52:08which absorbs the light energy needed to make photosynthesis happen.
0:52:10 > 0:52:16To summarise, photosynthesis takes the raw ingredients of water and carbon dioxide
0:52:16 > 0:52:20and uses light energy to make glucose and oxygen.
0:52:23 > 0:52:30This pondweed is called cabomba. Because it lives in water, we can see it releasing bubbles of oxygen
0:52:30 > 0:52:32as it photosynthesises.
0:52:40 > 0:52:43When we vary the amount of light the plant receives,
0:52:43 > 0:52:45we can see it affects the rate of photosynthesis.
0:52:50 > 0:52:55This one has full light and we can see it bubbling vigorously.
0:53:02 > 0:53:06This one has been shielded from the light and the photosynthesis has stopped.
0:53:20 > 0:53:23Our skin is constantly regenerating.
0:53:25 > 0:53:28Millions of skin cells die every day.
0:53:28 > 0:53:32But they are replaced by a process called cell division.
0:53:34 > 0:53:40Mitosis is one form of cell division and it's taking place in your body, thousands of times, every second.
0:53:45 > 0:53:49Before a cell divides, it makes a copy of every chromosome's DNA.
0:53:55 > 0:54:00The nuclear membrane dissolves and the chromosomes line up in the centre of the cell.
0:54:01 > 0:54:05The chromosomes are then separated to opposite sides of the cell.
0:54:07 > 0:54:11New nuclear membranes from around the chromosomes
0:54:11 > 0:54:13and the cell begins to divide.
0:54:16 > 0:54:22The two cells that result are genetically identical and so can replace others that have died.
0:54:27 > 0:54:33The only place in the body where mitosis isn't used to make new cells is the production of sex cells.
0:54:33 > 0:54:35This process is called meiosis.
0:54:37 > 0:54:39Meiosis starts with a normal cell, just like mitosis.
0:54:39 > 0:54:45But immediately before a cell divides, the DNA of every chromosome is copied,
0:54:45 > 0:54:49leaving the cell with twice its usual number of chromosomes.
0:54:51 > 0:54:54In meiosis, two chromosomes mix up their genes.
0:54:54 > 0:54:57They do this by a process called recombination.
0:54:59 > 0:55:01The cell then divides.
0:55:07 > 0:55:10The chromosomes line up in the centre and spindles attach.
0:55:10 > 0:55:14As they are pulled apart, the cell starts to divide.
0:55:16 > 0:55:23The resultant four cells, known as haploid, have only half the normal genetic material.
0:55:24 > 0:55:26This is important, as if they are successful,
0:55:26 > 0:55:28they will meet a gamete cell,
0:55:28 > 0:55:31which is an egg or a sperm,
0:55:31 > 0:55:36and combine to produce a unique diploid cell, which is an embryo.
0:55:42 > 0:55:44VOICE CRACKLES OVER RADIO
0:55:44 > 0:55:51On July 20th, 1969, humans landed on the moon for the first time.
0:55:51 > 0:55:54This huge leap for mankind was made possible by the work of a scientist
0:55:54 > 0:55:57who lived more than 300 years earlier.
0:55:58 > 0:56:03Isaac Newton revolutionised our understanding of the world.
0:56:06 > 0:56:08His work on how things move is at the heart of everything,
0:56:08 > 0:56:10from spaceship design...
0:56:11 > 0:56:13..to car safety.
0:56:14 > 0:56:21We can illustrate the principles of Newton's laws of motion, using a rocket-powered sled on an ice rink.
0:56:21 > 0:56:25Of course, these conditions are not perfect, because on Earth
0:56:25 > 0:56:28we can never create a completely frictionless environment.
0:56:28 > 0:56:32But it should give you an idea of what the laws mean.
0:56:35 > 0:56:38Newton's first law states that if something is stationary,
0:56:38 > 0:56:42it won't start moving unless something pushes it or pulls it.
0:56:45 > 0:56:49It also says that if something is already moving, it will keep moving in the same way
0:56:49 > 0:56:51unless another force acts on it.
0:56:52 > 0:56:56If this ice was frictionless and there was nothing in the way,
0:56:56 > 0:56:58the rocket would slide forever.
0:57:00 > 0:57:03These rockets have three different strength engines.
0:57:03 > 0:57:05Although they all start from the same place,
0:57:05 > 0:57:07they demonstrate Newton's second law,
0:57:07 > 0:57:11which says that the acceleration of an object
0:57:11 > 0:57:14is proportional to the force acting on it.
0:57:16 > 0:57:18It also says that the more mass an object has,
0:57:18 > 0:57:21the less it will accelerate for a given force.
0:57:49 > 0:57:53The force an object experiences depends on how quickly its momentum changes.
0:57:59 > 0:58:01So if something comes to a sudden stop,
0:58:01 > 0:58:05it experiences a greater force than if it comes to rest gently.
0:58:10 > 0:58:16Newton's third law tells us that forces are always produced in equal but opposite pairs.
0:58:16 > 0:58:23It is often simplified to - for every action, there is an equal and opposite reaction.
0:58:24 > 0:58:29In this demonstration of Newton's third law, we've fixed a canon to the sledge.
0:58:29 > 0:58:35When the canon fires the ball, the ball pushes back on the canon with an equal force.
0:58:39 > 0:58:42Subtitles by Emma Johnston, Red Bee Media Ltd
0:58:42 > 0:58:45E-mail subtitling@bbc.co.uk