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Solar-powered lamp and charger, made in Shenzhen, Guangdong, China, 2010

This series has been, for me, an exhilarating journey through two million years of human endeavour, passion and ingenuity. We began in East Africa with a chopping tool - a roughly shaped stone that allowed us to take control of our environment and to change both the way we live and the way we think. And I want to finish with another tool, or more precisely with a bit of technology that's also transforming the way we can live and think - in East Africa where our story began, but also in South Asia and in many other parts of the world. It's a portable solar energy panel that powers a lamp. In fact it's sunshine, captured, harvested and stored, to be taken out and used whenever and wherever we need it.

"Now I can do my lessons till midnight because of solar light. Previously I have [had] to spend lots of time in the ration shop to collect kerosene oil for use [in] lamps at night for my studies. Now I can save my time and money too." (Aloka Sarder)

"Solar energy is at the heart of the new industrial revolution, the low-carbon industrial revolution which is just beginning. It's a revolution which will be enormously important in the history of mankind." (Nick Stern)

Our hundredth object gives to people all over the world - who have until now been off-grid, that is, without access to any mains electricity supply - a quite new level of control over their environment. Solar power, thanks to low-cost lighting, and power kits like the one I've chosen, is changing lives in many parts of the world. And it may yet - who knows? - play a key role in solving the world's energy problems.

I'm standing on the roof of ´óÏó´«Ã½ Broadcasting House, and I've got the solar panel and lamp with me - the latest addition to the collection of the British Museum. The lamp is made of plastic, it's got a handle, and it's about the size of a large coffee mug. The solar panel looks like a small silver photograph frame. When this solar panel is exposed to eight hours of bright sun - and today we're lucky, even in London the sun is bright - then the lamp can provide up to one hundred hours of even, white light. At its strongest it can illuminate an entire room - enough to allow a family with no electricity to live in a quite new way - and, once paid for, it depends only on sun.

Photovoltaic panels contain rows of solar cells made from silicon, wired together and then encased in plastic and glass. When exposed to sunlight, the cells generate electricity, which can charge and re-charge a battery. It's largely made of durable plastic, its rechargeable batteries are a recent invention, and its photovoltaic cell depends on the silicon-chip technology which lies behind personal computers and mobile phones. And all this supra-national new technology can now be harnessed, thanks to the energy source that's been with us since the world began. It comes from 93 million miles away . . . it's the sun. Here's Professor Nick Stern of the London School of Economics, known for his work on climate change:

"One of the great advantages of solar energy is that as far as we humans are concerned, it's almost limitless. Why? Because in one hour we get as much energy from the sun on the earth as we use right across the planet in one year. So for us it's virtually unlimited. And further, the cost of accessing that limitless supply of energy is really crashing down. Just in the last couple of years the cost of a solar panel has fallen by about a half."

Although silicon is cheap and sunshine is free, solar panels big enough to generate the gargantuan amounts of electricity that rich countries devour are still prohibitively expensive. The poor are more modest in their demands and so, paradoxically, this technology which is costly for the rich is cheap for the poor. Many of the world's poorest people live in the sunniest latitudes, which is why this new source of modest amounts of energy works so well in South Asia, sub-Saharan Africa and tropical America. There, in a poor household, a small number of volts can make a very big difference.

If you live in the tropics without electricity, your day ends early. Light at night is supplied by candles or by kerosene lamps. Candles are dim and don't last. Kerosene is expensive and gives off toxic fumes. Kerosene lanterns and cooking stoves cause an estimated two million deaths every year, most of them women, because the fumes are especially dangerous in enclosed spaces where most cooking is done, affecting lungs, heart and eyes. Then there is the fire risk. Homes made of wood or other natural materials are highly inflammable, at constant risk from candle flames and kerosene spills.

Photovoltaic solar panels change almost every aspect of this rural domestic existence. Lighting on tap at home means that children, and adults, can study at night, improving their education and therefore their futures. Homes become cleaner and safer, and they become cheaper. Micro-credit schemes allow payments for a solar lamp like this to be spread, so although the initial cost is high, the debt can be paid off quite quickly out of the considerable savings on kerosene - and once the debt is paid, your light is free. Here is Aloka Sarder, mother and adult student from Dayapur village in rural West Bengal, who is using one of the simple lamp kits in her home:

"For last one year I am using the solar lights. It's very useful . . . [more] than the kerosene lamps. Now I can work at night, my children can do their lessons at night. And you know we are living in the storm-prone area. If there is storm, then kerosene lamps . . . not work. In that way solar light works as electric lights for us, and I am happy."

Larger panels can provide power for cookers, fridges, televisions, computers and water pumps, so that many of the defining amenities of towns can now be available to villages. But there's more. Both towns and villages can be set free by solar power, even when there is a mains electricity supply. Here's Nick Stern again:

"One of the great things about solar power is freedom from the grid. In many parts of the world, particularly the developing world and particularly South Asia and Africa, it is extremely unreliable. Also the energy is unreliable from the point of view of interventions by corrupt people. It's all too easy to flick a switch and turn off your energy supply, and then demand payment to put it back on. With solar power you can organise it yourself, you are in control. So it's really empowering, relative to relying on the grid system."

So it's not surprising that in Africa and Asia, on or off grid, the demand for solar panels is enormous - they give independence. Here is Boniface Nyamu, a teacher from a girls' school in Kibera, Kenya - one of the densest urban areas in Africa - where they have been taught how to make solar panels and lamps that they then sell or hire out. It's helping to bring in extra pupils at the school, as well as giving light to the community:

"We were taught how just to make it light. But the students discovered that they can also connect wires, so that it can also charge a mobile phone, an mp3, mp4, and maybe the camera. This panel works in two ways. One, it provides light, that is a torch - it can be used as a torch. And at the same time - during daytime when we don't need light - it can be used to charge mobile phones, and any other rechargeable thing that falls below five volts."

On our lamp there is a charging socket, and beside it is a universally recognised symbol - a mobile phone. Our solar panel could give the 1.6 billion people without access to an electrical grid the power they need to join the global mobile conversation. Putting communities in touch, giving access to information about jobs and markets, and providing the basis for informal and highly effective banking networks, so that local businesses can start up on a shoe-string. A recent study of mobile phone use among the rural poor, commissioned by the World Bank, reported that labourers, farmers, rickshaw drivers, fishermen and shopkeepers - all said that their income gets a real boost when they have access to a mobile phone. As Nick Stern confirms, women especially benefit:

"They can have their own solar panel, and charge people to use it, either for a lamp or a mobile phone. They can do it mostly from their own house. They will need to borrow a bit to buy it, but on the whole micro-finance to women is more reliable. Women seem to pay their bills, pay their credit, a bit more reliably than men. So it has that sense of opportunity and empowerment for women."

This liberating, low-cost, green, clean technology is not only transforming lives in Africa and Asia. It may ultimately help to save the planet, reducing our current dependence on fossil fuels and their contribution to climate change. It's a hope that was expressed years ago by an unexpected prophet of renewable energy: Thomas Edison. In 1931 Edison observed to his friends Henry Ford and Harvey Firestone:

"I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that."

The power of the sun seems a good place to end this global history, because solar energy is a dream of the future that echoes the oldest and most universal of human myths, that of the life-giving sun. You could see our solar-powered lamp as an echo of this myth - the heroic fire-stealing Prometheus reduced to the humble role of home help. Just as we bottle summer fruits so that the warmth and nourishment of summer can see us through winter, everybody has dreamed of harvesting the sun to have its light and power available at will. In the very first programme of this history, the Egyptian priest Hornedjitef took with him a scarab, magical symbol of the regenerative sun, to lighten the darkness of the afterlife. I think if he was setting out on that journey now, he would definitely take a solar-powered lamp as back-up.

This hundredth object brings me to the end of this particular history of the world. For me, the series has demonstrated the power of things to connect us to other lives across time and place, and to ensure that all humanity can have a voice in our common story. Above all, I hope it has shown that the notion of the human family is not an empty metaphor, however dysfunctional that family usually is - we all have the same needs and preoccupations, the same fears and hopes. Humanity is one.

It's good to be able to end this series on a note of hope. We began with the noise of a dying star. I want to finish with another cosmic noise from millions of miles away. It's the music created by vibrations in the sun's atmosphere . . . it's the noise of a new day.