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On 15 September 1830, the first commercial railway line was opened, connecting Liverpool with Manchester. The trains moved under the same steam power that had previously pumped water and moved textile looms. A mere twenty years later, Britain had tens of thousands of miles of railway tracks.1 Henceforth, people became obsessed with the idea that machines and engines could be used to convert one type of energy into another. Any type of energy, anywhere in the world, might be harnessed to whatever need we had, if we could just invent the right machine. For example, when physicists realised that an immense amount of energy is stored within atoms, they immediately started thinking about how this energy could be released and used to make electricity, power submarines and annihilate cities. Six hundred years passed between the moment Chinese alchemists discovered gunpowder and the moment Turkish cannon pulverised the walls of Constantinople. Only forty years passed between the moment Einstein determined that any kind of mass could be converted into energy – that’s what E = mc2 means – and the moment atom bombs obliterated Hiroshima and Nagasaki and nuclear power stations mushroomed all over the globe.
Sapiens
Yuval Noah Harari
The last 500 years have witnessed a phenomenal and unprecedented growth in human power. In the year 1500, there were about 500 million Homo sapiens in the entire world. Today, there are 7 billion.1 The total value of goods and services produced by humankind in the year 1500 is estimated at $250 billion, in today’s dollars.2 Nowadays the value of a year of human production is close to $60 trillion.3 In 1500, humanity consumed about 13 trillion calories of energy per day. Today, we consume 1,500 trillion calories a day.4 (Take a second look at those figures – human population has increased fourteen-fold, production 240-fold, and energy consumption 115-fold.)
Sapiens
Yuval Noah Harari
Even if you manage to calculate how many apples equal one pair of shoes, barter is not always possible. After all, a trade requires that each side want what the other has to offer. What happens if the shoemaker doesn’t like apples and, if at the moment in question, what he really wants is a divorce? True, the farmer could look for a lawyer who likes apples and set up a three-way deal. But what if the lawyer is full up on apples but really needs a haircut?
Sapiens
Yuval Noah Harari
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