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(a) Use of hydrogen fusion to supply energy is a dream that may be realized in the next century. Fusion would be a relatively clean and almost limitless supply of energy, as can be seen from Table 7.1. To illustrate this, calculate how many years the present energy needs of the world could be supplied by one millionth of the oceans’ hydrogen fusion energy. (b) How does this time compare with historically significant events, such as the duration of stable economic systems?
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Final Answer

a) 25 million years.

b) The earliest humans evolved ~3 million years ago. The energy supply would last much longer than human time scales.

Solution Video

OpenStax College Physics Solution, Chapter 7, Problem 29 (Problems & Exercises) (1:24)

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Video Transcript
This is College Physics Answers with Shaun Dychko. If one-millionth of the hydrogen in the world's oceans were converted into energy, we would have this much energy, converted energy by fusion by the way, so if all of the hydrogen was converted into fusion then -- in other words all the water which has a molecular formula H-2-O was turned into just hydrogen, and then that hydrogen was fused into helium, then the energy released would be ten to the thirty-four joules. One-millionth of that means divided by one times ten to the six. Then we have in one year the world's current energy consumption is four times ten to the twenty joules. So the way I've set it up here you can see the units work out to years and so we have 2.5 times ten to the seven years which is 25 million years of energy being provided with one-millionth of the world's hydrogen in the oceans being fused. Well, that's a long time. The earliest humans evolved about three million years ago so this timescale is much longer than human timescales.