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Where Does Energy Come From? (And Where Is It Going?)

Friday, April 8, 2011

Word is there’s a worldwide energy problem. Apparently, if we don’t change our ways, worst-case-scenario pundits talk about an ELE (for non-texters, that’s an Extinction-Level Event). Not a big deal considering that life on Earth has already survived several ELEs, but it would be a shame if humans were responsible for a preventable ELE.

In talk of potential solutions to such a crisis, it might help to step back and look at the big picture: To first understand what energy actually is, so we can talk more sensibly about where it comes from.

Energy insight in a coffee cup

Fortunately, Einstein helped a lot by discovering that E=mc2. What does this mean?  That energy and mass are equivalent. Consider a cup of coffee: It has more energy when it’s hot than when it’s cold. This means it has more mass. It weighs more, and is harder to move around. (In this example, the difference is so small it would be hard to measure. But nature doesn’t care about human practicalities; for nature, it’s a matter of principle.) As the coffee cools, energy flows into the surrounding air, warming it up, and causing it to have more mass. That was Einstein’s insight: any flow of energy is actually a flow of mass.

“Wait a minute…doesn’t E=mc2 mean just nuclear energy—reactors and bombs?” Not so. It applies to all forms of energy: solar, wind, hydroelectric, geothermal, fossil fuels, bio-fuels, nuclear fission and fusion, etc...It’s universal. It’s just that nuclear processes involve millions of times more energy than chemical processes (e.g., burning gasoline), making the mass differences big enough for humans to practically measure.

Eating sunlight (and nuclear energy all around us)

Here`s my favourite example: In the heart of the Sun, nuclear fusion converts mass into light (and other particles we’ll ignore), which, together with carbon dioxide, is absorbed by plants, forming sugars (in physics terms, certain molecules form that have extra energy, and hence extra mass). This extra mass comes from the Sun. The food energy in that apple you had for lunch is really a bit of the Sun’s mass. We are literally eating the Sun. We are that connected to the physical world! (As a physicist, this is one of my “happy thoughts.”) Thus we arrive at a little-appreciated but very cool fact: the bottom of the food chain is not phytoplankton in the oceans. It’s the Sun itself! Physics trumps biology! (OK, now I’m being petty.)

From this perspective, virtually all energy is nuclear. (One of the few exceptions I can think of is geothermal, which is partly nuclear and partly gravitational energy from way before the solar system was formed, but that’s another story...) Nuclear energy is the King. Either the Sun itself—a gigantic nuclear reactor nature has kindly provided, from which we get solar, wind, hydroelectric, fossil fuels, bio-fuels, etc. Or nuclear reactors humans build.

Getting a lift from a little star-power

Of these there are two types: fission (splitting large atomic nuclei) and fusion (fusing together smaller atomic nuclei). Today we have only fission reactors. They can have some nasty side effects, especially if things go wrong. 

But fusion reactors are different. One of the largest science and engineering projects in human history, ITER, is our latest attempt to build a fusion reactor. “The power of the stars!” Much cleaner and far safer than current fission reactors, and – depending on reactor design – with enough raw fuel in the oceans to outlast the planet many times over.

So what am I trying to say? Nuclear is a seven letter word, not four.


Written by: Richard Epp

Richard Epp has a Masters degree in electrical engineering and a PhD in theoretical physics from the University of Manitoba. He held postdoctoral research positions around the world working in general relativity before becoming Scientific Outreach Manager at Perimeter Institute for Theoretical Physics.