On the Orders of Magnitude of Energy (And why classical Wizards are idiots).

(Originally posted by me elsewhere, but I thought I’d repost it here for fellow fantasy writers and system wonks):

Let’s start with this all-important link: http://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)

You can reasonably safely skip down the chart until you get to about 10^-7 to 10^29 range, as this is more or less straining the limits of ordinary human capacity to visualize.

Specifically, let’s take a happy hop-and-skip to about the 10^-1 to 10^9 range, which is more or less our day-to-day energetic interactions.

As I read through this chart, what really struck me, over and over again, is how relative to human expectations, light and motion are cheap, while heat is expensive. Of course, these are all subjective perceptions; energetically, a Joule is a Joule. But it can be pretty weird to realize that your friendly neighbourhood chocolate bar (1.2×10^6) has about one quarter of the energy of a Kilogram of TNT (4.2×10^6), and about 5 times the energy of a WW2 “pineapple” style hand grenade.

The next energy equivalence that really struck me was solar energy vs bullets: Specifically, the solar constant at our distance from the sun is 1.4×10^3 Joules per second. The kinetic energy of an M16 rifle round is 1.8×10^3. Got a decent solar panel and a way to convert energy into motion? You could be firing off bullets all day on solar power.

Need to melt some ice? Each gram will cost you 3.3×10^2. Need to kill a man via X-rays? Now available for the low, low price of 3×10^2.

What’s that, you’re an old-fashioned wizard who lays waste to his foes via lightning bolts (1.1×10^9 J) or fireballs (ballpark it to 1KG of TNT 4.2×10^6 J) or a tornado (> 1×10^15 J)? Maybe you’re the classier sort of evil sorcerer who boils an opponent’s blood (5 litres, heating (4.184 J/ml/celsius) from 37 to 100 celsius, 5000 ml x 4.184 x 63 = 1.3×10^6. Why, it only proves your mettle to use hundreds of thousands of times more energy to strike down your foes than necessary, right?

But what if you’re one of those awful modern sorcerers who rather likes using that would-be energy of a lightning bolt, and firing off one hundred and fifty thousand .458 Winchester Magnum rounds (elephant gun, 7.3×10^3 J per round) instead?

And that doesn’t even touch on how terrifying conjuring is, energetically. Magically creating mass from nothing but energy? (9×10^13 J per gram!) Conjuring a dove (900-2100 g) pretty quickly starts demanding Tsar Bomba levels of energy.

So I guess what I’m trying to say is, forget Gandalf. The guy at your kids birthday party, pulling a rabbit (400-2000 grams) out of his hat? Back away slowly, and pay his invoice.

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4 thoughts on “On the Orders of Magnitude of Energy (And why classical Wizards are idiots).

  1. All of this speculation is based on an unstated assumption – that the main factor in the cost for producing energy is the J value. This is not true for the normal world and I see no reason it would be true for the magical one.
    1) There may be energy forms that are more difficult to create from magic than others.
    2) The more concentrated an energy form is, the harder it is likely to be to create. So a random dispersion of heat may require no more than the J cost, while focusing the same amount of heat may require far more. Same for just about any other energy form.
    3) Under the many-worlds hypothesis, the easy route for a conjurer isn’t creating mass, it is finding it and moving it around.
    4) This also ignores computational costs. Simple forms of energy that the magician understands are probably easy to create. But what happens if he tries to create something he doesn’t fully understand, e.g. just about anything living? Does it simply not happen, or does some magical computation occur that delivers the (perhaps wrong) result anyway? Does that computation cost anything? All computations in our world do, even thought that cost is coming down quickly.

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