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Between question and answer, hunch and knowledge, fantasy and physics, there lies the experiment. On today's episode, we send our intrepid young researchers, Jacob and his sister Erica, out into the field. Their task: to determine the amount of energy in hay. Energy is all around us, but it can be tricky to measure. It's contained in all the objects here-- this mug, the doughnut inside it, and my brain. We measure energy by the effect it has on objects. We release energy by burning things and see the effect of that energy by using a technique called calorimetry. Calorimetry measures the gain or loss of that heat energy. Whenever we observe one liter of water warmed by one-degree Celsius, we've measured one "big C" calorie. You mean like the calories in food? Exactly. The calories on food packaging represent the amount of energy stored in the food. If sunlight warms one liter of water by five degrees, you've just measured 5 calories of the sun's energy. When anything warms water, that means there's energy we can measure. Yes! Now go forth and gather the data.

Ow! [laughs]

[laughs] Oh, man.

They're just like little kids. They are little kids. True. How can we figure out how much energy is stored in this hay? Cars get energy from gas. Goats get energy from hay. What do you mean? Here, feel. It's warm. Whoa! So goats are like little machines powered by hay fires in their bellies. Can we burn some hay to measure how much energy it takes to run a goat machine? We'd have to be careful. We'd have to measure out precise amounts of hay and water, then track the temperature of her tummy. No. I'm talking about fire safety. You want to see a sped-up version of what's inside a goat's stomach?

(Erica) Yes. All right, here we go. There's a lot of energy there. Let's measure it. This is the amount of hay that one goat eats in one day. I have five one-liter bottles of water. Every degree that the water goes up will represent five calories from the hay. We're at 28 degrees. Let's see how hot it can get. Let's do it.

(Jacob) Wow. Forty-eight degrees. Got real hot. When we measured the temperature of our water, it was 28 degrees Celsius. Then after we heated it with the hay fire, it was 48 degrees Celsius. We were able to raise 5 liters of water by 20 degrees Celsius. Raising 5 liters of water by 20 degrees Celsius is the same as raising 1 liter by 100 degrees Celsius. We know it takes 100 calories to do that. So we measured 100 total calories in a goat's meal.

[baaing]

We measured 100 calories in one serving of goat food. There's 16 servings in every bale, so we measured 1,600 calories for a bale of hay. That seems low. When we were burning our hay fire, a lot of energy escaped out. This is actually an underestimate, so at least 1,600 calories are in a bale of hay. Come on, Jane, Monique!

Let's go...to Boston. [bleating]

[bleating]

(Jacob) Go. In fact, Erica and Jacob let more than a little energy escape unmeasured. They found 1,600 calories in the hay, or about four donuts. According to my calculations, over 80,000 calories are in hay. Two-hundred donuts. That's a lot of donuts. But do not despair, for when it comes to energy, one thing is certain. While it may change forms, energy is neither created nor destroyed. It's out there, and perhaps we'll find it in our next experiment.

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