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How much do we eat? (part 2) - CERisE's Testing for L

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March 1st, 2006


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04:40 pm - How much do we eat? (part 2)

Would you like to chew on a star?
Bring photons home in a jar?

Either way, I'm quite certain you won't be better off than you are. Even that guy from the Tick who took a bite out of the moon would shy away from this meal!

Stars are a little complicated. There's a number of different reactions which can occur. There's the proton-proton chain of stars around as hot as 10^7 K, and the triple-alpha process for stars with temperatures of 10^8 K, and the carbon-nitrogen-oxygen process of heavier stars. Moreover, the output is typically in megaelectronvolts (MeVs).

The proton-proton chain produces some 23.4 MeV, the triple-alpha chain produces 7.2 MeV, and the carbon-nitrogen-oxygen chain produces 25.03 MeV. Those energy outputs are easy enough to figure out in Calories (1 MeV is approximately 3.826732736219 * 10^-17 Calories), but there isn't a definite link between the size of the star and the number of those reactions occurring in a second.

So let's consider our sun. We figure it uses proton-proton chain reactions. It produces some 3.86e33 ergs a second (or 9.219451609822*10^22 kilocalories) and masses approximately 1.989*10^30 kg. That's approximately 7.015991031771*10^31 oz. Uh-oh , Indy! The sun in all its nuclear fusion glory actually does quite poorly on this scale. In order to get your 2000 Calories out, you'd have to eat a whopping 47,562,421 tons o' sun!

So what if we selected a different star? The Death Star of Star Wars fame! It blows up planets! And thanks to that (and the relatively entertaining discussion on the linked page), we have an idea of a lower bound of the energy output -- a mere 2.4*10^32 joules or 5.73*10^28 Calories. It sure beats the sun! Since it took the first Death Star a day to charge, it can be assumed that the power for life support, the turbolaser banks, computers, &c. was significant, but relatively small

From this forum, there's some discussion about the mass of the Death Star. Someone claims 5*10^10 tons assuming that the average material weight is that of iron and that 1/10 of the Death Star is open space.

It's worth noting that this is the first Death Star, not the second.

Using those numbers, the Death Star holds at least 3.58125*10^13 Calories per ounce. If you ate but a mere 1/17906250000th (only 5.6*10^-11 of an ounce) of the Death Star, you'd be all set that day.

No, really. I don't recommend it. Vader would have something to say about that. And if it turns out I was wrong about my assumptions on energy and size, it could have serious ill effects on your diet!

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