I Did Nothing
Aug. 2nd, 2007 11:14 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
tanarillNothing at all. All day. Okay, that's not exactly true, but I spent about half an hour rerendering virtual walls because someone had failed miserably to make the walls match in the drawing. To the point where there were five-foot gaps in the 3D drawing that aren't there in RL.
The other thing I did today was get about eight gallons of 32.5% urea solution. Urea is (NH2)2CO2, and if you add it to high-temperature diesel exhaust it takes away NOx. As NOx emissions are a major precursor to acid raid . . . goodness all around. Except urea solution, being mostly water, is freaking heavy. But I got that stored, labeled, and MSDS'd. Now all I need is the actual parts to test. Which ought to have arrived last Friday.
And then I played Tetris.
You’ll probably have noticed that I’ve been saying almost nothing about calories. This is because a food calorie is an arbitrary unit of energy; essentially, when I say a food is energy-rich or energy-dense, that means it has a lot of calories. A good way to think about it is this:
Put a pot on the stove. Add ten grams of liquid water at exactly 0C*. Heat it until the water boils. Congratulations, you have added one food calorie to the ice, in the form of heat energy. You probably used a lot more energy than that, because some of it went to heating the pan and the air, but the amount that was used to heat the water was one food calorie.
Some of you will have just caught on to a very important fact: a food calorie and a calorie as defined everywhere else aren’t the same thing. In fact, a food calorie is what’s commonly called a kilocalorie, one thousand regular calories. (A regular calorie is defined as the amount of energy it takes to raise on gram of water one degree C.**) I will refer to them as kCal, when I talk about them at all.
Another point: we talk about a 2000 calorie per day meal. That’s 2000 kCal per day, or 2,000,000 regular calories. It’s enough energy to raise one gram of water two million degrees C, but when you consider the fact that people are basically forty to fifty liters of water and we regulate our temperature to 36.8C even though we are constantly losing heat, it’s more reasonable. In essence, if all the calories in all the food we ate were going to heat, we’d raise our body heat by about 50C a day to replace heat lost to the environment. That’s not where all the energy is going, but it’s a good demonstration of how terribly inefficient humans are***.
Now I want you to consider one more thing. It’s considered healthy if you consume enough energy a day to raise your body temperature by 50C. (Provided you are 47 liters of water, which you aren’t. If you are a 65 kg adult (143 lb), about 47 kg of it is water and the rest is other stuff. You heat the other stuff too, and use the energy to do lots of things, but . . .) To get fat, you have to eat more than this, or not use all of that energy up in one day. Most fat people do both. They eat so much energy, and use up so little, that their bodies decide to use an evolutionary trick designed to help survive long, cold winters, and put the energy into long-term storage. In other words, their bodies make . . .
* Which is possible. Don't argue.
**Although this value changes depending on the starting temperature. Science says that it's 4.184 joules. I'm not going to explain what a joule is.
***And how powerful the sun is. I mean, it hits the earth with enough energy every day to keep every living thing on the planet alive, and living things aren't very efficient. And we're not even getting a tiny portion of the energy.****
****Incidentally, if we could harvest all of that energy, over even a tiny portion of the earth's land surface, there would be no energy issues ever again. Ever.
I bet you can finish that sentence :P Feel free to ask any questions, and more tomorrow!
The other thing I did today was get about eight gallons of 32.5% urea solution. Urea is (NH2)2CO2, and if you add it to high-temperature diesel exhaust it takes away NOx. As NOx emissions are a major precursor to acid raid . . . goodness all around. Except urea solution, being mostly water, is freaking heavy. But I got that stored, labeled, and MSDS'd. Now all I need is the actual parts to test. Which ought to have arrived last Friday.
And then I played Tetris.
You’ll probably have noticed that I’ve been saying almost nothing about calories. This is because a food calorie is an arbitrary unit of energy; essentially, when I say a food is energy-rich or energy-dense, that means it has a lot of calories. A good way to think about it is this:
Put a pot on the stove. Add ten grams of liquid water at exactly 0C*. Heat it until the water boils. Congratulations, you have added one food calorie to the ice, in the form of heat energy. You probably used a lot more energy than that, because some of it went to heating the pan and the air, but the amount that was used to heat the water was one food calorie.
Some of you will have just caught on to a very important fact: a food calorie and a calorie as defined everywhere else aren’t the same thing. In fact, a food calorie is what’s commonly called a kilocalorie, one thousand regular calories. (A regular calorie is defined as the amount of energy it takes to raise on gram of water one degree C.**) I will refer to them as kCal, when I talk about them at all.
Another point: we talk about a 2000 calorie per day meal. That’s 2000 kCal per day, or 2,000,000 regular calories. It’s enough energy to raise one gram of water two million degrees C, but when you consider the fact that people are basically forty to fifty liters of water and we regulate our temperature to 36.8C even though we are constantly losing heat, it’s more reasonable. In essence, if all the calories in all the food we ate were going to heat, we’d raise our body heat by about 50C a day to replace heat lost to the environment. That’s not where all the energy is going, but it’s a good demonstration of how terribly inefficient humans are***.
Now I want you to consider one more thing. It’s considered healthy if you consume enough energy a day to raise your body temperature by 50C. (Provided you are 47 liters of water, which you aren’t. If you are a 65 kg adult (143 lb), about 47 kg of it is water and the rest is other stuff. You heat the other stuff too, and use the energy to do lots of things, but . . .) To get fat, you have to eat more than this, or not use all of that energy up in one day. Most fat people do both. They eat so much energy, and use up so little, that their bodies decide to use an evolutionary trick designed to help survive long, cold winters, and put the energy into long-term storage. In other words, their bodies make . . .
* Which is possible. Don't argue.
**Although this value changes depending on the starting temperature. Science says that it's 4.184 joules. I'm not going to explain what a joule is.
***And how powerful the sun is. I mean, it hits the earth with enough energy every day to keep every living thing on the planet alive, and living things aren't very efficient. And we're not even getting a tiny portion of the energy.****
****Incidentally, if we could harvest all of that energy, over even a tiny portion of the earth's land surface, there would be no energy issues ever again. Ever.
I bet you can finish that sentence :P Feel free to ask any questions, and more tomorrow!
![[identity profile]](https://www.dreamwidth.org/img/silk/identity/openid.png){kind=small}
no subject
Date: 2007-08-03 05:54 am (UTC)Just pointing that out.
no subject
Date: 2007-08-03 11:19 am (UTC)After work, which is where I am.
no subject
Date: 2007-08-03 08:56 pm (UTC)And by high school freshmen I mean people who have taken 8th grade science at some point in the past hundred years. Which is hopefully the majority of your readers.
no subject
Date: 2007-08-03 09:44 pm (UTC)