Gedanken game time: What is the largest (in volume) gift you could buy or make for under $20? Some ground rules:

1. You can't get anything for free. i.e. "ask family and friends for all of their packing peanuts."
2. On the other hand, anything you can make or do yourself is okay. Inflating balloons with your own breath, for instance.
3. No one else can help you. This is an individual project.
4. Machines and devices to help you are okay, but buying anything you don't already own will go towards the $20.
5. On the other hand, things you already own can't be used as a part of the end-result.
6. You have to be able to bring the gift itself to a party.
7. The party is in one week.

Not many people know that there is very little copper in modern pennies. In 1982, they were changed from 95% copper to simply copper-plated zinc. If you cut open a penny made after that date, you’d see the grey-colored metal on the inside. In fact, in 1981, pennies of both recipes were made, and collectors have to listen to the sound they make when they bounce to tell the difference. Do it yourself with a penny from the 70s and one from the 90s; the difference will be obvious.

The price of copper closed last night at $3.48 a pound. That means that a 3.1 gram penny has about 2.26 cents of copper in it. Melt down a big wad of those, and you can make yourself a tidy profit. The price of zinc has been escalating in the last few months, too, so it might not be long until it’s worthwhile to melt down new pennies, too.

Since I switched from Bloglines to a local install of reBlog (see the Lifehacker post by Mathowie), I’ve been using it to save links to stuff that I find interesting, but don’t feel are quite important enough to post as individual things here. So I’ll probably start doing something like what Khatt’s been doing: occasional link dumps. Here’s four things I’ve enjoyed lately from Make Magazine’s great blog:

• DIY reverse lens mount for macro photography - Cheap, effective, and DIY. Basically that's my photography mantra lately. And I've been interested in trying some macro photography, especially with spring quickly approaching.
• Parking meter keychain - Invaluable for city dwellers with cars. It's got a timer built-in! Amazing!
• How to make an upside down planter - Hm, I seem to already be shifting into a living-in-a-city mindset.
• MAME + iMac - I'm considering doing something like this with M's grandpa's unclaimed first-generation iMac.

There’s a company called DNA11 that makes up big, nice looking, (expensive) pieces of art based on your own genome. I was perusing MetaFilter last week when I came across a question about finding a place that would do the same procedure, cheap, and just give a digital scan or a standard print that could be blown up. I liked the idea.

When I saw that one of the answers was offering to do it, I sent him an email post-haste. A few days later, he sends me (and several other Mefites) how to participate, along with a layman’s introduction to polyacrylamide gel electrophoresis.

Nomad refuses to carry coinage. I recall one time (likely apocryphal) he purchased a soda for $1.25 at a train station, and then put his change (all seventy-five cents) on top of a garbage can and left it. I can’t remember if I did the sterotypical thing and picked it up, but I’m sure I called it foolish.

But it got me thinking; is carrying change a waste of energy? If you carried a pocket-full of coins all day, could you purchase more calories of food than you burned carrying it? I thought about it for a while, and I couldn’t reason it out, so I decided to calculate it. The answer somewhat surprised me.

Coins are quite light. The U.S. Mint says that a penny weighs 2.5 grams, a nickel 5g, a dime 2.268g, and a quarter 5.67g. Figuring out how much walking “all day” is was difficult. I got numbers (for an average American adult) that varied from a quarter-mile to five miles. I decided to go with a middle-ground number, 2.7 miles. Looking at some numbers for calorie consumption during walking, I estimated that a person burns one calorie per pound of weight per hour of walking at 2mph. Once I had all of my data, the calculations were pretty easy.

Essentially what that means is that if you carried a whole dollar of pennies around for a day, you would burn almost three-quarters of an additional calorie. Even the least calorie-dense foods (like, say, Pepsi One) are enough to make it worth it, and some of the most calorie-dense foods (like the Big Mac) provide you with several hundred calories per dollar.

(Pennies require the most energy-per-dollar to carry. A nickel would cost 0.297 calories per dollar, and dimes and quarters both run a measly 0.068.)

All t-shirts at Threadless are on sale for only $10 apiece until June 6. Stock up!

I meant to post this earlier, but I kept forgetting. If you buy the new Star Wars DVDs at either Saturday Matinee or FYE, it only costs $50. And if you get it by today, it comes with a $15 rebate. I wasn’t planning on buying it myself, but for only thirty-five dollars, it’s definitely worth it.