Archive for the ‘best of the blog’ Category.

The case of the disabled logins

(Details have been changed to protect the guilty and to make the story more entertaining.)

I work for a company that builds robotic kiosks (think vending machines that cut keys), which are stationed in various stores across the country. One morning, I arrive at work to find a coworker looking troubled. “We’ve got a kiosk in Florida that’s stuck in the middle of shutting down. Can you take a look?” This isn’t my area of expertise, but somebody’s got to deal with this, and it looks like I’m somebody.

I try to SSH into the kiosk, but the connection is refused with the message, The system is going down for power off in 1 minute!. “It’s been saying that since I arrived half an hour ago,” my coworker explains. “It’s not actually going to shut down in a minute.” Read on to learn how we managed to log in again. →

Will It Lens? Table of Contents

Welcome, all! Here are links to everything in the “Will It Lens?” series.

  • Part 1: introduction, melting pennies, dimes, toothpaste, Tylenol, milk, chalk, gourd, can.
  • Part 2: equipment upgrades, CDs, disposable silverware, brass penny, burned pennies.
  • Part 3 (Food Edition): popcorn, grape, kumquat, Frosted Mini Wheat, jelly beans, Reese’s Pieces.
  • Part 4: wood, quarter, soap, dishwasher detergent, bacon, egg, honey, seashell, almonds, gummy bears, M&Ms.
  • Part 5 (Temperature Breakthrough): marshmallow, peeps, copper, iron, sand, glass
  • More to come soon eventually!
  • Gallery of all pictures: This contains every picture we took. There’s a lot of junk in here; the good pictures are in the blog posts above.


  1. Can you melt glass?

    This surprised us, but yes! Normal glass is more properly called “sodalime glass,” which has a much lower melting point than pure silicon dioxide (which we originally thought glass was made of, and which we haven’t been able to melt yet). However, we have trouble melting clear things because they don’t absorb the sunlight. Nonetheless, we melted a dark brown glass in part 5.

  2. Can you melt sand?

    Kinda. The sand we tried is a mixture of quartz, feldspar, and iron. We can melt the last two, but we haven’t melted quartz yet. Look at part 5 for more details.

  3. Can you lens electronics?

    We probably could, but we don’t want to because the fumes are really noxious. There’s lead and other stuff that’s terrible for your lungs in there.

  4. Can you use a second lens to focus the light even more?

    No, that’s not how optics works. For a slightly more thorough answer, see the Light Sharpener FAQ over at

  5. Where did you get the lens? How much did it cost?

    I think we got it from here. When we ordered it, I think it was about $120, plus shipping. If you include the wood for the frame and stand, the welding goggles, and the skillet, we’ve probably spent over $200 on lens-related stuff so far.

  6. You should lens something that will burst and explode all over the place!

    That would be very entertaining, but we need to clean everything up before lunch is over, so we’re not doing anything too messy in the foreseeable future (no unopened pop cans, no aerosols, etc.). If we ever take the lens out to the middle of the desert, we will consider lensing messy things.

  7. You should lens an iPhone, iPod, or other hip status symbol.

    First, see question 3 about electronics. Then, remember that we’re paying for all of this with our own money. We’d prefer not to lens anything that costs more than a couple dollars. Everything we’ve tried so far has cost under $1 each (almost everything is under $0.25 each).

  8. Isn’t it illegal to destroy money?

    Not unless you do it with the intent to defraud someone. Remember the last time you went to the zoo? You probably saw one of those machines that will take your penny, flatten it out, and stamp an image of a penguin or something on it as a souvenir. Melting a penny is no more illegal than one of those machines.

Other articles that link to this series:

Stand Back, I’m Going to Try Science!

My father is a chemical engineer at a large company. He volunteers in an outreach program where the company gives him science demonstrations aimed at precocious elementary schoolers, and he periodically goes to schools and birthday parties and stuff to show how neat science is. One of the kits he does is all about cryogenics, where he gets about a gallon of liquid nitrogen (LN2), and demonstrates what happens to things when you freeze them really cold. He talks about how matter can be a gas, a liquid, or a solid, and how its properties change as it goes from one state to another and changes temperature (racquetballs become brittle, flowers become crumbly, small amounts of LN2 boil into large amounts of nitrogen gas, etc).

He did a demonstration a couple days ago, and still had some LN2 left over from it. Ordinarily he just pours the rest out on the street (it boils away quickly, and no one notices since air is already about 78% nitrogen). However, this time we convinced him to keep it around for a few days so we can try freezing other things. Some stuff about LN2, and some safety tips, followed by a bunch of pictures →

C++ is bad: problems with the ternary operator

In today’s installment of “why not to program in C++,” I give you the following quiz, which Dustin, Steve, Tom, and I had to figure out today (Dustin’s code was doing the weirdest things, and we eventually traced it down to this):

Suppose you start out with the following code:

class Argument;
Argument x;
void Foo(const Argument& arg);
bool test;

You can assume that all of these are defined/initialized elsewhere in the code. For each pair of code snippets below, decide whether the two snippets are equivalent to each other.

# Code Snippet
Code Snippet
if (test) Foo(x);
else Foo(Argument());
Foo(test ? x : Argument());
{ // limit the scope of y
  Argument y;
  Foo(test ? x : y);
Foo(test ? x : Argument());
Foo(test ? x : x);
Foo(true ? x : Argument());

Edit: what I meant by the curly braces in Question 2 is that you shouldn’t consider “y is now a defined variable” to be a significant difference between the two snippets.

The answers are worse than you'd think. →

In honour of Patricia C. Wrede

Today at work we bandied about an interesting logic puzzle, and understanding the answer totally blew my mind. It goes like this:

All dragons have either red eyes or green eyes. If a dragon ever knows its own eye color, it will die on the next stroke of midnight. Moreover, dragons, like all mythical beasts, are perfect logicians. That is to say, if it is possible to infer a fact from what is already known, dragons cannot help but make this deduction.

There is a town in which n dragons live, where n is small enough that every day, every dragon interacts with every other dragon. One day, an oracle, renowned for always speaking the truth, comes to the town. She gathers together all the dragons, looks at each one, and then loudly proclaims, “At least one dragon here has red eyes!”

  1. What happens in the town?
  2. Suppose that at least three dragons have red eyes. Now, not only does every dragon already know that at least one dragon has red eyes, they also know that every other dragon knows this, too. What information does the oracle add that the dragons didn’t have already?