# Latest Posts

## Excerpts from my Kindergarten report card

May 26, 2012 7:43 am 2 Comments

The Cottage School, Boulder, CO. Spring 1986

• “He sometimes has problems controlling his energy, yet is able to listen and follow directions well.”
• “Logan enjoys reading our Public Library books.”
• “Logan gets excited about doing art projects but seems to steer away from this area during free choice.”
• “He often tires about 11:30, feels puny and wants hugs. Lunch usually brings him out of this slightly torpid .. state.”
• “His biggest drawback is his tendency to desert one work for another, leaving a mess behind.”
• “Continues to be constantly curious and able to assimilate information with amazing ease.”
• “He has finally begun to respond to requests that he refrain from always blurting out the answers during group lessons.”

Sound like anyone you know?

## Planetary orbital foci

May 24, 2012 12:59 pm Leave your thoughts

Planetary orbits are not perfectly circular; in fact, they are ellipses. An ellipse is a mathematical shape approximately equivalent to what is typically called an oval. An ellipse, though, meets some very specific criteria. One is that, unlike a circle, it has two foci instead of a single center. Where a circle is defined as the set of points whose distance to the center are some constant distance (the radius), an ellipse is the set of points whose distances to the two foci add to a constant. This allows you to construct an ellipse with some pins, some string, and a pencil.

So what are the two foci of planetary orbits? Well, one is the Sun. The other one? Just some random spot in space. And because each planet has a different size orbit with a different eccentricity (a measurement of how non-circular the orbit is), each planet has a non-Sun focus in a different place. Here is a Google doc spreadsheet with information on each planet’s orbit. A visualization after the jump.

## Cans of beer at Citizen’s Bank Park

May 17, 2012 1:49 pm 1 Comment

Earlier this year, Citizen’s Bank Park (the home of the Philadelphia Phillies) began selling several different brands of beer in 24-ounce tallboy cans. Canned beer (like boxed wine) has been on a resurgence in recent years, thanks to improvements in technology and some open-minded brewers. Harpoon Brewery started canning some summer beers a couple of years ago, but now they are spending more than a million dollars to add canning machinery to their main brewery in Boston.

Canned beer at a ballpark, however, is a good idea in almost every single sense I can think of:

• Since the beers don’t have to be poured, there’s no spillage and no foam to pour off, which means essentially zero waste.
• They get cold faster than bottles.
• The non-beer weight of these cans is far less than that of kegs and carbonation systems, which means less wasted delivery cost.
• Lines will be shorter since all the person behind the counter has to do is pull a can out of the fridge and open it (and they did tests — opened cans don’t fly as far as opened plastic bottles). They’ll also be shorter since the cans are bigger than cups — people won’t head back for more as often.
• Aluminum is just about the most efficient thing to recycle: only about 5% of the energy required for non-recycled aluminum
• You don’t have to potentially toss any extra (like you have to do with kegs). This means that the park could carry a wider variety of beers and not have to worry about what to do with the unsold cans of the less popular brands.

And there’s just something about drinking a cold beer out of a can that says “summer” more than a bottle or a cup.

Here’s a list of what beer is available where in the park. Most everywhere has cans of Stella Artois and Yuengling, two very good lagers. I’m not sure if the Oskar Blues and Sierra Nevada brands are in the tallboys or if they’re only available in normal 12-ounce cans. I will investigate when I’m at the game against the Red Sox this coming Saturday, and report back.

Update, 21 May: The 24-ounce cans are pretty much only available in Yuengling Lager, and we only found them on the lower level. Most of the other types of beer are in more-typical 16-ounce cans (500mL in the case of Stella Artois). Still: great selection, decent price, all the above points about convenience still stand.

May 11, 2012 7:55 am 3 Comments

Submitted for your approval, a thread from the non-work mailing list at Wayfair, replete with bread puns:

• I hope they don’t banh mi for this.
• Alright, I think you guys have taken this farl enough.
• You’re probably rye.
• We’re on a roll!
• I’m at my wheat’s end!
• You guys got muffin left?
• Maybe everyone injera-ed themselves trying to come up with more puns. (..later..) Oh, man, someone already did injera. Boy do I feel like a sconehead.
• At yeast its finally over
• A toast to the end of this thread
• Best WRAP this one up
• I agree. It’s time to leave it a-scone and get back to work.
• You all knead to wrap this up, quit loaf’n and get back to work

## Choosing random keys

May 4, 2012 10:45 am Leave your thoughts

Say you had code that generated random keys. These random keys were 6 letters long, all caps, with no duplicates. Here’s a few, as an example:

 `NTCYAR` `DHIEWM` `INBVTX` `IOELUC` `RKNBJX` `GKRANB` `DRYVQU` `YIFKTS` `VAUPSG` `ALWPOS` `CERSUY` `WAHJVM` `MTXJSZ` `RNLFXZ` `VFIEXT` `VEOKIH`

What are the chances that the key that you generate will be in alphabetical order? For instance, above, there’s only one in alphabetical order (CERSUY, in bold) And then, if you think you have that, generalize: For any string of length k distinct characters chosen from a set of n, what are the chances that they will be in order? My answer after the break.