Dividing a sandwich fairly

I like to read various Stack Exchange websites, and one of them has a wonderful discussion of how you might divide a sandwich between three people fairly. Most of us are familiar with the two-person version: one person cuts and the other person gets the first choice. But what about if there are three people, or more?


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Knots, Knots, and Avast ye Landlubbers

Several years ago I became interested in mathematical knot theory, so I got a book called The Knot Book by Adams. I also got the Ashley Book of Knots by Clifford Ashley, which is a 600-page encyclopedia of actual knots in ropes/string/etc. I’d forgotten about both books until last night, when a key plastic piece on our bedroom blinds broke: the part that joins the lower single cord to the upper multiple cords that actually go to the blinds.

I whipped out the Ashley Book and found the perfect bend, #1463, which is good for joining two cords that have different thickness. I’ve shown my results below, but note that the actual knot is in the upper left and the rest of it is just my quick work to make sure that the thicker piece stays bent and doesn’t straighten out and try to pull through. I don’t think Ashley would approve of that part.

My KnotCU
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A secret underground “lair” in DC

When visitors come to the Washington, DC, area I like to have an off-the-beaten-path option for them. Something that most people would just walk or drive by and not notice. One of these options used to be the Einstein Statue, but recently they’ve redone the landscaping so it’s much harder to miss as you drive down Constitution Avenue.

It turns out that there is a “secret” underground “lair” in DC that you can enter and feel almost like you’re in a James Bond movie. In the photo, below, note the inconspicuous little building between the Smithsonian Castle (on the left) and the Freer Gallery (on the right). Looks like a visitor’s welcome center or something, right?


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A silent lightning storm

Turns out that what we called “heat lighting” as kids — lightning that has no accompanying thunder — is simply lightning that’s more than about 10 miles away. Tonight, while we were out walking, there was a huge lightning storm about 25 miles north of us. There was so much lightning that it looked like it was a timelapse video. I taped 90 seconds on my phone and uploaded it to Youtube.
Silent Lightning Storm

Sometimes tech really can affect lives

An incredible pair of glasses for kids that lets adults adjust them without formal training. It uses two lenses with a liquid between them and a small attachment for adding or removing the liquid to adjust them. (More liquid creates more of a bulge, creating a stronger prescription, less goes the other way.) If it works as well a advertised, it could revolutionize education throughout most of the world.