The underground PVC water pipes outside my home are frequently cracking or leaking at the joints. After making several repairs I turned to reddit for advice on making repairs.

Someone recommended using 4 elbows! The joint is assembled by sliding the top part into the bottom 2 elbows. Instead of having to dig out the pipes enough to bend the pipes to fit couplers on each end.

       _____    _____
      |   __====__   |
      |  |2      3|  |
       ||          ||
       ||          ||

____ _|  |1      4|  |_ _____
____|____|        |____|_____

fig. 1

I heard from a professional plumber that the extra elbows can cause a drop in pressure, but more importantly there are more joints that could fail. So the extra digging is worth the trouble.

But can this technique be applied even if the pipes are skewed?

I saw a documentary that claimed melting polar ice caps are causing sea levels to rise. Something was fishy about that claim so I made some simplifying assumptions, drew a free body diagram and started doing algebra. I won't reproduce the algebra here because it turns out there is a common sense way to reach the same conclusion.

A quine is a computer program which takes no input and produces a copy of its own source code as its only output.

I first read about this kind of program in the ACM article Reflections on Trusting Trust (August 1984 Volume 27 Number 8 Page 761).

Here is my solution

Click to reveal

The purpose of a Useless Machine is to turn itself off when activated. Kits and built examples are available for purchase. While researching I found LEGO models but without kits or instructions.

Challenge accepted!

I'll explain how I setup the DNS records for an apex domain (fidelcoria.com) with a redirect from www.fidelcoria.com to fidelcoria.com.

If you're new to GitHub Pages visit pages.github.com to learn the basics.

Clocks and watches originally had a single hand. Obviously, this made it hard to tell time accurately. Until the minute hand was invented.

I came up with another way to read the minutes without a minute hand. Since the position of the hour hand past the hour marking implies the minutes... zooming into the hour hand shows minutes at a better resolution. For example, at 6:30 the tick marks will show the hour hand to be half way between 6 and 7. While at 7:05 you can zoom in to see the tick marks showing 5 minutes past 7.