So, being a science geek has its upsides sometimes. Last weekend we went up to Yankee Siege, a place where real-life geeks demonstrate some physics principles using a trebuchet and some pumpkins. How do they do this? Well, they use the trebuchet (pronounced “TREH-boo-shay”) to fling pumpkins (and not just any old pumpkins—these are regulation competition pumpkins) at a mock castle some 1,200 yards away. Yankee Siege folks are the World Champions at Punkin Chunkin, having used their trebuchet to fling a pumpkin 1,394 feet. Here are two pictures of their counterweight trebuchet, a 35-40,000-pound handmade machine. The counterweight is the big four-sided diamond of wood hanging down from the lever (which in the second picture is pointed nearly down to the ground in “launch” configuration—in fact, it has just started its launch sequence. (You can read more about its construction here.)

A trebuchet getting ready for a flinging in NH. Image © 2006 Carolyn Collins Petersen

Where does the physics come in? From Wikipedia, I found this: “The object of a good design is to transfer as much energy as possible from the falling counterweight (the diamond-shaped box behind the lever arm in the second picture) into the projectile (in this case, a pumpkin in a net that is attached by a rope to the end of the long, pointy lever arm (pointing up in the first picture and in action in the second picture). The maximum range for a hypothetical 100% energy transfer, Rmax, of the projectile can be shown to be Rmax = 2hmc / mp, where h is the distance the counterweight falls, and mc and mp are the mass of the counterweight (the box) and projectile (the pumpkin), respectively. The efficiency of a real trebuchet is then easily determined as the ratio of the actual range achieved to the calculated maximum range.”

So, in other words, you’re taking the energy of the counterweight (which is really heavy) as it falls to the ground under the force of gravity and using it to fling the pumpkin (which might weigh 20 pounds) as far as you can.

Trebuchet at Yankee Siege in NH. Image © 2006 Carolyn Collins Petersen

At Yankee Siege on Saturday afternoon we saw them fling pumpkins into the woods behind their fake castle, at least 1,300 feet away. We got to see them do it three times (it takes about a half an hour to get the trebuchet ready for a launch attempt). Between times we wandered around and looked at the machinery, got some cold cider to drink, and visited the farm stand across the road. It was a major hoot, and we got to see physics in action on a warm, colorful autumn afternoon.

Wanna try your own hand at designing a virtual trebuchet? Visit the The Treb Challenge.

It’s Getting Closer

Griffith Observatory, Los Angeles, California

So, my Google News alerts have been chiming at me today telling me that there’s news about Griffith Observatory. There was a press conference today, attended by a hundred or so press types in Los Angeles, where the mayor of LA announced that the observatory would be open to the public on November 3 after being closed for four years for renovations.

It’s getting exciting folks, because I’ve been part of that whole renovation thing for the past year and a half. My role? Working as senior exhibit writer for the entire exhibition program. I’m still working on a few last-minute changes to copy for the final exhibit panels to be created, but for the most part, my part of the project is nearly finished. It’s been a fun one, and I’m going to miss the daily emails and teleconferences with the rest of the team. But hey, we have to let our baby get born! And it’s going to be a heck of a baby!