Earlier in this winter January week in Texas with 60 - 70 temperatures, I was staring out my classroom window and remembering one event in my high school years. I don't remember the class/teacher/activity-purpose. All I remember is that one day we got to go OUTSIDE during class. This memory has lasted 26 years or so. So I related this to my 6th period class, and after their clamoring I promised we'd do something mathy outside some day.
Well, we started conic sections this week, and Friday was going to be a wee bit disrupted from other things, so I thought we'd go outside for part of the class and build a human ellipse to start off the unit. I had a long stretch of nylon yellow rope that I tied into a loop. Two students were the foci, one student was the pencil. Those 3 were inside the loop. The foci stayed fixed, and the "pencil" moved around while keeping the rope taut. The rest of the students were the "pencil traces" and moved to the "pencil's" spot after she left it.
We made 3 or so ellipses and I prompted them first each time about what they thought would happen if the foci moved in or out. We discussed circles. We got some sun. I think they have a sense of the ellipse properties now for when we get to them.