The basic idea behind unschooling, as I understand it, is that children are naturally curious and will learn everything they need to know by following their interests rather than a canned public school or homeschool curriculum. For example, a child who wants to understand how tall an apatosaurus really was will naturally discover measurement concepts and retain them better than a child who is given a lesson on feet and inches because that's what comes next in the math book. The context and the child's desire to understand make the learning more meaningful.
An example from my own life: When I was working as an office manager after graduating from college, I was having trouble with a laser printer leaving black dots in the margins of everything it printed. After working on the problem awhile (cleaning the drums, printing various kinds of documents etc.), I noticed the dots were exactly six inches apart. From my knowledge of periodicity from the astronomy classes I took in college, I was able to determine that there was a nick in the printing drum of the printer, it could not be fixed and we needed a new one. Imagine the regular rotation of Jupiter as marked by the appearance of its Great Red Spot.
I was so proud of myself for having applied something I learned in astronomy to real life. When I told my husband about it, he said, "That's basic physics. You don't have to get into planet rotation to figure that out." He was wrong, though. I did need to make that analogy.
I took intro to physics in high school because I was supposed to. It was a prerequisite for AP biology. I remember eeking out a B and having a personality conflict with the teacher, but I remember nothing about what we were supposed to have learned. I took astronomy in college because I was interested in it. I don't remember everything we learned, but apparently enough of the basic physics seeped through that I was able to diagnose my printer problem.
You can also make the case that the astronomy lesson took because it was visual, where most of my HS physics class wasn't, which is a valid point, but I don't think that's the entire story.
Another example: I never got beyond algebra 2 in high school because it was painfully boring. The most important thing I learned was how to express a real world problem I am having "in math" so I can figure out the answer (i.e. How much do I give the pizza delivery boy? Cost of pizza x 1.15=X) Yet I use the statistical analysis skills I learned in archaeology classes all the time. What is the relative worth of an item in my war relief collection, based on the number of duplicates on the market? Where are the ants on my orchids likely getting into the house? For me, those are archaeology questions because my interest--my context for having learned the skill--is archaeology.
So I guess, particularly in terms of math and physics, I am as much unschooled as I am schooled.