The keystone and the over-arching arch

Yesterday, I woke up grumpy. No, I was grumpy; there wasn't a dwarf in bed with me. Not so far as I remember. What I was trying to remember was why I was feeling grumpy. Oh yes. Field trip today.

Now field trips are opportunities. For a non-driver such as myself, this is a chance to go somewhere without wanting to blow up OC Transpo (Ottawa-Carlton, for those of you outside the area), or strangle one of their drivers. I can see younger daughter's class in action, and share in her day. I can learn something.

Unfortunately, this involves getting in a school bus with at least 50 kids. It also entails being partially responsible for said kids. Oh gawd...

The afternoon's excursion was to the Museum of Science and Technology. Now, as science museums go, this is... an okay museum. I've been there. Never particularly feel drawn back. It's in one of the ugliest areas of town, and doesn't have the pizzazz of Science World in Vancouver nor the Ontario Science Centre in Toronto which are both really, really nifty places and well worth the detour if you're in either of those cities. However, CMST does have a nice school programme and younger daughter's school, which despite being public (that means for the general unwashed, if anyone from Britain is peeking in), still manages to raise funds for frequent field trips.

We had a nice lady who enlisted several young sparks to illustrate which aspects of simple machines go into bridge making. So one young girl discovered she could lift the instructor on a teeter-totter affair by moving the centre closer to the load. Another boy found that he could easily pull down the centre of a flexible beam between the instructor's hands, but not if the beam was held in an arch, and this was something to do with the push and pull forces being switched to the ends. I spent this time being a comforting presence behind younger daughter and being rather loudly shushed by her when I attempted to confer with another mother on scientific principles.

Then we had to break into smaller groups to tackle a bunch of bridge-building kits. Most of the kids made a beeline to the impressive set ups for beam bridges and suspension bridges. One little girl, bless her heart, approached younger daughter to partner her and we headed for the neglected arch bridge kits. Using a diagram, we had to assemble blocks labelled A to F. Each letter represented a different shape, so there about a dozen rectangular "E's", about four oddly-shaped "B's", and mysteriously, only one "F", which went in the dead centre. There were exactly as many blocks as needed, and we only had a diagram for one half of the bridge, so it took us two attempts to get them in the right pattern. These were not interlocking blocks; it was rather like building something out of pebbles from the beach, and I didn't see how they could possibly hold together. The first time we tried to stand it up, it tumbled down like the Frank Slide. However the second time, we removed the prop, and a lovely and tiny little arch stood there, and miraculously, both girls took turns holding an arabesque in their snow boots on it!

We watched the others finish tying up their suspension bridges and have them blown with a high power fan while a toy truck rolled across, while across the room, others piled their boots on precariously balanced beam bridges. By this time, younger daughter was zoning out, and I was grateful that the afternoon was nearly over.

But not before the bus trip home with loud choruses of "Ninety-nine Bottles of Beer on the Wall" (every damn field trip, I tell you...) and a particularly nasty ditty that goes: "This is a song that gets on everybody's nerves..." And it does. "Speed up the bus," howled someone behind me. My feelings precisely.

I'd taken the precaution of removing younger daughter's packsack from her locker just before the field trip and took her directly home through the mercifully muffled and deserted snowy streets. But I meditated on that singular "F" block in the arch. It's called a "keystone", and it completes the arch and permits it to carry vertical loads. The weight on the keystone forces the other blocks in the arch together, which is why our tiny higglety-pigglety arch was able to bear the weight of a girl in snow boots. Considering that the arch bridge is the strongest of the three types of bridges, that's saying a lot for the keystone. The single thing that takes the pressure and forces everything else to stick together. What is the keystone in your life?