Son: The absorptivity is the ratio of the energy absorbed by the wall to the energy incident on the wall, for a particular wavelength. This will be proportional to where is the intensity of black body radiation at wavelength and temperature .
My son made the bold suggestion yesterday that I should go back to work. But - and this is key - that he should stay home by himself. This was prompted by me saying that when his mother got out of work I was going for a run - so he'd have to go with her while his sister did a dance class thing that she loves. He has fun as well bombing his little trains around the play area - but said that he'd made his mind up that he was staying home with me instead. I repeated I was off out on that run ("I fully intend on eating the rest of these Mini Eggs - which means I need to do at least five miles so I don't feel terrible about buying another bag later this week and then eating all them as well...") and he looked at me like I'd missed the obvious. Which was that he'd stay home. After going through how you can't leave a nearly-three year old at home alone I made the ludicrous point that I could go back to work if that was the case. Which he liked a lot. "I'll play trains and eat moose juice." he proudly argued. I'm sure you can see the fundamental flaw in that argument. After asking him which moose he intended to milk to get this so-called moose juice he shrugged. So I asked him what Kirchoff's law of thermal radiation was and had that dreaded pang that he'd just start reciting formula and explaining it to me in such a way that it would suddenly be clear that I had no idea what it really was either.
Actually he has also made another unrelated bold pronouncement. That being that whatever color a truck is indicates what cargo is inside it. Hence whenever we see the UPS truck he yells "they're delivering chocolate!" Importantly we see it parked up outside people's houses - meaning my son thinks it's perfectly reasonable for chocolate to be delivered in bulk right to your door. There is a yellow truck that we tend to see parked outside the local gas station that he claims is delivering much-needed bananas to the community. Mind you he claimed the white trucks we see are responsible for delivering snow to the surrounding areas - suggesting his understanding of weather patterns is woefully inadequate.
On another track entirely - I've also suffered another one of those moments were I thought I was being rational but it makes no sense. That being I watched the first 20 minutes or so of Harry Potter: The Chamber Of Secrets with my daughter. During which time I marveled at the acting of Julie Walters, Robbie Coltrane, Alan Rickman and Mark Williams. Whilst thinking that they were wonderful choices for the characters they were playing I suddenly had the strong pang of, "Yeah - I think I want to go home...." Which seemed rational and like I'd been suppressing a truth for fear of admitting it. Then I realized I'd got that strong urge by watching a children's movie about witches.
Right - we're off to wait for the bus. So until I tidy up the thing I'd actually written for today you can watch this video of my daughter pretending to be a bull.