She has been! She was playing around with their device for measuring the temperature; she tried it with various things and eventually settled on very strong distilled spirits. With some dye she got at the market, because it was clear and didn't show up very well against the glass. It...sort of works better? It's smaller, at least, which means she can put it in more precise spots. 

Also she was working with their glass enclosure and the weather barrier trick, and...she's kind of confused about something and would like him to help her check it? 

Sure, he can take a look at whatever it is. 

Sandra has three different glass enclosures of varying sizes, and one of them has a sort of tripod in it, adjustable either by Fetching or by lifting up the glass tank and doing it herself by hand. 

She shows him her new temperature-measurer. It's a very slim glass tube with lines etched on it, and a slightly larger bulb of dark brownish liquid inside, which right now goes about a third of the way up the slender stem. 

Sandra lifts up the tank, puts the tripod to its lowest point, and sticks it to the top of the tripod by dint of lodging the bulb into a ball of still-soft wet clay, and then puts the tank back down. "Heat it up for me, would you?" 

He heats it up, keeping an eye on the liquid.

It rises, closer to two-thirds of the way up now, and then settles there. 

"All right," Sandra says after a bit. "Can you use Fetching on the tripod legs to extend it higher?" 

"Okay." Getting all three legs at the same time so it doesn't fall over is tricky, but he takes it slowly and gets it all the way up without tipping it.

" . . . Am I looking at this from a funny angle or did the measured temperature go up when I moved it?"

"- Oh, you saw it too. I...think it's real, probably, if both of us noticed and I didn't even hint it to you? That's the part I was really confused about." 

"So either there's something other than the temperature affecting what the device shows, or the air is warmer higher up in the box." He holds the back of one hand up to the glass near the bottom and the other hand at the top.

It's subtle, but - the top surface of the glass does definitely seem to feel warmer than the glass wall right where it rests against the floor. 

"I don't think it's just a measurement issue. I'd say I must have heated the air unevenly, but you noticed the same thing when you heated it."

"- It's so weird! Hmm. I...could try heating it unevenly on purpose - trying to get the bottom hotter - and seeing if it equals itself out somehow?" 

"Good idea!" He'll move the measuring device up and down during the process.

Eventually: "It sure looks like the heat ends up at the top no matter where it starts out."

"Huh. That's fascinating. I wonder... Do you have any idea why? - I guess smoke goes up into the air, from a fire, it doesn't just sit there..." 

"Yeah--I wonder if it has anything to do with how hotter air expands."

"Oh. Hmm. That...maybe makes sense? I'm thinking of how some things float in water and others don't, and I think it has to do with whether the same amount of water - by weight, I mean - would take up more or less space? A scholar studied it once. And...maybe air is like water, that way?" She makes a face. "It doesn't feel like water." 

"You mean something like--it heats up, it takes up more space, and the hot air sort of floats on the colder air? I guess if you have a sealed container of air and water the air is always on top because the water is heavier, and that's sort of like air being a thing that can float, and oil floats on top of water--but there aren't any other things like air that can float on top of regular air."

"- Huh. Would we know? Maybe there's a layer of something like oil on top of water, but way up in the sky..." 

"Oh wow, you're right. . . . Are clouds that? They're on top of the air at least temporarily; maybe they're lighter before they turn into rain."

"- Oh! You know what seems like it floats on air, is steam. If you're cooking, right, the steam goes up... Maybe clouds start off as - kind of like steam, because that is just water, and then they float up until the steam turns back into raindrops..." Frown. "Except that that'd imply the air is boiling, and it definitely isn't!" 

"Well, we don't interact with the rain until it's falling, right, so maybe it starts out hot enough to float and then cools down and falls, and if you actually touched a cloud it would be hot? And fog is like steam and clouds, and it's cold and goes down, you see it in valleys . . ."

"- Oh, that's true. Or you'll see it on the surface of a lake but not higher up... Weird." 

"Now I wish I could go touch a cloud to see if they're actually hot."

"Maybe if you went up a -" Sandra stops herself. Grimaces. "I was going to say the top of a mountain. But the tops of mountains are cold. They've got snow even when nowhere else does. Now I'm just really confused!" 

"So am I!"

"I guess maybe mountains are special somehow, and if you build a really tall tower, not on a mountain, it'd be warmer? ...Hmm, now I'm wondering if you could make an...air-boat, I guess. Somehow make something like enough to float on air the way boats do on water."