In a wet lab doing biology research, controlling temperatures can be the difference between a reaction that works and one that fails- sometimes it's a matter of a few degrees. Because of this, there is generally a decent supply of thermometers in the lab.
The thermometers are in the Celsius scale, which is much more scientific than Fahrenheit and easier to use. (For a humorous and interesting description of how the Fahrenheit system came into existence, you can check out this article). So, I can tell you all kinds of numerical points on the Celsius scale, but I haven't ever found the need to really develop the ability to convert from Fahrenheit to Celsius or vice versa, although I'm getting good at estimating. In Celsius, 37 is body temperature, which is the temperature that a lot of reactions go at (that's the temperature that all the reactions in your body happen at). I'm running a lot of reactions at 15 degrees right now, which is chilly but not really cold. Others take place at 55, which would be very steamy and hot for a temperature.
We generally still use analog thermometers in the lab, although I've seen a few digital ones kicking around. For some reason, I trust them less. The analog thermometers can come with mercury or dyed ethanol in the bulb. The mercury ones are more accurate and last longer, but as you can imagine, are much less safe if they break. When that happens, we have to get a special mercury clean-up kit and carefully track down all the little beads of mercury with a special amalgam sponge that will bind the mercury and make it inert. Cool, but not really fun to do.
A couple of summers ago, there was a rash of broken thermometers. This isn't really a big deal, except that the people breaking these thermometers were failing to report it. For some reason, my karma designated me as the person to be lucky enough to find them all.
The first broken mercury thermometer I found was dangerously close to the sink. That's just what we want, mercury going into the water system. I of course stopped what I was doing and immediately cleaned up the mercury. The second thermometer still makes me shudder a little. I was going to use a small oven in the lab, and I felt compelled to open it before I turned it on. I am eternally grateful that I did, because there was a broken thermometer with a little pool of mercury sitting in the bottom. If I had heated up the oven before opening it, it's quite possible that the mercury would have vaporized. I'm not sure what vaporized mercury will do, but somehow I don't think that inhaling mercury is the best idea I've ever heard.
The third thermometer just broke on the floor. Much less dangerous, but still very annoying. I was getting tired of cleaning up spill.
The most perplexing part of the whole scenario happened after the thermometers broke. Clearly, we were out a few thermometers (why isn't there a good synonym for thermometer?), so someone purchased a few more- and they were all marked in Fahrenheit! This did me no good. After a little while, there was a flurry of small, makeshift signs posted about showing the conversion factor for some of the more commonly used temperatures (aside from body temperature and boiling point, of course. It's rather tricky to try to think up what 65 degrees Celsius is in Fahrenheit on the spot, when time is critical. Ask me how I know).
We couldn't justify throwing away the Fahrenheit thermometers since they were perfectly good, but they still bug me. I think we've almost cycled through them all now and replaced them with (ethanol) Celsius ones, but I now involuntarily glance at the top of a thermometer every time I pick one up to make sure I'm working with the right system.