[kentonv]

> about 68 degrees Fahrenheit (20 degrees Celsius)

Pet peeve: When the original source had only one significant figure ("20 degrees", probably the scientist rounded to the nearest 10 because it's approximate), but the reporter translates it to another unit with more ("68 degrees", makes it sound more exact).

This shows up all over the place. Temperatures quoted in Fahrenheit always seem more exact, just because naturally whatever science they originate from was inevitably done in Celsius and then someone else converted the number without understanding significant figures.

68°F in particular shows up all over the place (like, it's the recommended thermostat setting in the winter to save energy), and it sounds like it's some sort of exact thing, but usually "about 70°F" would be a more accurate representation of the original source.

Also we say that human body temperature is 98.6°F, and a fever is 100.4°F or higher. Wow those numbers are so exact! Four significant figures on the second one! But actually these just map to 37°C and 38°C. Americans are constantly unsure if 99.0°F counts as a fever but the rest of the world probably understands 37.2°C is not...

[twiss]

In Celcius, it's less common to round to the nearest 10 degrees (or say things like "in the twenties" as you might with Fahrenheit), because that makes a much larger difference than it does in Fahrenheit. So I wouldn't necessarily assume that "20 degrees" only has one significant digit unless it's explicitly stated. (I haven't checked the original paper, though.)

However, converting something like 21°C to 69.8°F is indeed silly and should just be 70°F.

[fc417fc802]

You should assume that temperatures in scientific articles are accurate to the degree unless explicitly noted otherwise. In the vast majority of cases "routine" measurements are taken in Celsius with digital thermometers that display and are calibrated to one tenth.

Also don't significant figures only work within the same units? I believe for conversions you have to explicitly propagate error. You can skip that when moving between power of 10 units (as is typical when working in metric) using base 10 numbers but if the conversion doesn't match the base then the shortcut breaks.

> 68°F in particular shows up all over the place (like, it's the recommended thermostat setting in the winter to save energy)

I thought the recommended minimum setting to save energy was 55? Because any colder than that and you start risking pipes in enclosed spaces freezing due to temperature gradients.

[slyall]

20/68 is for human comfort/health.

[fc417fc802]

Sure but isn't that less a recommendation and more just what people typically find comfortable? Once I've adjusted to the seasonal change, a bit above 70 in a cold climate in the winter and I start to feel fairly uncomfortable if I'm moving around at all.

If you need to save money you want to lower the thermostat as much as possible and then use blankets or if that won't work for whatever reason then a space heater in a small room.