40 ms·

That's in the shadows, right?

xenocratus 5y ago
Technically speaking there is no "in the sun" temperature because it would depend on how much thermal energy the thermometer material absorbs from light.
- lmilcin 5y ago
  Exactly. Mass of air has temperature and an object like thermometer can come into equilibrium with air temperature. On the other hand an object in sunlight will have temperature that has very complex relationship with a lot of parameters including shape of the object or windspeed. Further, the object will not come into equilibrium and will show a gradient of temperature meaning the readout will depend on where you measure.
  - HappyDreamer 5y ago
    > including shape of the object or windspeed I suppose the air (the wind) tends to be colder than objects in the sun, since most sunshine pass straight through the air. A way to investigate this, is to step barefoot on flat black stones, in the summer sunshine
bertil 5y ago
There are two equilibrium temperatures, i.e. temperatures that likely don’t depend much on the device that you are using: * under a tent, i.e. in the shadow and sheltered from direct wind: commonly used and correspond to the temperature of the air; * wet bulb: more recently under attention, correspond to the effect of cooling by evaporation similar to what a healthy human body does. Wet-bulb often gives much lower number in a dry heat and is more significant for human survival. I’ve read that 32ºC or 88ºF are likely were prolonged exposure lead to adverse health but don’t quote me on that.
- lmilcin 5y ago
  "Under a tent" (or air temperature) is more useful. It is going to telly you how hot will be objects that come into equilibrium with air which you can't tell from wet bulb temperature. You can derive wet bulb temperature from air temperature and humidity. Also measuring air temperature is easier and more practical as it is just enough to measure temperature of an object that comes into equilibrium with air.
- the8472 5y ago
  > There are two equilibrium temperatures. The third one is radiative equilibrium. You could achieve that in a solar furnace, the object won't get hotter than the black body temperature of sunlight, which is ~5800K.

Technically speaking there is no "in the sun" temperature because it would depend on how much thermal energy the thermometer material absorbs from light.

lmilcin 5y ago
Exactly. Mass of air has temperature and an object like thermometer can come into equilibrium with air temperature. On the other hand an object in sunlight will have temperature that has very complex relationship with a lot of parameters including shape of the object or windspeed. Further, the object will not come into equilibrium and will show a gradient of temperature meaning the readout will depend on where you measure.
- HappyDreamer 5y ago
  > including shape of the object or windspeed I suppose the air (the wind) tends to be colder than objects in the sun, since most sunshine pass straight through the air. A way to investigate this, is to step barefoot on flat black stones, in the summer sunshine

bertil 5y ago

There are two equilibrium temperatures, i.e. temperatures that likely don’t depend much on the device that you are using: * under a tent, i.e. in the shadow and sheltered from direct wind: commonly used and correspond to the temperature of the air; * wet bulb: more recently under attention, correspond to the effect of cooling by evaporation similar to what a healthy human body does. Wet-bulb often gives much lower number in a dry heat and is more significant for human survival. I’ve read that 32ºC or 88ºF are likely were prolonged exposure lead to adverse health but don’t quote me on that.

lmilcin 5y ago
"Under a tent" (or air temperature) is more useful. It is going to telly you how hot will be objects that come into equilibrium with air which you can't tell from wet bulb temperature. You can derive wet bulb temperature from air temperature and humidity. Also measuring air temperature is easier and more practical as it is just enough to measure temperature of an object that comes into equilibrium with air.
the8472 5y ago
> There are two equilibrium temperatures. The third one is radiative equilibrium. You could achieve that in a solar furnace, the object won't get hotter than the black body temperature of sunlight, which is ~5800K.