Submitted by AspGuy25 t3_10k4ov8 in askscience
jermdizzle t1_j5pvjww wrote
Reply to comment by pjgf in Why does hot air cool? by AspGuy25
I first experienced this while deployed to Afghanistan. Some Brit showed me how to put my bottle of water into a sock and soak the sock with water from a nearby stream. I'd then swing the sock around for a few minutes just to get the water temperature below the 120+ degrees F it was likely at so that it didn't raise our body temp when we drank it. It would often hit 120+ F ambient air temp and sometimes the water would either be in the sun or on top of some surface that was even hotter than the air temp.
a_cute_epic_axis t1_j5qn7mx wrote
This is how a sling psychrometer works. It has two thermometers, one which has a cloth soaked in distilled water wrapped around the bulb. This produces a "wet bulb" and "dry bulb" temperature, from which you can determine humidity, enthalpy, dew point, etc. The wet bulb will always read the same or lower than the dry bulb. If they read the same, the RH% is 100%. If they are far apart, it's closer to 0%.
jermdizzle t1_j5riwi5 wrote
Very cool. So many early (and even more modern types, like inertial and star-based navigational systems) measurement and navigational tools rely on extremely simple and primitive concepts or operations, but they produce such useful data.
a_cute_epic_axis t1_j5rl0d1 wrote
> like inertial
One method simply measures how long it takes light to go through a coil, and if the coil is rotating it will take slightly longer or shorter than if it isn't. Three coils perpendicular (orthogonal?) to each other and you know how you're moving. Run the long term results through a filter and you can determine your latitude as well.
(Technically it's two beams in each fiber going opposite directions and they compare the phasing).
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