Viewing a single comment thread. View all comments

mylesmudge t1_jaiua6z wrote

As I understand it, the faster the molecules in a substance are moving the higher the temperature. If this is the case, how come wind makes things feel cooler? Wouldn't the molecules be hitting us at a higher rate, it seems that wind should make things feel warmer.

1

drhunny t1_jaizyc7 wrote

For a gas like air, temperature is related to the spread in molecular velocities, not the average molecular velocity.

Wind feels cool due to convective heat transfer. In still air, your skin loses heat to the air a millimeter away, but that air is now a bit hotter itself, and it can transfer heat back to you. In a breeze, the air next to your skin is constantly replaced with new air at the average temperature of your environment. This is also why clothing keeps you warm-- it creates a barrier between the air next to your body and the air in the environment so they don't mix.

5

Indemnity4 t1_jak3yhq wrote

Home experiment.

Hold you hand in front of your face. Open your mouth as wide as possible and breathe on your fingers. Does it feel hot, cold or neutral?

Repeat, but close your mouth as narrow as possible so breathing is a tightly focused flow. Does it feel hot, cold or netural?

Other important considerations. Your internal body temperature is ~37°C, but your outer skin temperature is closer to 20°C.

When standing still you have an insulating layer of air around you. Your body is wanting to push out excess heat to prevent cooking itself. It loses that heat by radiating it, or by convection where some carrier rubs over your skin and carries away "heat". If the air is not moving, you have transferred as much heat away as possible and the air in immediate contact with you is saturated with heat. Example: hiding under the bed covers or wearing clothes.

Wind moving over your skin is transferring heat by convection. It is picking up heat from your body and carrying it away, which makes your outer skin feel cooler.

1