Is it because the velocity of one water molecule relative to the other water molecules is low? When I stick my hand into a cold stream, why do I feel that it’s cold even though the water is moving fast into my hand? Shouldn’t the water flowing fast mean more collisions with my hand (which I thought is how we sensed temperature)?
In: Physics
The part where you’re putting your hand in to the water is partly what makes it deceiving.
Your hand is warmer than the water (obviously). When you stick your hand into the water, you’re heating up more water (and water flows by your hand, your hand heats up that water, and that water flows by. Then you hand heats up more water.) So the flowing water will actually feel colder than still water. The same sort of thing happens with wind chill factors.
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You’ve also inadvertently come across the idea of *special relativity*. It’s something that Einstein and other scientists have thought about.
Say that you’re on a riverbank, and you’re watching the water flow by. You have a thermometer on a stick, and you measure the temperature of the water.
At the same time, someone else is floating down the river on a boat. They are also measuring the temperature of the water with a thermometer on the side of the boat.
When the boat passes by your thermometer, which one is right?
To you, the boat thermometer is wrong because it’s moving, and has slightly more kinetic energy. But from the boat captain’s point of view, the boat and the water are going the same speed, and your thermometer is wrong.
But obviously, the water isn’t two different temperatures at once.
The short answer is that the difference between the two isn’t significant and don’t worry about it. But nifty and weird things happen when closer to the speed of light.
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