Eli5 If putting something under pressure increases the temperature why is the bottom of the ocean so cold?
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The first thing is that water is an odd substance in its density response to pressure. The maximum density of water occurs at a temperature slightly above freezing (about 4 degrees C for pure water). Second is that water is liquid, a fluid, and moves fairly easily.
Water that is colder or warmer than the 4 degrees max density temperature will be less dense, so will rise. If you cool that water OR heat it up (change its density), it leaves (convects away). The heat migrates with the water.
So, what happens? Water near 4 degrees flows down and water not quite as near to 4 degrees moves up. The densest water is down at the bottom, and it is densest because of its temperature.
It isn’t a closes system where work done must increase total energy (raise temperature eventually). The system is open, if work is done that somehow changes temperature, the material leaves and takes the heat with it.
The first thing is that water is an odd substance in its density response to pressure. The maximum density of water occurs at a temperature slightly above freezing (about 4 degrees C for pure water). Second is that water is liquid, a fluid, and moves fairly easily.
Water that is colder or warmer than the 4 degrees max density temperature will be less dense, so will rise. If you cool that water OR heat it up (change its density), it leaves (convects away). The heat migrates with the water.
So, what happens? Water near 4 degrees flows down and water not quite as near to 4 degrees moves up. The densest water is down at the bottom, and it is densest because of its temperature.
It isn’t a closes system where work done must increase total energy (raise temperature eventually). The system is open, if work is done that somehow changes temperature, the material leaves and takes the heat with it.
An increase in pressure will typically increase temperature. However this hand wavy rule refers to a closed system, and a pressure increase within that closed system. Neither of these are the case for the ocean.
The temperature of the bottom of the ocean is a result of fluid flow (heat rises) and very little energy ever making it to the bottom (absorption of atmospheric heating and sunlight by higher levels).
An increase in pressure will typically increase temperature. However this hand wavy rule refers to a closed system, and a pressure increase within that closed system. Neither of these are the case for the ocean.
The temperature of the bottom of the ocean is a result of fluid flow (heat rises) and very little energy ever making it to the bottom (absorption of atmospheric heating and sunlight by higher levels).
Water doesn’t compress. Or rather, it’s maximum density is at 4C. regardless if it’s on the surface of the ocean or at the bottom of the sea.
The reason YOU feel pressure when you dive deep is because you are not a solid nor are you all liquid. You have lungs that require air to keep you alive. If you free dive on a single breath, the air in your lungs gets compressed. The only way you can take a breath under water is if you breath in compressed air from a scuba tank, but you better keep breathing on the way back to the surface because if you hold that breath, the air will expand as you surface and you will burst your lungs.
Water doesn’t compress. Or rather, it’s maximum density is at 4C. regardless if it’s on the surface of the ocean or at the bottom of the sea.
The reason YOU feel pressure when you dive deep is because you are not a solid nor are you all liquid. You have lungs that require air to keep you alive. If you free dive on a single breath, the air in your lungs gets compressed. The only way you can take a breath under water is if you breath in compressed air from a scuba tank, but you better keep breathing on the way back to the surface because if you hold that breath, the air will expand as you surface and you will burst your lungs.
As you dig a hole into the surface of the earth the deeper you go the hotter it gets. If you start at sea level and dig 3 miles deep you will get a temp about 150 degrees hotter than the surface ground (~55F). So why is the ocean floor, where it is three miles below sea level so cold?
As you dig a hole into the surface of the earth the deeper you go the hotter it gets. If you start at sea level and dig 3 miles deep you will get a temp about 150 degrees hotter than the surface ground (~55F). So why is the ocean floor, where it is three miles below sea level so cold?
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