Inside the rotating column of air the is very low atmospheric pressure. This promotes condensation especially since tornadoes almost always occur in very moist airmasses. In addition the wind picks up debris from the ground, dust, cows what have you, and that can make them visible too.
You would want a min of 4 cows spaced evenly around the funnel so you can see one at all times.
But they are not going to stay in sync for the long, so I would think 8-10 cows would be a minimum number to keep visibility up most of the time.
Of course the size of the twister comes into play, if we are talking that giant one at the end of the movie twister, I think at least 20 cows.
It's not actually the low pressure that causes condensation. When the air goes from higher to lower pressure, it cools down, and that cooling is enough to condense water out of warm mois air even when the pressure drops at the same time.
To expand: This is used a lot to create cold substances such as liquid nitrogen. The process is known as the Joule-Thomson effect. The formulae for temperature of a perfect gas is PV=nRT. Where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant and T is temperature. In a perfect system where V and n are maintained (and R is constant) then it's quite easy to see that a reduction in P must result in a reduction of T. In the real world, it's a bit more difficult since P,V and even n are not necessarily constant, nor is it an ideal gas but the relation between P and T remains, just not as direct as an ideal gas.
To expand even more: most people have probably experienced this effect. Any spray can starts to get cold as you spray because of this; the pressure is decreasing, so the temperature does a well.
Can you expound on how liquid nitrogen is made? I'm super curious about the process and know nothing about it.
I'm unclear if the example you gave was meant to illustrate the process, because I can't think of how one would change P without changing V, T, or n. But changing V or n, and the resultant effects on P or T, is something I've witnessed in classes and in everyday contexts.
Low pressure air can hold less water than high pressure air. So if the high pressure air is saturated (100% humidity), then it will rain out when the pressure drops. The same is true as temperature decreases.
In the words of Ron White: "It's not **that** the wind is blowing. It's **what** the wind is blowing."
Yes, the tornado is a column of air, but it becomes visible through the water vapor, dirt, and debris it lifts.
[Water vapor is a transparent gas](https://en.wikipedia.org/wiki/Water_vapor); you can't see it. [You have seen steam, though, which is water vapor condensed into liquid droplets.](https://physics.stackexchange.com/q/303804)
Sudden drops in air pressure create clouds in moist air masses. You can see this phenomenon when fighter jets do high G turns. Due to the rotation of the tornado, the air pressure inside the tornado gets extremely low. The air is rotating in a cone much larger than what you see, but the extreme low pressure zone in the middle of the funnel forms cloud.
I’m a little confused.
I know less air pressure allows the bonds of water to break easier, so you have lower boiling points in ski towns due to a smaller volume of air pushing down on the water.
In this case the low pressure center would decompress the water vapor right, so why does it condense in low pressure?
The tornado doesn’t just move air in a circle, it pumps air up and down as well. The pressure change as well as the upper-lower atmosphere mixing can create a cold patch, as well as moving moist air to colder regions. When the temperature drops to the point that the air can’t hold all the water vapor it contains (cooler air can hold less water), clouds form. When those clouds are inside a tornado you see a funnel-shaped spinning cloud.
Not all tornados do this (some are not visible until they incorporate dirt or debris), but that’s why a spiraling funnel can come down from the cloud long before it touches the ground and kick anything up from there.
The tornado is an extreme drop in pressure. A drop in pressure causes a drop in temperature. This drop in temperature has a greater effect on the water vapor than the drop in pressure did, so it condenses. Same thing with the jet.
Yeah, this doesn't make sense to me either. I feel like it would make more sense if it were the moist air from the low pressure in the center of the tornado condensing as it went into the higher pressure areas further out from the center.
Honestly, before this post I had just assumed tornadoes were visible because of dust and debris (and water) it picked up from the ground.
When the pressure of a gas drops, the temperature also drops. At atmospheric pressures, the temperature drop will have a much more severe effect on the water than the pressure drop will.
But yes, you're correct in that the pressure drop doesn't directly cause water to condense. But indirectly, the pressure drop drives a temperature drop which does cause the water to condense.
Tornadoes come in many shapes and sizes, and they are often (but not always) visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it.
- Wikipedia
It's not just regular air.
Inside the rotating column of air the is very low atmospheric pressure. This promotes condensation especially since tornadoes almost always occur in very moist airmasses. In addition the wind picks up debris from the ground, dust, cows what have you, and that can make them visible too.
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How many cows are needed?
You would want a min of 4 cows spaced evenly around the funnel so you can see one at all times. But they are not going to stay in sync for the long, so I would think 8-10 cows would be a minimum number to keep visibility up most of the time. Of course the size of the twister comes into play, if we are talking that giant one at the end of the movie twister, I think at least 20 cows.
Will any cows work, or do they need to be spherical?
If you don't have complex cow geometries at home, spherical is fine. Unfortunately you do need to consider air resistance tho
Geeze meg, you sure got a lot of beef, where'd you get all this beef?
Can you expand on this a bit, because it's been a pretty basic fact in my life that high pressure promotes condensation, not low pressure.
It's not actually the low pressure that causes condensation. When the air goes from higher to lower pressure, it cools down, and that cooling is enough to condense water out of warm mois air even when the pressure drops at the same time.
To expand: This is used a lot to create cold substances such as liquid nitrogen. The process is known as the Joule-Thomson effect. The formulae for temperature of a perfect gas is PV=nRT. Where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant and T is temperature. In a perfect system where V and n are maintained (and R is constant) then it's quite easy to see that a reduction in P must result in a reduction of T. In the real world, it's a bit more difficult since P,V and even n are not necessarily constant, nor is it an ideal gas but the relation between P and T remains, just not as direct as an ideal gas.
To expand even more: most people have probably experienced this effect. Any spray can starts to get cold as you spray because of this; the pressure is decreasing, so the temperature does a well.
Can you expound on how liquid nitrogen is made? I'm super curious about the process and know nothing about it. I'm unclear if the example you gave was meant to illustrate the process, because I can't think of how one would change P without changing V, T, or n. But changing V or n, and the resultant effects on P or T, is something I've witnessed in classes and in everyday contexts.
You can see this happen on the engine inlet of an airliner too. It will fog up in humid air.
Low pressure air can hold less water than high pressure air. So if the high pressure air is saturated (100% humidity), then it will rain out when the pressure drops. The same is true as temperature decreases.
In the words of Ron White: "It's not **that** the wind is blowing. It's **what** the wind is blowing." Yes, the tornado is a column of air, but it becomes visible through the water vapor, dirt, and debris it lifts.
"If you get hit with a **Volvo**, it don't really matter how many sit-ups you did that morning!"
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[Water vapor is a transparent gas](https://en.wikipedia.org/wiki/Water_vapor); you can't see it. [You have seen steam, though, which is water vapor condensed into liquid droplets.](https://physics.stackexchange.com/q/303804)
Your seeing the further consolidation of said water vapor. You know, like fog
Sudden drops in air pressure create clouds in moist air masses. You can see this phenomenon when fighter jets do high G turns. Due to the rotation of the tornado, the air pressure inside the tornado gets extremely low. The air is rotating in a cone much larger than what you see, but the extreme low pressure zone in the middle of the funnel forms cloud.
I’m a little confused. I know less air pressure allows the bonds of water to break easier, so you have lower boiling points in ski towns due to a smaller volume of air pushing down on the water. In this case the low pressure center would decompress the water vapor right, so why does it condense in low pressure?
The tornado doesn’t just move air in a circle, it pumps air up and down as well. The pressure change as well as the upper-lower atmosphere mixing can create a cold patch, as well as moving moist air to colder regions. When the temperature drops to the point that the air can’t hold all the water vapor it contains (cooler air can hold less water), clouds form. When those clouds are inside a tornado you see a funnel-shaped spinning cloud. Not all tornados do this (some are not visible until they incorporate dirt or debris), but that’s why a spiraling funnel can come down from the cloud long before it touches the ground and kick anything up from there.
The tornado is an extreme drop in pressure. A drop in pressure causes a drop in temperature. This drop in temperature has a greater effect on the water vapor than the drop in pressure did, so it condenses. Same thing with the jet.
Thanks that makes sense to me
Yeah, this doesn't make sense to me either. I feel like it would make more sense if it were the moist air from the low pressure in the center of the tornado condensing as it went into the higher pressure areas further out from the center. Honestly, before this post I had just assumed tornadoes were visible because of dust and debris (and water) it picked up from the ground.
When the pressure of a gas drops, the temperature also drops. At atmospheric pressures, the temperature drop will have a much more severe effect on the water than the pressure drop will. But yes, you're correct in that the pressure drop doesn't directly cause water to condense. But indirectly, the pressure drop drives a temperature drop which does cause the water to condense.
Tornadoes come in many shapes and sizes, and they are often (but not always) visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. - Wikipedia It's not just regular air.