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Here in the U.S. we call that "Smokey Flavor." :P
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the pressure differential is from the act of cooling, and the fact the default pressure of the cold air going out is higher then that of the hot air which is heading for the sky. You make it seem as if the two are pushing AGAINST one another. They are not. the cold air is always winning the contest, and making the hot air either follow it or get out of the way.
Hot air rises because cold air pushes it upwards, i.e the entire weight of the atmosphere makes it rise like a cork in water.
The main point is that hot air entering the bubble reduces in volume instantly, creating a vacuum and drawing in yet more hot air behind it. This creates wind motion which perpetuates through all the incoming and outgoing air. If it's going in, it has to be going out somewhere to get rid of inertia, if nothing else. It isn't violently sucked into the hemisphere to just stop moving instantly. That would be like saying wind sucked into a funnel stops moving the instant it leaves the funnel.
At the same time, cold air is continually being exuded from the base of the hemisphere as the rising hot air draws in cold air to replace its motion. we now have ingoing and outgoing actions.
Pressure differentials.
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there is no pressure differential.But you have admitted that there is pressure differential, like, 3 posts ago.the pressure differenceIs there a disconnect in terminology or something? That might explain it.There's a miniscule difference in pressure between the top of the hemisphere and the bottom, from the weight of the air within the radius. This has nothing to do with temperature of the surrounding air, and is no different from the difference in pressure between the top and the bottom of an ordinary room. At most, this would cause small amounts of air to leak out from the bottom of the hemisphere and slide along the ground.
What doesn't exist is a pressure differential between the inside and outside of the radius as a result of the difference in temperature - the pressure difference that Das Bier identifies as the cause of these tornado-force winds. Such a difference in pressure would appear if the mold were teleported into the volcano or appeared out of nowhere, but if the mold approaches the volcano in any way the pressure will equalize well before it arrives, as the difference in temperature is compensated for by a difference in density within the sphere.
I am afraid you are just plain wrong. Here, let me make a picture.
What you see is a sphere of cold air(in blue) surrounded by hot air(orange). There are also two important points we will analyse-a black cross and a red cross.
Now, we will assume that there is absolutely no difference in pressure between the inside of the sphere and the outside of the sphere at the black cross point. We will also assume that there is no movement of air whatsoever, because that is what you say will happen. I will show that this leads to contradictions and is thus not the case.
Simplest equation that describes fluid(and gas) behavior in stationary processes is Bernoulli's equation. Because we are assuming that there is no flow in this case, it applies quite handily in this case, and can be simplified to dP=-rho*g*z, where dP is change in pressure, rho is density of the gas, g is acceleration due to gravity and z is the height difference between two points. This is true for any two points within a single "zone" because of math.
So, let's calculate the pressure on the inside and the outside of the sphere at the red X point. Assuming the height of the sphere to be 9.14 meters, g equal to 9.81 m/s^2, density of air at 0 degrees celsium to be 1.293 kg/m^3, density of air at 1000 degrees celsium to be 0.2772 kg/m^3, we get dP along the green path(from the inside of the sphere) to be 115.9 pascals, and along the purple path to be 24.8 pascals. Therefore, since we assumed that the pressure at the black X was equalised, we get a pressure differential between the inside and the outside of the sphere to be equal to ~91 pascals. That is equivalent to the pressure a glass of water would put on your hand if you held it, and is not insignificant.
Now, what does this mean. Since there is a pressure differential, this means that the air in that point would move. However, we assumed that wasn't the case. That means that either our calculations are wrong(they aren't) or one of our assumptions is faulty. We made two major assumptions:that pressures at the black X were equal and that there was no flow of air. Since at least one of them is wrong, we must conclude that either:
-Pressures at the black X are NOT equal, which means that there will be airflow
-There is airflow in the system, which means that there will be airflow
Therefore, there is no way that there isn't a flow of air. Now, we can make a very approximate calculation of how fast that airflow is, by using Bernoulli's equation for flowing liquids. That gives airspeed of 30-40 m/s, which is generally considered to be a very strong wind. I must stress that that calculation isn't meant to be accurate, since air will compress and generally exhibit turbulent behavior, which isn't taken into account by the formula, but it does give a good anchoring point.
The AOE of the mold won't extend into or past a solid object. So, for instance, the bottom of the boat could still melt out from the lava. Lava with a 40 degree outside temp would surround molten cores and crack and ward the interior as it pushed forwards and eventually sinks and melts the bottom of the vessel...if that's what you are wondering.
Airflow 'out' will occur at the lowest point it can. As soon as it starts, pressure differentials will accelerate the process. It will focus in strength around the first (highest) entry point, and then just start driving the system.
Your argument is akin to saying that a Volcano will have no input of cold air because the walls of the caldera are in the way. No, the incoming air just takes the lowest point, and if that happens to be the top of the caldera walls, that's where it comes in...air gets sucked in from around the volcano, and goes upwards from the middle of it.
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Everything has limits. That's why one patch of brown mold has not absorbed all of the heat that exists in the universe. I'd rule that molten lava would easily exceed the limits of brown mold to absorb heat and it would become crispy critterfied.An interesting "solution" to dealing with environments of extreme heat would potentially be to utilize things similar to brown mold or other dungeon hazards that alter the environment around them.
Has anyone worked out the fantasy physics of the interaction between brown mold and lava?
Magic trumps physics. Brown mold doesn't absorb heat in the standard physical sense, it automatically causes the area in a 30 foot radius around it to have a cold temperature - according to the Pathfinder weather rules, between 0 and 40 degrees Fahrenheit. A single patch of brown mold has not absorbed all of the heat in the universe because, interestingly enough, the universe is more than 30 feet wide. Other than that, there is no limit to its heat-cancellation abilities.
So, what happens when a patch of brown mold is dropped into a lava? Well, if the lava is close enough to fire to qualify, then it doubles in size just before it lands. But once it's done doubling, it is no longer next to lava, because the surrounding 30 foot radius is automatically cooled down to at least 40 degrees - which is well below the melting point of the surrounding rock. So when the mold lands on lava, it creates a hemisphere of solid material beneath it, a sort of stone raft. Except for the fact that lava, like most materials, increases in density as it solidifies, and the hemisphere will rapidly begin to sink, transforming into a sphere as more and more lava enters the mold's cooling radius.
In the end, you have a patch of brown mold surrounded by a 30 foot radius sphere of stone, sitting at the bottom of a pool of lava. The mold is happy, the volcano is happy, and so is magic itself: everyone is satisfied except for physics....
The bottom would be a filled hemisphere, sure, but as it sinks, the top would be a hollow hemisphere. While I wouldn't be able to measure the buyancy point for you, I am fairly certain that it would float, and not sink to the bottom.
I would also disagree, however, that instantly cooling the surrounding environment would have no significant impact on the universe. For starters, the cold ability is inconsistent... it only damages creatures within 5 feet. Yet cools everything within 30ft to "cold", which you say is 40 degrees. I'm fairly certain having one's internal organs cooled to 40 degrees, instantly, would at the very least create discomfort. Otherwise, we should consider this cold effect has little penetration power at maximal range. That's not the main point, though. Even if you allow for the violation of the rules of thermodynamy, convection remains a thing. In theory, one brown mould should be enough to freeze a planet over, it's just a matter of time. Maybe not the universe, but at least the planet.
A patch of brown mold doesn't guarantee an eventual ice age. Air can only flow through the area so fast, after all. So now in addition to radiating energy into space, the planet can also dump it into patches of brown mold.
For trivial proof that it needn't freeze the planet over, consider a patch of brown mold in the Arctic.
Goblin, the effect doesn't pass through solid objects, of which your skin is one. Cooling the outside of your skin to 40 degrees does absolutely nothing to you. IF it did, people would lose their faces walking outside in winter.
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Therefore, there is no way that there isn't a flow of air. Now, we can make a very approximate calculation of how fast that airflow is, by using Bernoulli's equation for flowing liquids. That gives airspeed of 30-40 m/s, which is generally considered to be a very strong wind. I must stress that that calculation isn't meant to be accurate, since air will compress and generally exhibit turbulent behavior, which isn't taken into account by the formula, but it does give a good anchoring point.You're right. I was wrong. Thank you for explaining the pressure differences so well, and the airspeed you calculated was much higher than I anticipated. I hadn't expected the weight of the air within the hemisphere itself to play so much of a role, but it appears that it would.
So, Operation Lava-Tornado is still very much in action. But what about Operation Lava-Boat? If a mostly enclosed vessel was made before entering the volcano and warded with strategically placed patches of brown mold, it could avoid the pressure difference issues, correct? If the only space for air to move in or out is at the top of the "boat," then it seems the destructive airflow out of the bottom of the cooled area could not occur. But there could be other forces at work as well - depending on the preexisting speed of the hot air in the volcano, an enclosed container might not do much good.
*Opens mouth* *Closes mouth* *Opens it again*
Wow. Someone admitted they were wrong on the internet. I'll need to invest into bomb shelters, apocalypse seems to draw near.
As for the boat, it will slowly grow because lava will crystallise on the cool surface of the sphere. It probably won't be all that fast, so it should stay reasonably buoyant.
>Goblin, the effect doesn't pass through solid objects, of which your skin is one. Cooling the outside of your skin to 40 degrees does absolutely nothing to you. IF it did, people would lose their faces walking outside in winter.
What makes you think that it doesn't?
I figure I can use all the logic and numbers and complex terminology I want, but if I can't identify false beliefs and replace them with true ones, then what's the point of caring about science?*Opens mouth* *Closes mouth* *Opens it again*
Wow. Someone admitted they were wrong on the internet. I'll need to invest into bomb shelters, apocalypse seems to draw near.
Well, yes, you should totally do that, it's just that this doesn't happen often.