# Would turning into dust freeze you?

I have an idea for a power/ability, but I want to know if it would work like I think it would.

Basically, the person has the power to separate themselves into separate hive mind cells and join back at will. These cells can levitate and separate the molecules of other materials, denser matter is harder to break through.

But when they 'dust', would they lose a lot of heat energy, or would they lose heat through movement since they have immeasurably more surface area? I don't mean how can I fix this, just, would it happen? I kinda like the idea of a hero with a really strong power but using it leaves him shivering.

They would be more vulnerable to any extreme of temperature

Let's look at two 1 kg dry bags of flour with an internal temperature of 37°C sitting on the floor in a room at 37C and minimal humidity. Now pour out Bag 1 and blow it around with a fan. The individual particles of Bag 1 will still have a temperature of 37°C. Bag 2 will also retain its temperature of 37°C.

Now take two new bags of flour, still with an internal temperature of 37°C, into a room at 20°C and repeat the experiment. The individual particles from Bag 1 will very quickly approach 20°C, while Bag 2 will be much slower to reach 20°C. It would be a matter of seconds I would think before the temperature would drop to below hypothermia levels.

Repeat the scenario again in a room at 45°C and the Bag 1 particles will heat up faster, while Bag 2 will take longer to heat up. As observed in the question, increased surface area will change temperature faster through conduction and radiation (convection is a bit iffy with the small particles), although see point 3 below.

However, there are three additional factors:

1. Evaporation - without some special mechanism to maintain the integrity of the particles the water in the superhero's body will evaporate away very quickly, resulting in the superhero reconstituting as a mummy. (Which could be a really scary, albeit fatal, ability to intimidate the bad guys with.) If the thought experiments above were repeated with wet bags of flour, the particles from Bag 1 in the 37°C scenario would cool instead of retaining their temperature and the particles from Bag 1 in the 20°C scenario would cool much faster.
2. Heat generation - a bag of flour is not a good approximation because human bodies are generating heat all the time. Maintaining a levitation field to keep all the particles together may mean even more heat generation, which could offset the heat losses from conduction and radiation. However, if this is the case then it exacerbates the evaporation issue and the risk of hyperthermia in environments over 37°C.
3. Non-interaction with other particles - if the molecules of the superhero's body avoid interaction with other molecules in order to pass through solid objects (implied by "separate the molecules of other materials" in the question) then convection and conduction are by implication not a factor and radiation is the only mechanism for heat transfer. This makes the calculation of heat loss quite different, as it would require calculating the black body radiation of each of the molecules of the superhero's body and summing these. However, if the levitation field is keeping all of the molecules close together (keeping the molecules as close together as if they were a solid) then many of these molecules will be radiating to each other, which makes the net radiation of the entire body approximate to the black body radiation of a normal human body. This raises the issue that if the molecules all remain very close to each other and do not lose heat through convection or conduction then the risk changes from hypothermia to hyperthermia - the human body needs to be able to dump some heat to its surroundings through conduction and/or convection in order to avoid overheating.

In short, heat loss is a factor that you can use to put limits on how long your superhero can remain in "dust" form without suffering hypothermia, but you need to ensure that the explanation of this power prevents death through dehydration as part of the process.

• Their body doesn't avoid interaction. It forces other material molecules apart until they break. Like making billions of tiny holes in it, or making it to weak to hold itself together. – ZoneWolf Jul 29 '18 at 6:35

They would lose heat when the cells dust, and the individual cells would be cold. When they come back together they would heat up, but not back to where they were to start.

But your entity can manipulate molecules. Compressing other molecules can make them heat up. While in his gaseous state maybe he works his power on other molecules to produce heat. Then he vampirically consumes this heat.

You could have him be stuck as a cloud of cold cells until he worked his power on some other stuff to warm him to the point where he can come back together. Maybe he has to use it on something else that is living...

• That would be cool, like a limit to how long they can use it or they have to use material to change back. – ZoneWolf Jul 29 '18 at 3:46

There would be a drop in temperature, but it might not be particularly extreme. If the cells are surrounded by still air, air is actually a pretty good insulator. I presume these cells are separated but stay in a relative "cloud" with a larger volume than the original form, so the increase in volume would create a relative vacuum between them. Air rushing in to fill this vacuum would heat up as it passes the outer layers of the cloud, and the temperature loss of cells near the center of the cloud would be less than the loss at the outer edge of the cloud.

The composition of the cells--and their environment--also makes a large difference in how well they could retain heat. Cells are made of mostly water, which transfers heat fairly well. This is why water cooled systems are more efficient than air cooled systems.

Air - h = 10 to 100 W/(m2K)
Water - h = 500 to 10,000 W/(m2K)


(from wiki)

So splitting apart in air would allow the cells to retain their heat much better than splitting apart in something with a higher heat transfer coefficient (such as solid metal or another liquid, which would induce rapid cooling).

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• Cellular air friction would be negligible as would the vacuum. Also, as soon as the cloud moves away from where it started it would be air cooled and has little to heat it back up – ZoneWolf Jul 29 '18 at 3:33

The jillions of single-celled organisms on Earth don't freeze when the temperature is above 0oC, so you should not expect the cells in your hive mind to freeze either.

When his hive mind cells reunite, they'd naturally be at ambient temperature, though, and that's a Very Bad Thing for warm-blooded creatures (except when ambient temperature is the same as body temperature).