Atmosphere Question

NoQuarter

Hi folks,

I was watching this:

https://www.youtube.com/watch?v=1PmYItnlY5M

and james may mentioned (at 5:38) at a certain altitude that saliva and his body in general would boil instantly if it touched the atmosphere.

Can anyone explain this?

Thanks.

themadhair

Saliva would boil due to the lack of pressure rather than temperature, but I don’t think he is correct about his body actually boiling. He would experience a condition called ebullism, which is where the liquids inside the body go gaseous. Since liquids going gaseous is technically boiling I assume this is what he is referring to.

glenbrook

Liquids boil (turn into gas) depending on temperature AND pressure. For instance, water boils at 100C at sea level, but if you go up to the top of Mount Everest, water will boil at 70C. The U2 spy plane flies at 21000m and pressure is around 4 kPa. The temperature is also very low, somewhere around -65C Lower than a few degrees below C, water cannot exist in liquid form, therefore we can assume that James May (being 60% water) would become a solid or a gas. Then again, blood and body fluids are not pure water and impure water freezes at a lower temperature and boils at a higher one. However, this effect is only a few degrees. Looking at a water phase diagram, I reckon he would turn into a solid, so I think he is WRONG. Of course, if he was unceremoniously dumped into the air at 21000m, he would have some body heat, so I suppose his saliva would boil for a short while until his body lost heat and froze solid

NoQuarter

Thanks folks. Another myth.... BUSTED!