At what temperature does spittle freeze as it flies through the air to the ground from a height of twenty feet? This question is not important scientifically. Nor will it (probably) ever matter in our lifetimes (although there could be an instance in which someone will need to hit a target across a freezing torture chamber of spit/ice that will release a secret lever and allow one of my blog readers to escape with their life and consequently save the life of countless others... although I doubt it). However, let the geniuses of the internet sort out the details. Spit first, ask questions later.

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Blogger Worldgineer said...

Damn I want to answer this one. But my crazy schedule demands I don't spend 15 minutes with pencil and paper right now. I will give you the bits to start with:

Diameter 1/4 inch
Spittle has properties of water (freezing point, heat capacity, conductance)
Air resistance is negligable
Sarah's mouth is 5' from ground.

How you'd solve:
Use 32.2 ft/s/s and the equations of motion to find length of time in the air.
Then E = UAdT should get you most of the way there. To do it right you'll need calculus, but you can get very close without it.

5/12/06 22:09  
Anonymous lostdog said...

Wow, world. That's impressive.

I spent fifteen minutes with Google, but didn't come up with a conclusive answer. Jack London mentions the phenomenon in one of his books, but he was generally thought to be exaggerating (or "writing fiction", as it's otherwise known). I find a loose consensus that spit should freeze before it hits the ground at temperatures of about -40, but no reliable personal accounts turned up, mostly just speculation and friend-of-a-friend type yarns.

Found this video of boiling water freezing before it hits the ground: http://www.youtube.com/watch?v=zFj_i6HtebM&search=science
but apparently the water has to be boiling first because water's weird stuff that does lots of strange things.

So: maybe -40 and below. Or maybe not. I found lots of half-truths, rumours and flat-out lies*, but no reliable conclusions. I suppose that's what comes from looking to the internet rather than proper science to answer questions.

*including a guy who claimed to have started to pee in the snow and then had to run away as his wee started to solidify, leaving a kind of icy trail behind him.

6/12/06 16:35  
Anonymous lostdog said...

I also found this on YouTube, which is completely unrelated to spit, but still quite cool:

6/12/06 16:38  
Blogger k_sra said...

Worldgineer, I can no more finish the math with the tools you've provided then I could climb Mount Everest with a pair of claw hammers, but I am in gleeful awe of your nerdiness yet again.

And lostdog found some awesome YouTube stuff! Check it:

Water Bubble in space
Eating tea with chopsticks
Alka Seltzer

8/12/06 08:47  

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