The Earth is one of those extremely rare, special places in the Universe where water can exist, stably, as a liquid. So much of it exists here on Earth, that if you were to add up all the oceans on Earth together, it would weigh more than 10^18 tonnes, more massive than the biggest asteroid ever, and about as massive as Pluto's giant moon, Charon.
But water only has a very small window in which it can be a liquid. For instance, if you took some warm water up to a very high elevation, it would start to boil, and become a gas! The higher up you took it, the lower and lower your boiling point would be.
Why? Because higher altitudes on Earth mean lower pressure. If there's not enough force pressing the water into a liquid phase, then there's no force binding the water molecules together. If you simply allow them to diffuse away, they will. And that's the definition of a gas, which is what you'll wind up with.
On the other hand, water has no business being a liquid at low temperatures, either. You can see -- from this diagram below -- that if you start with liquid water, you can turn it into a gas by lowering the pressure, but you can also turn it into a solid by lowering the temperature.
So my question is this:
If you took a glass of water into outer space, would the water freeze or would the water boil?This is a question that seems awfully tough, because in addition to knowing about water:
We also need to know about outer space. Space is a lot of things: cold, dark, and empty come to mind right away. And they come to mind, pretty much, as soon as you leave the Earth.
Well, the temperature of space is, at its coldest, just the temperature of the leftover glow from the Big Bang. This radiation, known as the Cosmic Microwave Background, bathes the entire Universe in a temperature of only 2.7 Kelvin. That's less than 3 degrees above absolute zero, or -455 degrees Fahrenheit! But there's also -- literally -- no pressure in space. So, what happens? Who wins? Does the water freeze or boil?
Oddly enough, the answer is first one, and then the other! It turns out that having a pressure vacuum will cause the water to boil almost instantly. In other words, the effect of boiling is much, much faster than the effect of freezing.
But the story doesn't end there. Once the water has boiled, we now have some isolated water molecules in a gaseous state, but a very, very cold environment! These tiny water vapor droplets now immediately freeze (or, technically, desublimate), and become ice crystals.
We've observed this before. According to astronaut observations, where they've observed their urine get expelled from the ship:
When the astronauts take a leak while on a mission and expel the result into space, it boils violently. The vapor then passes immediately into the solid state (a process known as desublimation), and you end up with a cloud of very fine crystals of frozen urine.Sounds like it would be a fantastic thing to watch, doesn't it? Well, we've done almost the same thing on Earth. What happens if you take boiling water and, on a very, very cold day, throw it up into the air?
The water finishes boiling and becomes a gas, the gas freezes (or desublimates), and ice crystals -- a.k.a. snow -- results! And that's what happens to water in space. Oh, to be able to try this at home...
Physical Science
Comments
I have tried this at home! But then, I do live in Canada...
Posted by: rfguy | June 29, 2009 2:27 PM
That was brilliant! :)
Posted by: Jamie | June 29, 2009 2:32 PM
For a practical application of Fig 2, move to Los Alamos, NM. At 92 C, you boil spaghetti al dente in 20 min, and your potatoes take an hour plus.
Posted by: Mu | June 29, 2009 3:05 PM
We used to do this as kids growing up in MN. Science, sometimes, is so much like magic :)
Posted by: Clinto | June 29, 2009 3:10 PM
Why not get a pressure cooker, then?
Posted by: Sili
| June 29, 2009 3:15 PM
That snowflake looks disturbingly familiar. Did you get permission from the photographer? If it's who I think it is, I'm sure he'll be happy to let you use the photo (and you can put a link to his web page where many high quality photos can be found).
@Mu: A good quality pressure cooker with a pressure adjustment works very well - if you can find it. You can just crank down the pressure setting so that water boils around the usual sea level boiling point. I'd take a normal pressure cooker and modify it, but I'm not saying anything because I wouldn't want to be sued if something goes wrong. :P
Posted by: MadScientist
| June 29, 2009 3:29 PM
MadScientist,
Nope, don't know the photographer; just took it from google images. If you know the guy, send me his site info (and/or a link to his photo) and I'll link to it in the article.
As for the snow/boiling water trick, it seems that about -40 degrees is where you want to be for this stunt to work. I should've tried it the one winter I spent in Madison, WI...
Posted by: Ethan Siegel | June 29, 2009 3:55 PM
http://www.straightdope.com/columns/read/118/would-a-glass-of-water-in-space-freeze-or-boil
Check out this old straight dope, which happened to recently be reposted to the front page of straightdope.com
Posted by: Jeff Mitchell | June 29, 2009 7:02 PM
As for the pressure cooker suggestion, it's the perfect way to produce mashed spaghetti and al dente potatoes, due to problems of getting the timing just right. Also, I found starches in certain kind of pressure cookers quite dangerous, since the foam gets into the valve mechanism and makes them sticky.
For a funny anecdote, when I first moved their I grabbed a pack of cake mix and looked at the "high altitude" instructions, which were for 3000 - 6000 ft. I was baffled what to do at 7500.
Posted by: Mu | June 30, 2009 8:27 AM
Ethan,
You write the coolest blog. I learn something new almost every time I read it. I've always wondered what happened first in space - freezing or boiling.
I should have guessed, because every material has a thermal capacity, i.e. an ability to retain heat. So it stands to reason that it would respond first to the instantaneous drop in pressure, and then as it gives up its heat more slowly, drop in temperature to the freezing point. Makes sense, but I never stopped to think about it. I thought the "Urean Nebula" just went straight to ice, and I wondered why it didn't boil.
Answer: It did!
Posted by: Jodie | June 30, 2009 9:13 PM
Forgive my ignorance - where does the heat in the liquid go that quickly?
Posted by: Cory | July 6, 2009 3:55 PM
The heat gets lost during evaporation and consequent expansion of the resulting gas into the vacuum.
Posted by: Mu | July 6, 2009 4:07 PM
thats not a snow flake ...its a pee flake....
Posted by: Chunky soup | September 3, 2009 7:40 AM
hei..would you like to teach me how to make 2nd diagram (liquid,gas and solid)??
reply me pls.thanks
Posted by: finesa | September 8, 2009 6:25 AM