# Why does everything freeze in space without pressure? **URL:** \ **Category:** Factual Questions\ **Created:** [March 11, 2001, 4:55pm UTC](https://boards.straightdope.com/t/why-does-everything-freeze-in-space-without-pressure/57553 "2001-03-11T16:55:20Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Speaker\_for\_the\_Dead](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@Speaker\_for\_the\_Dead](https://boards.straightdope.com/u/Speaker_for_the_Dead)\ **Post date:** [March 11, 2001, 4:55pm UTC](https://boards.straightdope.com/t/why-does-everything-freeze-in-space-without-pressure/57553/1 "2001-03-11T16:55:20Z")
From what I remember, the lower the pressure, the lower the boiling point. However, I also remember that the lower the temp, the higher chance that it’s frozen (our imaginary substance). So why are a lot of things frozen in space instead of gas. I realize that things like hydrogen and helium are still gasses because of their incredibly low freezing point, but why not anything else? ---
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [March 11, 2001, 5:09pm UTC](https://boards.straightdope.com/t/why-does-everything-freeze-in-space-without-pressure/57553/2 "2001-03-11T17:09:26Z")
The relationships between state, pressure and temperature are more complicated than you suppose. To tell what state a substance will be in space, you really have to look at the phase diagram. For instance, here’s the one for water: [http://www.sbu.ac.uk/water/phase.html](http://www.sbu.ac.uk/water/phase.html) At a pressure of 0 Pa (a vacuum), the temperature still has to be above 200 K for water to be a gas. Below 200 K it will be ice. So in space it will be ice. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [March 11, 2001, 5:09pm UTC](https://boards.straightdope.com/t/why-does-everything-freeze-in-space-without-pressure/57553/3 "2001-03-11T17:09:32Z")
When you lower atmospheric pressure, not only do you lower the boiling point, but you raise the freezing point. In space water boils and freeze at the same time; there is no liquid phase to water in space and therefore goes directly from ice to vapor (Sublimation) Dry ice (frozen carbon dioxide) does the same thing here on earth ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [March 11, 2001, 5:10pm UTC](https://boards.straightdope.com/t/why-does-everything-freeze-in-space-without-pressure/57553/4 "2001-03-11T17:10:59Z")
I am not a physics maven but as a WAG I think you may be apple and oranging by comparing outer space to general rules for freezing/boiling with terresterial atmospheric pressure involved. Outer space is very low pressure and extremely cold. I would imagine it is cold enough so that the relative lack of pressure is inconsequential with respect to freezing. Forewarning to the physics mavens if I’m wrong I _said_ it was a WAG. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [March 11, 2001, 6:43pm UTC](https://boards.straightdope.com/t/why-does-everything-freeze-in-space-without-pressure/57553/5 "2001-03-11T18:43:23Z")
**SmackFu** has the correct answer. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [March 11, 2001, 10:11pm UTC](https://boards.straightdope.com/t/why-does-everything-freeze-in-space-without-pressure/57553/6 "2001-03-11T22:11:40Z")
Anyone notice that that water site (a great site, by the way) has an [explanation](http://www.sbu.ac.uk/water/explan.html#mpemba) of why hot water may freeze faster than cold water? It’s the Mpemba Effect… 🙂 Ref: [Cecil’s wisdom](http://www.straightdope.com/classics/a2_098b) and [The “Comments on Cecil’s Column’s” discussion](http://boards.straightdope.com/sdmb/showthread.php?threadid=49867)