Does water freeze or boil in space?
Here on Earth, it’s liquid all the way. But in space, that’s impossible!
“You can’t cross the sea merely by standing and staring at the water.”
-Rabindranath Tagore
If you brought liquid water into outer space, would it freeze or would it boil? The vacuum of space is awfully different from what we’re used to here on Earth. Where you stand now, surrounded by our atmosphere and relatively close to the Sun, the conditions are just right for liquid water to stably exist almost everywhere on our planet’s surface, whether it’s day or night.
But space is different in two extremely important ways: it’s cold (especially if you’re not in direct sunlight, or farther away from our star), and it’s the best pressureless vacuum we know of. While standard atmospheric pressure on Earth represents about 6 × 10^22 hydrogen atoms pushing down on every square meter at Earth’s surface, and while the best terrestrial vacuum chambers can get down to about one trillionth of that, interstellar space has a pressure that’s millions or even billions of times smaller than that!
