Sunsets are all Wet

Sunsets can be fabulously beautiful. Get the conditions just right and they are awe inspiring. Every other woman's profile on dating sites cite "walks on the beach at sunset" as a favorite activity. "Spiritual" people have been known to pity the poor slobs (i.e.: people like me) who cannot see the greatness of god or the glory of nature in a sunset. It is true… I do not see that. I think I see a little more.


When I see a sunset, perhaps off a beach in Hawaii, my thoughts have been known to wonder down a number of paths. Here is one spontaneous, extemporaneous, well thought out, chain of idle musings, while staring at the horizon.


My first thoughts go to the beauty. When the clouds are just right, with the  sunlight, forced to colors from the redder end of the spectrum, bouncing off them,   the sense of 3D hugeness is hard to avoid. The sun itself goes pear shaped as it touches the horizon. All of that is caused by water and warm wet air. The clouds are suspended micro-droplets of water. Evaporating water changes the density of the air and its refractivity. Nice, very nice, but boring to watch. So again my mind wanders...


I then see the ocean. Water.  Dihydrogen monoxide. H2O. The most dangerous chemical on Earth (floods and such take more lives than any other natural disaster).


The Earth has a lot of it. The average depth of the oceans is about four kilometers. If the Earth's surface where a little less dimpled, we would all be under thousands of meters of water. Having lots of water is not unique to the Earth in the solar system. But having water in all three forms -- solid, liquid and gas -- on the surface, is.


"Water, water everywhere" is true in one sense. Hydrogen makes up 75% of the matter in the universe. Helium, a "noble" non-reactive, chemically boring gas, makes up 23% of the universe. The remaining 2% is everything else. Oxygen is number three on the hit parade at 1%, taking half of what is left, and carbon is number four  at 0.5%, again taking half of what is left. Hydrogen compounds are everywhere. The simplest hydride of oxygen is water. H2O. So it should be no surprise that there is a lot of it about.


Water is both an acid and a base at the same time. The universal solvent. Real chemistry needs a solvent because most chemistry of note requires a liquid where the atoms are close together, but can move freely, get cozy with each other, and then move on. Water was required to create most of the minerals that today make up both the crust of the Earth and our bodies. Most of the Earth's hydrogen is bound up in water. Oxygen reacts strongly with almost everything  (just ask the astronauts who lost their lives on Apollo 1) and is big part of the crust of the planet. If not for life on Earth, there would be no oxygen in the atmosphere today. The Earth would have "rusted" it all out. In a feedback loop, life created oxygen, which created new minerals, which created more new life and so on. Most of the Earth's crust came from life, directly or indirectly. And that needs water. In that sense, there is truth to the idea of a living planet (aka Gaia).


Water has a few more unique properties. Have you ever noticed that ice floats? Of course you have. But why? As a general rule, gases are less dense then liquids, and liquids are less dense than solids. Most solids sink in the molten version of themselves. But not water. And that is a damn good thing. It is a result of the dipole nature of  the water molecule. As it solidifies, the dipole molecules line up in such a way as to decrease density slightly (about 9%). If ice sank, here is what would happen. Some ice would form in winter. It then sinks into the colder and colder water where it will never melt. Slowly, the water column would fill with ice from the bottom up. And finally all the water on Earth would be solid (a snowball world). The Earth would be white as a cue ball and highly reflective. New incoming solar radiation would be reflected back into space, keeping the Earth frozen forever.


Water creates snowflakes and rime and other crystals. Delicate little displays of fantastic mathematical symmetries. Fabulously beautiful.


Water in space is creepy. What would happen if you hand-wrung a water-soaked towel on the Space Station? The water would simply move from the inside of the towel to the outside. Now you have a cylinder of water between you hands, with a towel going down the center. But it gets weirder. Due largely to surface tension, the water would spontaneously start creeping up (or down?) your arms. Shades of "The Blob".


To a chemist, water is strange. It bucks a lot of trends. Its boiling and freezing points are much higher than other similar hydrides like hydrogen sulfide,  which boils at -62 degrees C. Water's boiling point "should" be lower still. water 's Heat of Vaporization is also exceptionally high (this makes it ideal for steam engines). Ditto water's surface tension and cohesion. These properties result in rain, rather than what I would imagine as a choking falling mist. All these properties make water act like water.


Where did all the water come from? There was none on the hot primordial Earth. We are not 100% sure, but a lot probably came from comets containing cubic miles of the stuff impacting the Earth. And just a few hundred millions years later, life and water was all over the place.


Water is everywhere. On planets, and in nebulae (giant gas clouds), comets, and other cold objects  between the stars.


After the sun sets, the stars come out. Perhaps you can see Andromeda, the remotest naked eye object and our twin galaxy, two million light years away? You will need good eyes and dark skies, and you will need to be north of the equator. Whole civilizations could have risen and fallen multiple times in the 2 million year transit time of the light. What would a civilization that is one million years old look like? But I digress...


Where was I? Oh yeah. Yep… the sunset sure is purdee.         


Full disclosure: OK, I had to look up the boiling point of H2S and the percentages for carbon and oxygen in the universe, so it is unlikely that those numerical values would have been featured in my spontaneous daydream.