Whenever I want to remind myself of the awesomeness of the universe, I try to remember that trees are pretty much made of air solidified by light.

You probably already learned about this when studying photosynthesis in school, but somehow I didn't make the connection (or at least I can't remember). It was only recently that I read somewhere Thich Nhat Hanh saying that a tree is mostly made out of air, so I had to look it up, and it turns out to be true!

One usually assumes that trees come out of the ground, right? Roots go deep to get nutrients, you need to water it or it dies, and so on. But it turns out that almost half of the (dry) mass of a tree is just pure carbon, and the other half is mostly oxygen. And where do these come from? Well, the air, of course! And it's with the help of sunlight (photosynthesis) that the tree manages to take in CO2 and transform it into sugars, from which everything else derives.

Interestingly, the water used in photosynthesis is split into hydrogen and oxygen, but of these only the hydrogen ends up being used, while this oxygen is discarded. Why is this oxygen not used when the one from CO2 is? ... the magic of nature ...

Also, the tree itself doesn't get any carbon from the ground (afaik). Actually, the amount of minerals that make up the "mass" of the tree is really quite tiny (though still essential, of course).

There was a famous experiment proving this where a guy (Jan Baptist van Helmont; fancy name) grew a willow tree in a measured amount of soil. Quoting from Wikipedia

[...] After five years the plant had gained about 164 lbs (74 kg). Since the amount of soil was nearly the same as it had been when he started his experiment (it lost only 57 grams), he deduced that the tree's weight gain had come entirely from water.

(he was actually partially wrong, as the extra mass cannot come just from water. He didn't account for the contribution done by Carbon and Oxygen)

Another neat part (physics is so elegant) is that thanks to the "conservation of energy", the amount of sunshine energy that the plant used in photosynthesis to process the CO2 is almost the same amount of energy that you get back when you burn a dry piece of wood. The cellulose (carbon) of the wood mixes back in again with the oxygen in the atmosphere, yielding once again CO2. It's like the wood in a tree is a sort of magical battery that was charged with the energy of the sun.

When you burn it, the tree becomes air again, and most of the part that is left behind (the ashes) is actually the parts of the tree that didn't come from the air in the first place.

Crazy stuff, right?

On paper it can sound so academic, but if you think about it, it's just such a beautiful, awesome thing. The trees, those things that look so solid, sometimes even so permanent, are really made out of air that's frozen by the sun (I think this was said by Richard Feynman, though I couldn't really find the original quote). We take them for granted as a concrete entity, when really they embody the beautiful interplay of energy that's so prevalent in stuff around us.

I'm sure you can find similarly awesome phenomena all around us. Just look at your own body, for example: the exchange of oxygen, absorbing nutrients during digestion, our brains, muscles, skin.

It's like the universe is full of beings that are more like temporary whirlpools of energy. Little eddies that form for a while out of interlocking pieces of the cosmic puzzle, just to dissipate again later, and then begin the dance anew somewhere else.

Our human reality is often so constrained to "human things", and more often than not to ugly ones. Politics. War. Worries. Responsibilities. There's so much more out there than we usually let ourselves perceive. It's so easy to forget that the universe is not human, and easier still to forget that we ARE the universe.

Carl Sagan has a beautiful quote about this. ... well, I tried looking for it but couldn't find the exact source, so maybe it's one of those paraphrased quotes, or something that someone came up with and attributed to Carl Sagan? Anyway, I think it's still wonderful and very apt here even if it's not "real", so I'll just write it as I remember hearing it ...

The story goes that Carl Sagan was giving a talk, and someone from the audience said:

"Why do you say all these nice things about the universe, when in fact the universe is vast, cold, vicious, and cares absolutely nothing for us".

To which Dr. Sagan answers,

"My brother, you are the universe".

...

You are the universe.