Al Stahler: Autumn leaves

The universe is lazy. Take a rock as typical: A rock would rather fall down, than up.

This is true on all levels. We (and by “we”, I include rocks) … we are made of atoms, glued together. Atoms can detach from one another and re-glue themselves in new combinations. This juggling of atoms is a chemical reaction. Chemical reactions prefer to go downhill.

Allow me to define “downhill.”

A rock – following the laws of the universe – would “rather” be on the ground, than up in the air. When a rock falls downward – following its druthers – it releases energy … energy we can use, to, say, crack a walnut.

When atoms re-glue themselves into an arrangement they prefer, they release energy … and we can say the reaction has gone “downhill.”

Fire is a chemical reaction. The atoms in a chunk of wood are glued together, hundreds, thousands at a time, in large clumps. They would “rather” be glued together, just three atoms at a time, in much smaller clumps of carbon dioxide (one carbon, two oxygens) and water (two hydrogens, one oxygen). When we allow the atoms to follow their druthers – allow them to rearrange – the atoms release energy: Light and heat. Releasing energy, the reaction has gone “downhill.”

The whole universe “wants” to go downhill, releasing energy as it falls. To lift something uphill – to lift a rock – we’ve got to put energy into it.

Re-arranging the atoms in carbon dioxide and water, to make wood – pushing the atoms “uphill” – takes energy.

The food we eat is composed of atoms in large clumps, atoms that (like those in wood) would rather be carbon dioxide and water. Our bodies perform chemical reactions that allow the atoms follow their druthers, to re-arrange themselves into carbon dioxide and water, releasing energy as they do so – the energy we need to live.

It takes energy to squeeze the atoms in carbon dioxide and water into new arrangements. To make food from carbon dioxide and water, green plants obtain energy from sunlight. They capture that energy with pigments – especially, the green pigment chlorophyll.

But chlorophyll cannot capture all the energy in sunlight – which is why it’s green. Chlorophyll reflects green, and the energy in that light goes to waste.

Plants have other pigments that can capture green light. Absorbing green, these pigments reflect yellow and orange, leading to their name: carotenoids, from “carrot.” Carrots contain lots of carotenoids.

Carotenoids are always present in leaves, but their color is overwhelmed by the green of chlorophyll … until autumn, when many plants stop producing chlorophyll, allowing the yellows and oranges of the carotenoids to glow through.

IN THE SKY

Storms – YES! If somehow there’s a break in the clouds tonight (Thursday), bright planet Jupiter will be close to the moon.

Next Wednesday night (12/7), planet Mars will be close to Earth, and close, in the sky, to the full moon. Close to us, and also in “full” phase, Mars will be bright.

Using Mars as a skymark, watch the moon move, through the night. If you’ve got a good view to the east, Mars will be completely hidden – occulted – by the moon, soon after they both rise, early Wednesday evening.

Al Stahler enjoys sharing science and nature with friends and neighbors, in The Union and on KVMR-FM. He teaches classes for both kids and grown-ups, and may be reached at a.a.stahler11@gmail.com.