Why leaves change color

The Marginalian by Maria Popova:

Autumn is the season of ambivalence and reconciliation, soft-carpeted training ground for the dissolution that awaits us all, low-lit chamber for hearing more intimately the syncopation of grief and gladness that scores our improbable and finite lives — each yellow burst in the canopy a reminder that everything beautiful is perishable, each falling leaf at once a requiem for our own mortality and a rhapsody for the unbidden gift of having lived at all. That dual awareness, after all, betokens the luckiness of death.

But autumn is also the season of revelation, for the seeming loss unveils a larger reality: Chlorophyll is a life-force but it is also a cloak, and when trees shed it from their leaves, nature’s true colors are revealed. 

Photosynthesis is nature’s way of making life from light. Chlorophyll allows a tree to capture photons, extracting a portion of their energy to make the sugars that make it a tree — the raw material for leaves and bark and roots and branches — then releasing the photons at lower wavelengths back into the atmosphere. A tree is a light-catcher that grows life from air.

This article finishes with this:

The poetic astronomer Maria Mitchell captured this best in her rueful and rapturous observation that “we have a hunger of the mind which asks for knowledge of all around us, and the more we gain, the more is our desire,” and yet “we reach forth and strain every nerve, but we seize only a bit of the curtain that hides the infinite from us.”


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