National Geographic: Rhythms of Life

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From the first dawn of creation

to the end of time

our world, our lives,

and every living thing

are attuned to a cosmic song

a celestial cadence

of light and dark

of ebb and flow

of heat and cold

all set into motion by the epic

dance of the sun, moon, and earth.

These are the rhythms of life itself.

Before there could be day or night

before there was a spring or fall

a star, our sun,

had to flare into life.

From the seething stuff of stars,

over time, the planets of

our solar system took shape.

Four billion years ago, or more,

one such place was born

the planet called, Earth,

our home.

But for nearly a billion years,

it would be a home inhospitable

to any form of life

a red and angry globe

a churning mass of fire, poison gas,

and molten rock

At the core of the planet

raged an inferno.

For thousands upon thousands

of centuries,

this infant planet suffered the

violent pains of growth and change,

as it formed and reformed itself.

From the very beginning,

the earth knew night and day.

But a night and day

not like any we know now.

Fueled by the forces of creation,

the earth raced through

its daily cycle,

spinning five times as fast

as it does today.

A few brief hours of starlight.

A few brief hours of sun.

Day followed night at a dizzying pace.

Earth and sun were not alone

in their orbits.

But cosmic visitors

rarely came to stay

until one cataclysmic encounter

transformed the heavens

and earth forever.

One theory tells of a cosmic accident

a huge asteroid

on a collision course.

It may have been the birth of the moon

and so many of

the rhythms of life.

But first, the moon would have been

a cloud of fragments,

circling the planet like

the rings of Saturn

before coming together into

a huge, barren satellite.

Too small to hold a

protective atmosphere,

the moon itself has long been

bombarded by debris ever since.

Without wind or rain

to smooth the scars,

its face bears everlasting witness to

the violent nature of outer space.

On the earth below,

an atmosphere was brewing from endless

clouds of poison gasses

and water vapor,

expelled from beneath the crust.

Closer to the sun, the precious water

might have boiled away.

On a colder planet it would be

locked into eternal ice.

But on the earth,

water vapor condensed

falling back as rain upon the land.

And so the first oceans were born.

Over millions of years,

the seas rose to flood the earth.

But these were not the cool,

life-giving waters we know today.

The primal atmosphere provided

little protection.

It had no blanket of ozone

to filter out lethal radiation.

Virtually unobstructed,

the sun's unforgiving rays seared

whatever they touched.

Much closer than now,

the moon also played a violent part,

tugging at the seas with a force

countless times greater than today.

The first tides were mountains

of water, miles high.

Torn by sun and moon, the surface

waters offered no hope for life.

Still, there was sanctuary below.

In the ocean, the first building

blocks of life amino acids emerged.

They incubated in water heated by

the planet's internal fires

and fed on a bubbling broth

of nutrients

straight from the heart of the earth.

But even the ocean's depths were not

safe from a cataclysmic universe.

In a galaxy still littered

with the debris of genesis,

asteroid strikes may have vaporized

the oceans, laying the seabed bare.

More than once, life on earth

may have been snuffed out.

Yet the fire and rains of creation

kept their hold on earth,

and the oceans rose again.

Life has proven stubborn here.

Some three billion years ago, as the

earth cooled and calmed once again,

new forms appeared, the heralds

of life as we understand it.

In quiet, sheltered pools,

algae spread.

Colonies of single-celled organisms,

they thrived off abundant sunlight

and carbon dioxide.

And in their waste they left behind

oxygen, the precious breath of life.

This was the birth of photosynthesis,

a new, life-giving cycle

that transformed the earth.

For countless millennia,

algae flourished in the brief days

so bright with sun.

And now the cosmic rhythms

were changing.

Gradually, the moon and its tides

slowed the earth's mad spinning,

and the forces that bound planet and

satellite together loosened their hold.

The moon retreated to

where she stands today,

still slipping imperceptibly

away over time.

With the moon more distant,

the tides fell.

Calmer waters bred more algae

and more oxygen.

And with the oxygen came ozone,

protection from the sun's

most lethal rays.

At last, the stage was set

for the next phase of creation.

Like the fire of a new sun, the spark

of new life appeared in the waters.

Still just single-celled plants,

but organisms far more complex

than any that had come before.

Within each was a genetic code

that reflected the rhythms

of earth and heaven,

a biological clock

to guide their lives.

Daytime would be the time

to feed on the power of the sun.

Reproduction would be saved

for the shelter of night.

Millions of years later,

this clock still synchronizes almost

all life to the very spin of the planet.

From the depths of a steep-walled

lagoon

in the South Pacific island of Palau,

a herd of underwater farmers

rises to meet the dawn.

A swarm of jellyfish,

tens of thousands strong.

Without eyes, the jellyfish do not

use the light to see.

They need it to grow their food

gardens of brown algae

that flourish within their

transparent bodies.

Denied sunshine,

they would starve.

As the sun arcs overhead,

shadows of the surrounding walls

darken the surface of the lagoon.

Just below, the jellyfish ferry their

microscopic passengers,

keeping them always in the light.

When the sun sinks,

so do the jellyfish,

dropping down to the ocean floor

where the algae can find their own

nourishment.

Even without sight, the jellyfish will

know when the sun returns again.

In the surface waters of the oceans

most creatures take their cue

to feed or rest

from the rhythm

of light and dark.

Now, members of the night

shift hurry to take the stage.

Roused by light-sensitive cells that

announce the return of darkness,

these prickly browsers

set out to graze.

Sea urchins find their prey

and their way around

by touch and by taste.

Each night clouds of plankton rise

from the deep to feed

drawing out the coral who fish

the waters with feathery nets.

A few, sharp-eyed fish operate by

sight in the dim light before dawn.

Like a cat in the dark, the lionfish

can pick out its prey.

The lionfish will slip into a crevice

to hide from the daytime;

eyes sensitive enough for half light

may be too delicate for bright sun.

Daybreak brings the morning

rush hour to the reef.

Far more complex than jellyfish

or sea urchins,

most fish depend on sight to survive.

Without the sun they are virtually

blind to navigate their world,

to find their food,

or signal to their kind.

A kaleidoscope of colors enhances

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