Notes

The Cosmos is all that is or ever was or ever will be. Our feeblest contemplations of the
Cosmos stir us - there is a tingling in the spine, a catch in the voice, a faint sensation, as if a
distant memory, of falling from a height. We know we are approaching the greatest of
mysteries.

The size and age of the Cosmos are beyond ordinary human understanding. Lost
somewhere between immensity and eternity is our tiny planetary home. In a cosmic
perspective, most human concerns seem insignificant, even petty. And yet our species is
young and curious and brave and shows much promise. In the last few millennia we have
made the most astonishing and unexpected discoveries about the Cosmos and our place
within it, explorations that are exhilarating to consider. They remind us that humans have
evolved to wonder, that understanding is a joy, that knowledge is prerequisite to survival. I
believe our future depends on how well we know this Cosmos in which we float like a mote
of dust in the morning sky.

Those explorations required skepticism and imagination both. Imagination will
often carry us to worlds that never were. But without it, we go nowhere. Skepticism enables
us to distinguish fancy from fact, to test our speculations. The Cosmos is rich beyond
measure - in elegant facts, in exquisite interrelationships, in the subtle machinery of awe.

We have loved the stars too fondly to be fearful of the night.


A few million years ago there were no humans. Who will be here a few million years
hence? In all the 4.6-billion-year history of our planet, nothing much ever left it. But now,
tiny unmanned exploratory spacecraft from Earth are moving, glistening and elegant,
through the solar system. We have made a preliminary reconnaissance of twenty worlds,
among them all the planets visible to the naked eye, all those wandering nocturnal lights
that stirred our ancestors toward understanding and ecstasy. If we survive, our time will be
famous for two reasons: that at this dangerous moment of technological adolescence we
managed to avoid self-destruction; and because this is the epoch in which we began our
journey to the stars.

Some 3.6 million years ago, in what is now northern Tanzania, a volcano erupted,
the resulting cloud of ash covering the surrounding savannahs. In 1979, the
paleoanthropologist Mary Leakey found in that ash footprints - the footprints, she believes,
of an early hominid, perhaps an ancestor of all the people on the Earth today. And 380,000
kilometers away, in a flat dry plain that humans have in a moment of optimism called the
Sea of Tranquility, there is another footprint, left by the first human to walk another world.
We have come far in 3.6 million years, and in 4.6 billion and in 15 billion.

For we are the local embodiment of a Cosmos grown to self-awareness. We have
begun to contemplate our origins: starstuff pondering the stars; organized assemblages of
ten billion billion billion atoms considering the evolution of atoms; tracing the long journey
by which, here at least, consciousness arose. Our loyalties are to the species and the planet.
We speak for Earth. Our obligation to survive is owed not just to ourselves but also to that
Cosmos, ancient and vast, from which we spring.

The time will come when diligent research over long periods will bring to light things
which now lie hidden. A single lifetime, even though entirely devoted to the sky, would not
be enough for the investigation of so vast a subject . . . And so this knowledge will be
unfolded only through long successive ages. There will come a time when our descendants
will be amazed that we did not know things that are so plain to them . . . Many discoveries
are reserved for ages still to come, when memory of us will have been effaced. Our
universe is a sorry little affair unless it has in it something for every age to investigate . . .
Nature does not reveal her mysteries once and for all.
- Seneca, Natural Questions, Book 7, first century

The Cosmos was discovered only yesterday. For a million years it was clear to everyone
that there were no other places than the Earth. Then in the last tenth of a percent of the
lifetime of our species, in the instant between Aristarchus and ourselves, we reluctantly
noticed that we were not the center and purpose of the Universe, but rather lived on a tiny
and fragile world lost in immensity and eternity, drifting in a great cosmic ocean dotted
here and there with a hundred billion galaxies and a billion trillion stars. We have bravely
tested the waters and have found the ocean to our liking, resonant with our nature.
Something in us recognizes the Cosmos as home. We are made of stellar ash. Our origin
and evolution have been tied to distant cosmic events. The exploration of the Cosmos is a
voyage of self-discovery.

As the ancient mythmakers knew, we are the children equally of the sky and the
Earth. In our tenure on this planet we have accumulated dangerous evolutionary baggage,
hereditary propensities for aggression and ritual, submission to leaders and hostility to
outsiders, which place our survival in some question. But we have also acquired
compassion for others, love for our children and our children’s children, a desire to learn
from history, and a great soaring passionate intelligence - the clear tools for our continued
survival and prosperity. Which aspects of our nature will prevail is uncertain, particularly
when our vision and understanding and prospects are bound exclusively to the Earth - or,
worse, to one small part of it. But up there in the immensity of the Cosmos, an inescapable
perspective awaits us. There are not yet any obvious signs of extraterrestrial intelligence
and this makes us wonder whether civilizations like ours always rush implacably, headlong,
toward self-destruction. National boundaries are not evident when we view the Earth from
space. Fanatical ethnic or religious or national chauvinisms are a little difficult to maintain
when we see our planet as a fragile blue crescent fading to become an inconspicuous point
of light against the bastion and citadel of the stars. Travel is broadening.

There are worlds on which life has never arisen. There are worlds that have been
charred and ruined by cosmic catastrophes. We are fortunate: we are alive; we are
powerful; the welfare of our civilization and our species is in our hands. If we do not speak
for Earth, who will? If we are not committed to our own survival, who will be?


We look back through countless millions of years and see the great will to live
struggling out of the intertidal slime, struggling from shape to shape and from
power to power, crawling and then walking confidently upon the land, struggling
generation after generation to master the air, creeping down into the darkness of the
deep; we see it turn upon itself in rage and hunger and reshape itself anew, we
watch it draw nearer and more akin to us, expanding, elaborating itself, pursuing its
relentless inconceivable purpose, until at last it reaches us and its being beats
through our brains and arteries ... It is possible to believe that all the past is but the
beginning of a beginning, and that all that is and has been is but the twilight of the
dawn. It is possible to believe that all that the human mind has ever accomplished is
but the dream before the awakening . . . Out of our . . . lineage, minds will spring,
that will reach back to us in our littleness to know us better than we know ourselves.
A day will come, one day in the unending succession of days, when beings, beings
who are now latent in our thoughts and hidden in our loins, shall stand upon this
earth as one stands upon a footstool, and shall laugh and reach out their hands
amidst the stars.

- H. G. Wells, ‘The Discovery of the Future,’ Nature 65, 326 (1902)

All my life I have wondered about the possibility of life elsewhere. What would it be like?
Of what would it be made? All living things on our planet are constructed of organic
molecules - complex microscopic architectures in which the carbon atom plays a central
role. There was once a time before life, when the Earth was barren and utterly desolate. Our
world is now overflowing with life. How did it come about? How, in the absence of life,
were carbon-based organic molecules made? How did the first living things arise? How did
life evolve to produce beings as elaborate and complex as we, able to explore the mystery
of our own origins?

And on the countless other planets that may circle other suns, is there life also? Is
extraterrestrial life, if it exists, based on the same organic molecules as life on Earth? Do
the beings of other worlds look much like life on Earth? Or are they stunningly different -
other adaptations to other environments? What else is possible? The nature of life on Earth
and the search for life elsewhere are two sides of the same question - the search for who we
are.

The surface of the Earth is the shore of the cosmic ocean. From it we have learned
most of what we know. Recently, we have waded a little out to sea, enough to dampen our
toes or, at most, wet our ankles. The water seems inviting. The ocean calls. Some part of
our being knows this is from where we came. We long to return.

https://archive.org/stream/Cosmos-CarlSagan/cosmos-sagan_djvu.txt