Cosmos

by Carl Sagan

love. And as he used to say: “When you’re in love, you want to tell the world.”

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

Science is an ongoing process. It never ends. There is no single ultimate truth to be achieved, after which all the scientists can retire. And because this is so, the world is far more interesting, both for the scientists and for the millions of people in every nation who, while not professional scientists, are deeply interested in the methods and findings of science.

The known is finite, the unknown infinite; intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. Our business in every generation is to reclaim a little more land. —T. H. Huxley, 1887

The Cosmos is all that is or ever was or ever will be.

They remind us that humans have evolved to wonder, that understanding is a joy, that knowledge is prerequisite to survival.

The surface of the Earth is the shore of the cosmic ocean.

No planet or star or galaxy can be typical, because the Cosmos is mostly empty.

Far more species have become extinct in the history of the Earth than exist today; they are the terminated experiments of evolution.

The secrets of evolution are death and time—the deaths of enormous numbers of lifeforms that were imperfectly adapted to the environment; and time for a long succession of small mutations that were by accident adaptive, time for the slow accumulation of patterns of favorable mutations.

We are like butterflies who flutter for a day and think it is forever.

Biology is more like history than it is like physics. You have to know the past to understand the present.

“God provides for every animal his means of sustenance,”

Kepler’s first law of planetary motion is simply this: A planet moves in an ellipse with the Sun at one focus.

Upon being asked how to distinguish the faithful from the infidel in the siege of a largely Albigensian city, Domingo de Guzmán, later known as Saint Dominic, allegedly replied: “Kill them all. God will know his own.”

The doors of heaven and hell are adjacent and identical. —Nikos Kazantzakis, The Last Temptation of Christ

But the fact that only a few of the lunar craters have extensive ray systems also reminds us that, even on the Moon, some erosion occurs.*

But science is a self-correcting enterprise. To be accepted, all new ideas must survive rigorous standards of evidence.

Science is generated by and devoted to free inquiry: the idea that any hypothesis, no matter how strange, deserves to be considered on its merits. The suppression of uncomfortable ideas may be common in religion and politics, but it is not the path to knowledge; it has no place in the endeavor of science. We do not know in advance who will discover fundamental new insights.

Venus turns once every 243 Earth days, but backwards, in the opposite direction from all other planets in the inner solar system.

cycle. It is always raining sulfuric acid on Venus, all over the planet, and not a drop ever reaches the surface.

Many mythic heroes in Greek and Norse mythology, after all, made celebrated efforts to visit Hell.

Human beings have a demonstrated talent for self-deception when their emotions are stirred,

These voyages worked much evil as well as much good.

*Or, to make a different comparison, a fertilized egg takes as long to wander from the fallopian tubes and implant itself in the uterus as Apollo 11 took to journey to the Moon; and as long to develop into a full-term infant as Viking took on its trip to Mars. The normal human lifetime is longer than Voyager will take to venture beyond the orbit of Pluto.

to live well you must live unseen.

He felt that poverty in a democracy was preferable to wealth in a tyranny.

largely abandoned for two thousand years. Without experiment, there is no way to choose among contending hypotheses, no way for science to advance.

economy. A major problem in the contemporary (political) Third World is that the educated classes tend to be the children of the wealthy, with a vested interest in the status quo, and are unaccustomed either to working with their hands or to challenging conventional wisdom.

The longer the baseline from which we make our two observations, the greater the parallax and the better we can measure the distance to remote objects.

The great legacy of Aristarchus is this: neither we nor our planet enjoys a privileged position in Nature.

Our Sun or suns might set, but the night would never come.

We make our world significant by the courage of our questions and by the depth of our answers.

We have loved the stars too fondly to be fearful of the night. —Tombstone epitaph of two amateur astronomers

Space and time are interwoven. We cannot look out into space without looking back into time.

Thou shalt not add thy speed to the speed of light.

Thou shalt not travel at or beyond the speed of light.

(There are no penalties for breaking laws of Nature, because there are no crimes: Nature is self-regulating and merely arranges things so that its prohibitions are impossible to transgress.)

If you cut an atom, you transmute the elements.

The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.

Thus there is almost certainly not enough time for the evolution of advanced forms of life on any accompanying planets; and it will be rare that beings elsewhere can ever know that their star will become a supernova: if they live long enough to understand supernovae, their star is unlikely to become one.

A very small initial nonuniformity suffices to produce substantial condensations of matter later on.

Gravity is opportunistic, amplifying even small condensations of matter.

That we live in a universe which permits life is remarkable. That we live in one which destroys galaxies and stars and worlds is also remarkable. The universe seems neither benign nor hostile, merely indifferent to the concerns of such puny creatures as we.

This red shift, observed in the spectral lines of distant galaxies and interpreted as a Doppler effect, is the key to cosmology.

It is said that men may not be the dreams of the gods, but rather that the gods are the dreams of men.

It would take more than the age of the universe for light to circumnavigate it.

Knowing a great deal is not the same as being smart; intelligence is not information alone but also judgment, the manner in which information is co-ordinated and used.

The right hemisphere of the cerebral cortex is mainly responsible for pattern recognition, intuition, sensitivity, creative insights. The left hemisphere presides over rational, analytical and critical thinking. These are the dual strengths, the essential opposites, that characterize human thinking. Together, they provide the means both for generating ideas and for testing their validity. A continuous dialogue is going on between the two hemispheres, channeled through an immense bundle of nerves, the corpus callosum, the bridge between creativity and analysis, both of which are necessary to understand the world.

Books are like seeds. They can lie dormant for centuries and then flower in the most unpromising soil.