|
Key insights from
Cosmos
By
Carl Sagan
|
|
|
What you’ll learn
We’ve all looked up into the night sky and pondered the vast
expanse beyond, been humbled in the presence of the ocean or mountains or
the stars, and wondered about our place in this universe. Carl Sagan’s
classic book Cosmos looks at some of history’s seminal scientists
who have changed the way we see our world. Their discoveries have fueled
exploration, at first intercontinental, now interplanetary, and, perhaps,
someday, interstellar. Sagan’s book stands as an enthusiastic
acknowledgement of the most curious and adventuresome species on the
planet, and a warning about their growing carelessness.
Read on for key insights from Cosmos.
|
|
1. Eratosthenes
made an accurate estimate of the world’s size using only sticks and
shadows—and the world has never been the same.
Humankind has long marveled at the immensity and majesty of
the world and the expanse beyond its horizons. To contemplate the Cosmos is
to dwell on one of life’s oldest, most compelling mysteries.
Evolution has wired us to explore, to brave the unknown, to
discover and learn. And so we have. We now know, for example, that light
travels at a speed of 186,000 miles per second—that’s seven times around
the earth in just one second! We now know that it takes eight minutes for
light from the sun to reach earth, making the sun eight light minutes away.
In all the Cosmos, there are about ten billion trillion stars, and probably
as many planets. We know the chances of a star being at just the right
distance from a water-filled planet to foster and sustain life are
infinitesimally small.
These are facts that we take for granted in our modern
world, but there were far more knowledge gaps in the ancient world. Despite
these gaps and a dearth of technology, some ancient speculations are
shockingly accurate. Our planet’s relatively small size was discovered
about 2,200 years ago in Alexandria, Egypt, by the director of the Library
of Alexandria, Eratosthenes.
In a papyrus document that Eratosthenes found in the
library’s archives, he read that if you placed a stick exactly upright on
June 21, it would cast no shadow at high noon. Eratosthenes found that in
Alexandria, 800 kilometers from Syene, a vertical stick would cast a
considerable shadow on that same day and time. Why the discrepancy?
Eratosthenes hypothesized that the earth’s surface must be curved. What is
more, the dramatic difference between the absent shadow in Syene and the
long shadow in Alexandria would make the curve significant. By observing
how the shadows fell at various times of the day and year in Alexandria and
Syene, he concluded that if you traced the sticks from their locations to
the center of the earth, they would form a seven-degree angle. This was
about a fiftieth of the world’s 360-degree circumference. So Eratosthenes
multiplied the 800-kilometer distance between the towns by fifty to arrive
at the figure of 40,000 kilometers. This matches modern estimates of the
earth’s circumference within just a few percentage points.
Eratosthones’ scientific discovery gave the intrepid courage
to venture beyond the Mediterranean shores. The voyages became more and
more ambitious. Over a millennia later, the tradition continued. It can be
argued that Eratosthones began the exploration of new worlds by showing
earth’s finite dimensions. A query had begun that would culminate in the
exploration of not just other continents but other planets. As the blank
edges of the map have been filled in, the human drive to explore has pushed
us to look beyond planet earth.
Of all that has emerged since the Big Bang fifteen to twenty
billion years ago, human beings are currently the most remarkable
emergence—a species that, heretofore, is the most intelligent, capable and
driven to understand its place in the Cosmos, to understand the universe
itself and even to shape it.
|
|
2. Astronomy is a
far better tool than astrology for making sense of our connection to the
Cosmos.
We live in a universe that toes a line between stagnancy and
chaos. The world is not so rigid that it’s free from anomalies and change,
nor so random that common patterns can’t be discerned. Objects will always
gravitate toward earth’s center when dropped. The sun rises and sets in the
east and west, respectively.
This is the kind of world in which science is possible, and
what we learn through scientific inquiry gives us tools for humanity’s
betterment. There’s clearly a harmony between the sun, moon, stars and
planets. People have had this intuition for millennia, and do their best to
make sense of it. Throughout our history, humans have barked up the wrong
tree, pursuing astrological signs instead of scientific explanations.
Astrology refers to the practice of looking at the positions
of stars, moons, and planets to gain predictive power. While this might
strike the modern sensibilities as superstition from the hinterlands, the
modern developed world is hardly free from the influence of astrology. For
example, we still find a daily horoscope in major U.S. newspapers, which
many consult religiously. Even in countries where the latest scientific
findings are readily available, this trend is common. For every astronomer
doing good science, there are ten astrologers perpetuating nonsense.
The legacy of astrology is even embedded in everyday
language. The etymology of many familiar words and phrases relate to
astrology. The word “disaster,” for example, comes from the Greek word for
“bad star.”
We are grasping for a meaningful connection with the
universe. We deeply desire to feel that what happens to us on earth
reverberates out into the cosmos and vice-versa.
As it turns out, we are connected, not via superstitions,
but by concrete cause-and-effect occurrences in space and time, involving
matter and energy. We are here not because of mystical forces but because
of evolutionary ones.
|
|
3. Kepler and
Newton showed us better than anyone that Nature can be understood through
simple, elegant mathematical equations.
As a young man, Kepler was a seminarian, but he realized
that he found greater joy in exploring Creation than the Creator himself. A
top-tier theorist, he relied on Tycho Brahe’s observations of planetary
movement—the most detailed and accurate in Kepler’s day—received only when
Tycho was on his deathbed.
After years of toiling and begging for research grants and
the latest observational data on planetary movement, Kepler discovered that
the lack of perfect harmony in the calculations of the orbits was because
Copernicus and others had assumed that planets moved on a circular course.
When he tested the figures using an ovular model, the numbers aligned
better, but not perfectly. Then, in an experience that Kepler described as
truth disguised and sneaking in the backdoor, he was surprised and elated
to find that the observations aligned perfectly with the elliptic model.
This meant that there was a harmonious pattern to the planets after all.
From this monumental discovery came the formulation of precise laws of
planetary motion as well as theories about a force akin to magnetism that
would explain why the planets moved at different speeds at different points
on the ellipse.
Isaac Newton picked up on Kepler’s hunch several decades
later, mapping out formulated mathematical laws behind the force called
gravity.
Newton built on Kepler’s mathematical work and theories to
give an even fuller account of the music of the spheres. He used the same
observations Tycho Brahe documented and Kepler used to generate more
general mathematical principles, giving a framework for planetary systems.
Newton proved his genius on another occasion when Swiss scholar
Johan Bernoulli posed a challenge to his fellow mathematicians known as the
Brachistochrone Problem. Leading minds of that era, including Leibniz,
asked for a-year-and-a-half in place of the six-month deadline originally
proposed. Within twenty-four hours of receiving the challenge, Newton had
derived a solution and, in the process, developed an entirely new branch of
mathematical study known as calculus of variations. He published the paper
anonymously, but Bernoulli immediately recognized it to be Newton’s work.
“We recognize a lion by his claw,” Bernoulli is said to have remarked.
It is possible that no greater scientific mind has ever
graced this pale blue dot than Newton.
Kepler and Newton gave posterity invaluable mathematical
tools with which to work and refine. Their work marked an important turning
point in scientific inquiry. It showed that there were mathematically
expressible patterns to Nature that applied both to earth and the planets
beyond.
|
|
|
|
4. Stars are
inaccessible to us at this point in our scientific understanding.
If you were to pick up a fistful of sand, you would find
about 10,000 grains in your hand. In a clear night sky away from the city,
you’d see about as many stars. What is amazing is that this glittering
expanse is the tiniest proportion of what is out there. In this universe of
ours there are far more stars than there are grains of sand in the world’s
beaches and deserts.
The stars have been a source of wonder throughout history.
We’ve been trying to decipher images in the sky. The images that we
see have been pretty consistent from any point on the earth because the
stars are equidistant to anywhere we would choose to look up into the night
sky. So the Southern Cross will look like the Southern Cross in Sydney or
Sao Paolo, and the Big Dipper will look like a dipper in Boston or
Bucharest. We see the constellations in 2-D, and we would need an entirely
different vantage point before we could see it in 3-D.
Stars are far from static entities, however. They have
shifted into the positions we have come to recognize and they will
eventually shift away from them. Even 500,000 years ago, the Big Dipper
didn’t look like a dipper at all. The zodiac symbols that many people have
come to trust implicitly will be obsolete in a million years when the Leo
constellation no longer looks like a lion at all, and drifts far from the
sun’s trajectory.
Many stars shift. All are born, and then eventually go out
in a massive blaze of glory.
Our hunger for exploration takes us beyond the solar system
and its planets to the exploration of stars and systems beyond. The
Voyager ships are currently hurtling through space, but at the rate they’re
going, it would take forty millennia to reach the star closest to the Sun.
Until we design interstellar crafts that can move faster
than a ten-thousandth the speed of light, it’s a long shot. Various
societies have proposed designs that would, in theory, enable a craft to
travel at a tenth of the speed of light. At that speed, it would arrive at
Alpha Centauri (the star system nearest to our solar system, only 4.3 light
years away) in about forty years. It’s unlikely that this would be attained
before the middle of the twenty-first century. A machine approaching the
speed of light would not be possible for millennia.
|
|
5. If we ever do
make contact with extraterrestrial life, the way we treat terrestrial life
does not bode well for those encounters.
For tens of millions of years, whales have engaged in a
beautiful song that can carry across the oceans and be heard on the other
side of the world. The baleen whale, for example, produces a song at 20
Hertz that another baleen whale can hear over 10,000 kilometers away.
Since the 1800s, however, one species has developed
technologies sophisticated enough to disrupt these love songs. We humans
are that species. With the invention of the steam engine came ships that
create substantial noise pollution. Such vessels and even noisier progeny
disrupt these subtle, sub-aquatic utterances. What is more, people are
harvesting the organs of whales for makeup and other commodities. Their
murderous obliteration of the whales over the last several centuries is
inhumane and disruptive of primordial mammalian rhythms.
Some hope for a day when we make contact with
extraterrestrial life. But how are we doing with terrestrial life? Animals
are going extinct and differing religious and political ideologies are
tearing our own species to pieces.
Like the baleen whale that sends its love song out into the
oceans beyond in hope of establishing contact, so we humans have put some
signs of our existence out into space. On the Voyager, there are
phonographs and info about genetic sequences, our planet and civilizations
in the hopes that extraterrestrials could pick up and learn about us. It’s
worth a try. Writing has only been around for several thousand years, but
genetic sequences that we hold in common with our common ancestor have been
around for billions of years; so DNA is perhaps the most apt expression of
who we are.
If we happen to find other intelligent life, let us hope
that they will look upon us with greater kindness than we have for one
another. Many of us seem bent on beliefs that will bring about the
destruction of this small blue planet we call home.
|
|
Endnotes
These insights are
just an introduction. If you're ready to dive deeper, pick up a copy of Cosmos here. And since we get a commission on
every sale, your purchase will help keep this newsletter free.
*
This is sponsored content
|
|
|
This newsletter is powered by Thinkr, a smart reading app for the
busy-but-curious. For full access to hundreds of titles — including audio —
go premium and download the app today.
|
|
No comments:
Post a Comment