Circling one star among hundreds of billions, in one galaxy among a hundred billion more, in a Universe that is vast and expanding ever faster – perhaps toward infinity. It’s easy to forget that we live in a place of astonishing grandeur and mystery. Register to explore the whole course here: https://school.bighistoryproject.com/bhplive?WT.mc_id=Slideshare12202017

1. AN OPEN LETTER BY BREAKTHROUGH INITIATIVES
Circling one star among hundreds of billions, in one
galaxy among a hundred billion more, in a Universe
that is vast and expanding ever faster – perhaps
toward infinity. It’s easy to forget that we live in a
place of astonishing grandeur and mystery.
10
ARE WE ALONE?
Now Is the Time to Find Out

2. BIG HISTORY PROJECT ARE WE ALONE? 2
Who are we?
A mature civilization, like a mature individual, must ask itself this question. Is
humanity defined by its divisions, its problems, its passing needs and trends? Or do
we have a shared face, turned outward to the Universe?
In 1990, Voyager 1 swiveled its camera and captured the ‘Pale Blue Dot’ - an image of
Earth from six billion kilometers away. It was a mirror held up to our planet - home of
water, life, and minds. A reminder that we share something precious and rare.
But how rare, exactly? The only life? The only minds?
For the last half-century, small groups of scientists have listened valiantly for signs of
life in the vast silence. But for government, academia, and industry, cosmic questions
are astronomically far down the list of priorities. And that lengthens the odds of
finding answers. It is hard enough to comb the Universe from the edge of the Milky
Way; harder still from the edge of the public consciousness.
Yet millions are inspired by these ideas, whether they meet them in science or science
fiction. Because the biggest questions of our existence are at stake. Are we the
Universe’s only child - our thoughts its only thoughts? Or do we have cosmic siblings
- an interstellar family of intelligence? As Arthur C. Clarke said, “In either case the
idea is quite staggering.”
That means the search for life is the ultimate ‘win-win’ endeavor. All we have to do is
take part.
Today we have search tools far surpassing those of previous generations. Telescopes
can pick out planets across thousands of light years. The magic of Moore’s law lets
our computers sift data orders of magnitude faster than older mainframes - and ever
quicker each year.
These tools are now reaping a harvest of discoveries. In the last few years,
astronomers and the Kepler Mission have discovered thousands of planets beyond our
solar system. It now appears that most stars host a planetary system. Many of them
have a planet similar in size to our own, basking in the ‘habitable zone’ where the
temperature permits liquid water. There are likely billions of earth-like worlds in our
galaxy alone. And with instruments now or soon available, we have a chance of
finding out if any of these planets are true Pale Blue Dots – home to water, life, even
minds.
There has never been a better moment for a large-scale international effort to find life
in the Universe. As a civilization, we owe it to ourselves to commit time, resources,
and passion to this quest.
But as well as a call to action, this is a call to thought. When we find the nearest exo-
Earth, should we send a probe? Do we try to make contact with advanced
civilizations? Who decides? Individuals, institutions, corporations, or states? Or can
we as species - as a planet - think together?
Three years ago, Voyager 1 broke the sun’s embrace and entered interstellar space.
The 20th century will be remembered for our travels within the solar system. With
cooperation and commitment, the present century will be the time when we graduate
to the galactic scale, seek other forms of life, and so know more deeply who we are.
Artist’s concept of Voyager 1 in flight.

3. BIG HISTORY PROJECT ARE WE ALONE? 3
This open letter was signed by:
• Yuri Milner—Founder Breakthrough Prize, Founder DST Global Cori Bargmann—
Investigator, Howard Hughes Medical Institute; Torsten N. Wiesel Professor, The
Rockefeller University
• Sarah Brightman—Soprano
• Magnus Carlsen—World Chess Champion
• Ding Chen—Professor and Principle Investigator of the Search for Terrestrial
Exo-Planets Mission, Chinese Academy of Sciences
• Frank Drake—Chairman Emeritus, SETI Institute; Professor Emeritus of Astronomy
and Astrophysics, University of California, Santa Cruz; Founding Director, National
Astronomy and Ionosphere Center; Former Goldwin Smith Professor of Astronomy,
Cornell University
• Ann Druyan—Creative Director of the Interstellar Message, NASA Voyager;
Co-Founder and CEO, Cosmos Studios; Emmy and Peabody award winning Writer
and Producer
• Stephen Hawking—Professor, Dennis Stanton Avery and Sally Tsui Wong-Avery
Director of Research, University of Cambridge
• Paul Horowitz—Professor of Physics and of Electrical Engineering, Emeritus,
Harvard University
• Garik Israelian—Professor and Staff Astrophysicist, Institute of Astrophysics of
Canary Islands
• Lisa Kaltenegger—Director, Carl Sagan Institute; Associate Professor of Astronomy,
Cornell University
• Nikolay Kardashev—Director, Astro Space Center of PN Lebedev Physics Institute
• Mark Kelly—Astronaut
• Eric Lander—President and Founding Director of the Broad Institute of MIT and
Harvard; Professor of Biology, MIT; Professor of Systems Biology, Harvard Medical
School
• Alexey Leonov—Cosmonaut
• Avi Loeb Frank—B. Baird Jr. Professor of Science, Chair of the Astronomy
Department and Director of the Institute for Theory and Computation, Harvard
University
• Seth MacFarlane—Writer, Director and Actor
• Geoff Marcy—Professor of Astronomy, University of California, Berkeley
• Lord Martin Rees—Astronomer Royal, Fellow of Trinity College; Emeritus Professor
of Cosmology and Astrophysics, University of Cambridge
• Kenneth Rogof—Thomas D. Cabot Professor of Public Policy and Professor of
Economics, Harvard University; International Grandmaster of Chess
• Dimitar Sasselov—Phillips Professor of Astronomy, Harvard University; Founding
Director, Harvard Origins of Life Initiative
• Sara Seager—Professor of Planetary Sciences and Professor of Physics, MIT
• Sujan Sengupta—Associate Professor, Indian Institute of Astrophysics, Ministry of
Science and Technology
• Seth Shostak—Professor, Senior Astronomer and Director, Center for SETI research
• Thomas Stafford—Astronaut
• Jill Tarter—Astronomer; Bernard M. Oliver Chair for SETI Research, SETI Institute
• Kip Thorne—Feynman Professor of Theoretical Physics Emeritus, California Institute
of Technology; Scientific consultant and an executive producer, Intersteller
• James Watson—Chancellor Emeritus, Cold Spring Harbor Laboratory; Nobel Prize
Laureate
• Steven Weinberg—Professor of Physics and Astronomy, University of Texas at
Austin; Nobel Prize Laureate
• Edward Witten—Professor, School of Natural Sciences, Institute for Advanced Study
• Pete Worden—Chairman, Breakthrough Prize Foundation
• Shinya Yamanaka—Professor and Director of the Center for iPS Cell Research and
Application, Kyoto University; Nobel Prize Laureate

4. BIG HISTORY PROJECT ARE WE ALONE? 4
About Breakthrough Initiatives
The Breakthrough Initiatives are a
program of scientific and technological
exploration, probing the big questions of
life in the Universe. Founded in 2015 by
Yuri and Julia Milner, Breakthrough
Initiatives explores the Universe, seeks
scientific evidence of life beyond Earth,
and encourages public debate from a
planetary perspective.
Source
Breakthrough Initiatives, http://break-
throughinitiatives.org/AreWeAlone
Cover image: Andromeda galaxy, or
M31, is our Milky Way’s largest galactic
neighbor. Credit: NASA/JPL-Caltech.
Public domain. http://www.galex.
caltech.edu/media/glx2012-03r_img01.
html
Image of Voyager 1. Credit: NASA/JPL.
Public Domain. http://solarsystem.nasa.
gov/galleries/artists-concept-of-voyag-
er