Active SETI Strategy:Communicating with Extraterrestrial Life

William AntoneLuis Cartagena

Jorene Ooi

Outline● Active vs. Passive Seti● Technology● Targets● Past & Present Messages● Message Content

Active SETI

Credit: pbs.org

Active SETI

Radio Messaging● radio telescopes● detectable across galaxy

repetitionnanosecond pulsesdetectable across galaxy

xLaser Messaging

New Strategy for Transmission

● combining powerful lasers with large optical telescopes

● pulse sensor + keck telescope → can outshine the star at 1000 light years

● Sun-like stars or solar-system-like Exoplanets System● nearby stars● known planets● should not be limited

Where to point?

Physical Messages

Credit: NASA

The Morse Message (1962)● From Evpatoria

Planetary Radar● Directed to Venus● “MIR, LENIN, SSSR”

Credit: NASA

Arecibo Message (1974)

Credit: Cornell University

Evpatoria Planetary Radar

● Cosmic Call 1 (1999)○ four transmissions○ arrival: 2051-2069

● Cosmic Call 2 (2003)○ five transmissions○ arrival: 2036-2049

Credit: S. Korotkiy

Teen Age Message (2001)● Section 1:

monochromatic radio wave

● Section 2: 15-min “1st Theremin Concert for Aliens”

● Section 3: greeting texts, image glossary

Credit: Alexander Zaitsev

A Message from Earth (2008)● Gliese 581 c● 20 light years away● Arrival date: Feb

2029● crowdsourced

messages translated into binary

Credit: Lynette Cook / NASA

“Wow!” Signal

● “Wow!” signal detected Aug. 15, 1977● Ohio State University Radio Observatory (OSURO)

Credit: Jerry Ehman, Paul Schuch

Wow! Reply (2012)● Sent by National Geographic & Arecibo Observatory● Twitter messages and videos from celebrities

"We are not delicious. In fact, we're kind of gamey, and we get stuck in your teeth. It's really embarrassing at a job interview. If you want something good to munch on, go to the nearby Crab nebula. And bring a bib. Seriously, all you can eat."

Credit: Frank Micelotta / Getty Images

Electromagnetic Leak

“If extraterrestrial civilizations are monitoring our TV broadcasts, then this is what they are currently watching.”

Credit: Abstruse Goose

We’re already doing enough?● Would radio and TV signals generate an

“automatic reply”?● Current TV signals too low in gain● Likely only a transitory activity

Message Length LimitationsSignal to Noise RatioWide Bandwidth: Harder to detect

Efficient communicationNarrow Bandwidth: Easier to detect

Inefficient communication

Message Length LimitationsRepetition will be necessary

Assume one-way message

Creating Artificial LanguageHuman Language

Culturally dependentImpreciseOverly Complex

Constructing the MessagePreamble (Facts we presume them to know)

NumbersScienceGroup Theory and Sets

“Encyclopedia Galactica” (All about us)

Numbers

Source: Evpatoria Message

Group Theory and SetsHuman: = Man or Woman 7 billion humans included in EarthM + 80 years => {} W + 80 years => {}

Interstellar Rosetta Stone

Elementary encyclopedia of terrestrial knowledge

Used in Cosmic Call 1 and Cosmic Call 2

263,906 bits, 127 symbols, 2078 lines over one “page”

Credit: Seed Magazine

Interstellar Rosetta Stone

Size and ordering of solar system

Mass and radius of Jupiter and the Sun

Credit: Seed Magazine

Interstellar Rosetta Stone

Biosphere

Chemical composition of Earth atmosphere, continents, oceans

Altitudes

Credit: Seed Magazine

Interstellar Rosetta Stone

Average height

Denotes “up” and “down”

Credit: Seed Magazine

Interstellar Rosetta Stone

Human population, average mass, average temperature

Perceptual limitations (light and sound)

Credit: Seed Magazine

Interstellar Rosetta Stone

Molecular structure of adenine, thymine, guanine, and cytosine

Credit: Seed Magazine

Interstellar Rosetta Stone

Typical cell , size and quantity

DNA structure and location in the nucleus

Credit: Seed Magazine

Conclusion● Many different technologies to communicate● Large amounts of space to target● Constructing a message is difficult