Where Is Everybody ?

Where Are the Extraterrestrials?

During a lunchtime conversation at Los Alamos more than 50 years ago, four world-class scientists agreed, given the size and age of the Universe, that advanced extraterrestrial civilizations simply had to exist. The sheer numbers demanded it. But one of the four, the renowned physicist and back-of-the-envelope calculator Enrico Fermi, asked the telling question. If the extraterrestrial life proposition is true, he wondered, "Where is everybody?"

• Aliens are already here among us: Here are entries ranging from the great Leo Szilard's suggestion that they are already here, and we know them as Hungarians, to the theorists who claim that aliens built Stonehenge and the Easter Island statues.
• Aliens exist, but have not yet communicated: The theories in this camp range widely, from those who believe we simply don't have the technologies to receive their signals, to those who believe the enormities of space and time work against communication, to those who believe they're hiding from us.
• Aliens do not exist: Here are the doubters' arguments, from the Rare Earth theory to the author's own closely argued and cogently stated skepticism.

The proposed solutions run the gamut from the crackpot to the highly serious, but all deserve our consideration. The varieties of arguments -- from first-rate scientists, philosophers and historians, and science fiction authors -- turn out to be astonishing, entertaining, and vigorous intellectual exercises for any reader interested in science and the sheer pleasure of speculative thinking.

Contents

Where Is Everybody?

Of Fermi and Paradox

• Solution 1 They Are Here and They Call Themselves Hungarians
• Solution 2 They Are Here and Are Meddling in Human Affairs
• Solution 3 They Were Here and Left Evidence of Their Presence
• Solution 4 They Exist and They Are Us -- We Are All Aliens!
• Solution 5 The Zoo Scenario
• Solution 6 The Interdict Scenario
• Solution 7 The Planetarium Hypothesis
• Solution 8 God Exists

• Solution 9 The Stars Are Far Away
• Solution 10 They Have Not Had Time to Reach Us
• Solution 11 A Percolation Theory Approach
• Solution 12 Bracewell-von Neumann Probes
• Solution 13 We Are Solar Chauvinists
• Solution 14 They Stay at Home . . .
• Solution 15 . . . and Surf the Net
• Solution 16 They Are Signaling But We Do Not Know How to Listen
• Solution 17 They Are Signaling But We Do Not Know at Which Frequency to Listen
• Solution 18 Our Search Strategy Is Wrong
• Solution 19 The Signal Is Already There in the Data
• Solution 20 We Have Not Listened Long Enough
• Solution 21 Everyone Is Listening, No One Is Transmitting
• Solution 22 Berserkers
• Solution 23 They Have No Desire to Communicate
• Solution 24 They Develop a Different Mathematics
• Solution 25 They Are Calling But We Do Not Recognize the Signal
• Solution 26 They Are Somewhere But the Universe Is Stranger Than We Imagine
• Solution 27 A Choice of Catastrophes
• Solution 28 They Hit the Singularity
• Solution 29 Cloudy Skies Are Common
• Solution 30 Infinitely Many ETCs Exist But Only One Within Our Particle Horizon: Us

• Solution 31 The Universe Is Here for Us
• Solution 32 Life Can Have Emerged Only Recently
• Solution 33 Planetary Systems Are Rare
• Solution 34 We Are the First
• Solution 35 Rocky Planets Are Rare
• Solution 36 Continuously Habitable Zones Are Narrow
• Solution 37 Jupiters Are Rare
• Solution 38 Earth Has an Optimal "Pump of Evolution"
• Solution 39 The Galaxy Is a Dangerous Place
• Solution 40 A Planetary System Is a Dangerous Place
• Solution 41 Earth's System of Plate Tectonics Is Unique
• Solution 42 The Moon Is Unique
• Solution 43 Life's Genesis Is Rare
• Solution 44 The Prokaryote-Eukaryote Transition Is Rare
• Solution 45 Toolmaking Species Are Rare
• Solution 46 Technological Progress Is Not Inevitable
• Solution 47 Intelligence at the Human Level Is Rare
• Solution 48 Language Is Unique to Humans
• Solution 49 Science Is Not Inevitable

Conclusion Solution 50 The Fermi Paradox Resolved . . .

Notes and Further Reading

References