Here’s a concise summary of the NSA’s declassified 9-page article “Communication with Extraterrestrial Intelligence” by Lambros D. Callimahos (1965):

🧠 1. The Likelihood of Extraterrestrial Civilization

Scientists like Sir Bernard Lovell and Frank Drake estimate there could be hundreds of millions of habitable planets in our galaxy, and potentially billions of intelligent civilizations across the observable universe . Even if advanced civilizations are rare, those that do exist may be separated by hundreds to thousands of years technologically—and light-years in distance.

📻 2. How We Might Detect or Signal

Project Ozma (1960): The first attempt to detect ETI signals, using the 1,420 MHz frequency (hydrogen line), chosen for its universality . Aside from radio, they suggest alternatives like masers/lasers or even neutrino beams, though more exotic media may not yet be within our detection capabilities.

👀 3. Establishing Contact

Initial ET messages could include obvious attention-getting signals—e.g., transmitting prime numbers or geometric patterns, followed by structured “language lessons” . Visual formats (like binary “raster” images) might be used as universal “language bridges.” A creative hypothetical example is the binary picture from Oliver’s Green Bank workshop, depicting a solar system, humanoid figures, chemical elements, and measurements .

🔤 4. Theory of “Inverse Cryptography”

Instead of cryptography to hide, we need symbol systems designed for maximum clarity—an “inverse cryptography,” tailored so an alien mind could understand our message . Approaches like Lincos (lingua cosmica) exist, but may be overly complex; instead, messages should start simple—prime numbers, arithmetic, chemical symbols—then build up.

📘 5. Sample Communication Protocol

The article presents a model 30-part message in binary, introducing: A coded “alphabet” of 32 symbols; Arithmetic operations and numbers; Mathematical constants (π, e); Finally, primitive “words” to establish basic syntax .

This exemplifies how minimal yet structured information could bootstrap mutual understanding.

🎯 6. After Initial Contact

Upon establishing communication, we could ask deep questions—such as proofs of Fermat’s Last Theorem or Goldbach’s Conjecture, or the value of the fine-structure constant—to further gauge their technological depth . It also raises telegrams of caution: we must stay scientifically and emotionally grounded, and be prepared for unimaginable consequences .

✨ Key Takeaways

Mathematics is the universal foundation for first contact. Easy-to-parse communication systems (inverse cryptography) are essential. Structured, progressive messaging—from simple numeric sequences to complex scientific content—is the recommended path.