WOW! Signal — 15.08.1977 · 72 Seconds · Big Ear · Sagittarius · Never Repeated

August 15, 1977, 10:16 PM EDT: Big Ear radio telescope (Ohio State) receives narrowband signal. Strength: 30-sigma above noise (astronomically extraordinary). Frequency: 1420.456 MHz — the hydrogen line, universally regarded as the interstellar communication frequency. Duration: 72 seconds — exactly as long as a terrestrial signal would remain in Big Ear's field of view. Astronomer Jerry Ehman writes on the printout: 'Wow!' Only on 1 of 50 possible channels. Characteristic rise-and-fall pattern = cosmic origin. NEVER DETECTED AGAIN: Hundreds of follow-up observations — no signal. DIRECTION: Constellation Sagittarius. RA 19h25m ± 3s, Dec -26°57' ± 20'. ZETA RETICULI CONNECTION (disputed): Sagittarius direction = general, not specifically ZR. However: temporal congruence — 1977 = Operação Prato Brazil, global UFO peak phase. 2025 Arecibo-Wow! study (peer-reviewed): possible maser explanation proposed. Avi Loeb 2025: possible connection to 3I/ATLAS object speculated. SETI consensus: Most compelling SETI candidate of all time to date — despite lack of repetition.