UNITED STATES / 15 August 1977, local observing date
The Wow! signal: six samples, many interpretations
Big Ear recorded a striking narrowband signal represented by six intensity symbols. The file examines the printout, receiver geometry and the limits of an observation without an established repeating source.
Delaware, Ohio — Big Ear observing area · Approximate terrestrial receiving-site area. The marker is not the position or distance of the unknown radio source.
Assessment: A documented radio observation; an artificial extraterrestrial transmitter is not established.
Investigation and inspector’s assessment
Observation brief
On the local evening of 15 August 1977, the Big Ear telescope recorded the signal later marked by Jerry Ehman with the handwritten word Wow. The sequence 6EQUJ5 represents binned intensity, not a received sentence. The six entries span about seventy-two seconds of the instrument’s sampling cycle. They describe the passage through the receiving pattern; they do not independently measure the total lifetime of the emitter. [W1] [W2]
Reading the receiver correctly
Ehman’s technical accounts explain the two-horn arrangement and corrections needed to interpret the recorded coordinates. The unresolved horn assignment leaves alternative sky positions. A map pin in Ohio identifies where the data were collected, not an extraterrestrial destination. The distinction matters because a precise-looking coordinate can conceal an unresolved instrumental ambiguity. [W1] [W2]
Inspector’s assessment
The central task is to reproduce what the printout means before explaining its cause. Preserve the original characters, then add a separate column for the intensity intervals each encodes. Do not replace binned values with exact measurements. Distinguish integration time, processing time and elapsed time. A trend that resembles a beam crossing is informative, but the test should also consider what other sources could produce the same sampling pattern.
Limits of a single detection
A one-off observation can be genuine and still be insufficient for source identification. An attractive frequency, apparent strength and an absence of an immediate explanation do not jointly establish intelligence. Compare hypotheses by predictions: recurrence, bandwidth, motion, visibility in both horns and what other instruments should detect. This dossier does not endorse an absolute claim that all natural or terrestrial explanations have been eliminated; it documents the historical measurement and how to interrogate it.
Documentary chronology
- 15 August 1977
Big Ear records the intensity sequence during its survey. [W1] [W2]
- Subsequent printout review
Ehman notices and marks the sequence after data collection. [W2]
- 1997–1998
The twentieth-anniversary account sets out analysis and corrections. [W2]
- 2007–2010
The thirtieth-anniversary report revises and expands the discussion. [W1]
Dates distinguish the event, the creation of a record and its later publication. Approximate dates remain approximate.
Evidence ledger
Hypothesis review
A transient or intermittent celestial source
Open source class
- Supporting considerations
- The signal’s behaviour is analysed against the telescope beam pattern.
- Limits and objections
- A beam-shaped response alone does not identify a source or explain non-repetition.
- Discriminating test
- Evaluate repeat observations against both candidate sky positions and documented sensitivity.
Terrestrial interference or an instrumental pathway
Alternative source class
- Supporting considerations
- A complete signal audit must examine receiver and interference possibilities.
- Limits and objections
- A generic interference label is not an identified transmitter.
- Discriminating test
- Specify a mechanism and test its expected frequency, timing and horn response.
An artificial extraterrestrial transmission
Unverified interpretation
- Supporting considerations
- The observation motivated SETI interest.
- Limits and objections
- No decoded content or independently established transmitter follows from these records.
- Discriminating test
- Require reproducible detections and independent instrument confirmation before attribution.
Inspector’s next steps
Decode the recording convention
Convert the six symbols to intervals using the published convention, retaining the source values. Mark this as a derived table rather than raw receiver data.
Keep both location solutions
Document coordinate epoch, horn assumptions and corrections. Do not average two alternative positions into a fictional third one.
Build a follow-up ledger
For any follow-up study added later, list its sky coverage, frequency band, sensitivity and observing duration. A null result only constrains what that search could detect.
These are proposed research tasks, not completed fieldwork or requests already sent to an archive.
Documents and source register
Original reports, scans, catalogue records and later analyses are identified separately. Alternate copies of the same document do not add independent evidence. Follow the named archive for full access information.
Jerry Ehman: 30th anniversary technical report
Revised in 2010; includes printout reproductions, corrections and a detailed discussion of instrument geometry.
Language: en
Open original source ↗Jerry Ehman: 20th anniversary report
Earlier version useful for tracing corrections. It is not an independent observation.
Language: en
Open original source ↗Big Ear frequently asked questions
Observatory context and explanations for frequently repeated misunderstandings.
Language: en
Open original source ↗Big Ear surveys and technical articles index
Background to the instrument and its surveys. Individual articles have their own scope.
Language: en
Open original source ↗Downloadable working files
The pack contains the English dossier, a structured case record, source register, chronology, evidence ledger, hypothesis comparison and inspector task sheet. Downloaded source documents, when available for redistribution, are identified in the pack manifest. Other documents remain direct source links.
- English dossier · Markdown
- Structured case · JSON
- Chronology · CSV
- Evidence ledger · CSV
- Hypothesis comparison · CSV
- Source register · CSV
- Inspector task sheet · Markdown
- File manifest and attribution · JSON
Eklipsis authored this synthesis and its working sheets. The original archives and researchers retain credit for their documents. This is a documentary investigation, not a claim that Eklipsis conducted the historical fieldwork.