On 8 September 1990, an estimated 300 to 500 residents of Greifswald, East Germany, watched two formations of lights form geometric patterns in the sky. What the lights were remains unresolved.
Greifswald matters because it is a high-witness-count European mass sighting with reported photographs — yet it lacks an official investigation and the cause remains open.
Shortly before German reunification, residents of Greifswald watched two formations of bright lights form geometric patterns and then reconfigure. The display lasted roughly 15–20 minutes.
Documented
The mass observation of two light formations is documented.
The estimated 300–500 witnesses give the case an unusually large observational base for a European sighting. Some witness photographs were taken.
Documented
The witness base and reported photographs are documented.
No official investigation established a cause. Proposed explanations include flares, aircraft, and atmospheric phenomena — but none is established.
Debated
The identity of the lights is contested; whether the formations share one cause is unresolved.
The witness photographs’ provenance is not fully established and they have not resolved the cause. The case remains an unresolved mass sighting.
Unverified
Any extraterrestrial origin, or any single cause asserted as certain, is unverified.
These sources do different jobs: the German research archives preserve the case, the photographs are the reported evidence, and the Wikipedia entry compiles the record. None identifies the lights.
The civilian research record.
The reported event imagery.
The later compiled account.