The Hessdalen Lights
1981
In December 1981, people in the Hessdalen valley in central Norway began reporting strange lights: glowing balls that hovered over rooftops, drifted along the valley floor or raced away at impossible-looking speeds. Unlike most UFO stories, this one drew scientists with instruments, and they found that the lights were real enough to measure. Four decades later, nobody can say for certain what they are.
What people reported
Project Hessdalen's 1984 technical report, written by engineer Erling Strand, describes a valley about 12 km long with around 150 residents, where unknown lights suddenly started appearing in December 1981. They could stand still for over an hour, drift slowly or accelerate sharply, and were seen just above roofs, close to the ground or higher in the sky. Most were white or yellow-white, sometimes with a small red light; on photographs they looked like bullets, footballs or upside-down Christmas trees.
Wikipedia gives the same picture: bright white, yellow or red lights that float through and above the valley, by day and by night, lasting from seconds to over an hour, sometimes moving at enormous speed and sometimes hovering. Both Wikipedia and a 2016 article in Frontiers in Earth Science say the lights were seen 15 to 20 times a week between 1981 and 1984, and that sightings have since fallen to roughly 10 to 20 a year.
How long the lights have been around is less clear. Wikipedia says unusual lights have been reported there since at least the 1930s, while the Frontiers article says reports go back more than a century.
What investigators found
In 1983 a group of volunteers launched Project Hessdalen to study the lights. Wikipedia says it was started by Norwegian and Swedish UFO organisations, and Strand's report explains that no official institutions seemed interested, so a handful of people set up the project themselves. Its field work in early 1984 used cameras with spectral gratings, a seismograph, a magnetometer, radar and other instruments.
Strand's conclusion was cautious but important: the team had not found out what the phenomenon was, but they had shown it could be measured, including by radar and laser. The report records one light tracked by radar at about 8,500 metres per second, and the Frontiers article cites velocities of 8,000 to 9,000 metres per second. Some instruments, such as the Geiger counter and seismograph, recorded nothing.
Monitoring continued. Wikipedia says an automatic measurement station was set up in the valley in 1998, and that later research, under a programme called EMBLA, brought in Østfold University College in Norway and Italy's National Research Council. The Frontiers article describes the lights as free-floating balls from tens of centimetres up to 30 metres across, often with short radio spikes, and estimates the brightest as radiating around 19 kilowatts.
The theories
Some sightings have ordinary causes. Wikipedia notes that some were identified as stars and planets, aircraft, car headlights or mirages. For the rest, several scientific ideas have been proposed, and both Wikipedia and the Frontiers article list the main ones.
One suggests the lights involve a poorly understood burning of dust from the valley floor containing scandium. Another proposes that radon decay ionises dust and air into a glowing 'dusty plasma'. A third suggests the valley acts like a giant battery, with its rocks and river generating electricity. Wikipedia also mentions piezoelectricity from quartz-bearing rocks under strain.
None has won general acceptance. The Frontiers authors say no model so far accounts for all the observations, and that the energy source behind the lights remains unknown. Wikipedia likewise says there is no consensus.
Why it matters
Hessdalen is rare among 'strange lights' stories because it has been watched with instruments for decades, not just reported by passers-by. The Frontiers article argues that phenomena like this deserve more scientific attention. For now, the lights remain something that can be photographed, tracked and measured, but not yet explained.
Further reading
- Project Hessdalen: Final technical report 1984 (Erling Strand)
- Frontiers in Earth Science (2016): To investigate or not to investigate?
- Wikipedia: Hessdalen lights