On November 19, 2008, thousands of residents in and around Philadelphia, Pennsylvania, watched in awe as dozens of stationary light pillars loomed up in the evening sky. Speculation about the origin of the lights on NBC's Philadelphia Weather Stories forum, ranged from the plausible ("aurora borealis") to the implausible ("fallout from the Alaskan volcano that erupted in August"), and from the creative ("moonlit bands of snow") to the completely unscientific (UFOs and aliens).

Witnesses spoke of a wonderful experience. One couple from West Chester was brought to tears, while a woman from Boothwyn thought she was "going nuts". Others referred to the lights as "eerie", "pretty", "awesome" and "very cool".

In reality, the Philadelphia lights were the pillar-shaped images of city lights mirrored in a sea of floating ice-crystals. Balloon soundings suggested that the ice cloud had formed at an altitude of 2.4 km (about 8,000 feet). This relativey short distance to the ground explains why so many lights were mirrored in the sky.

The above photo is one of a series of seven, taken by David WEI from Plymouth Meeting, Pennsylvania, at around 9 p.m. EST facing southeast. David used a Canon 40D camera fitted with a 17 mm wide-angle lens. The exposure time was presumably 1.3 seconds and the aperture was set at f/2.8.

Click "next picture" to view a second photo from this series.

[© David WEI - photo shown with permission (David runs his own photo website at davidwei.smugmug.com)]