The Norway spiral mystery
On December 9, 2009, Norwegians were treated to an unusual spiral visual display in the sky. It is now widely considered to have been caused by a failed Russian rocket test. Belated admission by Russian authorities that such a failure had occurred seemed to confirm this explanation. However, there is some ambiguity about the available visual data that might cause one to doubt this conclusion. In particular, there are differences between the video and still photo records of the event. The still photos show a much more extensive spiral than do the videos. Some have suggested that the still photos are time exposures, thus accounting for the larger spiral display. This report examines whether or not this is a viable explanation. A further unexpected observation strongly suggests that the overall event was not as simple as it first appeared.
First, we examine the possibility that a time exposure could have given the unsmeared spiral pattern seen in the still images. We do this by overlaying successive frames from a video and evaluating the result. If the spiral and the object creating the spiral have a lateral motion, smearing of the image would be expected. Estimating the relative motion of the spiral in a video requires a common reference point on the ground. A suitable video for this was suggested by Hoagland who used it for the same purpose. Three frames were extracted at the 42, 45, and 47 second marks. Cropped frames from the video, seen in the left column of Figure 1, show that the spiral moved a small amount to the left in those five seconds. The corresponding enlarged centers of the spiral are displayed in the right column, and these show that the center of the spiral is indeed rotating as the phase at the origin shifts in successive frames. The speed of rotation was estimated by Amini to be about one Hz.
|Figure 1. Successive frames from a video of the Norway Spiral.|
|Figure 2. Video frames of Figure 1 superimposed.|
Remarkably, the phase of the spiral visible at its center appears to be the same in all these images. The last image is somewhat blurred, but its phase seems not unlike that of the previous five images. This consistency across images is highly unlikely assuming that the object at the center of the spiral was rotating at one Hz and the pictures were taken at different times.
|Figure 3. Still photos of the Norway Spiral|