March 7, 2004
The Earth has carried you around the Sun again, steady as ever, while the stars kept their patient watch.
An Anomalous SETI Signal
Birthday · March 7, 2004
A little universe, just for you
Your date.
Ready to give.
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APOD published March 7, 2004. Credit: SETI League. A publication-date match, not a photo taken on your date. Independent of NASA.
No one knows for sure what caused this signal. There is a slight possibility that it just might originate from an extraterrestrial intelligence. The bright colors on the blue background indicate that an anomalous signal was received here on Earth by a radio telescope involved in a Search for Extraterrestrial Intelligence (SETI). A search for these signals is ongoing by several groups including volunteer members of the SETI League. Time labels the vertical axis of the above plot, and frequency marks the horizontal axis. Although this strong signal was never positively identified, astronomers have identified in it many attributes characteristic of a more mundane and ultimately terrestrial origin. In this case, a leading possibility is that the signal originates from an unusual modulation between a GPS satellite and an unidentified Earth-based source. Many unusual signals from space remain unidentified. No signal has yet been strong enough or run long enough to be unambiguously identified as originating from an extraterrestrial intelligence.
Image credit: SETI League