No. 98: Mar-Apr 1995
Using cosmic-ray data and stellar spectra gathered by seven satellites, P.C. Frisch, at the University of Chicago, has constructed a cosmic scenario that reminds us of F. Hoyle's science fiction tale, The Black Cloud. According to Frisch, until just a few thousand years ago, the solar system was cruising through interstellar space that was almost devoid of matter. Then, perhaps within historical times, 2,000-8,000 years ago, the solar system plunged into an interstellar gas cloud. This cloud is believed to be the remnant of the bubble of matter shot into space perhaps 250,000 years ago by a supernova in the Scorpius-Centaurus region.
This tenuous cloud of gas feeds matter into the solar system, some of which interacts with the solar wind and, therefore, affects the geomagnetic field, too. Climate changes may have been caused by entry into this cloud, and very likely the flux of cosmic rays impinging on the earth would have been modulated.
(Frisch, Priscella C.; "Morphology and Ionization of the Interstellar Cloud Surrounding the Solar System," Science, 265:1423, 1994. Also: Peterson, I.; "Finding a Place for the Sun in a Cloud," Science News, 146:148, 1994.)
Comment. Note that the 2,000-8,000-year span brackets many key developments in human civilization. Also, see under ARCHEOLOGY in this issue. For a potentially serious effect this cloud may have on carbon dating. Getting back to Hoyle's "black cloud," we recall that his molecular cloud was sentient and intelligent, being a form of gaseous-phase life. Did our real gas cloud, now seemingly mute, communicate with ancient humans? "Clouds of the Gods." Sounds like a good book title!