Dorminey, Bruce, <br/><br/>
Dark Threat. 
Bruce Dorminey. 
 -  Astronomy,  2005. 
 - SIRS Enduring Issues 2006.  Article 56,  Science,  1522-3264; .
<br/><br/> Articles Contained in SIRS Enduring Issues 2006.  Originally Published: Dark Threat, July 2005; pp. 40-45. 
<br/><br/> "In February 1984, University of Chicago paleontologists David Raup and J. John Sepkoski published a short paper in the Proceedings of the National Academy of Sciences announcing that extinction rates in Earth's geologic past appeared to be periodic. Raup and Sepkoski attributed this observed periodicity to galactic forces acting on our surrounding cometary reservoir as we travel through the Milky Way." (ASTRONOMY) This article discusses mass extinctions on Earth, what may have caused them and what could cause future extinctions. 
<br/><br/><label>ISSN: </label>1522-3264; 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Brown dwarfs<br/>Comets--Collisions with Earth<br/>Extinction (Biology)<br/>Nemesis (Star)<br/>Oort cloud<br/>Solar system--Motion in space<br/>Stars
<br/><br/><label>LC Class. No.: </label>AC1.S5 
<br/><br/><label>Dewey Class. No.: </label>050