I discovered science fiction and fantasy in my early teens, at about the same time I became interested in science and in writing. Many of my fellow undergraduates at Caltech shared my interest in science fiction. Blacker House, where I lived during my undergraduate years, had its own library, well-stocked with science fiction that I enjoyed. Two of my Caltech friends and fellow students, David Brin and Harry Turtledove, went on to be well-known professional science-fiction writers.

I began writing science fiction before I went to Caltech, and continued after I graduated. My first sales came while I was working at Laser Focus magazine, and in my typical disorganized way my first published fiction was in a computer magazine at about the same time I sold a nonfiction story to Analog Science Fiction. 

When I began freelancing full time, I faced economic reality and concentrated on nonfiction. Nonfiction magazines paid much better and commissioned me to write articles; science fiction took me more time to write, the magazines paid much less, and I had no guarantee anybody would buy it. As you can see from the list below, I have continued writing fiction over the years, but I have published about a hundred times more nonfiction.

I should note that "The Neanderthal Correlation" was published before any Neanderthal DNA was discovered in modern humans.

Links are included to stories that are available online.

"The Clear Space Foundation," 29 September 2021 in Nature Futures
"At Climate Court" 25 October 2019 in Little Blue Marble
"Hello, Hello" 11 September 2019 in Nature Futures
"A Slice of Time," 28 April 2016 in Nature Futures
"Postcards from Lemuria," in Conspiracy!, edited by Judith K. Dial and Thomas Easton, NESFA Press, 2016
"When Last I Saw the Stars," Nature Futures 13 May 2015
"Mr. Tesla's Radio Rainmaker," in Deco Punk, edited by Judith K. Dial and Thomas Easton, Pink Narcissus Press, 2015
"The Internet of **** Things," Nature Physics, July 2014
"Daybreak," in Extreme Planets Anthology, edited by David Conyers, David Kernot, and Jeff Harris, (Chaosium Inc., 2014)
"The Chatter of the Beams," in Impossible Futures Anthology Edited by Judith K. Dial and Thomas Easton, Pink Narcissus Press, 2013
"The Speed of Dark Energy," Nature  Futures 28 August 2013
"Waiting for Chronomatic," Nature 4 July 2012
"Event Horizon," Nature 20 July 2011
"Clear Proof: The Final Demonstration of the Failure of Cold Fusion) Nature 9 November 2009
"The Neanderthal Correlation," Nature, May 22, 2008 (on line at Nature)
"Quantum Entanglements," Nature Physics, April 2007 (on line at Nature Physics)
"Operation Tesla," Nature, October 5, 2006 (on line at Nature)
"Directed Energy," Nature, April 13, 2006
"Draft Dodger's Rag," Analog, March 2004
"By the Lake," Analog, November 2002
"Squirrels," HMS Beagle, issue 80 (late June 2000) (site is no longer on-line)
"The Rumor of the Ruined City," Asimov's SF, April 1999
"The Crystal Highway," Odyssey, December 1997
"The Saucer Man," Interzone, August 1997
"The Awful Truth," appeared on Middle Georgia Web Magazine and on Jackhammer
"A Life of its Own," Analog, January 1997
"Engineering Reality" appeared on the now-defunct electronic Galaxy
"The Number of the Beast," in Alien Pregnant By Elvis, Esther Freisner and Martin Greenberg Eds., DAW, 1994
"The Greenhouse Papers" Analog, November 1991
"Aunt Horrible's Last Visit," Vampires, Jane Yolen and Martin H. Greenberg, eds.. Harper Collins, 1991
"Rehearsals for Retirement", Analog, mid-Dec 1990
"Boxes," After Hours, Autumn 1990
"Extinction Theory" Analog, March 1989
"Saratoga Winter," Twilight Zone, Oct 1982
"On 202", Twilight Zone, Dec. 1981, reprinted in Year's Best Horror Stories X, Karl Edward Wagner ed.; New England Ghosts, Frank D. McSherry Jr., Charles G. Waugh and Martin H. Greenberg eds.; and in Great American Ghost Stories, Frank D. McSherry Jr., Charles G. Waugh and Martin H. Greenberg eds. 
"Crossing the Wastelands," New Dimensions 9, Robert Silverberg ed. (Harper and Row, New York, 1979)
"Lifeboat", New Dimensions 8, Robert Silverberg ed. (Harper and Row, New York, 1978)
"The Princess and the P6," Datamation, April 1976