Probably the dirtiest little secret of our genre is that there is no such thing as hard SF about deep space. Hard SF? Its that particular kind of science fiction that prides itself on scientific rigor. Allen Steele <http://www.allensteele.com> has written that "Hard SF is the form of imaginative literature that uses either established or carefully extrapolated science as its backbone." Or as Gregory Benford <http://www.authorcafe.com/benford> has so often put it when he advocates for hard SF: "Id rather have tennis played with the net up."
Alas, the net of scientific rigor catches the vast majority of the spaceships that we science fiction writers have imagined. The fact is that we arent going to the stars if our current understanding of the universe holds; theyre too far away and were far too mortal. Or if we do make it out of our solar system, it will be only to visit our very nearest neighbors. Alpha Centauri <http://homepage.sunrise.ch/homepage/schatzer/Alpha-Centauri.html> is "only" 4.3 light years away. Thats 25,278,149,538,273 miles, folks. It is sobering to consider that the fastest spaceships weve ever built travel at only 0.00004 percent the speed of light. If we limit ourselves to careful extrapolation, its possible to imagine a spaceship that will travel someday at, say, 1 percent the speed of light, but that still makes the trip to Alpha Centauri four hundred and thirty years longeach way.
But wait, some faithful reader might say. What about faster-than-light drives? FTL is pretty to think about and solves all kinds of plot problems, but, according to what we know now, its impossible. Traveling faster than the speed of light has about as much meaning in the real world as traveling slower than stopped. Intrepid starship captains engaging their warp drives and daring explorers making the leap to hyperspace make about as much hard SF sense as Aladdin flying his magic carpet to Mars.
Which didnt stop NASA from launching the Breakthrough Propulsion Physics (BPP) Project <http://www.grc.nasa.gov/WWW/bpp> in 1996. Its purpose was "to seek the ultimate breakthroughs in space transportation: (1) propulsion that requires no propellant mass, (2) propulsion that attains the maximum transit speeds physically possible, and (3) breakthrough methods of energy production to power such devices." While the project generated considerable enthusiasm in science fiction circles, it was controversial in the scientific community and all funding was cut in January of 2003. While there is a wealth of technical information on the site for the uber-geek, mere mortals may want to click to Warp Drive, When? <http://www.lerc.nasa.gov/WWW/PAO/warp.htm>, a marvelous introduction to the problems and possibilities of FTL by Marc Millis <http://www.grc.nasa.gov/WWW/PAO/html/warp/marc.htm>, one of the creators of NASAs BPP. Its clear that Marc Millis believes that we will someday make the breakthroughs necessary to build interstellar ships, although he is a cautious enough scientist to answer the question So, can we do it? <http://www.lerc.nasa.gov/WWW/PAO/html/warp/socanwe.htm> with a graphic that screams Sorry, not in the foreseeable future. Physics not yet known.
Wil McCarthy <http://www.wilmccarthy.com> offers a very readable summary of FTL in his two part Lab Notes <http://www.scifi.com/sfw/issue195/labnotes.html> and <http://www.scifi.com/sfw/issue199/labnotes.html> over at Science Fiction Weekly <http://www.scifi.com/sfw>. In the second of these two columns he discusses how quantum mechanics mayor may not, who knows?give us a way to send our information faster than light, if not ourselves. Entangled quantum tunneling offers us a glimpse of how this might be accomplished, although that glimpse could well be a mirage. As Wil writes, "We may never find a way around these slippery barriers. In fact, there are so many barriers, everywhere we look, that many scientists have long considered the cause hopeless."
Ill pause here for an encomium. We live in what I consider the golden age of science explainers. Of the many wonderful writers helping us understand our baffling universe, I think Wil is among the very best. His columns at SFW are lively and nicely transparent to this English major; I can recommend his book Hacking Matter <http://www.wilmccarthy.com/hm.htm> to both SF fans and practitioners. What bugs me is that he is also one of science fictions most dazzling novelists. Grr! The only flaw I can find in his stellar career is that he is only a very occasional contributor to Asimovs.
Yet another take on FTL travel are the Great Moments in Science <http://www.abc.net.au/science/k2/moments/gmis9805.htm> pages of Dr. Karl S. Kruszelnicki, Fellow at the School of Physics at the University of Sydney. Dr. Karl offers compelling counter-arguments to some of the speculations of the BPP, although he points us toward the controversial energy source of zero point energy <http://www.calphysics.org/zpe.html> as the breakthrough discovery we can use to power our starships.
In 1994, Miguel Alcubierre, a physicist at the University of Wales in Cardiff, published a paper in Classical and Quantum Gravity <http://www.iop.org/EJ/journal/0264-9381> entitled "The Warp Drive: Hyper-fast Travel Within General Relativity" <http://www.astro.cf.ac.uk/groups/relativity/papers/abstracts/miguel94a.html> in which he argued that it was theoretically possible to warp spacetime and zip at nearly infinite speed across the universe. You might accomplish this trick by compressing spacetime in front of your starship and expanding it behind. The operative word here is "might" because in order to build an Alcubierre Drive you need to be able to manipulate exotic matter, that is, matter with a negative energy density. This stuff is highly speculative and even if it does exist, no one has the slightest idea how to contain it, much less bend it to our purposes. Meanwhile, Mitchell Pfenning and Larry Ford of Tufts University crunched the numbers on the Alcubierre Drive and discovered that in order to warp an area of spacetime smaller than an atom you need to expend ten billion times the energy that exists in the entire universe!
In the abstract of his paper, Miguel Alcubierre writes, "It is shown how, within the framework of general relativity and without the introduction of wormholes, it is possible to modify spacetime in a way that allows a spaceship to travel with an arbitrarily large speed." In part, the initial enthusiasm with which the Alcubierre Drive was greeted arose from the fact that it did not rely on wormholes. Kip Thorne <http://www.cco.caltech.edu/~kip> wrote the book on wormholes in his classic Black Holes and Time Warps <http://www.epinions.com/book_mu-2178385>. In it, he tells how his friend, the late great Carl Sagan <http://www.carlsagan.com>, asked him to read the manuscript of Contact <http://www.probe.org/docs/contact.html> and vet the gravitational physics. This was a good thing, because Sagan had his heroine plunging into a black hole in order to arrive at a planet in orbit around Vega, which plunge would certainly have killed her. Thorne recommended that Sagan change the black hole to a wormhole. Although there are enormous difficulties in creating a transportation system using wormholes, such a system is at least possible. Sort of. Thinking about the problem led Thorne to consider questions that pushed physics to its farthest edge. He asked himself "What things do the laws of physics permit an infinitely advanced civilization to do, and what things do the laws forbid?" Note that this question does not address the likelihood that Homo sapiens sapiens will ever become infinitely advanced, or indeed that we will ever travel through wormholes.
Because building a wormhole <http://www.daviddarling.info/encyclopedia/W/wormhole.html> transportation system is a really big job, even for an infinitely advanced civilization. For one thing, there is still some question as to whether wormholes occur naturally. If they do, they are many times smaller than an atom. The trick is to capture one of the little buggers and then force its mouth way, way, way open and then coat the mouth with some of that highly speculative exotic matter (our old friend from the Alcubierre Drive) to keep the wormhole from collapsing in a catastrophic explosion. And then theres the problem of an exit strategy. Assuming that you could pass through the wormhole mouth, where would you come out? Unless you built another wormhole mouth wherever it was that you wanted to go, you would be taking a one way trip to a random destination. All in all, the prospects for wormhole engineering do not look promising.
Heres another encomium: the link immediately above comes from one of the best written and most comprehensive space sites on the web, The Encyclopedia of Astrobiology, Astronomy, and Spaceflight <http://www.daviddarling.info/encyclopedia/ETEmain.html>. The encyclopedia is the work of David Darling <http://www.daviddarling.info/index.html>, the British astronomer and science writer, currently living in Minnesota. Entries range from A for Andromeda, the classic 1962 SETI novel by Fred Hoyle and John A. Elliott, to Benjamin M. Zuckerman, the astronomer and a pioneer in the search for extrasolar planetary systems. This is a monumental site that should be on everyones favorites list.
In 1964 Russian astrophysicist Nikolai Kardashev <http://www.daviddarling.info/encyclopedia/K/Kardashev.html> proposed a way to classify advanced civilizations. A Type I civilization can use the energy resources of an entire planet, or about 1016 watts. A Type II civilization can harness the energy of a star, about 1026 watts. A Type III civilization would be able to tap the energy of an entire galaxy, about 1036 watts. On this scale, we are a Type 0 civilization, although we have certain aspirations to become a Type I in this century. In The Physics of Interstellar Travel <http://www.mkaku.org/articles/physics_of_space_travel.shtml> physicist Michio Kaku assigns theoretical advances in spacecraft propulsion systems to these various levels of civilization, pointing to our future in space. You need to check this out! He writes, "Most scientists doubt interstellar travel because the light barrier is so difficult to break. However, to go faster than light, one must go beyond Special Relativity to General Relativity and the quantum theory. Therefore, one cannot rule out interstellar travel if an advanced civilization can attain enough energy to destabilize space and time."
I recently came across a very cool site called SciFan <http://www.scifan.com>, that has been online since 1999. Produced by French fan Olivier Travers <http://webvoice.blogspot.com> with the help of his girlfriend Sophie Bellais, SciFan is all about helping readers find what they want. The site classifies 44,968 books and 11,923 writers by themes and series. Each book entry gives the publisher and pub date, related themes and often as not a summary and brief review. When you query the database about FTL interstellar travel, it yields up pages and pages of some of the best science fiction ever written.
But that should come as no surprise. I hardly need to point out that interstellar travel has been the meat and potatoes of our genre for the last fifty years. It was never my intention here to disparage the work of my many literary betters. Hey, I love galaxy spanning yarns; its no secret that Ive written FTL stories myself. Id love it if someday some young whippersnapper shoves this column in my face and says, "Hey Kelly, you were so damn wrong."