Webmaster’s Comment: Reader, I would like to introduce you to at least some of the psychopaths who believe that the human brain and soul are comprised only of firing neurons and have no reservations about destroying others’ lives and souls to satisfy their professional ambitions and curiosity. God, please send these devils to hell ASAP.
I. The Neuroscientist Who Wants To Upload Humanity To A Computer
Randal Koene is recruiting top neuroscientists to help him make humans live forever
By Adam Piore May 16, 2014; POPULAR SCIENCE (May 16, 2014)
The Neuroscientist Who Wants to Upload Humanity to a Computer
THE HUMAN BRAIN
Chris Parsons/Getty Images
Everything felt possible at Transhuman Visions 2014, a conference in February billed as a forum for visionaries to “describe our fast-approaching, brilliant, and bizarre future.” Inside an old waterfront military depot in San Francisco’s Fort Mason Center, young entrepreneurs hawked experimental smart drugs and coffee made with a special kind of butter they said provided cognitive enhancements. A woman offered online therapy sessions, and a middle-aged conventioneer wore an electrode array that displayed his brain waves on a monitor as multicolor patterns.
On stage, a speaker with a shaved head and a thick, black beard held forth on DIY sensory augmentation. A group called Science for the Masses, he said, was developing a pill that would soon allow humans to perceive the near-infrared spectrum. He personally had implanted tiny magnets into his outer ears so that he could listen to music converted into vibrations by a magnetic coil attached to his phone.
None of this seemed particularly ambitious, however, compared with the claim soon to follow. In the back of the audience, carefully reviewing his notes, sat Randal Koene, a bespectacled neuroscientist wearing black cargo pants, a black T-shirt showing a brain on a laptop screen, and a pair of black, shiny boots. Koene had come to explain to the assembled crowd how to live forever. ”As a species, we really only inhabit a small sliver of time and space,”Koene said when he took the stage. ”We want a species that can be effective and influential and creative in a much larger sphere.”
Koene’s solution was straightforward: He planned to upload his brain to a computer. By mapping the brain, reducing its activity to computations, and reproducing those computations in code, Koene argued, humans could live indefinitely, emulated by silicon. “When I say emulation, you should think of it, for example, in the same sense as emulating a Macintosh on a PC,” he said. “It’s kind of like platform-independent code.”
The audience sat silent, possibly awed, possibly confused, as Koene led them through a complex tour of recent advances in neuroscience supplemented with charts and graphs. Koene has always had a complicated relationship with transhumanists, who likewise believe in elevating humanity to another plane. A Dutch-born neuroscientist and neuro-engineer, he has spent decades collecting the credentials necessary to bring his fringe ideas in line with mainstream science. Now, that science is coming to him. Researchers around the globe have made deciphering the brain a central objective. In 2013, both the U.S. and the EU announced initiatives that promise to accelerate brain science in much the same way that the Human Genome Project advanced genomics. The minutiae may have been lost on the crowd, but as Koene departed the stage, the significance of what they just witnessed was not: The knowledge necessary to achieve what Koene calls “substrate independent minds” seems tantalizingly within reach.
The concept of brain emulation has a long, colorful history in science fiction, but it’s also deeply rooted in computer science. An entire subfield known as neural networking is based on the physical architecture and biological rules that underpin neuroscience.
Roughly 85 billion individual neurons make up the human brain, each one connected to as many as 10,000 others via branches called axons and dendrites. Every time a neuron fires, an electrochemical signal jumps from the axon of one neuron to the dendrite of another, across a synapse between them. It’s the sum of those signals that encode information and enable the brain to process input, form associations, and execute commands. Many neuroscientists believe the essence of who we are—our memories, emotions, personalities, predilections, even our consciousness—lies in those patterns.
In the 1940s, neurophysiologist Warren McCulloch and mathematician Walter Pitts suggested a simple way to describe brain activity using math. Regardless of everything happening around it, they noted, a neuron can be in only one of two possible states: active or at rest. Early computer scientists quickly grasped that if they wanted to program a brainlike machine, they could use the basic logic systems of their prototypes—the binary electric switches symbolized by 1s and 0s—to represent the on/off state of individual neurons.
NEUROSCIENTIST RANDAL KOENE
Joseph Schell
A few years later, Canadian psychologist Donald Hebb suggested that memories are nothing more than associations encoded in a network. In the brain, those associations are formed by neurons firing simultaneously or in sequence. For example, if a person sees a face and hears a name at the same time, neurons in both the visual and auditory areas of the brain will fire, causing them to connect. The next time that person sees the face, the neurons encoding the name will also fire, prompting the person to recollect it.
Using these insights, computer engineers have created artificial neural networks capable of forming associations, or learning. Programmers instruct the networks to remember which pieces of data have been linked in the past, and then to predict the likelihood that those two pieces will be linked in the future. Today, such software can perform a variety of complex pattern-recognition tasks, such as detecting credit card purchases that diverge dramatically from a consumer’s past behavior, indicating possible fraud.
Of course, any neuroscientist will tell you that artificial neural networks don’t begin to incorporate the true complexity of the human brain. Researchers have yet to characterize the many ways neurons interact and have yet to grasp how different chemical pathways affect the likelihood that they will fire. There may be rules they don’t yet know exist.
But such networks remain perhaps the strongest illustration of an assumption crucial to the hopes and dreams of Randal Koene: that our identity is nothing more than the behavior of individual neurons and the relationships between them. And that most of the activities of the brain, if technology were capable of recording and analyzing them, can theoretically be reduced to computations.
On a warm afternoon in late January, I follow Koene up the stairs of the second-floor walkup he shares with his girlfriend on the edge of San Francisco’s Portrero Hill. He leads me through a small living room crammed full of synthesizers and Legos and into a bedroom, where a standing desk represents his home office. It holds oversize computer screens and laptops arrayed like the electronics of a star-ship command center. It’s a modest setting, but Koene is only in the third decade of his quest—a mere blink of an eye when you consider that his goal is immortality.
Koene, the son of a particle physicist, first discovered mind uploading at age 13 when he read the 1956 Arthur C. Clarke classic The City and the Stars. Clarke’s book describes a city one billion years in the future. Its residents live multiple lives and spend the time between them stored in the memory banks of a central computer capable of generating new bodies. “I began to think about our limits,” Koene says. “Ultimately, it is our biology, our brain, that is mortal. But Clarke talks about a future in which people can be constructed and deconstructed, in which people are information.”
It was a vision, Koene decided, worth devoting his life to pursuing. He began by studying physics in college, believing the route to his goal lay in finding ways to reconstitute patterns of individual atoms. By the time he graduated, however, he concluded that all he really needed was a digital brain. So he enrolled in a masters program at Delft University of Technology in the Netherlands, where he focused on neural networks and artificial intelligence.
It was while at Delft in 1994 that Koene made an important discovery: a community of people who shared his ambition. Exploring the new medium of the Internet, he stumbled upon the “Mind Uploading Home Page,” owned by Joe Strout, an Ohio-born computer buff, aspiring neuroscientist, and self-described immortalist. Strout facilitated a discussion group that Koene quickly joined, and its members began to debate whether extracting information from the brain was technologically feasible, and if it was, what they should call it: downloading, uploading, or mind transfer. They eventually settled on “whole brain emulation.” And then they outlined career goals that would help them advance their cause.
Koene chose to pursue a Ph.D. in computational neuro-science at McGill University, and later landed at a Boston University neurophysiology lab, where he attempted to replicate mouse brain activity on a computer. Strout pursued an advanced degree in neuroscience, then moved on to the lab of a computational neurobiologist at the Salk Institute. “We were all trying to push research problems in whatever way we could,” Strout says. “The trouble was that for the elder neuroscience researchers, this wasn’t a topic they could discuss publicly. They would talk about it over a beer. But it was too fringe for people who were trying to get grants for research.”
By mapping the brain, humans could live indefinitely.
By then, many of the other group members had earned their credentials. And in 2007, computational neuroscientist Anders Sandberg, who studies the bioethics of human enhancement at Oxford University, summoned interested experts to Oxford’s Future of Humanity Institute for a two-day workshop. Participants laid out a roadmap of capabilities humans would need to develop in order to successfully emulate a brain: mapping the structure, learning how that structure matches function, and developing the software and hardware to run it.
Not long afterward, Koene left Boston University to become the director of neuroengineering at the Fatronik-Tecnalia Institute in Spain, one of the largest private research organizations in Europe. “I didn’t like the job once I figured out they weren’t into taking any risks and didn’t really care about futuristic things related to whole brain emulation,” Koene says. So, in 2010, he moved to Silicon Valley to take a job as head of analysis at Halcyon Molecular, a nanotechnology company that had raised more than $20 million from PayPal cofounders Peter Thiel and Elon Musk, among others. Though Halcyon’s goal was to develop low-cost, DNA-sequencing tools, its leaders assured Koene he would have time to work on brain emulation, a goal they supported.
By the time Halcyon abruptly went out of business in 2012, Koene had created Carboncopies.org, which serves as a hub for mind-uploading advocates. He had also made a lot of contacts. Within months, he secured financial backing from Dimitry Itskov, a Russian dot-com mogul who hoped to upload himself to a “sophisticated artificial carrier” and considered whole brain emulation an essential step.
“We need to provide a foundation so the new field of brain emulation is taken seriously,” Koene tells me from his bedroom command center. He opens a color-coded chart on one of the screens. It consists of overlapping circles filled with names and affiliations, divided into wedges representing the roadmap’s objectives. Koene points to the outermost circle. “These are the people who just have compatible R&D goals,” he says. Then he indicates the smaller, inner circle. “And these are the people who are onboard.”
It’s all of these individuals, mainstream neuroscientists, who will advance whole brain emulation, Koene says—not trans-humanists, who he observes “lack rigor.” And they’ll do so even if philosophically their goals are quite different.
The human brain is made up of billions of nerve cells connected by trillions of synapses. Together, they encode information, such as personality and memory. Scientists at Harvard’s Center for Brain Science have developed a technique called “Brainbow” to map this circuitry in exquisite detail. The cerebral cortex, at the top of this image, stores memory and controls conscious activity, such as motor skills and vision. By making a 3-D dataset of high-resolution images, scientists can trace the brain cells to reveal connections.
Livet, Weissman, Sanes, and Lichtman/Harvard University
Today, as it happens, every pillar of the brain-uploading roadmap is a highly active area in neuroscience, for an entirely unrelated reason: Understanding the structure and function of the brain could help doctors treat some of our most debilitating diseases.
At Harvard University, neurobiologist Jeff Lichtman leads the effort to create a connectome, or comprehensive map of the brain’s structure: the network of trillions of axons, dendrites, and synapses that convey electro-chemical signals. Lichtman is working to understand how experiences are physically encoded at the most basic level in the brain. To do so, he uses a device that incorporates innovations made by a brain-uploading proponent, Kenneth Hayworth, who spent time as a postdoc in Lichtman’s lab. It slices off razor-thin pieces of mouse brain and collects them sequentially on a reel of tape. The slices can then be scanned with an electron microscope and viewed on a computer like the frames of a movie.
By following the threadlike extensions of individual nerve cells from frame to frame, Lichtman and his team have gained some interesting insights. “We noticed, for instance, that when an axon bumped into a dendrite and made a synapse, if we followed it along, it made another synapse on the same dendrite,” he says. “Even though there were 80 or 90 other dendrites in there, it seemed to be making a choice. Who expected that? Nobody. It means this thing is not some random mess.”
When he started five years ago, Lichtman says, the technique was so slow it would have taken several centuries to generate images for a cubic millimeter of brain—about one thousandth the size of a mouse brain and a millionth the size of a human one. Now Lichtman can do a cubic millimeter every couple of years. This summer, a new microscope will reduce the timeline to a couple of weeks. An army of such machines, he says, could put an entire human brain within reach.
At the same time, scientists elsewhere are aggressively mapping neural function. Last April, President Obama unveiled the BRAIN Initiative (for Brain Research through Advancing Innovative Neurotechnologies) with an initial $100 million investment that many hope will grow to rival the $3.8 billion poured into decoding the human genome.
Columbia University neuroscientist Rafael Yuste proposed a large-scale brain activity map that helped inspire the BRAIN Initiative, and he has spent two decades developing tools aimed at tracking how neurons excite and inhibit one another. Yuste likens the brain’s connectome to roads and the firing of its neurons to traffic.
Studying how neurons fire in circuits and how those circuits interact, he says, could help demystify diseases such as schizophrenia and autism. It could also reveal far more. Our very identity, Yuste suspects, lies in the traffic of brain activity. “Our identity is no more than that,” he says. “There is no magic inside our skull. It’s just neurons firing.”
To study those electrical impulses, scientists need to record the activity of individual neurons, but they’re limited by the micromachining techniques used to produce today’s technology. In his lab at MIT, neuro-engineer Ed Boyden is developing electrode arrays a hundred times denser than the ones currently in use. At the University of California, Berkeley, meanwhile, a team of scientists has proposed nanoscale particles called neural dust, which they plan to someday embed in the cortex as a wireless brain-machine interface.
Whatever discoveries these researchers make may end up as fodder for another ambitious government initiative: the European Union’s Human Brain Project. Backed by 1.2 billion euros and 130 research institutions, it aims to create a super-computer simulation that incorporates everything currently known about how the human brain works.
There is no magic inside our skull, it’s just neurons firing.
Koene is thrilled with all of these developments. But he’s most excited about a brain-simulation technology already being tested in animals. In 2011, a team from the University of Southern California (USC) and Wake Forest University succeeded in creating the world’s first artificial neural implant—a device capable of producing electrical activity that causes a rat to react as if the signal came from the animal’s own brain. “We’ve been able to uncover the neural code—the actual spatio-temporal firing patterns—for particular objects in the hippocampus,” says Theodore Berger, the USC biomedical engineer who led the effort. “It’s a major breakthrough.”
Scientists believe long-term memory involves neurons in two areas of the hippocampus that convert electrical signals to entirely new sequences, which are then transmitted to other parts of the brain. Berger’s team recorded the incoming and outgoing signals in rats trained to perform a memory task, and then programmed a computer chip to emulate the latter on cue. When they destroyed one of the layers of the rat’s hippocampus, the animals couldn’t perform the task. After being outfitted with the neural implant, they could.
Berger and his team have since replicated the activity of other groups of neurons in the hippocampus and prefrontal cortex of primates. The next step, he says, will be to repeat the experiment with more complex memories and behaviors. To that end, the researchers have begun to adapt the implant for testing in human epilepsy patients who have had surgery to remove areas of the hippocampus involved in seizures.
“Ted Berger’s experiment shows in principle you can take an unknown circuit, analyze it, and make something that can replace what it does,” Koene says. “The entire brain is nothing more than just many, many different individual circuits.”
That afternoon, Koene and I drive to an office park in Petaluma about 30 miles outside of San Francisco. We head into a dimly lit, stucco building decorated with posters that superimpose words like “focus” and “imagination” over photographs of Alpine peaks and tropical sunsets.
Guy Paillet, a snowy-haired former IBM engineer with a thick French accent and a cheerful Santa Claus–like disposition, soon joins us in a conference room. Paillet and his partner had invented a new kind of energy-efficient computer chip based on the physical architecture of the brain—an achievement that had earned them inclusion in Koene’s chart. Koene wanted an update on their progress.
Paillet reports that he is negotiating to take over an economically troubled computer chip–fabrication foundry in the South of France. Would Koene be willing to serve as a scientific advisor and possibly a fund-raiser on a related project, he asks? Koene shifts impatiently in his chair. “I just had an idea,” he announces. “You are thinking of getting into the foundry business. At the same time people at UC Berkeley are thinking of building new types of neural interfaces. When they get their prototype to work, would you consider . . . .”
“That’s a very good idea!” Paillet interrupts, before Koene can even finish asking whether he might fabricate their device too.
Many scientists seem to puzzle over a question more fundamental to the brain uploaders’ goal: What’s the point?
As we pull out of the parking lot, Koene is ebullient. I had just witnessed his job at its best. “This is what I do,” he says. “You have got tons of labs and researchers who are motivated by their own personal interests.” The trick, he says, is to identify the goals that could benefit brain uploading and try to push them forward—whether the researchers have asked for the help or not.
Certainly, it seems, many scientists have proven willing to consult and even collaborate with Koene. That was clear last spring, when scientists from institutions as varied as MIT, Harvard University, Duke University, and the University of Southern California descended on New York City’s Lincoln Center to speak at a two-day congress that Koene organized with the Russian mogul Itskov. Called Global Future 2045, the conference’s objective was to explore the requirements and implications of transferring minds into virtual bodies by the year 2045.
Some of those present, however, later distanced themselves from the event’s stated “spiritual and sci-tech” vision. “We were trying to get people with a lot of funding who can do big things to start investing in important questions,” says Jose Carmena, one of the Berkeley neuroscientists working on neural dust. “That doesn’t mean we have the same goal. We have similar goals along the way, like recording from as many neurons as possible. We all want to understand the brain. It just happens that they need to understand the brain so they can upload it to a computer.”
Carmena’s reticence was shared by other researchers, some of whom grew alarmed at even a faint possibility that their opinions about the technical plausibility of brain uploading—however qualified and cautious—might somehow be misinterpreted as an endorsement. “There is a big difference between understanding and building a brain,” Yuste says. “There are many things that we more or less understand but we cannot build.” For example, the brain’s hardware could prove critical, he explained, “or there could be intrinsic stochastic events, like in quantum physics, that could make it impossible to replicate.”
Harvard’s Lichtman was more comfortable speculating on the concept. “I am not sure any new laws of physics have to be invented as they go forward,” he says. “It’s not completely impossible, like the idea of putting a cow head on a dog. It’s a science-fiction idea, but making a brain of silicon does not seem crazy to me.” In fact, he thinks the movement has helped advance neuroscience and hopes people like his former postdoc Hayworth succeed—not so they can live forever but to accelerate cures for brain dysfunction.
Hayworth, for his part, is now a senior scientist at Howard Hughes Medical Institute’s Janelia Farm Research Campus, a leader in connectomics, where he is developing techniques to precisely image much larger sections of brain than currently possible. He also founded the Brain Preservation Foundation, which has offered a prize for inventing a method that can preserve the brain until emulation technology catches up. “I know this is a controversial topic,” he says, “and there aren’t a heck of a lot of scientific institutes of any type that relish being dragged into it. Hopefully at some point that will change.”
In the meantime, many scientists seem to puzzle over a question more fundamental to the brain uploaders’ goal: What’s the point? Existing indefinitely in the confines of computer code, Lichtman points out, would be a pretty boring life.
Earlier in the day, I had asked Todd Huffman, a member of Strout’s early discussion group, whether the quest really boiled down to achieving immortality. Koene and I had dropped by Huffman’s company, which received venture capital to develop automated brain-slicing and imaging technologies. Huffman was wearing pink toe nail polish on his shoeless feet and sported a thick beard and bleached faux-hawk.
“That’s a very egocentric and individualist way of characterizing it,” he responded. “It’s so that we can look at the thought structures of humans who are alive today, so that we can understand human history and what it is to be human. If we can capture and work with human creativity, drive, and awareness the same way that we work with, you know, pieces of matter,” he said, “we can take what it is to be human, move it to another substrate, and go do things that we can’t do as individual humans. We want as a species to continue our evolution.”
Brain uploading, Koene agreed, was about evolving humanity, leaving behind the confines of a polluted planet and liberating humans to experience things that would be impossible in an organic body. “What would it be like, for instance, to travel really close to the sun?” he wondered. “I got into this because I was interested in exploring not just the world, but eventually the universe. Our current substrates, our biological bodies, have been selected to live in a particular slot in space and time. But if we could get beyond that, we could tackle things we can’t currently even contemplate.”
II. Mind Transfer Through Sci-Fi History
1929: The World, the Flesh, the Devil, by J.D. Bernal
In a passage that captivates generations of futurists, Bernal predicts mankind will one day leave the body behind and achieve immortality, even replacing the “organic brain cell by a synthetic apparatus.”
1956: The City and the Stars, by Arthur C. Clarke
One billion years from now in the city of Diaspar, a central computer creates new bodies for a rotating group of citizens, storing their minds in its memory banks between lives.
1962: The Creation of the Humanoids
One way to know if your friends aren’t droids with mind-uploads is to stake out the robot temple around 4 a.m. That’s when human personalities “shut off” for an hour and humanoids make their daily pilgrimage back to HQ.
1966: “What Are Little Girls Made of?”,_ Star Trek_
A lovelorn Enterprise nurse beams down to the planet Exo III with Kirk to search for her fiancé. Alas, he turns out to be a mad scientist who transferred himself to an android body after suffering frostbite.
Courtesy: Everett Colletion
1968: 2001: A Space Odyssey
In the film’s finale, mission pilot David Bowman hurtles through space and time until he is transformed into a fetal being enclosed in an orb of light—a reference to mind uploading explained in Arthur C. Clarke’s novel of the same name.
Courtesy: Everett Collection
1982: Tron
Not only does an underhanded and mediocre rival rip off videogames designed by the protagonist, he then has the audacity to digitize him into the mainframe using an experimental laser.
1989: “The Schizoid Man,” Star Trek: The Next Generation
A terminally ill scientist wins Data’s trust by whistling “If I Only Had a Heart” and discussing the existential challenges faced by the Tin Man. (Data can relate.) Then he uploads his mind into the android’s brain.
1992: Freejack
Mercenary Mick Jagger and henchmen travel back in time to try to snatch Emilio Estevez. A rich guy stored in a future “spiritual switchboard” wants to upload his mind into Estevez’s body and steal his fiancée.
Courtesy: Everett Colletion
2000: The 6th Day
In the future, an eye scan copies brain contents for transfer to a cloned body. When Arnold Schwarzenegger returns home to discover his clone has moved in with his family, he recruits him to help blow up the cloning facility.
2004: Battlestar Galactica
Dying in battle isn’t that big a deal to members of the cybernetic civilization called the “Cylons.” They have backup copies of their brains and can simply upload them to new bodies when something goes wrong.
2009:_ Avatar_
A paraplegic soldier uses a device to telepathically control a genetically grown body and spy on a race of 10-foot-tall, blue aliens. The aliens, and ultimately the soldier, upload their memories to the planet’s neural network.
Courtesy: Everett Colletion
2014: Transcendence
Anti-technologists in the Una-bomber mold target an artificial intelligence researcher working to bring about the Singularity. Before dying, he uploads his mind into a computer and becomes a power-hungry megalomaniac.
Shawn Mikula’s technique stains and preserves an entire mouse brain in plastic resin (inset). The brain can then be imaged (a) in order to reconstruct neural circuits (b)—in this case, tracing a single neuron (green) along with synapses (yellow and orange) and nearby cell bodies (blue).
How to Store a Brain (and Everything in It)
While the first upload of a human brain remains decades—if not centuries— away, proponents believe humanity may be far closer to reaching another key technological milestone: a preservation technique that could store a brain indefinitely without damaging its neurons or the trillions of microscopic connections between them.
“If we could put the brain into a state in which it does not decay, then the second step could be done 100 years later,” says Kenneth Hayworth, a senior scientist at Howard Hughes Medical Institute, “and everyone could experience mind uploading first hand.”
To promote this goal, Hayworth cofounded The Brain Preservation Foundation, a nonprofit that is offering a $106,000 technology prize to the first scientist or team to rise to that challenge. He says the first stage of the competition—the preservation of an entire mouse brain—may be won within the year, an achievement that would excite many mainstream neuroscientists, who want to map the brain’s circuitry to better understand memory and behavior.
Current preservation methods (aside from cryonics, which has never successfully been demonstrated to preserve the brain’s wiring) involve pumping chemicals through the body that can fix proteins and lipids in place. The brain is then removed and immersed in a series of solutions that dehydrate naturally occurring water and replace it with a plastic resin. The resin prevents chemical reactions that cause decay, preserving the brain’s intricate architecture. But in order for all of the chemicals to fully permeate brain tissue, scientists must first slice the organ into sections 100 to 500 microns thick—a process that destroys information stored in connections made along those surfaces.
Shawn Mikula, a researcher at the Max Planck Institute for Medical Research in Heidelberg, Germany, developed a protocol that appears to safeguard all of the brain’s synapses. It preserves the extracellular space in the brain so that the chemicals can diffuse through myriad layers of the whole organ. Then, if the brain is sliced and analyzed at a future date, all of its circuitry will remain visible. Hayworth is currently using electron microscopy to examine the mouse brains sent to him as proof of principle. (In order to win the technology prize, the protocol must also be published in a peer-reviewed journal.) So far, Hayworth says, Mikula’s technique seems effective.
If immortality is defined as brain preservation via plastination, Mikula says, then it’s a reasonable extrapolation of his research results. But as for actually uploading it to a computer: “Who can predict these things? Science is modern-day magic,” Mikula says, “and in the absence of a strong argument against the future feasibility of mind uploading, anything is possible.”
This article originally appeared in the May 2014 issue of Popular Science.
tags: science may 2014 brain science neuroscience science fiction