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The Myths and Reality About Interstellar Travel
Science fiction writers and moviemakers have shown us countless visions of humanity spread out across the Universe, so you might be forgiven for thinking that we’ve already got this in the bag1). Unfortunately, we still have more than a few technical limitations to overcome—like the laws of physics as we understand them—before we can start colonising new worlds beyond our Solar System and galaxy.
That said2), several privately funded or volunteer initiatives such as the Tau Zero Foundation3), Project Icarus4) and Breakthrough Starshot5) have emerged in recent years, each hoping to bring us a little bit closer to reaching across the cosmos. The discovery in August of an Earth-sized planet orbiting our nearest star has also raised fresh hopes about visiting an alien world.
Is travelling to other galaxies possible? And if so, what kinds of spacecraft might we need to achieve it? Read on to get up to (warp6)) speed:
WHERE WOULD WE GO?
Where wouldn’t we go? There are more stars in the Universe than there are grains of sand on Earth—around 70,000,000,000,000,000,000,000—and billions of these are estimated to have one to three planets in the so-called “Goldilocks zone7)”: not too hot, not too cold.
As we’re just starting out, the best contender so far is our nearest stellar neighbor—the triple star system of Alpha Centauri8), 4.37 light-years away. This year, astronomers at the European Southern Observatory9) discovered an Earth-sized planet orbiting Alpha Centauri’s red dwarf star10) Proxima Centauri11). The planet, named Proxima b, is at least 1.3 times the mass of the Earth but has a very tight orbit around Proxima Centauri, taking just 11 Earth days to complete the trip.
What has astronomers and exoplanet12) hunters especially hot under the collar13) is that this planet is in the right temperature range for liquid water, which is a useful proxy14) for habitability.
The downside is we don’t know if it has an atmosphere, and given its closeness to Proxima Centauri—closer than the orbit of Mercury around our Sun—it would likely be exposed to dangerous solar flares15) and radiation. It is also tidally-locked16), which means the planet always presents the same face to its star; something that would completely alter our notions of night and day.
HOW WOULD WE GET THERE?
That’s the $64 trillion question. Even at the fastest speeds of our current technology, a quick jaunt17) to check out Proxima b would see us arriving in around 18,000 years, by which time there’s every chance our Earth-bound descendants would have arrived there well ahead of us and grabbed all the glory. But many smart minds—and deep pockets18)—are being turned to the challenge of finding a faster way to cross vast distances of space.
Breakthrough Starshot—a $100 million initiative privately funded by Russian billionaires Yuri and Julia Milner—is focusing on propelling a tiny unmanned probe by hitting its extremely lightweight sail with a powerful Earth-based laser. The idea is that if the spacecraft is small enough—and we’re talking barely a gram—and the sail light enough, the impact of the laser will be enough to gradually accelerate the craft to around one-fifth of the speed of light, taking it to Alpha Centauri in around 20 years.
The Milners are counting on miniaturisation technologies to enable this tiny craft to carry a camera, thrusters19), a power supply, communication and navigation equipment so it can report on what it sees as it flashes past Proxima b. Hopefully the news will be good, because that will lay the foundation for the next and more difficult stage of interstellar travel: people-moving.
WHAT ABOUT WARP DRIVE20)?
Star Trek made it all look so easy, but everything we currently know about the laws of physics tells us that faster-than-light travel—or even travel at the speed of light—is not possible. Not that science is throwing in the towel21). Inspired by another propulsion system that has captured the imagination of science fiction creators, Nasa’s Evolutionary Xenon Thruster22) project is developing an ion23) engine which is hoped to accelerate a spacecraft to speeds up to 90,000mph (145,000km/h) using only a fraction of the fuel of a conventional rocket.
But even at those speeds, we won’t be getting far out of the Solar System within a single generation of spacefarers. Until we work out how to warp time and space, interstellar travel is going to be a very slow boat to the future. It might even be better to think of that travel period as the end itself, rather than a means to an end.
HOW WOULD WE SURVIVE ON AN INTERSTELLAR VOYAGE?
Warp drives and ion propulsion are all very sexy, but they’re not much use if our interstellar voyagers starve, dehydrate or suffocate long before they even leave our own Solar System. Researcher Rachel Armstrong argues we need to start thinking about the ecosystem that interstellar humanity will occupy out there in between the stars. “We’re moving from an industrial view of reality to an ecological view of reality,” she says.
As professor of experimental architecture at the University of Newcastle in the UK, Armstrong talks about “worlding”: “It’s about the inhabitation of spaces, not just the design of an iconic object,” she says. The inside of a spacecraft or space-station today is sterile24), and industrial, she argues. Armstrong believes we instead need to think ecologically about our vessels—about the vegetation that is grown, and even the kinds of soils we take with us. In the future, she envisages giant biomes25), full of organic life, not the cold, metal boxes of today.
CAN’T WE JUST SLEEP ALL THE WAY THERE?
Cryosleep26), hibernation or some form of stasis27) are favoured solutions to the prickly problem of how to keep people alive on a voyage that might take longer than a human lifespan. A facility full of cryopreserved28) bodies and heads at the Alcor Life Extension Foundation29) are testament to human optimism that we will one day work out how to safely freeze and thaw humans, but again, no such technology currently exists.
One suggestion, which is explored in movies such as Interstellar and books such as Neal Stephenson30)’s Seveneves, is to send frozen embryos that could—presumably—survive those hardships by virtue of not needing to eat, drink or breathe. But this raises the very “chicken and egg” problem of who would raise these fledgling humans when they arrive at their destination.
SO, WILL IT ACTUALLY HAPPEN?
Probably not in the lifetime of anyone old enough to read this article, but in the longer term, there’s cause for optimism. “From the outset of human existence we’ve looked up at the stars and projected our hopes and fears, anxieties and dreams there,” says Armstrong. And with the launch of projects to tackle the engineering, such as Breakthrough Starshot, “this is no longer just a dream, this is an experiment now”.
科幻小说家和电影制作人已经为我们展现了人类足迹遍布宇宙的无数种构想，所以你如果觉得星际航行这件事已十拿九稳，那也情有可原。令人失望的是，我们还需要突破不少技术限制——比如我们目前所理解的物理学定律——才能走出我们的太阳系和银河系，开始征服新世界的旅程。
尽管如此，近年来还是出现了诸如Tau Zero基金会、伊卡洛斯计划以及突破摄星等多个由私人出资或志愿发起的项目，希望使我们距离跨越宇宙的目标更近一些。我们8月份发现了一颗与地球大小相似的行星(编注：英文原文发表于2016年10月)，围绕离我们最近的恒星运行，这也为我们造访外星世界增添了新希望。
真的有可能航行去其他星系吗？如果可能的话，我们需要怎样的太空飞船才能实现这一目标呢？继续读下去就能(以超光速)了解最新进展：
文章摘自：《新东方英语》杂志2017年5月号
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