This article originally appeared on The Conversation.
Some climatologists argue it may be too late to reverse climate change, and it’s just a matter of time before the Earth becomes uninhabitable – if hundreds of years from now. The recent movie Interstellar raised the notion that we may one day have to escape a dying planet. As astrophysicists and avid science fiction fans, we naturally find the prospect of interstellar colonization intriguing and exciting. But is it practical, or even possible? Or is there a better solution?
Science fiction has painted a certain picture of space travel in popular culture. Drawing on stories of exploration from an age of tall ships, with a good helping of anachronisms and fantastical science, space exploration is often depicted in a romantic style: a crew of human travelers in high-tech ships wandering the galaxy, making discoveries and reporting back home. Perhaps they even find habitable words, some teeming with life (typically humans with different-colored skin), and they trade, colonize, conquer or are conquered. Pretty much, they do as humans have always done since the dawn of their time on Earth.
How closely do these ideas resemble what we may be able to achieve in the next few hundred years? The laws of physics and the principles of engineering will go a long way to helping us answer this question.
The “Pillars of Creation,” a photograph of part of the Eagle Nebula, is one of the most iconic images ever taken by the Hubble telescope. Yesterday, astronomers released a bigger, better, sharper version of the pillars, taken almost two decades after the first.
But an ironic twist – and what we didn’t know twenty years ago – is that the Pillars might have been long ago torn apart by a distant explosion. The photos we snap of them today are high-tech and modern but their subject is clouded by thousands of light-years of remove. Like the post-mortem photography of the Victorian era, the resulting images are lifelike, and beautiful, and sad.
Nearly a century ago, Edwin Hubble’s discovery of red-shifting of light from galaxies in all directions from our own suggested that space itself was getting bigger. Combined with insights from a handful of proposed non-Euclidean geometries, Hubble’s discovery implied that the cosmos exists in more than the three dimensions we’re familiar with in everyday life.
That’s because parts of the cosmos were moving further apart, yet with no physical center, no origin point in three-dimensional space. Just think of an inflating balloon seen only from the perspective of its growing two-dimensional surface, and extrapolate to four-dimensional inflation perceived in the three-dimensional space that we can see. That perspective suggests that three-dimensional space could be curved, folded, or warped into a 4th dimension the way that the two dimensional surface of a balloon is warped into a 3rd dimension.
We don’t see or feel more dimensions; nevertheless, theoretical physics predicts that they should exist. Interesting, but are there any practical implications? Can they become part of applied physics?
But that hasn’t stopped the Curiosity rover from running around saying “This spot would have been habitable” and “That spot definitely has water.” And it hasn’t stopped astronomer Nathalie Cabrol from searching for the ever-elusive “biosignatures”: evidence, like geological graffiti, that proclaims “LIFE WUZ HERE.”
But it isn’t as easy as finding a spray-painted tag. First of all, the life almost certainly isn’t alive anymore. And second of all, it probably hasn’t been alive for a long time. Around 3.5 billion years ago, Mars changed from being a relatively nice place into the frozen radiation-zapped desert it is today. It was never San Juan, but it does seem to have had a milder climate, water oceans, and a thick, protective atmosphere. If this young sub-Caribbean Mars was home to life, that life may have left its mark. The problem is that we aren’t totally sure what that mark might look like.
It’s a beautiful October morning in Houston, but I am grumpy and bleary-eyed as I make my way into Mission Control. I’ve just come off a string of Orbit 1 shifts (midnight to 0800) working as CAPCOM in the International Space Station Mission Control Center. (CAPCOM is the call sign for the astronaut on the ground who speaks to the crews that are in space.) Now I’ve slam-shifted back to daylight hours to work as CAPCOM during a simulation of the rendezvous planned for an upcoming shuttle mission.
I see my friend Ray J in the parking lot, and he waves me over. Ray J is a pilot in the astronaut class ahead of mine. We’ve flown dozens of training flights together in the T-38, and he is a good friend and mentor. And he is always smiling, even at 0645. We chat for a minute, which mainly involves me complaining about my schedule, and then he asks, “So, have you talked to Scooter lately?” I raise my eyebrows at him. Scooter is way senior to me, a flown guy, a space shuttle commander. Of course I haven’t talked to Scooter. Scooter sometimes stops by the office I share with Mike Massimino because they flew on the last Hubble mission together, but it’s not like he’s coming there to shoot the breeze with me. So I say, “No. Why do you ask?” “Oh,” says Ray J nonchalantly, “I was just wondering how he’s doing.”
That was weird, I think as I head into Mission Control. But then I forget all about it and spend the next ten hours working the simulation. That evening, as I’m propped up on the couch at home trying to stay awake until a reasonable bedtime, my phone rings. It’s Steve Lindsey, the chief of the Astronaut Office. This is definitely weird. Why is he calling me at home? This can’t be good.
The new movie “Interstellar” is set in a not-so-distant future, but distant enough that they’ve managed to build something still elusive in 2014: a spaceship that can travel between solar systems. Such starships have been a technological mainstay in science fiction for decades, but they remain a crazily complicated proposition in everything from propulsion to human reproduction.
Still, that hasn’t stopped researchers from trying. Last month, a bunch of rocket scientists, microbiologists and entrepreneurs gathered in Houston’s George R. Brown Convention Center to discuss—in level and serious tones—how to become a spacefaring civilization. The meeting is called the 100-Year Starship symposium, and it’s brought brains together once a year since 2011 to figure out what we need to do now if we want to have an interstellar spacerocket a century from now.
The group has made progress defining the challenges and pointing their noses toward solutions, but much work remains (like, say, building a starship). To quote Contact, it “sounds less like science and more like science fiction.”
Nonetheless, the 100-Year Starship adherents—backed by NASA and the Defense Advanced Research Projects Agency (DARPA)—keep plugging away. At their most recent gathering, 7 major hurdles emerged from their three days of discussion. Read More
It’s popular to talk about how the original Star Trek, set in the 23rd century, predicted many devices that we’re using already here in 2014. It started with communicators that manifested as flip-open cell phones that many already consider too primitive, moved through computers that talk and recognize human voices and provide instant translation (all of which are constantly improving), to medical applications such as needle-free injection, anti-radiation drugs, and a medical tricorder.
But looking at the more exotic Star Trek technologies, it’s harder to find credible reports that we’re close to a Trek-like world. This is true for Star Trek’s transporter: Despite some success in “quantum teleportation,” which could have applications for computers and possibly communication technology, no experts are saying that this is about to lead to a technology for beaming humans or any other objects from place to place.
It’s also true for space travel. Star Trek depicted a world where people would move between planets and star systems (at least nearby systems) frequently and very swiftly. The United Federation of Planets contains worlds separated by dozens of light-years, which ordinary Earthlings regularly traverse over time periods measured in days to weeks.
Clearly that’s one aspect of Star Trek technology that is far from being a reality in the present day. But the topic isn’t just in the realm of sci-fi: Scientists are taking various approaches to try to create the next generation of space propulsion, beyond the chemical rockets that require most of the mass of the ship to be fuel.
If we want spaceflight to become routine for humans as aviation did, we’ll need major innovations. Are any just around the corner?
The collective space vision of all the world’s countries at the moment seems to be Mars, Mars, Mars. The U.S. has two operational rovers on the planet; a NASA probe called MAVEN and an Indian Mars orbiter will both arrive in Mars orbit later this month; and European, Chinese and additional NASA missions are in the works. Meanwhile Mars One is in the process of selecting candidates for the first-ever Martian colony, and NASA’s heavy launch vehicle is being developed specifically to launch human missions into deep space, with Mars as one of the prime potential destinations.
But is the Red Planet really the best target for a human colony, or should we look somewhere else? Should we pick a world closer to Earth, namely the moon? Or a world with a surface gravity close to Earth’s, namely Venus?
To explore this issue, let’s be clear about why we’d want an off-world colony in the first place. It’s not because it would be cool to have people on multiple worlds (although it would). It’s not because Earth is becoming overpopulated with humans (although it is). It’s because off-world colonies would improve the chances of human civilization surviving in the event of a planetary disaster on Earth. Examining things from this perspective, let’s consider what an off-world colony would need, and see how those requirements mesh with different locations.
Updated 9/16/14 10:15am: Clarified calculations and added footnote
We humans like to think ourselves pretty advanced – and with no other technology-bearing beings to compare ourselves to, our back-patting doesn’t have to take context into account. After all, we harnessed fire, invented stone tools and the wheel, developed agriculture and writing, built cities, and learned to use metals.
Then, a mere few moments ago from the perspective of cosmic time, we advanced even more rapidly, developing telescopes and steam power; discovering gravity and electromagnetism and the forces that hold the nuclei of atoms together.
Meanwhile, the age of electricity was transforming human civilization. You could light up a building at night, speak with somebody in another city, or ride in a vehicle that needed no horse to pull it, and humans were very proud of themselves for achieving all of this. In fact, by the year 1899, purportedly, these developments prompted U.S. patent office commissioner Charles H. Duell to remark, “Everything that can be invented has been invented.”
We really have come a long way from the cave, but how far can we still go? Is there a limit to our technological progress? Put another way, if Duell was dead wrong in the year 1899, might his words be prophetic for the year 2099, or 2199? And what does that mean for humanity’s distant future?
In 1971—16 years after Einstein’s death—the definitive experiment to test Einstein’s relativity was finally carried out. It required not a rocket launch but eight round-the-world plane tickets that cost the United States Naval Observatory, funded by taxpayers, a total of $7,600.
The brainchild of Joseph Hafele (Washington University in St. Louis) and Richard Keating (United States Naval Observatory) were “Mr. Clocks,” passengers on four round-the-world flights. (Since the Mr. Clocks were quite large, they were required to purchase two tickets per flight. The accompanying humans, however, took up only one seat each as they sat next to their attention-getting companions.)
The Mr. Clocks had all been synchronized with the atomic clock standards at the Naval Observatory before flight. They were, in effect, the “twins” (or quadruplets, in this case) from Einstein’s famous twin paradox, wherein one twin leaves Earth and travels nearly at the speed of light. Upon returning home, the traveling twin finds that she is much younger than her earthbound counterpart.
In fact, a twin traveling at 80 percent the speed of light on a round-trip journey to the Sun’s nearest stellar neighbor, Proxima Centauri, would arrive home fully four years younger than her sister. Although it was impossible to make the Mr. Clocks travel at any decent percentage of the speed of light for such a long time, physicists could get them going at jet speeds—about 300 meters (0.2 mile) per second, or a millionth the speed of light—for a couple of days. In addition, they could get the Mr. Clocks out of Earth’s gravitational pit by about ten kilometers (six miles) relative to sea level. And with the accuracy that the Mr. Clocks were known to be capable of, the time differences should be easy to measure.