Space, the Final Frontier–and Why It Will Stay That Way
Long-time readers are aware I’m a science fiction buff. Heck, perusing the content here is enough to demonstrate that. As I’ve discussed in the past , I’m a Star Trek buff from way back. Most of my reading as a kid and young adult was science fiction. and so were many–perhaps most–of the movies I watched. Given all this, I have to apologize a bit to sf fans for this post. As the title implies, I’m going to try to show why the “final frontier” will always be just that–the final frontier–since, in my opinion, there will never be a substantial human presence in space. In short, alas, the future envisioned by Star Trek (or Star Wars or Battlestar Galactica or Andromeda or any other space-oriented media franchise) is never going to come to pass. I don’t like that either, but there it is. Let me explain.
As I’ve noted before (here and here), scientific illiteracy is rife in our culture, even in the context of science fiction movies, novels, and such, where the writers ought to know better. Probably one of the biggest areas of ignorance, misunderstanding, and misinformation is in the area of space travel. There are many issues involved. Therefore, I will consider each category of problems under the appropriate heading. Off into space we go, then!
It is a truth universally acknowledged, that a man in possession of an interstellar spaceship, must be in want of speeds greater than that of light. It is almost as universally acknowledged that this is, in fact, impossible. Even people with little or no understanding of science have the vague notion that Einstein said you can’t go faster than light. Sf buffs and the more scientifically inclined among us are aware that this dictum–that no object can be accelerated to a speed greater than that of light, or to put it in another way, that no signal may be transmitted from one point to another at a speed faster than that of light–is based on Einstein’s Special Relativity Theory.
Since this is fairly well-known, and since there are many available sources, I will note only two things about this limitation. First, I want to address a common objection I often hear from even fairly intelligent individuals. This is the “But who knows what we can do with future technology” argument. Technology is totally irrelevant in this case. Instead of diving into the math, let me give an analogy: Say that three thousand years ago, when the world was still thought to be flat, two sailors are engaged in conversation. The first one says, “Do you think that some day they’ll build ships so big and powerful that they’ll be able to sail clear to the edge of the world?” His companion says, “Sure–no doubt in the future, they’ll be able to do far more than we can today.” Now, though, we can see the obvious flaw–the Earth, being spherical, has no edge. Thus, no seafaring technology could ever produce a ship that can sail to the Earth’s edge. You can’t build ship to go to something that doesn’t exist! The problem isn’t technological; it’s about the nature of the world.
That brings up the second point: The reason the speed of light is an absolute limit is that among the various interesting phenomena that happen to objects as they approach the speed of light (see here for more discussion of this) is the fact that their mass increases asymptotically (that is, the closer the object gets to c, the speed of light, the faster its mass increases). Thus, as an object accelerates, it takes more and more energy to make it continue to accelerate. At low speeds–such as we observe–the extra mass and the concurrent increased need for energy is not noticeable. As one nears c, though, the mass increase becomes–well, massive. At the speed of light itself, the mass of an object–even a tiny one–would become infinite. To move infinite mass, you obviously need infinite energy–which equally obviously is impossible. Thus, one could never even reach the speed of light, let alone surpass it. As with the spherical Earth, it’s not a matter of technology, of bigger and more powerful ships; it’s a matter of the nature of reality itself.
Science fiction has offered many fictional, imaginary science work-arounds for speed limitations. Things like hyperspace and subspace are often suggested. Without going into detail, none of these are workable in the context of any known model of the cosmos. The only plausible suggestion for superluminal travel of which I’m aware is the Alcubierre warp drive. A loose analogy: A surfer doesn’t actually move–he balances his surf board on the crest of the wave, and lets the water itself move him. Similarly, the Alcubierre drive produces a “warp bubble” within which the ship itself is actually motionless. Space is literally warped, so that it rapidly expands behind the warp bubble and contracts in front of it. In effect, space itself moves, carrying the warp bubble and the ship it contains along with it. Since it is space that moves, not the ship, there is no violation of Special Relativity, and the trip to a vastly distant location can be arbitrarily short.
There are many practical and theoretical problems with the Alcubierre drive, which are discussed at the Wikipedia link above. Suffice it to say that for me there is one issue that is fatal to the whole concept. The Alcubierre drive, in order to produce the warp bubble and cause space to collapse around it, requires something known as “exotic matter“. Such matter would have negative mass (i.e., if you dropped a chunk of it, it would fall up), or in some interpretations, complex mass (i.e., its mass is given by an imaginary number, and such an object would always go faster than light and move backward in time). There is no equation or observation or rule in known physics that says such matter can’t exist; but there is not the slightest evidence that it does exist. Moreover, if it does exist, no one has the slightest idea where it is, how you’d find (or make) it, and how you’d manipulate it if you could get hold of some.
I look at exotic matter the same way I look at pixie dust. If you sprinkle pixie dust on yourself, and think a wonderful thought, then you can fly. This is true–we have it on the authority of J. M. Barrie. Now before you go thinking that I’ve gone completely around the bend, let me hasten to point out that pixie dust does not, in fact, actually exist. If it did, then as it is described, it would certainly allow you to fly; but it doesn’t. Similarly, exotic matter may well do everything that an Alcubierre drive requires it to do–but as far as we know, it doesn’t exist, either. Hell, for all we know, pixie dust is exotic matter. Exotic matter has negative mass–it falls up–so if you sprinkled enough on yourself to cancel out your own mass, plus some extra, you might very well fly! Apparently Tinkerbell was an advanced alien instead of a fairy….
Thus, the only marginally plausible method of faster-than-light travel would seem to be no more likely than flights to Never Never Land, at least based on current knowledge. However, I will mitigate the thus-far depressing direction that this section has taken by saying that speed in and of itself is not, in fact, the biggest problem with interstellar space flight. There are, after all, schemes for sub-luminal (slower-than-light) interstellar flight. These fall into two broad categories: travel that takes advantage of time dilation, and generation starships.
The same equations that dictate the increase in mass of objects as they approach the speed of light, as we discussed above, also dictate “time dilation”. This is the phenomenon whereby time onboard the ship is observed to pass at a different rate than in the exterior cosmos. The closer the ship approaches the speed of light, the slower time passes aboard it, with reference to the outside world. Thus, a ship moving at a high but attainable speed (e.g. 10, 20, 50, or some other such percent of the speed of light) might be able to make a trip of decades or even centuries in a mere few years or even months, from the perspective of the crew. This would admittedly preclude any return to Earth, as massive amounts of time might have passed by then; but it would make travel over very long distances within a human lifetime at least possible in principle.
The second suggestion is the so-called generation starship. This is the idea that a spaceship could be built which has a self-contained, self-replenishing ecosystem that can produce food and oxygen more or less indefinitely. A relatively large crew–hundreds or even thousands–would embark on a one-way trip. Generations would be born, grow up, grow old, and die aboard the ship as it plied its way through space. After a trip of hundreds or perhaps thousands of years, the many-times great-grandchildren of the original crew would arrive at the ship’s destination. As with travel by time dilation, there’d be no question of return; but a generation starship would work in principle.
Thus, if we’re willing to take our time, and to leave Earth permanently, travel to the stars would indeed be possible with time constraints not being problematic. There are other things, unfortunately, that are problematic–very problematic. Just to start out, there is…
During the course of long spaceflights, the ship would be far away from any gravitating bodies–stars, planets, and such–and therefore would experience near-zero gravity. The crew and everything on board would be effectively weightless. For very long flights–very, very long, in the case of generation ships–this would be a problem. To date, the longest any human being has remained in the weightless environment of low-Earth orbit is Valeri Polyakov, who spent 437 days, 18 hours on the old Soviet space station, the Mir. Data from him and other astronauts who have spent prolonged times in space show the effects of long-term weightlessness–muscle and bone atrophy, shifting of bodily fluids, decreased production of red blood cells, and weakening of the immune system. Problems with eyesight that persisted, in some cases, for years after return to earth, have also been observed.
Some of these changes can be managed–muscle and bone atrophy can be staved off by exercise. Others are less well understood. What effects might be observed after years in the weightlessness of space, to say nothing of generations born there is unknown. Any plausible long-term space journey would likely require some form of artificial gravity. Shows such as Star Trek depict true artificial gravity–that is, the ship has a gravity generator which, when switched on, produces gravity. Simple! Also, alas, impossible with known physics. A gravity generator would almost certainly require a theory of quantum gravity, a unified field theory, or perhaps a Grand Unification Theory. Alas, all of these are seen as Holy Grails of physics; and after a century, we are no closer to attaining them than we were in Einstein’s time. Even if one or more of these theories are proved, there’s no guarantee that there would be a way to apply them to make a gravity generator. Thus, while I don’t dismiss the possibility of a gravity generator, such a device is not possible within any model of physics that is likely to be developed any time soon.
A doughnut-shaped, rotating ship (much like Space Station V and the Discovery One in the classic 2001: A Space Odyssey) would produce the equivalent of gravity by centrifugal force. Such a system could not be used during periods of acceleration at the beginning of the trip or deceleration near the end, because since the acceleration would be at a right angle to the plane of rotation, you would likely have issues with experienced forces.
In the diagram below, the blue rectangle is a side view of a doughnut-shaped (toroidal) starship. The rotation would produce centrifugal force towards the edge of the torus, indicated by the thick arrow to the right. The engine, which would have to be located in the “doughnut hole”, with the exhaust facing downward (from the perspective of the diagram), when in action, would produce forces directed in the direction indicated by the thick arrow below. These two forces would produce a resultant force indicated by the thin diagonal arrow to the lower right. In effect, everyone would experience forces pulling them off to one side at an angle!
More plausible would be a non-toroidal ship which would accelerate at a constant rate of 1 g (9.8 m/s2). This would produce the effect of an Earth-normal gravitational force onboard the ship, in the same direction as the exhaust. The idea is that the ship would accelerate at 1 g for the first half of the trip, flip around, and then decelerate at 1 g for the remaining half of the trip. This way, except for the brief period of reorientation at the midpoint of the trip, the crew would experience the equivalent of normal gravity for the entire trip. This is the most likely solution; however, there are subtle issues with it. These mostly pertain to energy usage, especially for long trips that would require long periods of acceleration; but we’ll discuss energetics later.
Environment of Space
Weightlessness might be overcome, but radiation in space is a bigger issue. As noted here,
Astronauts are exposed to approximately 50-2,000 millisieverts (mSv) while on six-month-duration missions to the International Space Station (ISS), the Moon and beyond. The risk of cancer caused by ionizing radiation is well documented at radiation doses beginning at 50 mSv and above.
Another way to put it is that an astronaut receives, on the high end of the above estimate, the equivalent of 6000 chest x-rays! In the Star Trek franchise, it is explained that the main purpose of ships’ deflector shields isn’t to protect against Klingon disruptors, but to shield the crew from cosmic radiation. Unfortunately, there is no currently known way to actually construct deflector mechanisms. The only known form of effective shielding is lead, which would massively increase the mass of the ship, and thus the energy needed to move it. An alternate suggestion is that a small asteroid be hollowed out and used as a ship. The rock and minerals of the asteroid would be thick enough to shield against cosmic radiation without the inconvenience of ferrying up thousands of tons of lead. The mass of the ship and the increased energy needed to move it would still be issues though. It would also be much less appealing in appearance than the U.S.S. Enterprise! In any case, radiation is a problem that would have to solved somehow or other, particularly with a generation ship.
This is most relevant to generation starships, but would be of some relevance to relatively fast ships that still made trips of a duration of many years, ship’s time. Existing spaceships and space stations have carried the oxygen, food, and water necessary to the astronauts’ lives aboard the ships. The duration of the trips was short enough for this to be feasible. For long-term missions such as the various American, Soviet/Russian, and international space stations, supplies are periodically replenished by shuttles from Earth. In a multi-year deep space mission, restocking from Earth is obviously impossible. More significantly, though, the amount of oxygen, food, and water necessary for a generation starship could not possibly be stocked on a ship of any reasonable size. Even for relatively fast ships with small crews (a dozen or fewer) on missions of “only” a couple decades’ duration, stocking supplies might not be possible.
The suggested solution is to have a biologically self-contained system that could function indefinitely with no restocking. In short, the ship would be a floating greenhouse and farm. There would be areas for growing grain and vegetables, either with soil placed onboard or hydroponically; other areas would raise domestic animals for meat. Still other areas might contain entire miniature ecosystems of forests, lakes, and so on. The giant greenhouse ships in the classic movie Silent Running are a good example of this idea. The crew would grow their own food, recycle all wastes, and the plants would renew the atmosphere by taking up carbon dioxide and producing oxygen. Problem solved! Except…
Biosphere 2 was an ambitious experiment to test just this concept–that is, a totally self-contained and functioning ecosystem that could support humans indefinitely. It was a noble attempt, but many of the the plants and animals died, one of the crewmembers was allowed to leave the habitat for medical treatment of an injury, and in as little as sixteen months the oxygen content of the habitat had dwindled to the equivalent of an elevation of 13,000 feet. In short, had this been an actual mission into deep space, within a couple of years everyone aboard would be dead.
Of course, no one expects the first attempt at an ambitious project to be perfect, or even to succeed. However, after the two missions of Biosphere 2, no further attempts have been made to perform any similar experiments. Without such research, there is no way a self-contained spaceship could be made. Another thing that no one has thought of: A project to test the true feasibility of a generation ship would need to run for at least twenty years–even better, fifty to a hundred–in order to conclusively demonstrate the workability of long-term self-contained space flights. For full authenticity, it would require at least some of the members to have children and raise them to adulthood. But the ethics of having a crew commit essentially to spending the rest of their lives sealed off from the rest of the world, and even more, of bringing children into a situation they’d never agreed to, without the possibility of experiencing the outside world until perhaps middle age–well, the mind boggles.
So, the most likely means of making a multi-year space journey doable would involve a ship much like Biosphere 2; but while this could work in principle, we are nowhere near where we’d need to be to make it work.
Update 1 July 2019: Since I originally published this, I learned about two current ongoing projects to simulate a self-contained environment in space, one in Hawaii and one in Utah. Though not as elaborate, and not as completely self-contained as Biosphere 2, these experiments are a further step in the right direction. We are still a long way away from a generation starship, though.
A relatively small number of people confined in relatively close quarters for very long times is a recipe for social dysfunction. In the aforementioned Biosphere 2 missions, significant tensions and factionalism were a problem. The second mission ended early, in fact, because members of the first mission sabotaged it! Obviously, such things could be orders of magnitude worse in deep space. A generation starship might have a population large enough to diffuse such tensions; but there’s no way of knowing for sure.
I mentioned how the Enterprise’s deflector shields guard against cosmic rays. Equally importantly, they guard against space dust. “The hell?!” you say. Well, consider. If I hold the slug of a .45 bullet and throw it at you as hard as I can, it will bounce harmlessly off of you (unless I hit your eye). If I shoot a similar slug from a handgun, though, the slug will severely injure or kill you. What’s the difference? The kinetic energy of a moving object–its “energy in motion”–is given by the formula Ek=1⁄2mv2. That is to say, one half times the mass of an object (measured in grams in the metric system) times its velocity (in meters per second in the metric system) squared, give the amount of energy it contains. A very large object, such as a boulder or a truck, can have a large amount of kinetic energy at a relatively slow speed–such an object might kill me though it moves relatively slowly. On the other hand, even a small object such as a bullet slug, at a high speed (faster than 700 miles per hour, when fired from a gun) has enough energy to kill me, too.
Now consider: Here it notes,
[i]n Denmark rifle ammunition used for hunting the largest types of game there such as red deer must have a kinetic energy E100 (i.e.: at 100m range) of at least 2700 J and a bullet mass of at least 9 g or alternatively an E100 of at least 2000 J and a bullet mass of at least 10 g.
where J stands for “joules”, the metric unit of energy. 2700 J, thus, is sufficient to kill a deer. Now, using the formula given above, we can calculate the kinetic energy of a one gram piece of space dust (about the mass of a paperclip) moving at ten percent of the speed of light (29,979,245.8 m/s, or 67,061,520 miles per hour), as 449,377,589,368,409 J. That’s over four hundred forty-nine trillion joules, or more than one hundred sixty-six billion times as much energy as the Danish deer-hunting bullet is recommended to have! For another reference point, a kiloton bomb explosion (the equivalent of a thousand tons of TNT) is 4,000,000,000,000 J–less than a hundredth the energy produced by hitting the paper-clip-sized particle at ten percent of the speed of light!
Given the impossibility of deflector screens, which we noted above, only really, really thick walls would have even a chance of protecting against such small projectiles. Such projectiles are all over the place–there’s plenty of dust and grit in space, and being small, it would be impossible to see before you hit it, especially at speeds of ten percent of the speed of light, if not more. Once more, as noted, hollowed-out asteroids have been suggested as a solution. It’s not clear that even walls that thick would be sufficient to guard against high-speed collisions. In any case, space dust is, in my mind, the second biggest problem with interstellar space flight. The biggest problem is…
To make a spaceship or anything move takes energy. According to this article, the energy needed to accelerate one ton to ten percent of the speed of light is 125 terawatt-hours. The estimated world energy consumption in 2013 was 157,500 terawatt-hours. Thus, rounding off, it would take about 0.08 percent of the entire worldwide energy production to accelerate a mere ton to ten percent of the speed is light. We need to move more than a ton, though! This article estimates the mass of the U.S.S. Enterprise (reboot version, but close enough) to be about 462,000 metric tons. A metric ton is slightly larger than a standard ton, but for the purposes at hand here, we’ll not take that into account. A ship weighing 462,000 tons would take 462,000 times 0.08, or 36,960 percent of world energy production. To put that another way, to accelerate the Enterprise to a paltry ten percent of lightspeed (never mind warp drive!) would take the equivalent of all energy used on Earth at current rates for nearly three hundred seventy years!
Obviously, chemical fuel engines of the type modern rockets use are right out. It would be impossible to carry the massive amounts of fuel necessary for the desired accelerations (regular readers may recall that I griped about just this in discussing the Neflix miniseries Lost in Space). The only remotely plausible energy sources are nuclear fission or nuclear fusion.
Fission is workable and well-understood. However, it requires radioactive material such as uranium or plutonium. For relatively short trips of unmanned vehicles within the solar system, fission reactors might be plausible. For interstellar voyages, though, even though fissionable materials have much higher energy density than chemical fuel, the quantities needed might still be prohibitive. Further, it is estimated that fission engines might take centuries to reach ten percent of lightspeed. Additionally, for manned ships that will be underway for years, decades, or centuries, the wisdom of bringing large quantities of radioactive material on board, when it’s already a problem to protect the crew from external radiation, is debatable, to say the least. Nuclear pulse propulsion, which boils down to using nuclear explosions to move the ship, seems even more questionable, for obvious reasons.
Fusion–the same process that powers the sun–would be great if we could do it. Researchers have been attempting to design workable nuclear fusion plants for over fifty years. Fusion would be great–it uses hydrogen, the commonest element in the universe, for fuel; it produces little radiation, compared to fission; and the end product, helium, is harmless. However, the extremely high pressures and temperatures necessary to produce fusion, and the energy needed to control it, have resulted in all attempts to date requiring more energy to produce the fusion than is obtained from it. People I respect, such as Michio Kaku, claim that fusion will be achieved in our lifetime; other people I respect, such as John Michael Greer, are skeptical. As to me, I just don’t know. In any case, fusion-powered spaceships will never occur until we can get fusion working in the first place.
Of course, even with the greater efficiency of fusion, if it can be made to work, you’d still need large quantities of hydrogen, quantities which it might not be feasible to carry onboard. This is behind suggestions such as the Bussard ramjet, which uses magnetic fields to scoop up the hydrogen present in space. Whether the technology required is feasible, and whether the interstellar density of hydrogen is sufficient to make it work, are unknown.
There are lower-energy suggestions for interstellar flight, such as solar sails and beamed propulsion (shooting the sails with high-energy lasers), that have been proposed. Most of the proposals, though, are for very light, unmanned craft. The proposals for manned missions omit any explanation of the energy sources for the lasers and/or sails. At this point, such proposals remain highly speculative.
Matter-antimatter reaction, the energy source for the ships in the series Star Trek and Andromeda, would be the ideal energy source. When matter and antimatter touch, they annihilate, turning one hundred percent into energy. Thus, relatively small quantities of antimatter–a couple of metric tons per day, according to the Star Trek Technical Manual–would be sufficient. The problem is that we have no idea how to make or obtain the quantities of antimatter needed, having only ever produced a few atoms at a time. Containment would be a major issue, as well. Since antimatter could not be allowed to come into contact with matter for even an instant–since it would explode–very powerful magnetic fields would be necessary to suspend it in a vacuum. Such fields have been used in attempts to control and contain nuclear fusion of ordinary matter, mostly without success. Thus, applying them to antimatter seems even more daunting. Whether matter-antimatter drives will ever be possible is unknown, though I tend to think it’s very unlikely that they will.
Other highly speculative forms of propulsion, such as wormholes, artificial black holes, and similar schemes to get around the prohibition on faster-than-light travel have been proposed. Suffice it to say that at the current time, all such schemes require certain assumptions (like the aforementioned “exotic matter”) that may or may not be true, or have massive problems that may be insoluble (e.g. the necessity of a wormhole being stable, when we’re not even sure if stable wormholes exist or even can exist). Based upon what I’ve read about such proposals, none of them seem to me to be plausible now or ever.
By the way, propulsion is not the only thing that requires energy. The ship systems–life support, computers, electronics, gravity generators (if they’re ever invented), and so on–all need some source of energy. For biosphere-like generation ships, a big user of such energy would be the massive solar lamps needed for the plants on board. A generation ship is basically a city in space–and thus it would require the same amount of energy a typical city uses on top of what’s needed for propulsion. A smaller ship with a smaller crew would need less energy for non-propulsion uses, but it would still need significant quantities of energy.
We’ve seen quite a few problems, many of them major, with any form of manned interstellar space travel (many of the problems apply to unmanned travel, as well, particularly the issue of energy). Speed, the first mentioned, seems to me the smallest problem, given a crew that is all right with a one-way trip. Psychological issues could be a problem, but seem to me to be capable of resolution. Maintaining life support–oxygen, water, and food–seems to me a massive problem, but in principle it could be solved (though no one is currently doing to work to solve the problems). Conditions in space are also problematic, but soluble in principle, if not currently in practice. The two problems that seem to me to be insuperable are protection against space dust and particles, and energy. I don’t see any way of getting around those problems with any known technology, or any technology that seems likely to come online within the next century or more. I’m not sure even hypothetical future technologies can overcome these problems, since they boil down to properties of matter and energy required by the laws of physics.
For all these reasons, I make the following assertion: Human beings will never leave the solar system at all, let alone travel to other solar systems. I’m going to be pretty categorical on that. As for unmanned vessels, Voyager 1 actually did leave the solar system and enter interstellar space on 12 September 2013. It will, of course, quit functioning long before it passes within a light year of the next star (after our own) on its itinerary some forty thousand years from now. Whether we will ever send a functioning probe to another star from which it can send back information to us, I don’t know. That is certainly more plausible than sending humans there. The (in my view, over-hyped) possibility that ʻOumuamua is an artificial ship or probe of alien origin indicates that it is perhaps more feasible to make such an interstellar probe than we think. At present, though, we don’t know.
After this long post with a rather pessimistic conclusion, I will make the standard disclaimer that I could very well be wrong. People with a deeper understanding of the issues than I have are optimistic; but with due respect, I think they’re wrong. Another issue, rarely discussed, but frequently brought up by the above-mentioned John Michael Greer, is that our civilization may be passing a peak of energy usable for industrial purposes here on Earth, let alone in space. Future decades and centuries may be forced to scale back technology and apply what energy is available to earthly needs instead of space exploration. There’s no way to be sure of this, but it seems highly plausible to me.
In any case, that manned interstellar exploration (and perhaps even exploration within our solar system, beyond Earth’s orbit) has no future need not sadden us or make us lose a sense of purpose. Maybe our future is best described in T. S. Eliot’s “Little Gidding“:
We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time.
Through the unknown, unremembered gate
When the last of earth left to discover
Is that which was the beginning;
At the source of the longest river
The voice of the hidden waterfall
And the children in the apple-tree
I stand by everything I said above. However, to perhaps mitigate the buzzkill, I’d like to direct everyone’s attention to Mary Doria Russell’s brilliant, beautiful, and heartbreaking novel The Sparrow. Of all the science fiction novels I’ve read, this novel (and its equally excellent sequel, Children of God) presents the most accurate and plausible portrait of interstellar travel (from our system to the Alpha Centauri system) that I’ve ever seen. The accurate portrayal of space travel is the least of its virtues, though. I won’t say anything more about it, because I’d prefer potential readers to come to it without previews or synopses, and enjoy the amazing and touching story on its own merits. Enjoy!
Part of the series “Reviews, Views, and Culture, Pop and Otherwise“.
Also part of the series “Science and Technology“.
Posted on 02/02/2019, in physics, science, space and tagged Alcubierre warp drive, Andromeda, Biosphere 2, Bussard ram jet, interstellar travel, Little Gidding, physics, science, space, Star Trek, T. S. Eliot, The Sparrow, Voyager 1. Bookmark the permalink. 4 Comments.