Ask a random sampling of people if they think we will have colonized space in 500 years, and I expect it will be a while before you run into someone who says it’s unlikely. Our migration from this planet is a seductive vision of the future that has been given almost tangible reality by our entertainment industry. We are attracted to the narrative that our primitive progenitors crawled out of the ocean, just as we’ll crawl off our home planet (en masse) some day.

I’m not going to claim that this vision is false: how could I know that? But I will point out a few of the unappreciated difficulties with this view. The subtext is that space fantasies can prevent us from tackling mundane problems whose denial could result in a backward slide. When driving, fixing your gaze on the gleaming horizon is likely to result in your crashing into a stopped car ahead of you, so that your car is no longer capable of reaching the promised land ahead. We have to pay attention to the stupid stuff right in front of us, as it might well stand between us and a smart future.


I was completely astonished by the prevalence of the “space” reaction to the inaugural Do the Math post on galactic-scale energy. The post illustrated that continuing growth of our physical scale (energy) is not viable on a number of fronts—not the least of which is that Earth’s surface would reach the boiling point of water in a mere 400 years, based purely on thermodynamic arguments, and independent of which energy technology is employed. Many comments on the internets chided this view as being hopelessly unrealistic in its willful ignorance of the great space migration to come.

The connotation is that we should not heed repeated warnings about our current collision course with a finite world when—by some clairvoyant means that eludes me—we know we are destined to colonize the infinite void beyond. Space is therefore seen as an escape hatch for the human endeavor and from our arguably botched track record on Earth. Escapism may be more accurate.

Survey Says…
Before we get going on practical matters, let me share the results of a survey question I have posed to college students in my classes. Let’s see how you fare, imagining yourself to be in the same age bracket of 18–22:

Approximately how far have humans traveled from the surface of the Earth in your lifetime? [e.g., since 1980 or so]

a) 600 km (low Earth orbit, 0.1 times the Earth radius)
b) 6,000 km (about the radius of the Earth)
c) 36,000 km (geosynchronous orbit; about 6 Earth radii)
d) 385,000 km (about the distance to the Moon; 60 Earth radii)
e) beyond the Moon
I make the question visual, which you can do as well. Start with a standard Earth globe (12 inch or 30 cm diameter). The first answer is 0.6 inches (1.5 cm) from the surface, followed by 6 inches (15 cm), then a yard (meter), then 30 feet (9 m) for the Moon. Take a minute to picture this.


Earth-Moon system to scale, with response distances indicated

Out of a total of 109 students responding (one group in 2006, another in 2010), only 11% got the right answer: low Earth orbit. 52% thought humans had been as far as the Moon since the 1980′s, and 20% thought we had been farther than the Moon. Some were indignant on learning the truth: “What do we use the space shuttle for, if not to go to the Moon?!” I can only guess that some students imagined the International Space Station as a remote outpost, certainly beyond the Moon, and likely strategically located next to a wormhole. How disappointing it must be to learn that it merely hugs the globe.

I could easily get sidetracked on this astounding result. But I’ll just point out that the idea that we are no longer able to accomplish feats we once could do (like travel to the Moon) clashes with the prevailing narrative that we march forever forward. Not only can’t we get to the Moon at present, but the U.S. no longer has a space shuttle program—originally envisioned to make space travel as routine as air travel. And for that matter, I no longer have the option to purchase a ticket to fly trans-Atlantic at supersonic speeds on the Concorde. Narratives can break. I’ll leave it at that.

A Moment of Silence
A recent article in the Economist about the end of the space age—besides generating howls of protest—noted that, short of signs of life turning up on Mars, public interest in the surviving unmanned space program will wane. I think this is especially insightful given my survey of what young folks assume we’re already doing. It would be hard to sell this upcoming generation on an expensive plan to return to the Moon when the act of announcing the plan will backfire in angst that lunar trips are not already a routine part of NASA’s activities. Travel to Mars, carrying a multi-hundred-billion dollar price tag, is even less likely to see support.

John Michael Greer followed this piece with a delightfully well-written elegy lamenting the end of our space ambitions. Many of my sentiments are perfectly captured in this article, and I highly recommend the read.

Surely the termination of the NASA shuttle program has forced us to accept setbacks in our dreams of space. But this does not have to be a predictor of the future. After all, we could have decided to keep the shuttle program alive if economic and political winds had favored doing so, and we do not lack the know-how for going back to the Moon if it became a priority. Perhaps, then, we are looking at only a temporary bump in the road.

Down to Brass Tacks
However, there are practical realities to consider. If we extend our solar system model using the standard-size Earth globe as our reference, the Moon is 30 ft (9 m) away, and is about the size of an apple. The sun is 2.2 miles (3.6 km) away. Mars is sometimes as close as 0.8 mi (1.3 km) and sometimes as far as 6 mi (10 km). Light travels at a sprinting speed of 16 m.p.h. (26 kph) in this scale, but an energetically feasible transfer orbit to Mars would take 8.5 months, effectively traveling slower than a snail.

First, reflect on the vastly different scale in travel to the Moon vs. Mars. In our model, you could toss a rock to the Moon. But getting something to Mars is a whole different ballgame. Not even a slingshot would be up to the task. In practical terms, a three-day lunar journey becomes 260 days to Mars: almost 100 times as long. The closest star to the Sun, in this model, is about a million kilometers distant: 2.5 times farther than the actual Earth-Moon distance. On a separate model scale—compressed 17,000 times compared to our previous model scale—the density of stars in the local Milky Way (one star per 100 cubic light years) is analogous to grains of sand 50 km apart! Can you imagine this? Mostly empty, empty space, folks.

I often travel to the Apache Point Observatory in southern New Mexico to tend to my lunar ranging experiment. On a recent trip, I was excited to find a newly-installed solar system model consisting of planet signs positioned along highway 6563 (named by nerds after the wavelength of the hydrogen-alpha emission line of great importance in solar, stellar, and galactic astronomy). Even traveling at 15 times the speed of light, or 40 m.p.h., the scale is daunting (although, considering relativistic time dilation, a traveler would experience this pace if traveling at 0.998 times the speed of light). If you’ll forgive me, it really drives home the isolation even within the local oasis we call the solar system.

- See more at: http://physics.ucsd.ed...#sthash.vPDUt9Hx.dpuf