The ‘Why’ of Interstellar Flight

by Paul Gilster on January 15, 2009

From the standpoint of pure research, one of the arguments for not going to nearby stars is that by the time we develop the needed technologies, we’ll have no need to make the journey. After all, we’ll soon be able to learn vast amounts about nearby worlds from space-based telescopes, not to mention planned Earth-side instruments like the European Extremely Large Telescope, a 42-meter powerhouse 100 more sensitive than the best of today’s optical telescopes. Putting observatories on the far side of the Moon is another way we’ll see deeper than ever before.

Extend space research out fifty years, a hundred, and you have to reckon with capabilities we can only dream about today. Webster Cash (University of Colorado) has been championing one Sun-shade design (there are others) that in its fullest deployment could give us views of an exoplanet as if we were no more than a hundred kilometers away. Or consider the fusion of new propulsion technologies with space-based observatories that can tap the Sun’s gravitational focus. This would open up the galaxy for the detailed exploration of countless planetary systems, with the potential for exoplanet finds as far away as Andromeda.

An Earth-based Perspective

All this is given relevance (and perspective) by the upcoming launch of Kepler, which will look for transiting planets down to terrestrial size. And as I was pondering these issues, there came the news of not one but two ground-based detections of exoplanet atmospheres. Six hundred images of the hot Jupiter OGLE-TR-56b, from the ESO’s Very Large Telescope and Carnegie’s Magellan-Baade instrument in Chile, produced the first result. This one is quite a catch, the planet being some 5,000 light years away in the direction of galactic center. Listen to Mercedes López-Morales (Carnegie Institution) on last summer’s work:

“Others have tried to detect planetary atmospheres from Earth, but to no avail… The successful recipe is a planet that emits a lot of heat and has little to no wind in its atmosphere. Plus it has to be a clear, calm night on Earth to measure accurately the differences in thermal emissions when the planet is eclipsed as it goes behind the star. Only about one of every 3,000 photons from the star comes from the planet. This eclipse allows us to separate the emissions of the planet from those of the star. The magic moments came on July 2nd…”

In the same issue of Astronomy & Astrophysics comes news of the measurement of thermal emissions in the near-infrared from TrES-3b, another hot Jupiter studied from the ground. This work is out of the University of Leiden in the Netherlands, again relying on accurate information about the planetary transit that allows the strength of the planet’s light to be measured. The instruments involved were the William Herschel Telescope (WHT) on La Palma (Canary Islands, Spain) and the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea in Hawaii.

Given this early work on exoplanetary atmospheres from Earth, where will we be in fifty years? And if, let’s say in a century, we find ourselves with the capability of studying distant planetary systems in exquisite detail, will we still have the motivation to build ships to make the journey to them? From a planetary security perspective, we can theoretically safeguard our species by expanding out in our own system with space-based habitats and possibly terraforming as options. The question then remains: What is it that drives the push to interstellar flight?

Philosophy and Realism

Many answers suggest themselves, and I’m not inclined to wax philosophical here. I think a realistic answer is that as we expand into the Solar System and build the infrastructure to support human populations in space, we will inevitably develop the tools that make further explorations possible, including propulsion technologies to get us to the Oort Cloud and beyond. Human history tells me that there is always a portion of the population that is willing to get on a cramped ship and go to the other side of nowhere for reasons that vary from the pure exploratory impulse to the need to escape political or religious persecution.

And my guess is that at some point interstellar flight will begin in much the same way. Protecting the species by spreading into the cosmos is a laudable goal, but it couples neatly with this exploratory imperative that has shown up in the behavior of our ancestors and shows no signs of abating now. Indeed, a universal exploratory urge is part of the puzzle noted by Fermi’s paradox — ‘Where are they’ indeed, for we would expect anyone with the capability of making an interstellar journey to set about the task. That’s because we know deep down that that is exactly what we would do — will do — assuming we survive our technological coming of age and can develop the engines to make it happen.

MichalM.Mac January 15, 2009 at 12:28

Nicely Written !

John Hunt January 15, 2009 at 14:07

I think that the issue of “Why” is one of the most critical questions for the community of interstellar mission advocates need to figure out. If we cannot give a compelling rationale for the considerable expense of an interstellar mission then the first true interstellar mission will be a distant dream.

The issues of “later-faster” and now “later-better resolution” both bedevil science-driven missions. Generally the solution is to get to the point where probes are so fast and relatively inexpensive to justify spending the money now. But these are very high hurdles to get over.

But a survival-driven rationale overcomes both of these hurdles. If we really believed that we are facing near-term existential threats due to our own accelerating technology, then expense is practically irrelevant. If we survive long enough to make a faster ship then great! The previous ship served as insurance.

It is a fair question to ask if a “manned” interstellar mission is actually necessary for survival when we can create off-world colonies within our solar system. Generally, doing so could be done sooner, at less cost, and with more likelihood of being successful. Normally, I would agree. But Fermi has an obnoxious way of poking up his head. If we can survive via colonies in our solar system then so could have alien civilizations. As long as we cannot rule out universal self-extinction as the solution to Fermi’s Paradox then I think that it behooves us to try and figure out what is so difficult that no other civilization was able to achieve it before their self-destruction. To me, a “manned” interstellar mission seems like a plausible answer.

So this can be the “Why” for an interstellar mission.

Marcel F. Williams January 15, 2009 at 14:12

The telescopic discovery of nearby Earth-like worlds, within 50 light years distance, with nitrogen-oxygen atmospheres will probably be the driving force towards developing light approximating interstellar flight by the end of the century, IMO. However, when the interstellar age does arrive, I hope that Earth-like worlds will be viewed as ‘natural wonders’ to be preserved and explored and not colonized or exploited.

We probably already have the technological know how to fabricate our own rotating artificial worlds out of the raw planetary and asteroid materials of any star system. So there’s no need to spoil the natural beauty of an Earth-like world and its plant and animal inhabitants in order for humans to colonize other star systems in our region of the galaxy.

Marcel F. Williams

Lee January 15, 2009 at 16:19

The issues raised here also bear on the Fermi Paradox. One could ask: Why would an advanced civilization want to expand throughout the galaxy if it had both solved the problems on its home planet (particularly overpopulation) that would make emigration necessary, and had such advanced observation technology that it could see everything there is to see on every other planet in the galaxy (and, as the allusion to Andromeda in this article indicates, on many planets in other galaxies as well)? I think this is the biggest weakness of the Fermi Paradox–the failure to recognize that as civilizations become more advanced in terms of interstellar spaceflight, they would probably become equally advanced in other areas as well, thus calling the whole premise of the paradox (“Why aren’t they here?”) into serious question.

justcorbly January 15, 2009 at 19:27

Are there any materials that we know must be, or would most likely be, produced by artificial means that we could detect in the atmosphere of an exoplanet?

andy January 15, 2009 at 20:15

Regarding the assumption that civilisations would go out into the galaxy, here’s a article which points out that the improvement in sensor technologies is far outstripping propulsion technologies.

As for space travel for survival, it seems to me implausible, if only because of the difficulty and expense of getting something that is in some sense human to a suitable destination. Plus, space travel for survival does no good for those of us still left on Earth.

Adam January 15, 2009 at 21:37

I think Lee hits the nail on the head. Look at our advances in optical technology – we’re on the verge of useful invisibility. If we’re at that point then any ETIs in our solar system which have millennia of technical advancement ahead of us will be indetectable – except when They want to be found.

And consider how rapidly micro-scale machinery is evolving – robotic surveillance insectoids are starting to usefully come out of military labs. ETI surveillance would be even more naturalistic, its signals harder to distinguish from “natural” emissions. Imagine optical frequencies, Near IR or T-rays or anything we don’t currently monitor intensely – all could be used without us knowing.

Robert Freitas has estimated immense volumes of our Solar System are as yet unexamined to sufficient resolution to settle the question of “Are They Here?” Since he wrote we’ve mapped a tiny bit more, but immensity remains.

Paul Titze January 15, 2009 at 22:27

If there’s a mountain to climb, someone will climb it regardless of the dangers etc. I’m fairly confident that there’s a yet to come engine that will make interstellar travel practical and accessible. The biggest worry is will we have enough time to make it before civilization on Earth falls apart? Our time on this planet is borrowed time, when you have all your eggs in the same basket many things can go wrong, desease, overpopulation, loss of resources, nuclear holocaust, asteroid impact, famine, WWIII etc etc… Even if we do find solutions to all these possible future problems, what’s the backup plan? Get off the planet and find a new Earth.

Cheers, Paul.

Mark January 16, 2009 at 3:14

Re: Fermi Paradox:

They’re already widespread throughout the universe, but their “prime directive” of noninterference forbids them from messing with us or even letting us know of their existence.

And unlike on Star Trek, they never ever violate this directive. Not even a little bit.

John Hunt January 16, 2009 at 4:20

As for space travel for survival, it seems to me implausible, if only because of the difficulty and expense of getting something that is in some sense human to a suitable destination.

Technologies such as VASIMIR can get us to Alpha Centauri in something like 1/30 of the time it would take using chemical propulsion. Frozen embryos are described by those in the field as being viable “hundreds of years” or even “indefinitely”. It’s a question of the technology, not the physics.

Plus, space travel for survival does no good for those of us still left on Earth.

None of us here personally went to the moon. And yet we all believe that it was worthwhile. Likewise, none of us will survive an existential event. But if humanity were to live on elsewhere, I for one would feel that that is very worthwhile.

such advanced observation technology that it could see everything there is to see on every other planet in the galaxy

Would such observation technology be able to image a microfossil buried 50 meters underground? Telescopes can’t do everything!

Ronald January 16, 2009 at 6:20

Its strikes me that the usual dichotomy (if I may call it that) appears here in the discussion: those who advocate and/or predict that we will go interstellar and those that argue that an advanced civilization will be able to do ‘everything’ from within the vicinity of its own home planet.

I don’t see this contradiction; yes, it is definitely true that detection abilities advance (much) more rapidly than propulsion abilities. As others have argued, we will have mapped our galaxy and possibly even neighboring galaxies in great detail (long) before we will be able to go there. Just like early astronomers studied the mood and planets of our own solar system centuries before we sent vehicles there.
However, the original arguments for actually going there still stand firm: close-up study (i.e. beyond mere observation), risk-spreading and survival of human species and civilization, and the more philosophical/ethical issues of spreading life and civilizaion across the galaxy (with special emphasis on lifeless planets, leaving the life-bearing ones intact).

Ronald January 16, 2009 at 6:28

Paul: ‘mood’ and planets of course has to be ‘moon’ and planets, funny word-twist.

Peter January 16, 2009 at 11:51

Sensor and propulsion technologies aren’t mutually exclusive. They compliment one another. If we can send manned or robotic missions anywhere, then we can attach any variety of telescopes to them. The power of the telescopes would be magnified by the range of the craft they’re attached to.

This doesn’t apply to just telescopes. With manned missions especially, what we’d be doing is expanding our entire power base, perhaps exponentially. Anything we can do on earth we could then do wherever else we could go. All our technologies would get a far greater scope of applications.

Raven Daegmorgan January 17, 2009 at 2:44

The argument that “in fifty years we’ll have no need to make the journey” or “we’ll have better technology in fifty years”, to me, are cop-outs–failures to understand the nature and history of research and discovery and such attempts as they are made in the present with the technology available to that present moment.

The point of exploration is that when we explore, we discover things we never imagined we would discover when we undertook the exploration. One example every grade school child knows: Columbus was looking for a trade route to India, and he found a whole continent Europe was unaware of sitting in his way.

This is the point of any exploration: not what you are trying to achieve, but what else you might achieve or discover because of the attempt, which would not have been found otherwise, and which spur new realizations, new knowledge, new possibilities and paths forward which were not present previously and which have nothing to do with the original point of the exploration attempt yet which may be better than the realization of that point.

Ronald January 17, 2009 at 13:15

@Raven: 3 cheers!

Comments on this entry are closed.

{ 2 trackbacks }