Twisting the Copernican Tail

by Paul Gilster on August 25, 2008

The latest Carnival of Space offers several posts with an interstellar bent in addition to our own discussion, linked to from the Carnival, about antimatter rocketry and the recent thinking of JPL’s Robert Frisbee. I notice that Gerald Cleaver and Richard Obousy’s ideas about warp drive continue to get play, with particular reference to the amount of energy that this purely theoretical construct might demand. As with Alcubierre’s own warp drive speculations, the energy levels are daunting, in Cleaver and Obousy’s case the equivalent of converting the planet Jupiter into energy (that actually beats many Alcubierre demands!).

Thus NextBigFuture‘s comment, rising naturally from this conundrum:

…it makes no sense to assume being able to convert a planetary mass into energy without having increased control of technology and information and increased economy. It is like assuming a group of cavemen get the designs for a supersonic plane but only have the economy of their tribe of six to fund it. The assumptions would also be that they need to transport their rock caves and the woolly mammoths and buffalo herds that they hunt.

A point well taken, and one reason why blogger Brian Wang looks to laser propulsion as an alternative, a prospect that appeals to near-term thinkers because it takes us back into the realm of known physics. Moreover, in its various manifestations, beamed power leaves the propellant at home so that the spacecraft can carry a greater payload. What we need to learn, of course, is how sails behave in space, an examination we’ve yet to begin — let’s hope SpaceX can help us get the duplicate NanoSail-D package (whose existence was revealed in these pages) onto an upcoming Falcon flight. The ill-fated Cosmos sail built by the Planetary Society was itself capable of being used for microwave beaming experiments, and the sense here is that a world of useful experimentation awaits if we can just deploy that first true sail.

Mike Simonsen at Simostronomy takes a look at recent computer simulations from Edward Thommes and team that model planetary formation, with results that some have found unsettling:

What they found is that our solar system represents the rare cases, where gas giants form, but do not migrate to the inner planetary system, and the final orbits of the planets in the system are fairly circular and stable. In many simulations, lots of gas giants formed in chaotic environments with collisions and eccentric orbits. In other simulations, plenty of smaller rocky planets formed, but hardly any gas giants materialized out of the proto-planetary disk. Only under specific, unique conditions do planetary systems like ours evolve.

We’ve discussed the Thommes work with interest here, but failed to catch a National Science Foundation interview, in which the scientist described Earth-like planets as fairly common: “…they’re almost like weeds, they’ll sprout up under almost any conditions.” The uncommon aspect of our Solar System, then, is the existence of those gas giants in their particular orbits, posing the question of what happens to Earth-like worlds when gas giants migrate inward, as they seem to do in many simulations.

In a wider context, what happens if we do find out that a planet like ours really is rare? How would we cope with the overthrow of yet another paradigm, the Copernican perspective that has us constantly assuming we are living on an average planet in an average galaxy, and that given enough time we will inevitably find other intelligent species on similar worlds? Not that the Thommes team takes us anywhere near that conclusion, but it does offer a challenging look at planet formation theories that will only be confirmed or refuted once we have the resources in space to perform small exoplanet detections. And let’s just say it twists the tail of the Copernican assumption rather provocatively.

{ 11 comments }

tacitus August 25, 2008 at 12:51

Regarding obtaining a colossal amount of energy to power a stardrive, it’s worth remembering that it takes only an hour for the Sun to provide Earth with the same amount of energy it takes a year for the whole planet to produce. So when people talk about a spaceship needing several year’s worth of Earth’s total output of energy to fuel it, that kind of colossal energy requirement is actually available on tap. Of course, building the tap is still a teeny wee problem to solve. :)

Adam Crowl August 25, 2008 at 18:00

Hi tacitus

The Sun puts out 4.3 million tons of energy per second. Jupiter masses 1.9 trillion trillion tons – thus how many seconds is that? 442,000 trllion. Or 14 billion years. In otherwords its total Main Sequence energy output. A little tricky to handle even for a Kardashev II civilization, though “easy” for a K-III with 30 billion solar luminosities to play with.

But that energy demand is for a 10 metre spherical warp. If we shrank the warp to nanometer size the power demand drops – perhaps we can make a “pocket universe” go FTL, though just how we get a ship out at the other end is anyone’s guess.

kurt9 August 25, 2008 at 20:24

The ideal situation is that Earth-like planets are everywhere, alien intelligent life non-existent, and we develop a cheap method of FTL

MaDeR August 26, 2008 at 3:03

kurt9, reality rarely is “ideal” from our point of view. Ideally, we could be in double-planet system (really double, not this dead moon), both with living biospheres. Ideally, we could be in dense pocket of stars (lightweeks/months, not lightyears from closest star). Ideally, we already could rule this universe, but i am afraid that position is already taken.

Adam Crowl August 26, 2008 at 6:27

Hi kurt9

Earth-like or easily terraformable? Trashing other biospheres seems rather barbaric IMO. Better we bring life to dead worlds than deaden already living ones.

Ronald August 26, 2008 at 8:10

@Adam: OK, you assume total mass conversion, I was actually assuming just Helium-3 fusion, in which case the sun beats Jupiter hands-down (rays-down): the sun’s energy output in just over half a year equals the energy content of He-3 fusion of the atmospheres of all 4 gas giants!

@kurt9: I love your summary of matters and I fully agree! According to findings sofar (see Extrasolar Planets Encyclopedia and exoplanets team of University of San Francisco) small planets should be more common than big ones (the smaller the more abundant). Over the years I have read guesstimates varying from 6 billion to 30 billion terrestrial planets in our Milky Way galaxy.

Reasonably assuming that a significant proportion of these possess water (plus some kind of atmosphere) and will be terraformable, the future of humankind in our galaxy may be one of terraforming planets and spreading (varieties of) our live, much more so than settling living planets. The lack of intelligent competition (especially if techno-advanced) in that case will only be an advantage. It is nice to have (intelligent) neighbors, but not too close. In fact, this also refers back to the recent ‘Rare Earth After All?’ debate.

andy August 26, 2008 at 8:39

I agree with Adam Crowl here regarding encountering alien biospheres, plus to add that as yet we don’t know whether an alien biosphere will have any nasty effects on the people sent there. Ideal situation is Earth-like planets common, life (especially oxy-life) rare to nonexistent.

If life does turn out to be common, then the risks posed to us by alien biospheres may mean we may have to target either young planets (with the associated dangers of a young solar system: more frequent impacts, plus increased geological activity), or “cold start” planets around evolved stars. Subgiant stars such as Delta Pavonis and Beta Hydri may well be our best bet to find safe colonisation targets without the problems of alien oxy-life. Unfortunately this means that the interstellar travel problem becomes one of traversing 20 light years rather than 4, but it could (and perhaps should) be argued that pinning all the interstellar hopes on the Alpha Centauri system is overly optimistic anyway.

kurt9 August 26, 2008 at 12:42

MaDeR: I know full well that reality has a nasty tendency to not correlate with ideal desires at all. I was just engaging in wishful thinking.

Adam: Point taken. However, I think this unlikely to be a problem. The fact that multi-cellular organisms came much later than single-celled life on our own planet tells me that if there are “Earth-like” planets out there, the majority of them are likely to have nothing more than blue-green algae floating in the ocean. For the land its BYOL time (bring your own life).

Of course, all of this is irrelevant unless we develop some kind of advanced propulsion technology and these “Earth-like” worlds actually exist. Otherwise, its right back to O’neill’s giant “tin” cans (which is the most likely scenario anyways).

Ronald August 27, 2008 at 11:37

Spoiling alien biospheres (the ones with advanced life) may be a serious ethical issue, the danger of those biospheres to our colonists is probably small, since most microbial life will not be adapted to our kind of metabolism, just as Dutch Elm’s disease poses no risk to us humans.

So I would suggest: terraforming (the more suitable) terraformable terrestrial planets without life, plus settling the ones with only ‘primitive’ life.

philw1776 August 28, 2008 at 9:13

Assuming interstellar travel capability, I’ve stated that ideal stars for seeding ‘terrestrial’ planets would be bright young F type stars. With wide HZs there could be 2-4 or more possible terrestrial ocean bearing planets in one star system. The stars won’t live long enough for evolution to stumble across tricks like multi-cellular life, so seeding nascent oceans with photosynthethising organisms to create O2 atmospheres and protective ozone layers is a tempting target.

Christopher L. Bennett August 28, 2008 at 10:46

Adam Crowl wrote: “But that energy demand is for a 10 metre spherical warp. If we shrank the warp to nanometer size the power demand drops – perhaps we can make a “pocket universe” go FTL, though just how we get a ship out at the other end is anyone’s guess.”

So how about merging the Cleaver/Obousy warp model with the Chris Van Den Broeck “micro warp drive” that pinches the warp bubble off with a nanoscale “mouth”? Are the equations compatible?

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