Nisi cognitio finitas, infinitum sit necesse est ignoratio
Carnival of Space #93: From our own planet, to exoplanets – The Planetary Society Blog | The Planetary Society.
Carnival Time! Best pick – or most thought-provoking – is a strident advocacy of a Nuclear Pulse-Gun for launching massive cargo payload(s) to LEO and beyond at Brian Wang’s Next Big Future. Brian suggests we might need only one to kick-start the real space-age.
The Launch Pad: Carnival of Space #92.
Carnival of Space #92… plus an addendum because it is so freaking HUGE!!!
Carnival 92 Sideshow
Boffin: Earthlike worlds within 30 lightyears of here • The Register.
Alan Boss, of gravitational instability fame, has published a book (The Crowded Universe) claiming, surely as headline catcher, that every sun probably has a habitable planet. Habitable NOT inhabited. Just how long a planet orbitting a Blue Super-giant would last is a moot point as I suspect he means “almost every star”, which means the 99.9% that are Class A or cooler. If so then there’s a hundred billion habitable planets out in our Galaxy alone.
However he’s a “Civilization pessimist” who seems to think Intelligence doesn’t persist long enough for it to cross paths with other Intelligence. That seems kind of futile and lonely to me…
Within Any Possible Universe, No Intellect Can Ever Know It All: Scientific American.
An interesting proof of the ultimate limits of knowledge for any Being within a system. Even a mighty Kardashev Type IV Civilization will face unknowns if trying to operate within the Universe. Of course that does pose the possibility of inter-Cosmic entities linking up multiple Brane-i-verses through the Bulk and knowing them to their fullest extent thanks to their transcendent vantage point. I’m not sure if that’s possible, but it’s as possible as it is not, due to our ignorance of the Bulk and its non-gravitational physics.
[0810.2222] A Numerical Testbed for Hypotheses of Extraterrestrial Life and Intelligence.
The study in question by Duncan Forgan. It uses pretty standard assumptions based on Panspermia, Habitable Zones (Stellar & Galactic), plus some stochastic guesstimation of the emergence and fate of ETIs. Even assuming they last as long as their stars once they spread to all the planets of their system, there aren’t too many in the Galaxy.
Of course the question then is: what happens if They proceed to colonize other systems?
At “The Habitable Zone” a Belgian amateur astronomer, Raoul Lannoy, frequently gives us space-optimists a space-pessimist take on things. Recently Raoul brought up a Space Review piece on mass colonization of space – i.e. billions leaving Earth to inhabit the rest of the Solar System and beyond. Mark Eby had this to say… Mark’s response …essentially that in human history small bands of intrepid wanderers have been the ones to spread far and wide, beyond the ancestral range.
Unless a star-system is being evacuated then mass colonization seems rather more difficult than it is worth. As independent New Beginnings for the human race, Star Colonies would have great practical and symbolic value, helping preserve humanity against system-scale collapses from whatever cause might destroy a system. Spread across the Galaxy our species would seem protected against the largest known energetic events in the Universe… except, so far spread, we wouldn’t remain the same species for very long in cosmic terms. We’d undergo divergent evolution, unless a deliberate policy of genetic mixing was pursued. Even more rapid divergence would occur if the pioneers were those posited small bands – the so-called Founder Effect
would result in rapid fixation of any new alleles and genes while the effective population was small. Each new band settling into a different system would be a species divergence point unless more colonists followed.
Keeping those small intrepid bands in mind, once settled and grown strong, we have to ask if they will then spawn a new band of intrepid pioneers eager to venture further into the Galaxy. Geoff Landis modelled such a process as a discrete percolation process, which spread into the Galaxy not as an inexorable wave, settling every star system, but as dendritic filaments that left large unoccupied voids between them. This suggests our Galaxy could be well settled and we could still be left alone, as per the Fermi Paradox.
Alternatively They’re here and They’re watching us, but keeping quiet in any frequency we can scan. An old saying is that perfectly coded signals should be indistinguishable from noise…
Centauri Dreams » Blog Archive » A Science Fictional Take on Being There.
Paul Gilster, el Supremo of “Centauri Dreams”, discusses Robert Metzger’s description of very subtle high-resolution means for ETIs to spy – in detail – on the whole of Earth’s biosphere… gazillions of nanoprobes, indistinguishable from dust, riding piggy-back on everything interesting about Terra’s children, reporting back covertly to a network of larger probes that beam the data Home. If that’s not sufficiently paranoid, the ETIs might spy us via reading the space-time vibrations every atom of our world sends out through the “fabric of space-time” like a vast, taut tapestry. And they might do so from back Home…
we’ll never know, if we never go.
[0901.4235] High Velocity Dust Collisions: Forming Planetesimals in a Fragmentation Cascade with Final Accretion.
Forming planets is something of a puzzle – we can’t presently observe them directly in their early days, just the stars they orbit and the dust they’re cocooned in. We have a pretty good idea of how stars form and we can figure out how dust forms, but going from dust to planets has a few obscurities. Or rather from dust to small planet bits about 1-10 km across is obscure. Once there are billions of bite-sized planet bits they quickly accrete into planets according to all the computer simulations. That bit is easy and it forms planets much like the ones we see.
And, in recent years, the path from dust to centimetre size dust bunnies is looking nearly solved too. Zero-gravity experiments with dust on the Space Shuttle formed fractal fluffy aggregates that gradually smush together and get denser. But between a centimetre and a kilometre things get very tricky – the dust balls start seriously feeling the drag of the thin gas around them (the protoplanetary nebula) and this gentle drag is enough to plunge the growing dust-balls into the central star in 100-1000 years. So how do they survive?
Well once they’re about a kilometre across they’re safe, but growing 100,000-fold in size and a quadrillion-fold in mass is tricky. Presumably they butt into each other and ‘stick’, but just how has been doubtful. Now this study appears which answers some of the questions about dust-ball collisions by actually colliding dust-balls at the expected range of collision speeds. Surprisingly they tend to stay together, held together by the cohesion forces of dry dust (the stickiness of space itself we call “van der Waals forces”.) What bits fly off tend to be as big as the bits that collided, and so things seem to only get bigger.
So some of the process is now less obscure, but there’s still a ways to go. They’ll make planetesimals yet!
Carnival of Space #87 « The Martian Chronicles.
Some cool entries this week covering the Martian Methane discovery and matters of space policy.
Did life begin in a pool of acidic gloop? – life – 19 January 2009 – New Scientist.
First thing that strikes me is: well that’s obvious! Getting out of the lab and into the wild is guaranteed to break the conceptual mold. Deamer is a clever man and his work is very interesting.
Second, what if ribo-organisms could use sulfuric acid? Could they colonise the clouds of Venus? Weird particles float around in Venus’ clouds and no one has identified them for sure yet – perhaps they’re sulfuric acid life?
Third, making RNA is a significant step, but there’s still a big informational gap between some oligonucleotides and a living cell. The problem isn’t as bad as once imagined – ribo-organisms could have genomes about 7,000 bases long. But “random” sequence shuffling won’t make a functional genome in less than many quadrillions of Hubble times. Some higher level principle had to have organised the RNA to boot-strap life. Deamer and Szostak are still a ways from finding out just what it was.
Did dark energy give us our cosmos? – space – 17 January 2009 – New Scientist.
According to Paul Steinhardt and colleagues dark energy stretches out the Universe for a trillion years, then it bashes into another Universe in a higher dimension, causing a new “Big Bang”. The stretching ensures that the clashing Universes are flat enough that their encounter doesn’t create too many regions of over density that collapse into massive black-holes and gobble up space-time.
Makes me wonder if Life from a previous cycle can’t find a handy place to hide while the two clash together in a Big Bang. Thus Life could end up being older than the current space-time. Maybe.