Author: Adam

Centauri Dreams » Blog Archive » A Science Fictional Take on Being There

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.

Sedna’s All Alone…

[0901.4173] A Search for Distant Solar System Bodies in the Region of Sedna.

A study by the discoverer of Eris, Mike Brown, and colleagues, finds that Sedna, the putative inner Oort Cloud object, seems to be rather lonesome out there. There aren’t very many Sednas to be found – less than scores, more like a dozen or so. But the sensitivity to Sedna-sized objects (about 1800 km across) is out to about 100 AU, with larger bodies discernible against background stars out to 1,000 AU. There could be a whole bunch of smaller bodies, but they’re too dim for current scopes. Much further afield and the scope has to stare at the same patch of sky to see objects move for a lot longer than this study did.

[0901.4235] High Velocity Dust Collisions: Forming Planetesimals in a Fragmentation Cascade with Final Accretion

[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!

Microwave Power Beaming paper, Please

Microwave Power Beaming Infrastructure for Manned Lightcraft Operations.

Looking for a PDF copy of this paper – if any of you have it or know Prof. Leik Myrabo well enough to ask, can you send it my way? Budget is too tight to shell-out the ~$250AU needed for the Conference proceedings.

Expect Helium Showers This Aeon

Helium rains inside Jovian planets.

Extra heat from falling helium rain… who’d’ve thunk it?

Actually it’s been postulated for a few decades, but now the high-pressure experimental physical chemistry has caught up with the theorising and finally it seems to work. Saturn is most affected as Jupiter is still too hot from residual heat for the condensation to occur in a large fraction of the planet’s insides.

Enhanced fusion reactions in metal deuterides

[0901.2411] A model for enhanced fusion reaction in a solid matrix of metal deuterides.

A model for enhanced fusion reaction in a solid matrix of metal deuterides

Authors: K. P. Sinha, A. Meulenberg

Our study shows that the cross-section for fusion improves considerably if d-d pairs are located in linear (one-dimensional) chainlets or line defects. Such non-equilibrium defects can exist only in a solid matrix. Further, solids harbor lattice vibrational modes (quanta, phonons) whose longitudinal-optical modes interact strongly with electrons and ions. One such interaction, resulting in potential inversion, causes localization of electron pairs on deuterons. Thus, we have attraction of D+ D- pairs and strong screening of the nuclear repulsion due to these local electron pairs (local charged bosons: acronym, lochons). This attraction and strong coupling permits low-energy deuterons to approach close enough to alter the standard equations used to define nuclear-interaction cross-sections. These altered equations not only predict that low-energy-nuclear reactions (LENR) of D+ D- (and H+ H-) pairs are possible, they predict that they are probable.

…would be nice to see this in a peer-reviewed journal rather than the arXiv slush-pile, but it did get an airing at a conference. Would be nice if such “low energy nuclear reactions” were studied a bit more dispassionately. The “cold fusion” circus really poisoned the well for anyone wanting to look at the data for themselves.

Did life begin in a pool of acidic gloop? – life – 19 January 2009 – New Scientist

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.

Were Mercury and Mars separated at birth? – space – 19 January 2009 – New Scientist

Were Mercury and Mars separated at birth? – space – 19 January 2009 – New Scientist.

Brad Hansen discovers that modelling a ring of debris makes two large planets and interrupts the growth of two others, thus reproducing the planets as we know them. In the process a Mars-like object would be needed to collide with Earth to make the moon and something akin is needed to strip Mercury’s mantle bare, but those are secondary details.

Question is: How did the debris ring arise?

Michael Woolfson’s Capture Theory has a natural answer – the solar system had two more gas giants than its present configuration and they collided, their silicate/metallic remnants forming a debris ring from which planets could form. But why only gas giants? That’s the trick – as Woolfson points out, gas giants form naturally via gravitational instability from gas filaments produced in a tidally distorted protostar. Terrestrial planets don’t, and have to be explained another way.

The little publicised gap in planet formation modelling is that going from the observed circumstellar dust to the planetesimals assumed by standard planet-forming theories is very, very hard to do. The dust if too small gets blown away, and if too large (but not large enough) falls into the star due to gas drag. Finding a process to counter-attack these two loss mechanisms is a damned hard problem, and one Woolfson-style theories tries to avoid entirely.

In science telling such origin theories apart needs better observational data at higher resolutions than we can presently attain. But bigger and better telescopic devices are coming soon…

Did dark energy give us our cosmos? – space – 17 January 2009 – New Scientist

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.