Milky Way revision

January 6th, 2009

Via careful measurements with the Very Long Baseline Array, Mark Reid and colleagues have revised the rotation rate of the Milky Way, thus adding mass and pace to its magnificent gyre…

Milky Way — the galaxy — not so snack-sized

…thus it’s now measured to rotate at 254 km/s, not the 220 km/s used for decades by most astronomers.

Mark Reid works for Harvard’s Center for Astrophysics. Their news post is available here, but it’s not as informative as the MSNBC report, which summarises what Reid presented at the current 213th AAS meeting.

New Way to Climb a Rope

January 6th, 2009

Space elevators, aside from lacking carbon nanotubes of sufficient length and strength, also suffer from a power problem when launching from planet Earth. They can’t carry a power source sufficiently light weight to feasibly climb the ribbon to geosynchronous orbit and beaming the power to the climber seems rather problematic (requires lots of battle-strength lasers pointed at space which some might look askance at.) So what to do?

Seems a launch engineer for the ESA might have a solution which has the added benefit of also being applicable to Earthly Super-Skycrapers…

By Broomstick to GEO

…by carefully timed “jiggles” the ribbon itself can transfer upward motions to the climber. It’s hoped the system can be applied to proposed kilometre high Super-Skyscrapers as well, thus making its inventor some serious dosh.

Carnival of Space #85

January 3rd, 2009

Sorry… missed #84. The link is still available at Universe Today.

Now for #85… www.cheapastro.com… Space Carnival

…with a discussion on my favourite moon (no, not ours)… Triton

what’s wrong with Determinism?

January 3rd, 2009

Computationally even relatively simple biological molecules can’t be emulated exhaustively - they exceed the computational power of the entire Universe (if it were a computer that is), thus purely first principles descriptions of any complex system are a nonsense. “Determinism” assumes infinite computational ability - Laplace’s Demon - but such just doesn’t obtain in the physical Universe.

So where has free-will vanished to, when even simple biomolecules are beyond deterministic prediction? It’s not free-will that’s threatened, but simplistic Determinism. Everything derived from “no free-will” is just cant and tendentious posturing. Human behaviour can’t be predicted in an absolute deterministic sense, even if we were just classical computers in essence. So give up the whole line of “there’s no free-will” - it’s meaningless from a scientific and human-level point of view. Only a God’s eye-view can make an utterly deterministic computation… and guess what? He’s not sharing the results with us!

Here’s the thing. Turing’s Non-halting proof means there’s no way of knowing in advance what a bit of not very complex software is going to do - will it continue forever or will it stop? Why should humans be any less complex and any less beyond prediction?

You might think “Well that doesn’t mean that the program’s future behaviour is not determined by its previous states.”

But by what do you mean “determined”? And who can judge whether it is or isn’t 100% “determined” or partially stochastic or partially “random”? In principle you can’t! So “determined” is operationally meaningless. It serves no descriptive purpose for complex systems. Doesn’t mean that non-determined things can’t exhibit statistical regularities - radioactive decay is inherently unpredictable, but it’s still layfully obeying the Law of Large Numbers and so forth. But what it does mean is the ideas of “freedom” and “free will” aren’t meaningless because lower level laws are inherently deterministic either. The evolution of a system down a particular branch of probable outcomes (one of Everett’s Many Worlds) is no more predictable than its evolution down any other branch, yet the ensemble of Possible Worlds is governed by quantum mechanics, a deterministic theory.

Freedom, free-will and Determinism.

Meet the Cousins of Our Ancestors #1

January 3rd, 2009

No surviving species today is the same as a fossil or hypothetical form claimed to be an intermediate form, but living creatures preserve historical information that is otherwise lost to us in their unique adaptations and the adaptations they share with fossil/hypothetical forms. So whenever the press says a living creature is somehow “ancestral” or “primitive” it’s a furphy. A characteristic or two might retain features from long ago, but the lineages of all creatures alive today have been evolving for exactly the same length of time. Some lineages might evolve very quickly - if only to stay in the one place - but we’ve all had the same timespan to evolve in.

With that caveat consider the Ascidians or Tunicates, filter-feeders who, oddly, make a cellulose coat (’tunic’) and, at some point in their lives, share certain features with our own Chordate/Vertebrate lineage. So who are the Tunicates? Sea-squirts are the ones we encounter most commonly, but there are a few other fascinating Tunicates who don’t just cling to rocks - Salps (Thaliacea), Doliolids, and Pyrosomes.

Salps can form incredibly large colonial masses and suffer massive die-offs when their population overloads - this happily sends carbon to the bottom of the sea to get buried, and thus form a major part of the carbon cycle.

Doliolids also form colonies, though quite differently to salps. They have a rather complicated alternating breeding system - propagating asexually part of the time, then sexually.

Pyrosomes really piqued my interest because they form huge tubular colonies - many metres long and sometimes wide enough for divers to swim into. They’re also bioluminescent.

Isn’t the natural world amazing?

Merry Xmas and Happy New Year

December 29th, 2008

Hi All

Hope you had a joyful celebration of Christ’s Birth, even if you’re not a Christian. Which ever God (or not) you might invoke I hope the New Year will see you blessed by Him/Her/Ver/It…

Now we approach the Earth rounding its perihelion let’s remember that we all share the same planet, the same Sun and rain falls on us all. I went to see “The Day the Earth Stood Still” on Boxing Day - the premiere here in Oz - and quite enjoyed the flick. The “nano-bugs” that become an all-consuming “Gray Swarm” looked kind of familiar - the “nematodes” from “Red Planet” seem to belong to the same Class of CGI animated “bugs”. I won’t give away any more spoilers, but suffice to say it was a good remake of an old classic. I’m a Keanu Reeves/Jennifer Connelly fan, so anything either is in is watchable in my eyes, but without their respective X-factors it was still a good film. Lots of sub-texts, and some good head-nods to modern astrobiology and SETI theorising. The idea that ETIs might exist amongst us as indistinguishable human analogues (IHAs) has a long history and is underappreciated as a possible Contact/Observation strategy by advanced post-biological societies. The late Chris Boyce made the same point about 10 years ago, and it deserves serious consideration in any answer to the Fermi Paradox.

On that point Stephen Baxter has published an important new paper in The Journal of the British Interplanetary Society, which argues that reflected sunlight could have been used to communicate with early societies any time during the Neolithic. If ETIs exist, and were able to have visited, then they could well have communicated with humans anytime since the origins of urban societies (i.e. since at least 8,000 BC) as particulate pollution and greenhouse trace gases would have provided a distinctive observational signature to ETIs observing the Earth optically from other star-systems. Conversely we could well do the same once our telescopic facilities become large enough.

Carnival of Space #83

December 18th, 2008

Ian Musgrave - a Queenslander like me - is hosting #83…

Astroblogger Carnival… the Antipodean Edition

…these days he’s in Adelaide, South Australia (Ben Folds’ part-time home-town for a while.) Blogs hard on amateur astronomy, and gives Creationists a good kicking when they deserve it. Which is frequently ;-)

Did Gaia birth Selene?

December 17th, 2008

How did the Moon get here? Charles Darwin’s grandson, George, theorised that the Moon was spun off from the Earth, leaving a gaping hole we now know as the Pacific. Others theorised the Moon was captured from an independent orbit, or that the Earth and Moon somehow formed together.

Then in 1975, after Apollo and the first round of science results from studying Moon rocks, William Hartmann and colleagues proposed that the Moon was brutally bashed off the Earth by another planet. Since then this theory has come to dominate the debate, and has been refined, with the impactor being dubbed “Theia”. But there’s a problem. Theia had to impact the proto-Earth (call her “Gaia”) with almost no energy excess - in other words it didn’t ram the Earth, but merely fell into its gravity well.

Another puzzle is just how the various isotopic balances of the two, Earth and Moon, became so alike after such violent smashing together - according to the simulations the Moon accreted out of mantle material from Theia, not from Gaia. Yet the two are near identical. A sore puzzle indeed, implying they formed together at the same radial distance from the Sun.

Finally, for the two to form in the same region of space and for Theia to collide at such low energy, then she must have formed as a co-orbital of the other. In Gaia’s L4 or L5 point what become Theia formed, then the orbital arrangement destabilised when Theia’s mass exceeded about 1/24th of Gaia… but it had to accumulate something more like 1/10th of Gaia’s mass before the two collided. How did it survive an unstable orbital arrangement for so long?

How to reconcile the two? According to the work of Rob de Meijer, an ex-nuclear engineer now a nuclear geophysicist, and Wim van Westrenen, experimental geochemist, the solution comes from within Gaia. According to isotopic balances of various rare earth metals, the Core Mantle Boundary formed within 30 million years of Gaia forming. At this point in time natural radioactives - uranium 235 & 238, thorium 232, and plutonium 244, were present at much higher levels than the present day. A massive fast-breeder style runaway reaction occurred which vaporised a vast bubble of mantle material. This rose rapidly, as per Archimedes principle, and flung immense amounts of mantle rock and vapour into space, out to 100,000 kilometres. The debris mostly went into orbit and formed a heavy ring around the Earth which congealed into the Moon, with perhaps an extra Mini-Moon or two that eventually fell back. The theory is detailed in a Cosmos Magazine article from August 2008, but which has just gone online for all to discuss.

According to the study by de Meijer and van Westrenen the proto-Earth object had a spin of 2.3 hours, but once the Moon was expelled a large fraction of the angular momentum was transferred to it by tidal forces. This would have occurred pretty rapidly in the early stages as a semi-molten Earth would’ve allow a massive whole-body tidal response, rather than the much lower oceanic response that has dominated tidal dissipation to the present day. Once the Moon had moved out to ~200,000 km the response would’ve slowed and followed the more sedate tidal dissipation regime recorded in tidal rythmites through-out the Archean, Proterozoic and Phanerozoic geological record.

Speculations:

  • Did Venus birth Mercury? Venus is somewhat enriched in actinides (i.e. uranium and thorium and kin) relative to Earth, so a “Big Bang” there would’ve been *BIG*.
  • Was the bang given more *OOMPH* by variable speed of light, as per Louise Riofrio’s Variable-Cee cosmology? The Sun was potentially warmer due to higher c, so could the energy have been higher from uranium fission.
  • Only time will tell.

    ERRATUM
    Contrary to my opinion Venus isn’t enriched in Uranium & Thorium - data from Venera 8 showed enrichment, but this was anomalous compared to all the other landers that have since followed, Veneras and Vegas. Apparently Magellan’s SAR imaging data shows us that Venera 8 landed on a volcanic outflow rather different to all the other lander sites, so the observed enrichment is peculiar to that location, not Venus.

Origin of Sapience

December 11th, 2008

Humans experienced a brain expansion after they developed stone tools to augment their rather pitiful natural endowments. What provoked that shift? Chimps hunt without stone tools so it wasn’t hunting by itself that caused the change. Some 2.8 mya a supernova seems to have gone off close enough to the solar system to shower the planet in iron-60 and probably battered the place with cosmic-rays - chimps and gorillas seemed relatively untouched, but seemingly coincidentally Australopithecus garhi appears 2.6 mya with Oldowan stone tools. Then genus Homo springs forth at 2.5 mya.

Something fishy is going on, but just what can’t be pinned down. If human intelligence, “sapience”, on Earth was so contingent on odd events - like Aaron Filler’s macromutation 20 mya that caused the ape spinal change to preadapt them for bipedalism, a supernova at 2.8 mya, and notable spikes in cosmic-ray flux just prior to other shifts in intelligence - then I’ve got to wonder what other weird events are needed to push alien species towards sapience and not mere animal intelligence, which Earth has aplenty. Perhaps we really are an utter fluke and sapience is a “one in a trillion” event, turning up maybe once per Galaxy. Or Hubble volume?

The Ocean of Europa

December 11th, 2008

Europa is the second closest to Jupiter of Galileo’s “Medician Stars”, and one of the four known moons for centuries. Although akin to our Moon in size, it’s covered in ice that is criss-crossed by cracks and blotched with sulphurous looking colours. John Lewis first calculated in the early 1970s that such ice-covered moons would probably have sub-crustal oceans, warmed by the slow trickle of heat from radioactive decay. However when Voyager 1 & 2 flew past, in 1979 & 1980, they discovered that Europa and Io were far warmer than radioactive decay allowed. Io’s volcanism could only be powered by tidal energy from its constant kneading by Jupiter’s gravity. But what of Europa? Close-up views from the Galileo Orbiter revealed what looked like refrozen pack-ice, suggesting an ocean not too far down. But was there enough energy to sustain an ocean just beneath the ice? If so, where was the energy coming from?

A possible answer…

Swirling waters boost chance of life on Europa …from New Scientist Space News

Jupiter Moon Has Violent, Hidden Oceans, Study Suggests …from National Geographic News.

Heating the oceans of distant moons …from ars technica. John Timmer gives good technical details of the article causing all the fuss.

Distant moons may have liquid oceans … from World-Science. Site is sometimes a bit flakey but the article is ok.

The interesting thing comes from the fact the new tidal motions might be causing more rapid processing of oxidisers in the ice. Europa’s ice is energised by the storm of radiation trapped in Jupiter’s magnetic field, and lots of oxygen-rich ice is created, enough to energise any biosphere below… if it can get down there. Perhaps it can.

Catholic Sensibility posted some news on Paul Gilster’s post on Europa’s possible macrofauna… all sparked by an abstract that I reproduce here…

Europa is a prime target for astrobiology. The presence of a global subsurface liquid water ocean and a composition likely to contain a suite of biogenic elements make it a compelling world in the search for a second origin of life. Critical to these factors, however, may be the availability of energy for biological processes on Europa. We have examined the production and availability of oxidants and carbon-containing reductants on Europa to better understand the habitability of the subsurface ocean. Data from the Galileo Near-Infrared Mapping Spectrometer were used to constrain the surface abundance of CO2 to 0.036% by number relative to water. Laboratory results indicate that radiolytically processed CO2-rich ices yield CO and H2CO3; the reductants H2CO, CH3OH, and CH4 are at most minor species. We analyzed chemical sources and sinks and concluded that the radiolytically processed surface of Europa could serve to maintain an oxidized ocean even if the surface oxidants (O2, H2O2, CO2, SO2, and SO4 2?) are delivered only once every 0.5 Gyr. If delivery periods are comparable to the observed surface age (30–70 Myr), then Europa’s ocean could reach O2 concentrations comparable to those found in terrestrial surface waters, even if 109 moles yr?1 of hydrothermally delivered reductants consume most of the oxidant flux. Such an ocean would be energetically hospitable for terrestrial marine macrofauna. The availability of reductants could be the limiting factor for biologically useful chemical energy on Europa.

…note the highlighted sentence. (reference is: Kevin P. Hand, Robert W. Carlson, Christopher F. Chyba. Astrobiology. December 1, 2007, 7(6): 1006-1022. doi:10.1089/ast.2007.0156. found here)