Author: Adam

A Numerical Testbed for Hypotheses of Extraterrestrial Life and Intelligence

[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…

ER1470 Reconsidered II

A bit over a year ago a poster by Dr. Timothy Bromage on the craniofacial development of the hominid ER 1470 received a lot of press because his reconstruction made the hominid look more ape-like. Bromage wasn’t the first to reconstruct ER 1470 like that – Alan Walker had reconstructed it differently to his colleague Richard Leakey along Australopithecine lines – but Bromage’s team were the first to use laser-scanning and 3-D manipulation of the skull to fit it according to known developmental principles. A surprise result was the small estimate of 526 cc for the brainpan’s volume versus the previous estimate of c.750 cc. Now a new paper by Bromage and colleagues estimates a volume closer to 700 cc, thus closing the discrepancy between the two.

When looking for this newer paper by Bromage, which he had said was forthcoming, I found an awful lot of Creationist propaganda using his work’s relatively tentative conclusions as some sort of definite “evidence” against concluding the species represented by ER 1470 is a human ancestor. But the affinities of a single skull is largely irrelevant to that question and the baseless propagandising should disgust any honest seeker of the truth.

A Chemical Memory of the First Animals

Oldest Animal Fossils Discovered | Wired Science from Wired.com.

Demosponges produce a distinctive sterane as they decompose and traces of it have turned up in late Cryogenian sediments from 635 million years ago. That’s the oldest distinctive animal trace yet discovered – trails in the mud now being a ‘red herring’ because Protists can make them too.

BBC NEWS | Science & Environment | Number of alien worlds quantified

BBC NEWS | Science & Environment | Number of alien worlds quantified.

How many ETI civilizations out there? Just 361 to maybe 38,000 or thereabouts. One thing frustrates me with such figures is the lack of qualifiers reported by the science newsdesks – the assumptions Duncan Forgan used to derive the numbers are more important than the numbers themselves. And what can we really say? How little we really know…

More later after I read what he actually has to offer.

PLoS A New Protocetid Whale from Pakistan

New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism.

Phil Gingerich, and colleagues, have uncovered three members of a new proto-whale species, Maiacetus inuus, with the fascinating twist that one of them is a fetus awaiting birth, head-first. As marine mammals are born tail-first if they’re born in water, this indicates the proto-whales still hauled themselves ashore to give birth.

And Creationists, Young and Old Earthers both, once said there were no transitional forms from terrestrial to marine for the whales, and such would never be found… Hah! The danger of the argument from ignorance is that it is a two-edged sword. New facts can change our deductions in a flash.

Laser-armed Humvees

Humvee with frikkin laser on it takes out killer robot • The Register.

A laser-armed Humvee shot down a UAV at a useful range. That’s a start. What is really needed is high-power lasers to remotely detonate IEDs and take down RPGs and other hand-launched rockets. A clever approach to that task is to destabilise the rockets in-flight, since they’re have relatively simple-minded guidance, at best.

Eventually a “deflector field” could be created – any high-speed projectile on an inbound trajectory around a given volume could be thrown off-course and destroyed by the tracking-and-lasering combo. This would take a much more efficient “wallplug-to-laser-beam” ratio – most lasers pump out too much heat to be reused rapidly.

Hybrid fusion-fission reactors

Hybrid fusion-fission reactors to run on nuclear ‘sludge’ • The Register.

A good use for high-energy neutrons is burning up transuranic “waste” from conventional once-through fission reactors. As any Fast Neutron reactor wonk knows, once-through “waste” still has 95% of the uranium’s energy potential in it as not-so-easily fissioned U238 and things like plutonium etc. A stream of fast neutrons can allow the stuff to be fissioned without excessive reprocessing and absolutely no need to separate out the plutonium.

SKYLON is on the Move!

Brian Wang reports on another small step towards a flying SKYLON SSTO…

SKYLON takes-off

…massing 275 tons fuelled and orbitting ~12 tons of payload, capable of ~ 200 flights, it would drop the LEO access cost dramatically – if it had sufficient business. One SKYLON can orbit 2400 tons over its life-span – what could we make with 30 SKYLONs? Some 72,000 tons to LEO…

There’s been lots of paper-studies of Solar Power Satellites – in the 1970s the assumed photovoltaic efficiency was 10-15% and they estimated SPS masses at about 10,000 tons per gigawatt. Concentrator systems, using space-capable inflatables, could get that down to ~1500-3000 tons per gigawatt. The latest SPS designs get rid of the big flat arrays and now use mirrors to reflect light onto an integrated PV converter/microwave rectenna system, to avoid mass penalties from wiring up the array and heavy slip-rings for power-flow from arrays to rectenna. The rectenna can also produce a tighter beam that can be transmitted over a range of angles thanks to improved “optics” that modern microwave arrays now have. Metamaterials could be used to overcome diffraction issues, thus allowing ground-receivers to be flexible in size.

I went to check the makers of SKYLON, Reaction Engines Limited, website and they’ve just completed a study on the economics of SPS using SKYLON for space-launch…

January 2009 News

…thus they’re thinking the same thing. Perhaps the times are pregnant with opportunity for ideas like SPS?

GEO SPS could be eventually superceded by Criswell arrays on the Moon. And a SKYLON system can support Moon operations easily too. The ESA’s predecessor, ELDO, designed a two-stage Moon-capable OTV system that each component massed under 12.5 tons and could deliver 7 tons to the Moon. This could be used to build up equipment needed for cooking arrays straight out of the regolith, eventually wrapping the Moon in an equatorial power network.

Either way, once power is feasibly seen as coming from space it might be a driver for further serious investment in space-access and eventual commercial flights to the rest of the Solar System. With large space-power available we can use beamed power to fly a lot faster than via rockets. Robert Winglee & crew have proposed the Mag-Beam for an Earth-Mars transport system which is eminently feasible and able to get round-trip times down to ~3 months, for a beam-power of 300 MW. Not quite quick enough for a short holiday, but looking good.

Eventually robotics will enable self-replicating SPS factories to be constructed which, 10 years ago now, Gerald Nordley pointed out would enable large-scale interstellar travel. How so? Imagine a 1000 ton starship being propelled to 0.86c – or a 200,000 ton freighter pushed to 0.1c – which would require 180,000 exajoules of energy input. If it accelerates to that speed over 5 weeks the power level is 60 petawatts – or 4,000 times present World Power usage. But it represents but a fraction of the Sun’s 385 million exawatts of power. And that power could be tapped by an SPS array – if we could build it big enough. How big? Say we put the array at 0.1 AU where it’s exposed to 100 times the solar energy flux that Earth feels. Assuming 50% conversion efficiency the array needs to be a 936 km square, or 876,000 km2, some ~0.172% of the Earth’s surface area. If we built SPS at a pace sufficient to keep pace with our growing demand for energy ~2.6% it’d take 320 years. That’s a long wait, which some have accepted.

But I’m impatient. I want interstellar travel, at least in embryo, by 2100. So what if our self-replicating SPS starts off at 1 GW and doubles once a year. How many doublings do we need? Just 26. If we began in 2064 we’d be in time for the deadline. If we waited for a few more doublings then by the year 38 we’d be able to launch 30,000 of those starships per year. If we enshrouded 95% of the Sun, then we’d be able to fling the equivalent of 34 trillion tons of shipping to 0.87 c using the same efficiency I’d assumed before. Just another 20 years of SPS self-replication…

Kind of makes the Fermi Paradox more glaring, doesn’t it?

Except… Robert Freitas discussed interstellar trade in his “Xenology” book and a piece on “Galactic Empires”, basically concluding that if cargo pods can be sent and their kinetic energy recovered during decceleration, then no problem. It can be done for a lot cheaper than we currently imagine. You just have to be patient :o) Maybe ETIs get by with a lot less energy expenditure than my exuberant imaginary interstellar humanity.

NB – I’ve corrected the single ship power level from 60 exawatts to 60 petawatts, adjusting the resulting figures accordingly and I owe a debt of inspiration to Gerald Nordley for the modern day revival of the mass-beam concept.