by Paul Gilster | Jan 20, 2007 | Astrobiology and SETI |
Michael Anissimov looks out at a universe devoid of intelligence other than our own. Here’s a clip, referring to Frank Tipler’s 1980 paper “Extraterrestrial intelligent beings do not exist”:
It was quite a few years ago when I looked up to the stars, with Dr. Tipler’s book in my hand, that I realized he was right – the stars are empty, ready to be harvested and spun into pure energy with the help of gravitational singularity goodness. No aliens, green bug-eyed ones or otherwise, are waiting there to be inconvenienced.
And this:
Luckily, hypertelescopes may finally put the nail in the coffin of SETI – perhaps 100 years from now. We will be able to see even the simplest of flora, if they exist in large numbers on exoplanets. (Though what we should really be looking for are Dyson spheres or disappearing stars, and as far as we can tell, there are absolutely none.) After we look at a good thousand earth-sized objects and see nothing there but vast, dead wastes, we’ll start getting used to the idea that we are truly, actually alone.
My own guess is that ETI does exist but is spectacularly rare.
by Paul Gilster | Jan 19, 2007 | Missions, Outer Solar System |
The New Horizons mission may have one primary target, the Pluto/Charon binary at the edge of the Kuiper Belt, but the science along the way should be interesting indeed. Up next in late February is the Jupiter flyby, whose powerful gravity assist will boost New Horizons’ velocity past 23 km/s and provide the needed stress tests to put onboard instrumentation through its paces and refine the methods for data collection. But there’s plenty to do in Jupiter space beyond setting up for the 2015 Pluto encounter.
For one thing, Jupiter’s magnetosphere extends far beyond the planet itself, and New Horizons will be the first probe to move along the ‘tail’ of this stream of charged particles. These studies will complement the earlier magnetosphere work of Cassini and Galileo. All told, 700 observations of Jupiter and the Galilean moons are planned, with data gathering from January through June, including looks at the ring system and a close-up look at the ‘Little Red Spot’ the storm that’s brewing to the south of its much larger cousin.
Image: Jupiter’s magnetosphere diagrammed. Note the bullet shape defined by the incoming solar wind. New Horizons will move along the ‘long tail’ of this stream of particles. Credit: NASA.
New Horizons is currently 5.57 AU from Earth, moving at a heliocentric velocity of just under 20 km/s. As with any space mission, we wait for data, much of which will be stored on the spacecraft’s onboard recorders until March, when the main antenna will be re-oriented for transmission to Earth. The Pluto approach and encounter will involve five months of observations that should fill huge gaps in our knowledge of the distant world and its moons. Whether an additional Kuiper Belt object will also be investigated depends upon the mission’s status after Pluto, but as the Mars rovers have demonstrated, extended missions can surprise us with the resilience of their hardware and the depth of their results.
by Paul Gilster | Jan 18, 2007 | Astrobiology and SETI |
Some day alien civilizations may pick up television or radio signals from Earth. But does this mean they’re likely to visit us? Danish researcher Rasmus Bjørk (Niels Bohr Institute, Copenhagen) doubts it. “Even then, unless they can develop an exotic form of transport that gets them across the galaxy in two weeks it’s still going to take millions of years to find us,” says Bjørk in an article in The Guardian. “There are so many stars in the galaxy that probably life could exist elsewhere, but will we ever get in contact with them? Not in our lifetime.”
Bjørk is in the news because he set up a computer simulation to investigate how long it would take to explore the galaxy. Suppose we build eight probes which, along the way, send out eight more mini-probes, all headed for different stars that are likely to have life. Bjørk’s plan is to search only within the galactic habitable zone, to use flyby probes only, and to fan out the spacecraft at one tenth the speed of light. The aim is to investigate a volume of space containing 40,000 conceivably life-sustaining stars.
Here’s the method, from Bjørk’s paper on the subject:
The 40,000 stars are explored by sending out one host probe which travels to some faraway star referred to as the “destination star”. Once the probe arrives, it dispatches a number…of smaller probes, that in total investigate the 40,000 nearest stars. They do this by always moving to the star nearest to their current location that have not been explored already. The distance and position of this star can easily be determined from its parallax. After all the 40,000 stars have been explored the probes return to the destination star, where they dock with the host probe for maintenance and prepare to travel to a new destination star.
In other words, explore all 40,000 suitable stars within the box defined by Bjørk and the process begins again on a new box of stars. In this way the exploration wave moves through the galaxy. The results aren’t encouraging for those in a hurry: using eight probes, each with eight sub-probes, the time to explore a box of 40,000 stars is on the order of 100,000 years. Exploring a mere four percent of the entire galaxy takes a time comparable to twice the age of the Earth (specifically, 9.57 x 109 years).
An obvious objection is that self-replicating probes could do the job much more efficiently and in far less time (Frank Tipler has done interesting work on this question, arriving at times in the millions of years to explore the entire galactic disk). But Bjørk points out the problems with such probes. They might easily move beyond control of the humans who designed them, with fatal consequences. So he bases his study on non-replicating devices, reaching this possible answer to the Fermi Paradox: “We have not yet been contacted by any extraterrestrial civilizations simple because they have not yet had the time to find us. Searching the Galaxy for life is a painstakingly slow process.”
The paper is Bjørk, “Exploring the Galaxy using space probes,” accepted by the International Journal of Astrobiology and available as a preprint. A key Frank Tipler paper is “Extraterrestrial intelligent beings do not exist,” Quarterly Journal of the Royal Astronomical Society, Vol. 21 (1980), pp. 267-281.
Addendum: This thought from Adam Crowl on the Bjørk paper mirrors my own reaction:
Many assume that as soon as intelligences can make autonomous self-replicating robots then that’s what they’ll do, sending them forth with a ‘mission’ to colonise the galaxy with their kind of intelligent life. A self-replicator smart enough to be called ‘intelligent life’ is a ‘person’ in my view, but an arguably important aspect of personal identity is freedom and creativity, and I suspect even the longest-lived ‘persons’ will fatigue in the face of a task like colonising every star in the Galaxy. A more organic expansion will be what eventually completes the task and there’s no easy way of estimating how long, or how thorough, such an expansion will be.
by Paul Gilster | Jan 18, 2007 | Culture and Society |
What’s wrong with scientific papers? Ask physicist and science fiction author Gregory Benford, who tackles the question in a wonderful pastiche for COSMOS. “The sad truth is that hardly anybody ever reads a paper all the way through,” Benford writes. “A study by a British physics journal showed that the average number who get through the whole paper was 0.5 – and that included the author! Apparently, most scientists can’t bear to reread their own work.”
Benford’s ‘study’ appears under the title “How to write an awesome scientific paper.” Using the nom de guerre Bea Realist, he skewers over-inflated prose and bloated egos without mercy. A sample, touching on the awful overuse of the passive voice:
The scientist is, by his reliance on the passive voice, hobbled, leading to sentences like this one, in which the subject, a lumpy noun, is acted upon by pallid adjectives and wan verbs, all without ever saying exactly who the action is done by, so that the sentences get longer and longer as you read and never seem to end, even when there is clearly nothing more to say in the sentence, at which point the reader sometimes gets a meager little semicolon; this gives him a rest, so that he can go on and read another long phrase without really learning anything more, because the writer’s hand has kept on moving even though his brain is disengaged.
I’ll never approach the footnotes in an Acta Astronautica paper again without recalling such advice as “A scientist will always give greater attention to colleagues who cite him, if only to find where in the text you mention him.” And this: “The highest-risk strategy is to cite someone in the list of references but not in the text. Then he will have to read the whole paper.”
Don’t miss this send-up, which elicits a delighted chuckle of recognition again and again (and thanks to Fred Kiesche for the pointer). My only caveat: Lumpy, sodden prose is hardly the reserve of the sciences. Take the word of a former medievalist, who once wandered through acres of turgid papers on Anglo-Saxon alliteration and the metrics of Beowulf. To quote from some of these would be a merciless act. But to see academic writing in the act of genuine hara-kiri, may I suggest a reading tour through a variety of sociological journals? Any university library can help.
by Paul Gilster | Jan 17, 2007 | Astrobiology and SETI |
It’s a pleasure to see that Cosmic Search is now accessible on the Internet. Appearing first in 1979, this magazine devoted solely to SETI was well ahead of its time, trying to generate interest in a popular audience that had not yet become familiar with the concepts driving the search for life in the universe. In those days long before SETI@Home, I learned about Cosmic Search through the Society of Amateur Radio Astronomers, a group I had joined in the mistaken belief that I had could create my own receiving station and do interesting science.
That hope was never realized, a victim of my clumsiness with hardware, and I contented myself with reading and learning. Cosmic Search was a true gift, covering the range of SETI investigations and stuffed with reading from the likes of Philip Morrison, Frank Drake, Ronald Bracewell and many other familiar names. Go to the site, where you can scroll through the listings and see for yourself how SETI looked 25 years ago.
Cosmic Search will always be linked with the name of John Kraus, who designed and built Ohio State’s University Radio Observatory, known by the nickname ‘Big Ear.’ Kraus was able to supply the needed funds to get the magazine launched but the hoped for sales never materialized, and his creation expired after only thirteen issues. My own set is here in the office, tucked behind a run of late 1930s issues of Astounding, but now that the originals are so hard to find, I hope this archive will open the magazine to new readers who will benefit from its still timely thinking.
And a special word of thanks to Jerry Ehman, the Big Ear volunteer who put together the data files from scans of the originals. SETI buffs will recognize Ehman as the man who scribbled ‘Wow!’ on a printout from the Big Ear’s August 15, 1977 observations. The ‘Wow!’ signal was never repeated, and today Ehman believes that it was probably the result of terrestrial interference, but for just a while researchers pondered the possibility of an extraterrestrial signal from the direction of Sagittarius — that’s toward the galactic core — and at Ohio State’s pioneering observatory, all things seemed possible.
