by Paul Gilster | Jun 11, 2008 | Astrobiology and SETI |
When it comes to SETI investigations, the Low Frequency Array (LOFAR) being built in Europe offers intriguing possibilities. With a plan to encompass roughly 25,000 small antennae, arranged in clusters spread out over an area 350 kilometers in diameter, LOFAR may prove sensitive enough to detect the radiation leakage of transmitters in the radio and television bands from extraterrestrial civilizations. The array will operate between 10 and 240 MHz. When completed, it will offer not only myriad astronomical possibilities but SETI opportunities with a difference.
Michael Garrett (Leiden University) is general director of ASTRON, the Netherlands Institute for Radio Astronomy, now involved in building the new array. Garrett makes note of what’s possible if LOFAR’s formidable resources are turned to SETI:
“LOFAR can extend the search for extra-terrestrial intelligence to an entirely unexplored part of the low-frequency radio spectrum, an area that is heavily used for civil and military communications here on Earth. In addition, LOFAR can survey large areas of the sky simultaneously – an important advantage if SETI signals are rare or transient in nature.”
This story has a particular resonance for me. Back in the 1970’s, I put together a shortwave listening post that had it all — three receivers, including radioteletype capability, and all sorts of filters and peripheral equipment. I loved DXing the tropical bands, my specialty, looking for faint Indonesian local stations that would drift into the eastern US usually around sunrise for their brief window of receivability. In the evenings, I would hunt unusual, low-power South American stations, including the holy grail for shortwave listeners, the Falkland Islands, a fabulous catch that only a few old hands had made (I never did log the Falklands).
Even harder to get was Tristan da Cunha — I knew of no one other than a few South African DXers who could lay claim to that one. It occurred to me one night as I was logging a new station in my book that the right kind of equipment might catch a signal from another star. Back then, knowing little about these matters, I just assumed that signal would be a radio or TV signal, and that we would be listening in to the traffic of a civilization not so different from our own. I pondered what kind of antenna it would take, and wrote a speculative piece called ‘Where the Real DX Is’ for Glenn Hauser’s Review of International Broadcasting.
LOFAR’s frequency range covers areas I used to scan, but no one today is as naive as I was about expecting other civilizations to be like ours. But whatever we find, a SETI attempt via LOFAR is worth doing. Sure, nearby civilizations would be unlikely to be at the same level of electromagnetic development — radio and TV — that we are. On the other hand, it seems reasonable to search broadly through the spectrum in case we’re missing something obvious. It’s not as if SETI is LOFAR’s raison d’etre, but making researchers aware of SETI possibilities is only common sense.
So what is LOFAR about? The plan is to survey the universe with higher resolution and sensitivity than any previous surveys at these wavelengths, mapping everything from the reionization of hydrogen in the early universe to the formation of galaxies and the clusters that house them. Throw in the distribution of cosmic rays, the study of pulsars and transient events of all descriptions and you have an observatory that deepens our understanding in these frequency ranges and is certain to make serendipitous discoveries.
Image: A typical galaxy like the Milky Way contains as many stars as there are grains of sand on all the worlds beaches. Most of these stars have planetary systems and many will have the right conditions for life to flourish. LOFAR can potentially search for artificial radio signals from intelligent civilizations in nearby stellar systems. Credit: LOFAR.
Serendipity as in the discovery of ETI? LOFAR’s SETI potential has been under discussion in the Netherlands this past week at a workshop held in Dwingeloo. With stations spread throughout northern Europe, the observatory will be inspiring various SETI observing proposals as the project’s Phase I progresses to full capability. Prepare for the unexpected, even if it’s not the signature of an extraterrestrial transmitter. Every time we push into higher-resolution instrumentation or look at the universe in less studied wavelengths, something unusual tends to happen. Who knows what LOFAR’s version of gamma-ray bursts may turn out to be?
by Paul Gilster | Jun 10, 2008 | Tau Zero Foundation |
Tau Zero Foundation founder Marc Millis has been anything but idle this spring. The good news, which I am finally able to share, is that he and a team of scientists have been compiling a book that is truly a first of its kind. Frontiers of Propulsion Science is a collection of essays about where we are today and where we are going with propulsion research.
This book is the work of many hands, and if you’ll peruse the list, you’ll see it contains some of the major names in this field. Many of them, I am pleased to say, are Tau Zero practitioners (for background on what a ‘practitioner’ of TZF is, see this background document on the Foundation).
Published by the American Institute of Aeronautics and Astronautics, the book is intended for aerospace engineering and science audiences, with a goal of describing current research and offering pointers for following up these issues. And while this will be an expensive text, designed for a graduate school and above reading level, it is the intention of the Tau Zero Foundation to create a companion volume oriented to broader audiences that will aim to explain advanced propulsion for the layman.
Here is a list of authors and their papers (some titles may change):
- Foreword
Burt Rutan, Scaled Composites, LLC, Mojave, CA
- Preface
Marc G. Millis, NASA Glenn Research Center, Cleveland OH
- A Recent History of Breakthrough Propulsion Studies
Paul Gilster, Centauri Dreams, Raleigh, NC
- Limits of Interstellar Flight Technology
Robert H. Frisbee, NASA Jet Propulsion Lab, Pasadena CA
- Prerequisites For Space Drive Science
Marc G. Millis, NASA Glenn Research Center, Cleveland OH
- Review of Gravity Control within Newtonian and General Relativity Physics
Eric W. Davis, Institute for Advanced Studies at Austin, TX
- Gravitational Experiments with Superconductors: History and Lessons
George D. Hathaway, Hathaway Consulting, Toronto, Canada
- Nonviable Mechanical ‘Antigravity’ Devices
Marc G. Millis, NASA Glenn Research Center, Cleveland OH
- Null Findings of Yamishita Electrogravitational Patent
Kenneth E. Siegenthaler and Timothy Lawrence, US Air Force Academy, Colorado Springs CO
- Force Characterization of Asymmetrical Capacitor Thrusters in Air
William M. Miller, Sandia National Lab, Albuquerque NM
Paul B. Miller, East Mountain Charter High School, Sandia Park, NM and
Timothy J. Drummond, Sandia National Lab, Albuquerque NM
- Experimental Findings of Asymmetrical Capacitor Thrusters For Various Gasses and Pressures
Francis X. Canning, Simply Sparse Technologies, Morgantown WV
- Propulsive Implications of Photon Momentum in Media
Michael R. LaPointe, NASA Marshall Space Flight Center, Huntsville AL
- Experimental Results of the Woodward Effect on a µN Thrust Balance
Nembo Buldrini, ARC Seibersdorf Research, Seibersdorf, Austria
- Thrusting Against the Quantum Vacuum
Jordan Maclay, Quantum Fields LLC, Richland Center WI
- Inertial Mass From Stochastic Electro-Dynamics (SED)
Jean-Luc Cambier, US Air Force Research Labs, Edwards AFB, CA
- Relativistic Limits of Spaceflight
Brice Cassenti, Rensselaer, Hartford CT
- Faster-Than-Light Approaches in General Relativity
Eric W. Davis, Institute for Advanced Studies at Austin, TX
- Faster-Than-Light Implications of Quantum Entanglement and Nonlocality
John Cramer, University of Washington, Seattle WA
- Comparative Space Power Baselines
Gary L. Bennett, Metaspace Enterprises, Emmett, ID
- On Extracting Energy from the Quantum Vacuum
Eric W. Davis and H. E. Puthoff, Institute for Advanced Studies at Austin, TX
- Investigating Sonoluminescence as a Means of Energy Harvesting
John D. Wrbanek, Gustave Fralick, Susan Wrbanek, and Nancy Hall, NASA Glenn Research Center, Cleveland
- Null Tests of ‘Free-Energy’ Claims
Scott R. Little, EarthTech International, Austin TX
- General Relativity Computational Tools and Conventions for Propulsion
Claudio Maccone, International Academy of Astronautics, Italy
- Prioritizing Pioneering Research
Marc G. Millis, NASA Glenn Research Center, Cleveland OH
The current schedule calls for the AIAA volume to appear late in 2008 (we are about to enter the page proof process now). I am unaware of any other text quite like this, aimed explicitly at the concepts that could take us to the stars using the kind of breakthroughs in physics we are all interested in studying and following up where they seem promising. As a leading indicator of the now coalescing field of interstellar studies, Frontiers of Propulsion Science should break useful ground indeed.
by Paul Gilster | Jun 9, 2008 | Culture and Society, Sail Concepts |
One way to advance interesting science is to give it multiple uses. If you can make one aspect of what you’re doing broadly accessible to the public, you can use that lever to promote understanding (and funding) for the rest of it. All of which comes to mind as I look at Joe Davis (Massachusetts Institute of Technology), who has the engaging notion of building a tower to throw some of nature’s energy back into the sky. He would do this on an island off the US Gulf coast, one idea being to memorialize the victims of hurricane Katrina.
Stay with me on this, because the connection with interstellar travel is interesting. Imagine a hundred-foot tower something like a lightning rod, but with three vertical masts made of aluminum. When lightning strikes the tower, a resonant cavity is formed that breaks down nitrogen in the air and triggers an ultraviolet laser discharge, sending the beams back into the sky. Davis expects secondary laser discharges triggered by the first will be produced. And that may well remind you of interstellar sail ideas, a vast reflective sail being pushed by laser beam to the outer edges of the Solar System and beyond.
Image: MIT biology research affiliate Joe Davis works in his apartment in Cambridge on the prototype for a Hurricane Katrina memorial–a 109-foot tower that will send laser beams into the sky. He recently won a Rockefeller fellowship for the project. Credit: Donna Coveney.
Call it a lightsail rather than a solar sail, driven by those intense laser beams in ways that interstellar theorist Robert Forward so brilliantly detailed both in his scientific papers and his fiction. Forward, of course, took the idea well beyond the outer limits of our engineering, envisioning an enormous Fresnel lens between the orbits of Saturn and Uranus that would tune laser light from an installation close to the Sun, keeping the beam collimated so that it would remain narrow enough to continue pushing a reflective sail to another star.
Image: Scientist and author Robert Forward. Note the vest, one of many made for Forward by his wife Martha, and a trademark in his many public appearances. Credit: Salmon Library/University of Alabama at Huntsville.
Davis’ plan, of course, only suggests such concepts, and it’s hardly utilitarian for a specific space mission. But I like its multi-purpose design, and the fact that Davis is getting technical and financial support from private donors as well as the Rockefeller New Media Fellowship. The Mississippi coast is an ideal place to study the electrodynamics of natural storms, producing information that may be helpful down the line in future Katrina situations. So the ‘Call Me Ishmael’ project is a research effort as well as a monument like no other, which is why the Mississippi Arts Commission may get into the act, as local arts groups already have done.
Davis, a biologist who spent most of his childhood in Mississippi, crosses the line between science and art with evident ease. Again I think of Forward, whose energies were such that when he wasn’t developing breakthrough ideas for propulsion, he was to be found penning novel after novel in which those ideas took shape and were eased into the public consciousness. Never the most literary of novelists (as he would have been quick to tell you), he could nonetheless make a tale come alive with the power and originality of his concepts. Dragon’s Egg (Ballantine, 1980) is a good place to start, but you’ll want to read Rocheworld (Baen, 1990) for his ultimate take on lightsails to the stars.
Addendum: Larry Klaes forwards this interesting article in Scientific American on Joe Davis and his work. Note this snippet, which suggests the eclectic nature of Davis’ interest in deep space:
Davis set about creating what he calls “an infogene, a gene to be translated by the machinery of human beings into meaning, and not by the machinery of cells into protein.” His idea was to send a message in a bottle to extraterrestrials: to genetically engineer a sign of human intelligence into the genome of bacteria, grow them up by the trillions and fling them out across the heavens, to land where they may. …[T]he real message was of course aimed not at aliens, but at a public that has yet to digest the fact that DNA can encode any information, not just genetic sequences.
by Paul Gilster | Jun 7, 2008 | Exoplanetary Science |
The latest Carnival of Space is up at Out of the Cradle, where this week’s interstellar focus is delivered by Steinn Sigurdsson (Penn State), who takes a look at the new planet with the tongue-twisting name: MOA-2007-BLG-192Lb. We focused in on this one just a few days ago, intrigued by its small size (about three Earth masses) and its orbit around a low-mass star that is either a brown dwarf or a low mass M-dwarf.
But note the play in the numbers from this microlensing detection, which suggests the mass could actually be as low as 1.7 Earth masses or as high as 8.2. The discovery paper is stuffed with the relevant analysis of the statistics and how the team’s conclusions were arrived at. Let me quote Steinn on the possible significance of this find, which should have some resonance here:
It is very hard to draw a robust conclusion from a single data point, the formal uncertainties are infinite; but, this is a small corner of the observing parameters space, low mass stars have low cross-sections for microlensing, we only see them because there are so many of them.
That we already see evidence for a few Earth mass planet from microlensing observations, very strongly suggests that there are a lot of Earth mass planets out there, and that they are found all over the place.
It also tells us that the observational capability really is here. The microlensing groups, with enough stars to observe frequently enough, really can detect Earth mass planets around distant stars right now.
That last is significant, and you can see that we could be quite close to an Earth-mass planetary detection. The question is, by which method? For microlensing, transits and radial velocity methods are all in the hunt and becoming capable of such finds. In a comment below the post, Sigurdsson notes that the Las Cumbres Observatory Global Telescope Network, based on robotic, Internet-linked telescopes, could be a major player in such a detection depending on its choice of projects.
Note, too, the continuing interest in low-mass stars that this discovery will only accelerate. If we can expect Earth-mass planets around M-dwarfs and even brown dwarfs, the celestial inventory of such worlds is enormous, with conditions for life arising in settings far different than what we see around our own G-class star. MOA-2007-BLG-192Lb is probably not one of them — Sigurdsson considers it a planet with rocky core and substantial mantle of ice — but we can still wonder about worlds in more benign orbits, and consider that life around stars like our Sun may be heavily outnumbered by what is found around far dimmer stars.
Let me add that Bennett et al., “A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192” (accepted for publication in the Astrophysical Journal) is now available through the arXiv server.
by Paul Gilster | Jun 6, 2008 | Deep Sky Astronomy & Telescopes |
Start thinking about large telescopes on the Moon and the imagination quickly runs riot. With no atmosphere to contend with, a 50-meter instrument of the sort now under discussion would be able to dwarf what telescopes can do on Earth. Exoplanet detections would be commonplace, but that’s only a beginning, for this kind of telescope could take the spectra of the planets it finds and search for biomarkers.
Ponder this: Even a twenty-meter telescope would be seventy times more sensitive than Hubble, and able to detect objects 100 times fainter than what the James Webb Space Telescope will be able to see.
Now think about putting two telescopes on the Moon. Space them widely to take advantage of interferometry, creating an instrument that can, in essence, act as a single collecting surface. Mixing such possibilities with current work on detecting exoplanetary oceans and continents, we would be able to move quickly from the indirect signature of planets found by radial velocity, microlensing and transit methods to full-scale observation of planetary surfaces, key to the search for terrestrial-style worlds.
The trick, of course, is to get the necessary equipment to the Moon, but ponder the words of Peter Chen (NASA GSFC and Catholic University):
“We could make huge telescopes on the moon relatively easily, and avoid the large expense of transporting a large mirror from Earth. Since most of the materials are already there in the form of dust, you don’t have to bring very much stuff with you, and that saves a ton of money.”
Useful stuff, that dust. But Chen’s team has more than a few tricks up its sleeve. By using carbon nanotubes instead of carbon-fiber composite materials, they can bypass the need for glass to make telescope mirrors. The idea is to mix the carbon nanotubes with epoxies and lunar dust (the team used crushed rock of the same size and composition in their work) to create materials that can be spun to create a mirror blank. Coat this with aluminum and a highly reflective telescope mirror emerges. Says team member Douglas Rabin, “Our method could be scaled-up on the moon, using the ubiquitous lunar dust, to create giant telescope mirrors up to 50 meters in diameter.”
Spin-offs are also useful, and it doesn’t hurt the funding case one bit that this composite material could also be used to build the necessary habitats for a lunar base, not to mention mirrors needed for solar-power generation. Which goes to show that lunar dust, available in considerable abundance, can quickly be turned to our advantage. Sustaining a lunar observatory of this kind would inevitably lead to other kinds of science, including radio telescopes on the far side, placed so as to be free of present and future RF interference. All in all, a fine set of implications for a modest internal project at NASA running on a shoestring budget!
