by Paul Gilster | Mar 3, 2010 | Astrobiology and SETI |
What are the odds for survival of a technological society? We don’t know yet, having but one example to work with, but it’s interesting to speculate, as Ray Villard does in a recent online post, about the kinds of intelligence that may evolve in the universe. All too often we equate technology with intelligence, which may skew our view of projects like SETI. Energized by the American Association for the Advancement of Science meeting in San Diego last week, Villard is thinking that intelligent life may have appeared on our planet not once but twice, and one of those life-forms is never going to be found by listening to radio wavelengths.
The case for cetaceans seems strong. Here’s Villard on the matter:
Physiologically, dolphins have a brain architecture and brain mass-to-body mass ratio that is closer to that of humans than for any other species on Earth. Many years of experiments on captive dolphins show that they are self-aware, have a sense of self-identity, do detailed problem solving, interpret symbolic language, and exhibit empathy. Dolphins form complex societies with groups segregated by sex and age, alliances, and conduct long-term nurturing of the young.
And whereas apes and humans appear closely in evolutionary time, cetaceans do not, making the case for independent emergence of a far different kind of intelligence than humans possess, one adapted for life in the ocean. The argument is interesting on its own merits because the emergence of dolphins and whales as self-aware beings implies that evolution has established two different routes to intelligent life on the same planet. That would make a strong case that self-awareness is a common feature on any planets where complex life-forms establish themselves, and would seem to bode well for extraterrestrial civilizations.
SETI, of course, is quite another matter. A world populated only by dolphins and whales is not one that is going to be sending strong beacon signals at 1420 MHz to nearby worlds. The Fermi paradox? Maybe the ‘where are they’ question is answered by the thought that they’re on many nearby worlds, but don’t necessarily have the technological means to tell us so. Villard goes a step farther still and asks whether creatures that do develop technologies aren’t the most hubristic, the builders of guns, cars and refrigerators also being capable of creating thermonuclear devices and bacteriological weapons to destroy themselves.
At the AAAS meeting, Seth Shostak opined that we would have an interstellar greeting from another civilization within the next twenty-five years. He bases this on the fact that we’re reaching so many stars now that within two years, we’ll have surveyed as many stars as we did in the past fifty years, since Frank Drake first fired up Project Ozma to listen to Epsilon Eridani and Tau Ceti. Villard notes that this exponential rise offers the best chance for success when it reaches the top of the slope and begins to flatten out. He quotes Shostak as saying “If we don’t have a detection by the year 2035 then something is wrong with our fundamental assumptions.”
But our fundamental assumptions are constantly being challenged with every new discovery in planetary science and astrophysics. Why should SETI be any different? The possibility of intelligence evolving in such a way that it has no technology seems clearly demonstrated here on Earth. But we should also be asking whether even technological societies necessarily have the same urge to communicate that seems to drive us. Is reaching out across the stars a fundamental impulse of intelligent life, or is it a trait of our species alone, and if the latter, what is the impulse behind it? If we can’t assume alien civilizations will share our technologies, neither should we assume they would share our compulsions. A lack of SETI success by 2035 may simply tell us that the quest for knowledge of the wider universe may be a human philosophical quirk.
by Paul Gilster | Mar 2, 2010 | Deep Sky Astronomy & Telescopes |
Data from the Keck telescope (Mauna Kea), the Hubble Space Telescope and the Very Large Array have been used in conjunction with the findings of the Wilkinson Microwave Anisotropy Probe to offer up a new way to measure the size of the universe, as well as how rapidly it is expanding and how old it is now. By determining a value for the Hubble constant, the work confirms the age of the universe within a span of 170 million years as 13.75 billion years old.
I’m always fascinated with work involving gravitational lensing — just yesterday we looked at using the Sun’s lensing effects for potential SETI investigations — and here we have a classic case of measuring how light traveled from a bright, active galaxy along different paths to reach the Earth. A strong gravitational lens like the one used in this study, called B1608+656, creates multiple images of the same galaxy lying behind the lensing object. Studying the time the light took along each path, it was possible to gather information about the distance of the galaxy as well as the age of the universe and details about its expansion.
Image: When a large nearby object, such as a galaxy, blocks a distant object, such as another galaxy, the light can detour around the blockage. But instead of taking a single path, light can bend around the object in one of two, or four different routes, thus doubling or quadrupling the amount of information scientists receive. As the brightness of the background galaxy nucleus fluctuates, physicists can measure the ebb and flow of light from the four distinct paths, such as in the B1608+656 system imaged above. Credit: Sherry Suyu/Argelander Institut für Astronomie, Bonn.
The lensing effect produced four images of the background galaxy. What’s fascinating about lensing is that the time it takes a light ray to travel a short path can be longer than the time it takes to travel a longer path due to the gravitational time delay caused by the lensing object. This short video with physicist Sherry Suyu (University of Bonn) discusses the effect by analogy with travel times on Earth, and explains how the scientists were able to use the multiple images of the background galaxy to compute the tightened value for the Hubble constant — 21 kilometers per second per million light years. In other words, a galaxy that is a million light years away is moving away from us at about 21 kilometers per second.
An international team is behind this work, which is just out in the Astrophysical Journal. Having made a physical measurement of Hubble’s constant, says Phil Marshall (Stanford University), gravitational lensing “has come of age as a competitive tool in the astrophysicist’s toolkit.” The new value for Hubble’s constant is considered the best estimate of the uncertainty in the constant. Beyond that, however, is the fact that lensing is producing an estimate for the universe’s age that gibes well with other methods of analysis, meaning that we’re learning how to harness this remarkable natural tool for future investigations.
The paper is Suyu et al., “Dissecting the Gravitational Lens B1608+656. II. Precision Measurements of the Hubble Constant, Spatial Curvature, and the Dark Energy Equation of State. Astrophysical Journal 711 (1 March 2010), pp. 201-221 (abstract).
by Paul Gilster | Mar 1, 2010 | Missions |
I love what Dan Wertheimer, a Berkeley astronomer and one of the powers behind the SETI@Home distributed computing project, told a session at the recent AAAS meeting in San Diego. Wertheimer was talking about the possibility of using the Sun’s gravitational lens for SETI purposes, and as quoted by Alan Boyle, said that such an observatory could “read the license plates on an extrasolar planet.” That reminded me of Claudio Maccone’s whimsical but mind-boggling remark at the interstellar conference in Aosta last July, which went in much the same direction. What could lensing do? “We could see the roads of their cities. We could see the cars they are driving.”
Drake has made the case for using the Sun’s gravitational lens for SETI purposes for a long time now, and he repeated it at the TED 2010 conference in Long Beach. As to Maccone, he has long championed the FOCAL mission to the gravitational lens that would exploit the fantastic magnifications available at 550 AU and beyond. But it was Drake who first acquainted him with the topic back in 1987 at a conference on Lake Balaton in Hungary. Maccone then worked hard on both the equations and the mission possibilities, submitting a proposal to the European Space Agency in 2000 that the agency chose not to finance, although he was complimented for his vision.
Image: IAA Secretary General Jean-Michel Contant (left) with Frank Drake (center) and Claudio Maccone. Taken in London at the Royal Society Meeting of January 25-26, 2010. Credit: Claudio Maccone.
SETI and the gravitational lens make for fascinating possibilities. The 1992 Conference on Space Missions and Astrodynamics which Maccone led in Turin was the first time I am aware of that scientists and engineers began to study the possibilities of a mission. Solar sails were the propulsion method of choice, and Italy was the home of considerable work on sail concepts at the time, beginning with Quasat, a concept coming out of aerospace firm Alenia Spazio which would have been an inflatable radio telescope in Earth orbit. Quasat was never launched, but Maccone continued studying inflatable technologies with applications to extrasolar studies.
At one point, working with Jean Heidmann, Maccone suggested two kinds of FOCAL mission, one that would target astrophysical objects of interest, to be called ASTROsail, the other to study suspected artificial radio signals and to be called SETIsail. The later Aurora Project was conceived as a somewhat less ambitious solar sail attempt to reach the heliopause, with results of preliminary studies being presented at the International Academy of Astronautics meeting in Turin in 1996. Both Giovanni Vulpetti and Giancarlo Genta offered up impressive analyses of Aurora.
But back to Drake, who as the first SETI experimentalist (through his Project Ozma efforts in 1960) can be considered the godfather of the discipline. He and Nathan Cohen (Boston University) presented the case for using the gravitational lens for SETI at the 1987 bioastronomy conference in Hungary referenced above, and both have gone on to write non-technical accounts of lensing and its possibilities for SETI. SETIsail, meanwhile, grew from a targeted SETI mission to the lens to the ongoing FOCAL study, which could be used for many observations besides those involved in SETI itself.
For a look at this bit of solar sail and SETI history in context, see Heidmann and Maccone, “AstroSail and FOCAL: Two extrasolar system missions to the Sun’s gravitational focuses,” Acta Astronautica, Vol. 35 (1994), pp. 409-410. Maccone’s book on the mission is Deep Space Flight and Communications: Exploiting the Sun as a Gravitational Lens (Springer/Praxis, 2009). And if you really want to dig, read A. Einstein, “Lens-like Action of a Star by the Deviation of Light in the Gravitational Field,” Science Vol. 84, (1936), pp. 506-507.
It’s fascinating to speculate on how a SETI mission to the gravitational lens might actually be used. As Drake says, a kind of galactic Internet might be built up using lenses in different systems, but given the cost and time involved in reaching lensing distances, when would a mission be contemplated? Surely it would be after the reception of signals so promising that they left little doubt of their origin in another civilization. At that point, the prospect of using the lens to examine the system in question might prove irresistible, driving mission design and advancing our propulsion technologies. A FOCAL-style SETI mission could take us from the simple knowledge that we are not alone to a rich understanding of a culture on another world.
