The Fabric of the Universe: Exploring the cosmic web in 3D prints and woven textiles [CL]

We introduce The Fabric of the Universe, an art and science collaboration focused on exploring the cosmic web of dark matter with unconventional techniques and materials. We discuss two of our projects in detail. First, we describe a pipeline for translating three-dimensional density structures from N-body simulations into solid surfaces suitable for 3D printing, and present prints of a cosmological volume and of the infall region around a massive cluster halo. In these models, we discover wall-like features that are invisible in two-dimensional projections. Going beyond the sheer visualization of simulation data, we undertake an exploration of the cosmic web as a three-dimensional woven textile. To this end, we develop experimental 3D weaving techniques to create sphere-like and filamentary shapes and radically simplify a region of the cosmic web into a set of filaments and halos. We translate the resulting tree structure into a series of commands that can be executed by a digital weaving machine, and describe the resulting large-scale textile installation.

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B. Diemer and I. Facio
Wed, 15 Feb 17

Comments: 9 pages, 10 figures. Updated information about our art and science collaboration can be found at this http URL

Post-Detection SETI Protocols & METI: The Time Has Come To Regulate Them Both [CL]

Regulations governing METI are weak or non-existent. Post-detection SETI protocols are non-binding and too general. Vastly increased SETI capabilities, Chinese involvement in the field, and an intensified effort by METI-ists to initiate radio transmissions to the stars are among reasons cited for urgency in addressing the question of appropriate regulations. Recommendations include regulations at the agency level and laws at the national level as well as international treaties and oversight.

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J. Gertz
Tue, 31 Jan 17

Comments: 20 pages, 0 figures, Accepted for publication in the Journal of the British Interplanetary Society (JBIS)

Affordable, Rapid Bootstrapping of the Space Industry and Solar System Civilization [CL]

Advances in robotics and additive manufacturing have become game-changing for the prospects of space industry. It has become feasible to bootstrap a self-sustaining, self-expanding industry at reasonably low cost. Simple modeling was developed to identify the main parameters of successful bootstrapping. This indicates that bootstrapping can be achieved with as little as 12 metric tons (MT) landed on the Moon during a period of about 20 years. The equipment will be teleoperated and then transitioned to full autonomy so the industry can spread to the asteroid belt and beyond. The strategy begins with a sub-replicating system and evolves it toward full self-sustainability (full closure) via an in situ technology spiral. The industry grows exponentially due to the free real estate, energy, and material resources of space. The mass of industrial assets at the end of bootstrapping will be 156 MT with 60 humanoid robots, or as high as 40,000 MT with as many as 100,000 humanoid robots if faster manufacturing is supported by launching a total of 41 MT to the Moon. Within another few decades with no further investment, it can have millions of times the industrial capacity of the United States. Modeling over wide parameter ranges indicates this is reasonable, but further analysis is needed. This industry promises to revolutionize the human condition.

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P. Metzger, A. Muscatello, R. Mueller, et. al.
Tue, 13 Dec 16

Comments: 24 pages, 14 figures

The Log Log Prior for the Frequency of Extraterrestrial Intelligences [EPA]

It is unclear how frequently life and intelligence arise on planets. I consider a Bayesian prior for the probability P(ETI) that intelligence evolves at a suitable site, with weight distributed evenly over ln(1 – ln P(ETI)). This log log prior can handle a very wide range of P(ETI) values, from 1 to 10^(-10^122), while remaining responsive to evidence about extraterrestrial societies. It is motivated by our uncertainty in the number of conditions that must be fulfilled for intelligence to arise, and it is related to considerations of information, entropy, and state space dimensionality. After setting a lower limit to P(ETI) from the number of possible genome sequences, I calculate a Bayesian confidence of 18% that aliens exist within the observable Universe. With different assumptions about the minimum P(ETI) and the number of times intelligence can appear on a planet, this value falls between 1.4% and 47%. Overall, the prior leans towards our being isolated from extraterrestrial intelligences, but indicates that we should not be confident of this conclusion. I discuss the implications of the prior for the Search for Extraterrestrial Intelligence, concluding that searches for interstellar probes from nearby societies seem relatively effective. I also discuss the possibility of very small probabilities allowed by the prior for the origin of life and the Fermi Paradox, and note that similar priors might be constructed for interesting complex phenomena in general.

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B. Lacki
Wed, 21 Sep 16

Comments: 32 pages (aastex6), 5 figures, 4 tables

ET Probes: Looking Here as Well as There [CL]

Almost all SETI searches to date have explicitly targeted stars in the hope of detecting artificial radio or optical transmissions. It is argued that extra-terrestrials (ET) might regard sending physical probes to our own Solar System as a more efficient means for sending large amounts of information to Earth. Probes are more efficient in terms of energy and time expenditures; may solve for the vexing problem of Drake’s L factor term, namely, that the civilization wishing to send information may not coexist temporally with the intended recipient; and they alleviate ET’s reasonable fear that the intended recipient might prove hostile. It is argued that probes may be numerous and easier to find than interstellar beacons.

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J. Gertz
Fri, 16 Sep 16

Comments: 4 pages, no figures, JBIS Accepted

Space Development and Space Science Together, an Historic Opportunity [IMA]

The national space programs have an historic opportunity to help solve the global-scale economic and environmental problems of Earth while becoming more effective at science through the use of space resources. Space programs will be more cost-effective when they work to establish a supply chain in space, mining and manufacturing then replicating the assets of the supply chain itself so it grows to larger capacity. This has become achievable because of advances in robotics and artificial intelligence. It is roughly estimated that developing a lunar outpost that relies upon and also develops the supply chain will cost about 1/3 or less of the existing annual budgets of the national space programs. It will require a sustained commitment of several decades to complete, during which time science and exploration become increasingly effective. At the end, this space industry will capable of addressing global-scale challenges including limited resources, clean energy, economic development, and preservation of the environment. Other potential solutions, including nuclear fusion and terrestrial renewable energy sources, do not address the root problem of our limited globe and there are real questions that they may be inadequate or too late. While industry in space likewise cannot provide perfect assurance, it is uniquely able to solve the root problem, and it gives us an important chance that we should grasp. What makes this such an historic opportunity is that the space-based solution is obtainable for free, because it comes as a side-benefit of doing space science and exploration within their existing budgets. Thinking pragmatically, it may take some time for policymakers to agree that setting up a complete supply chain is an achievable goal, so this paper describes a strategy of incremental progress.

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P. Metzger
Tue, 6 Sep 16

Comments: 38 pages. Accepted for publication in Space Policy journal

Long-term consequences of observing an expanding cosmological civilization [CEA]

Suppose that advanced civilizations, separated by a cosmological distance and time, wish to maximize their access to cosmic resources by rapidly expanding into the universe. What sort of boundary forms between their expanding domains, and how does the presence of one limit the ambitions of another? We describe a general case for any expansion speed, separation distance, and time. We then specialize to the main question of interest. How are the future prospects for a young and ambitious civilization altered if they can observe the presence of another at a cosmological distance? We treat cases involving the observation of one or two expanding domains. In the single-observation case, we find that almost any plausible detection will be limiting to some extent. Also, practical technological limits to expansion speed (well below the speed of light) play an interesting role. If a domain is visible at the time one embarks on expansion, there exists an optimum value for the “practical speed limit,” and if the speed limit is much higher than optimal, one’s future will be severely limited. In the case of two visible domains, it is possible to be “trapped” by them if the practical speed limit is high enough and their angular separation in the sky is large enough, i.e. one’s expansion in any direction will terminate at a boundary with the two visible civilizations.

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S. Olson
Mon, 29 Aug 16

Comments: 7 pages, 7 figures