In radio astronomy, the science output of a telescope is often limited by computational resources. This is especially true for transient and technosignature surveys that need to search high-resolution data across a large parameter space. The tremendous data volumes produced by modern radio array telescopes exacerbate these processing challenges. Here, we introduce a ‘reduced-resolution’ beamforming approach to alleviate downstream processing requirements. Our approach, based on post-correlation beamforming, allows sensitivity to be traded against the number of beams needed to cover a given survey area. Using the MeerKAT and Murchison Widefield Array telescopes as examples, we show that survey speed can be vastly increased, and downstream signal processing requirements vastly decreased, if a moderate sacrifice to sensitivity is allowed. We show the reduced-resolution beamforming technique is intimately related to standard techniques used in synthesis imaging. We suggest that reduced-resolution beamforming should be considered to ease data processing challenges in current and planned searches; further, reduced-resolution beamforming may provide a path to computationally expensive search strategies previously considered infeasible.

We explain that black holes are the most efficient capacitors of quantum information. It is thereby expected that all sufficiently advanced civilizations ultimately employ black holes in their quantum computers. The accompanying Hawking radiation is democratic in particle species. Due to this, the alien quantum computers will radiate in ordinary particles such as neutrinos and photons within the range of potential sensitivity of our detectors. This offers a new avenue for search for extraterrestrial intelligence, including the civilizations entirely composed of hidden particles species interacting with our world exclusively through gravity.

If a space-faring civilization embarks on a program to send probes to interstellar destinations, the first probe to arrive at such a destination is not likely to be one of the earliest probes, but one of much more advanced capability. This conclusion is based on a scenario in which an extraterrestrial civilization (ETC) embarks upon an interstellar program during which it launches increasingly sophisticated probes whose departure speed increases as a function of time throughout the program. Two back-of-the-envelope models are considered: one in which the launch velocity of an outgoing vehicle increases linearly with the time of launch, and a second in which the increase is exponential with launch date. In this paper consideration is directed to an hypothesized probe arriving within the Solar System from a non-terrestrial civilization. Within the above scenarios, a first-encounter probe will be one that was launched well after the initiation of an interstellar program by an ETC. Consequently, such a probe would be the product of a relatively advanced phase of that ETC's technology. The more distant the site from which an ETC is launching probes, the greater will be the technology gap between a first-encounter probe and terrestrial technology. One possible ramification may pertain to interpreting the nature of Unidentified Aerial Phenomena (UAP). Are flight characteristics of any UAP singular enough as to be consistent with an origin from a distant ETC?

The controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar sail is considered using known physics for the two possible cases: controlled and uncontrolled flight. The reliability engineering challenges for an artefact designed to operate for ~105–106 year are also considerable. All three areas generate research programmes going forward. The uncontrolled case could be either ‘anonymous METI’ (messaging extraterrestrial intelligence) or ‘inadvertent METI’. In the controlled case the nature of the origin star, trajectory guidance from the origin star to the Sun, and the identity of a destination star are all undecided. The ‘controlled’ case has more strikes against it than the ‘uncontrolled’ case, but neither suffers a knock-out blow, as yet. Some of the issues turn out not to be major obstacles to the alien craft hypothesis, but others weaken the case for it. Most, however, imply new studies. Some of these, e.g. intercept missions for new interstellar objects, are concepts being developed, and will be of value whatever these objects turn out to be. Overall, these considerations show that a many-pronged, targeted, research programme can be built around the hypothesis that ‘Oumuamua is an alien craft. The considerations presented here can also be applied to other interstellar visitors, as well as to general discussions of interstellar travel.

Conventionally, intelligence is seen as a property of individuals. However, it is also known to be a property of collectives. Here, we broaden the idea of intelligence as a collective property and extend it to the planetary scale. We consider the ways in which the appearance of technological intelligence may represent a kind of planetary scale transition, and thus might be seen not as something which happens on a planet but to a planet, much as some models propose the origin of life itself was a planetary phenomenon. Our approach follows the recognition among researchers that the correct scale to understand key aspects of life and its evolution is planetary, as opposed to the more traditional focus on individual species. We explore ways in which the concept may prove useful for three distinct domains: Earth Systems and Exoplanet studies; Anthropocene and Sustainability studies; and the study of Technosignatures and the Search for Extraterrestrial Intelligence (SETI). We argue that explorations of planetary intelligence, defined as the acquisition and application of collective knowledge operating at a planetary scale and integrated into the function of coupled planetary systems, can prove a useful framework for understanding possible paths of the long-term evolution of inhabited planets including future trajectories for life on Earth and predicting features of intelligentially steered planetary evolution on other worlds.

First contact with another civilization, or simply another intelligence of some kind, will likely be quite different depending on whether that intelligence is more or less advanced than ourselves. If we assume that the lifetime distribution of intelligences follows an approximately exponential distribution, one might naively assume that the pile-up of short-lived entities dominates any detection or contact scenario. However, it is argued here that the probability of contact is proportional to the age of said intelligence (or possibly stronger), which introduces a selection effect. We demonstrate that detected intelligences will have a mean age twice that of the underlying (detected + undetected) population, using the exponential model. We find that our first contact will most likely be with an older intelligence, provided that the maximum allowed mean lifetime of the intelligence population, τmax, is ≥ e times larger than our own. Older intelligences may be rare but they disproportionately contribute to first contacts, introducing what we call a ‘contact inequality’, analogous to wealth inequality. This reasoning formalizes intuitional arguments and highlights that first contact would likely be one-sided, with ramifications for how we approach SETI.

It can be difficult to develop an effective and balanced search strategy in SETI, especially from a funding perspective, given the diverse methodologies and myriad orthogonal proposals for the best technosignatures. Here I propose a framework to compare the relative advantages and disadvantages of various proposed technosignatures based on nine ‘axes of merit’. This framework was first developed at the NASA Technosignatures Workshop in Houston in 2018 and published in that report. I give the definition and rationale behind the nine axes as well as the history of each axis in the SETI and technosignature literature. These axes are then applied to three classes of technosignature searches as an illustration of their use. An open-source software tool is available to allow technosignature researchers to make their own version of the figure.