The aim of this chapter is to highlight the possibility of applying the mathematicalformalism and methodology of quantum theory to model behaviourof complex biosystems, from genomes and proteins to animals, humans, ecologicaland social systems. Such models are known as quantum-like and theyshould be distinguished from genuine quantum physical modeling of biologicalphenomena. One of the distinguishing features of quantum-like models istheir applicability to macroscopic biosystems, or to be more precise, to informationprocessing in them. Quantum-like modeling has the base in quantuminformation theory and it can be considered as one of the fruits of the quantuminformation revolution. Since any isolated biosystem is dead, modelingof biological as well as mental processes should be based on theory of opensystems in its most general form – theory of open quantum systems. In thischapter we advertise its applications to biology and cognition, especiallytheory of quantum instruments and quantum master equation. We mentionthe possible interpretations of the basic entities of quantum-like models withspecial interest to QBism as maybe the most useful interpretation.

The precessions of the Keplerian orbital elements induced by several modified models of gravity are calculated. The latter ones are Yukawa, power-law, logarithmic, dark matter density profiles (exponential and power-law), once per revolution accelerations, constant accelerations, and Lorentz-violating symmetry.

The orbital precessions of the Keplerian orbital elements induced by the 1pN gravitomagnetic spin octupole moment of a rigidly rotating oblate spheroid are calculated in their full generality for an arbitrary orientation of the primary’s spin axis and a general orbital configuration of the test particle.

The search for extraterrestrial intelligence (SETI) represents a well-known area of astrobiology. This chapter is dedicated to technosignatures, that is, markers produced by extraterrestrial intelligences (ETIs). The famous Drake equation for roughly estimating the number of communicative ETIs is introduced, its various factors are defined, and some of its shortcomings and implications for detecting technosignatures are discussed. Next, the Fermi paradox is delineated: if ETIs are widespread, where are they? Three major classes of solutions to this classic paradox (e.g., we are effectively alone) are considered, along with their accompanying ramifications. After a brief segue into the Kardashev scale for grouping ETIs, the final segment of the chapter categorises the diverse landscape of technosignatures – ranging from artificial radio and optical signals to atmospheric pollutants and waste heat arising from energy harvesting and dissipation – and outlines the current limits derived for the frequency of technosignatures, as well as the anticipated future constraints in this context.

The impact of the 1pN gravitoelectric mass monopole acceleration, both in the test particle and in the two-body system of finite, comparable masses cases, is calculated for different types of observation-related quantities (Keplerian orbital elements, anomalistic, draconitic, and sidereal orbital periods, two-body range and range rate, radial velocity curve and radial velocity semiamplitude of spectroscopic binaries, astrometric angles RA and dec., times of arrival of binary pulsars, characteristic timescales of transiting exoplanets). The results are applied to a test particle orbiting a primary, a Sun–Jupiter exoplanet system, and to a S star in Sgr A*.

In this chapter we develop the contextual approach to quantum mechanics.This approach matches with the views ofBohr who emphasized that the quantum description represents complexes ofexperimental physical conditions, in the modern terminology – experimentalcontexts. In this chapter we formalize the contextual approach on the basisof contextual probability theory which is closely connected with generalizedprobability theory (but interpretationally not identical with it). The contextualprobability theory serves as the basis of the contextual measurementmodel (CMM). The latter covers measurements in classical, quantum, andquasi-classical physics.

This chapter is a step towards understanding why quantum nonlocalityis a misleading concept. Metaphorically speaking, quantum nonlocality isJanus faced. One face is an apparent nonlocality of the state update basedon the Luders projection postulate. It can be referred as intrinsic quantumnonlocality. And the other face is subquantumnonlocality: by introducing a special model with hidden variables onederives the Bell inequality and claims that its violation implies the existenceof mysterious instantaneous influences between distant physical systems(Bell nonlocality). According to the Luders projection postulate, aquantum measurement performed on one of the two distant entangled physicalsystems, say on S1, modifies instantaneously the state of S2. Therefore, ifthe quantum state is considered to be an attribute of the individual physicalsystem (Copenhagen interpretation) and if one assumes thatexperimental outcomes are produced in a random way one arrives at the contradiction. It is a primary source of speculation about aspooky action at the distance. But Einstein had already pointed out that the quantum paradoxes disappear, ifone adopts the statistical interpretation.

The manifold requirements for a world to sustain habitability on long timescales (continuous habitability) are delineated in this chapter. The first part offers a brief introduction to climate physics (e.g., greenhouse effect), and thereupon formulates the notion of the habitable zone, that is, the region where liquid water could exist on rocky planets orbiting stars; the boundaries of the habitable zone as a function of the stellar temperature are also presented. In the second part, the various stellar factors potentially involved in regulating planetary habitability are sketched: winds, flares and space weather, and electromagnetic radiation. The third part chronicles some planetary variables that may affect habitability: mass, plate tectonics, magnetic field, tidal locking, and atmospheric composition. The last part is devoted to examining the high-energy astrophysical processes that might impact habitability on galactic scales: candidates in this regard include supernovae, gamma-ray bursts, and active supermassive black holes.

The hidden variable project realized by Bell contradicts the uncertaintyand complementarity principles. The inequalities derived with Bell’s hidden variablesare violated for quantum observables. Thus, Bell’s hidden variables shouldbe rejected and the validity of quantum theory is confirmed. (This foundationalachievement deserved the Nobel Prize in 2022.) This scientific loop,ignorance of the uncertainty and complementarity principles – hidden variablesmodel – Bell’s inequalities – their violation – reestablishing the validityof the uncertainty and complementarity principles, was stimulating for quantumfoundations. However, Bohr and Heisenberg might say that such resultscan be expected from the very beginning. For them, the uncertainty andcomplementarity principles form the basis of quantum physics. And theycan’t be rejected, since they are the consequences of the so-called quantum postulate– the existence of an indivisible quantum of action given by Planck’sconstant h. The quantum postulate is the ontological basis of quantum theory.I formulated its epistemic counterpart in the form of the principle ofquantum action invariance.