We analyze interrelation of quantum and classical entanglement. The latternotion is widely used in classical optic simulation of the quantum-likefeatures of light. We criticize the common interpretation that quantum nonlocalityis the basic factor differentiating these two sorts of entanglement. Instead,we point to the Grangier experiment on photon existence, the experimenton the coincidence detection. Classical entanglement sources produce lightbeams with the coefficient of second-order coherence g(2)(0) ≥ 1. This featureof classical entanglement is obscured by using intensities of signals indifferent channels, instead of counting clicks of photodetectors. Interplaybetween intensity and clicks counting is not just a technicality. We emphasizethe foundational dimension of this issue and its coupling with theBohr’s statement on individuality of quantum phenomena.

In this chapter we start with methodological analysis of the notion of scientifictheory and its interrelation with reality. This analysis is based onthe works of Helmholtz, Hertz, Boltzmann, and Schrödinger (and reviewsof D’ Agostino). Following Helmholtz, Hertz established the “Bild concept”for scientific theories. Here “Bild” (“picture”) carries the meaning “model”(mathematical). The main aim of natural sciences is construction of thecausal theoretical models (CTMs) of natural phenomena. Hertz claimed thatCTM cannot be designed solely on the basis of observational data; it typicallycontains hidden quantities. Experimental data can be described by anobservational model (OM), often at the price of acausality. CTM-OM interrelationcan be tricky. Schrödinger used the Bild concept to create CTM forquantum mechanics (QM) and QM was treated as OM. We follow him andsuggest a special CTM for QM, the so-called prequantum classical statisticalfield theory (PCSFT). QM can be considered as a PCSFT-image, but notas straightforward as in Bell’s model with hidden variables. The commoninterpretation of the violation of the Bell inequality is criticized from theperspective of the two-level structuring of scientific theories.

The contextual measurement model (CMM) that was invented in Chapter 10 representsthe wide range of non-Bayesian procedures for probability updatebased on context updates (or state updates). In this chapter we compareBayesian classical probability inference with general contextual probabilityinference. CMM is the basis of the Växjö interpretation of quantum mechanics,one of the contextual probabilistic interpretations. This interpretationhighlights that quantum update of probability (based on the state update)is one of the non-Bayesian updates. Quantum mechanics is interpreted as aprobability update machinery.

An overview of General Relativity is provided to a basic level. Its different nature with respect to the Newtonian Universal Gravitation is outlined. A cursory resume of the post-Newtonian approximation and its importance in testing Einstein’s theory is offered. A brief overview on the modified models of gravity that appeared in the last decades is outlined. A plan of the book is provided.

To address the fundamental question of ‘Are we alone?’, a cornerstone of astrobiology, it is necessary to search for signatures of extraterrestrial life (biosignatures). This chapter is thus divided into two parts: in situ biosignatures and remote-sensing biosignatures. In the first, a variety of potential biomarkers are described, such as isotope ratios, individual and collective microfossils, homochirality (i.e., presence of molecules of the same handedness), distributions of biomolecular building blocks, and agnostic methods. In the second, the categories include gases (e.g., molecular oxygen and methane), surface components (e.g., pigments like chlorophylls), and temporal variations of certain features. This chapter concludes by delineating emerging criteria and techniques for evaluating the credibility of putative life detection.

We start with discussion on Bohr’s response to the EPR argument andexplain how Bohr was able to sail between Scylla (incompleteness) andCharybdis (nonlocality) towards the consistent interpretation of quantumtheory. We call the latter the Bohr interpretation and distinguish it fromthe commonly used orthodox Copenhagen interpretation. We point to connectionbetween the complementarity principle and the information interpretationof QM and briefly discuss its versions, starting withSchrödinger and continuing to the information quantization interpretation(Zeilinger, Brukner), QBism (Fuchs et al.), reality without realism (RWR,Plotnitsky), the Växjö interpretation (Khrennikov), and derivations of thequantum formalism from the information axioms (e.g., D’Ariano et al.). Oneof the main distinguishing features of the information interpretation is the possibility of structuring thequantum foundations without nonlocality and spooky actionat a distance.

This chapter discusses the requirements for a world to be deemed habitable at a given moment in time (instantaneous habitability), with an emphasis on the availability of energy sources and suitable physicochemical conditions. After a brief exposition of some concepts in thermodynamics, the significance of the molecule ATP (the ‘energy currency’ of the cell) and how it is synthesised in the cell by harnessing chemical gradients is described. The two major sources of energy used by life on Earth (chemical and light energy), and the various possible pathways for utilizing such forms of energy are sketched, most notably photosynthesis and methanogenesis. This is followed by delineating the diverse array of extremophiles that inhabit myriad niches on Earth that would be considered harsh for most life. The mechanisms that permit them to survive the likes of high/low temperatures, pressures, salinity, and radiation doses are reviewed.

In this chapter the contextual measurement model (CMM) is employed forprobabilistic structuring of classical and quantum physics. We start with CMM framing of classical probability theory (Kolmogorov 1933) servingas the basis of classical statistical physics and thermodynamics. Then weconsider the von Neumann quantum measurement theory with observablesgiven by Hermitian operators and the state update of the projective typeand represent it as CMM. The quantum instrument theory is a generalizationof the von Neumann theory permitting state updates of the non-projectivetype and it also can be represented as CMM. We also show connectionof the generalized probability theory with the space of probability measureswith CMM. Finally, linear space representation for contextual probabilityspace is constructed by using the construction going back to Mackey.

This chapter is aimed to dissociate nonlocality fromquantum theory. We indicate that the tests on violation of the Bell inequalitiescan be interpreted as statistical tests of observables local incompatibility.In fact, these are tests on violation of the Bohr complementarityprinciple. Thus, the attempts to couple experimental violations of the Bell-type inequalities with “quantum nonlocality” are misleading. These violationsare explained by the standard quantum theory as exhibitions of observablesincompatibility even for a single quantum system. Mathematically this chapter is based on the Landau equality. Thequantum CHSH-inequality is considered withoutcoupling to the tensor product, We point out that the notion of local realism isambiguous. The main impact of the Bohm–Bell experiments is on the developmentof quantum technology: creation of efficient sources of entangledsystems and photodetectors.

In this chapter contextual probabilistic entanglement is represented withinthe Hilbert space formalism. The notion of entanglement is clarified anddemystified through decoupling it from the tensor product structure andtreating it as a constraint posed by probabilistic dependence of quantum observablesA and B. In this framework, it is meaningless to speak aboutentanglement without pointing to the fixed observables A and B, so thisis AB-entanglement. Dependence of quantum observables is formalized asnon-coincidence of conditional probabilities. Starting with this probabilisticdefinition, we achieve the Hilbert space characterization of the AB-entangledstates as amplitude non-factorisable states. In the tensor productcase, AB-entanglement implies standard entanglement, but not vice versa.AB-entanglement for dichotomous observables is equivalent to their correlation. Finally, observables entanglement is compared with dependence of random variables in classical probability theory.