Quantum Darwinism demonstrates not only that preferred states are selected for their stability but also that information about them is broadcast by the same environment that causes decoherence and einselection. That environment acts both as a censor and as an advertising agent that disseminates information about pointer states while suppressing complementary information. Chapter 8 explores the implications and limitations of quantum Darwinism using models inspired by the structure of the Universe we inhabit. We perceive our Universe using light and other means of information transmission. We explore models that have a well-defined relation with our everyday reality, and where one can also selectively relax some of the idealized assumptions and investigate the consequences. Light is the communication channel through which we obtain most of our information. Fortunately, it is an ideal channel in the sense of quantum Darwinism, and simple but realistic cases are exactly solvable. The solution presented herein demonstrates the inevitability of the consensus between observers who rely on scattered photons: The emergence of classical objective reality (classical because pointer states are einselected, and objective because redundancy imposes consensus) is inevitable. This is how the classical world we perceive emerges from within the quantum Universe we inhabit.

Dust impacts observations of stars and gas in galaxies by absorbing and scattering photons. Correctly accounting for the effects of dust allows for more accurate studies of a galaxy's stars and gas while also enabling the study of the dust grains themselves.The impact of dust on measurements of individual stars in a galaxy can be straightforwardly modeled as extinguishing the stellar light. Dust extinction towards a star is defined as the combined effect of absorption of photons and scattering of photons out of the line-of-sight towards the star. For integrated measurements of regions of galaxies or whole galaxies that contain multiple stars intermixed with dust, the effects of dust are termed attenuation and are harder to model. Integrated measurements include stars extinguished with different amounts of dust and scattering of photons into the measurement aperture. The infrared dust emission powered by the absorbed photons provides a vital measurement of the amount of energy absorbed by dust. This infrared measurement is not possible for individual stars butprovides an important constraint in modeling the effects of dust on integrated measurements. The aim of this chapter is to provide the details of dust extinction, attenuation, and emission and recommendations for how to model the effects ofdust on observations.