The environment of FRB 121102 and possible relation to SGR/PSR J1745−2900

ABSTRACT Variations of the dispersion measures (DM) and rotation measures (RM) of fast radio bursts (FRBs) 121102 indicate magnetic fields ∼3–17 mG in the dispersing plasma. The electron density may be ${\sim}10^4\,$ cm−3. The observed time scales ∼1 yr constrain the size of the plasma cloud. Increasing DM excludes simple models involving an expanding supernova remnant, and the non-zero RM excludes spherical symmetry. The varying DM and RM may be attributable to the motion of plasma into or out of the line of sight to or changing electron density within slower moving plasma. The extraordinarily large RM of FRB 121102 implies an environment, and possibly also a formation process and source, qualitatively different from those of other FRB. The comparable and comparably varying RM of SGR/PSR J1745−2900 suggests it as a FRB candidate. Appendix A discusses the age of FRB 121102 in the context of a ‘Copernican Principle’.

EVIDENCE FOR INTELLIGENT EXTRATERRESTRIALS IS EVIDENCE AGAINST THE EXISTENCE OF GOD

The recent explosion in the discovery of exoplanets and our incipient ability to detect atmospheric biomarkers recommend reflection on the conceptual implications of discovering – or not discovering – extrasolar life. I contend that evidence for intelligent extraterrestrial life is evidence against the existence of God, because if there are intelligent extraterrestrials, there are likely to be evils in the universe even greater than those found on Earth. My reasoning is based on Richard Gott's Copernican Principle, which holds that in the absence of information to the contrary, we should take ourselves to be typical observers.

Cosmological spacetimes

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

The Copernican principle, intelligent extraterrestrials, and arguments from evil

The physicist Richard Gott defends the Copernican principle, which claims that when we have no information about our position along a given dimension among a group of observers, we should consider ourselves to be randomly located among those observers in respect to that dimension. First, I apply Copernican reasoning to the distribution of evil in the universe. I then contend that evidence for intelligent extraterrestrial life strengthens four important versions of the argument from evil. I remain neutral regarding whether this result is a reductio of these arguments from evil or the statement of a genuine evidential relationship.

Number Count of 2MRS Galaxies in the J, H, K Bands

The Copernican principle has been the motivation for the present study on the number density of galaxies. In this work we have carried out a number count of galaxies in the 2MRS catalog in the K, H and J bands. The results presented here have obtained on volume-limited samples with equal widths or redshift bins. The main result of this study is the number count of galaxies which have been plotted in concentric spherical shells with the observer at the center. The obtained result in the three bands show a similar behavior up to a distance of 1.7 × 102 Mpc and behave differently from there on.