The magnetic and cosmic ray and gravitational energy in some interesting astrophysical systems. --- A “how-to do-it” overview of some methods, and what they reveal.
Beginning with radio observations in the 1960’s and 70’s, I show some of the first Fourier synthesised images of extended, polarized extragalactic radio sources. I discuss their energy contents, their association with “singularities” at the nuclei of galaxies and how they spread part of their rest mass energy into nearby intergalactic space.
Separately, I describe some first attempts to obtain the global mass, or “weigh”, individual intervenor galaxies through weak gravitational lensing of extended, polarized background objects.
If time remains, I show, with examples, how recent ultra-high energy cosmic rays (UHECR’s) can be exploited used to probe magnetic fields in the “local” extragalactic Universe.