How dark is the universe? Optically – for visible light. Far away from star light and reflected dust. Here’s an interesting perspective on electromagnetic (EM) cosmic energy density – just for optical wavelengths. And without any clarification of fuzzy bounds for a galaxy’s reach. The entire electromagnetic spectrum is another story. • Live Science >… Continue reading How dark is the universe – optically?
Table of contents IntroductionAbout gamma photonsSolar gamma photons INTRODUCTION Rays, radiation, particles, waves, fields … what’s in a name, eh? There’s a history [1], an evolution of discovery and understanding. So that sometimes a “particle” by another name is something more interesting [2]. While quantum field theory (QFT) has penetrated the way many physicists think… Continue reading Gamma photons – formerly known as rays – the extreme EM spectrum
Ask people on the street “What are X-rays?” and you’ll likely get a variety of replies. About medical and dental X-rays. Stories about Superman’s X-ray vision. (Why does lead block X-rays?) Invisible particles that allow us to see through stuff. Technical explanations about electromagnetic radiation. So, street surveys typically reveal levels of understanding, which I’ll… Continue reading Levels of understanding – what are X-rays?
