Cosmic Ray Physics: An Introduction

Who has not gazed with wonder at the night sky, especially from a dark site far away from city lights? The great canopy of stars stretching overhead suggests that our world is part of a vastly larger cosmos. But how large is it? Where do we fit in? And how did it all begin? These questions have puzzled stargazers for thousands of years, and the search for answers helped spark the great advances of the scientific revolution in the 16th and 17th centuries. But only in our own time has the full picture of the true immensity, variety, and surpassing strangeness of the Universe come into focus.

Beyond the four centuries of sunspot observation and the five decades during which artificial satellites have monitored the Sun – that is to say for 99.99999% of the Sun’s existence – our knowledge of solar history depends largely on analogy with kindred main sequence stars, on the outcome of various kinds of modelling, and on indirect measures of solar activity.