ASTRONOMY 112 Stars, Galaxies, and Cosmology INTRODUCTION The Nature of Astronomy and Astronomy By Definition Scale, Structure, and a Tour of the Universe The Hierarchy of the Distribution of Matter Fundamental Forces The Seven Unique Things in the Universe Scale of the Cosmos Powers of Ten Composition of the Cosmos The Nature of Space and Time

The Nature of Astronomy “Looking at the stars always makes me dream- as simply as I dream over the black dots representing towns and villages on a map. Why, I ask myself, shouldn’t the shining dots of the sky be as accessible as the black dots on the map of France?” Vincent Van Gogh 1889

The Nature of Astronomy The inaccessibility of cosmic phenomena is one of the most intriguing features of the study of astronomy Although technology has greatly increased since the time of the ancients, astronomy remains primarily a passive science Experimental, Empirical but Primarily Observational Science Still provides great insight into the origin, history, evolution, and underlying physics and chemistry of celestial phenomena and the universe itself…

The Nature of Astronomy Since pre-history people have gazed into the sky and pondered the nature of the universe All early civilizations studied the stars and the motions of the five naked-eye planets known to them as the “wanderers” They used their observations to tell time, for navigation, to predict the coming of seasons, to explain eclipses, and to reinforce their religious beliefs Now, we apply empirical methods of science to understand the physical nature of these phenomena Now, we can explore with humans, robotically, and passively from great distances

Pseudoscience vs. Real Science Astronomy, By Definition Astrology, By Definition Empirical Science vs. Pseudoscience Scientific Models and Testing

Astronomy, by Definition the science concerned with celestial objects along with the observation and interpretation of the radiation from the component parts of the universe

Astrology, by Definition the ancient belief that the positions of the sun, moon, and planets with respect to the zodiac influenced earthly affairs and human lives

Astronomy, Astrophysics, and Cosmology Golden Age of Astronomy NASA’s Great Observatories Enormous telescopes worldwide and on orbit New Generation of Extremely Large Telescopes Planned Still, fundamental secrets of the universe remain mysterious The nature of dark matter, dark energy Era of the first stars The evolving decelerating, then accelerating universe

The Structure of the Universe Is the universe continuous, or discontinuous? Is the universe homogenous or inhomogeneous? Does the universe end? Levels in the hierarchy Fundamental forces that govern everything GUTS and TOES Laws of physics are ubiquitous

Hierarchy of the Distribution of “Luminous” Matter From quarks to the cosmos… 12 levels in the hierarchy… Fundamental Forces Cosmic Irony: The simplicity and complexity of the universe... Scale of the Cosmos Luminous matter does not include “dark” components

Scale of the Cosmos Supplemental Presentation…

Powers of Ten Supplemental Video…

The Universe in a Nutshell Matter Energy Dark Matter Dark Energy Time Space and

Size of the Universe Supplemental Presentation…

The Nature of Space and Time Space and Time are Different Aspects of the Same Phenomenon Into the Past Light Travel Time and the History of the Universe

Time required for light to travel to earth Into the Past Time required for light to travel to earth Moon 1.25 seconds Sun 8.5 minutes Centauri 4.5 years Betelgeuse 1,200 years Milky Way 100,000 years Andromeda 2.2 million years Virgo Cluster 60 million years Hydra Super Cluster 3 billion years Quasars 13 billion years Cosmic Microwave Background (CMB) 13.5 billion years