Unformatted text preview: AS 101 Lecture 2 AS Class Logistics: • If you did not get one last time, pick up:
Syllabus Problem Set 1 • Everyone should attend a day lab starting this week • Note: Will call on students. Last Class Today’s Class • Introduction to AS101 • Syllabus • Nature of Science & Astronomy • Time and Distance in Astronomy • The Celestial Sphere What is Astronomy? What One definition “The scientific study of material beyond the Earth’s Atmosphere” The scientific study of nature beyond the Earth’s atmosphere Astronomers also study the Earth What is Science? What One dictionary: To have knowledge Another: Principles and procedures for systematic pursuit of knowledge involving the recognition and formulation of a problem, the collection of data through observation and experiment and the formulation and testing of hypothesis What is wrong with these? Science requires Science Study of Nature Reductionism: a process of isolating components of complex phenomena into simpler independent components for study and explanation. Ocam’s razor: one should not increase, beyond what is necessary, the number of entities required to explain a phenomenon • Observation • Experimentation Nature of Science Nature Information is not science Any scientific idea can be overthrown Science is the process of building models of natural phenomena. Example: Mark Hylander: What is the difference between a scientific theory and a law? • Newton built a solar system model with the sun producing a gravitational field keeping the planets in their orbits. • Einstein built a better model of gravity because Newton’s Law of Gravity does not explain all observations. How old is the Universe? Universe? Matthew Goldberg: How old do scientists think the Universe is? The Cosmic Calendar
• • if the entire age of the Universe were one calendar year one month would be approximately 1 billion real years Time and Distance in the Universe Time Universal speed limit: Speed of light c = 3x108 m/s
• Nothing moves faster than c • The modern laws of physics disallow any transition from below c to above it No objects No energy No information Light, although fast, travels at a finite speed. It takes:
• • • • Looking back in time Looking The farther out we look into the Universe, the farther back in time we see! 1 second to reach us from the moon 8 minutes to reach us from the Sun 8 years to reach us from Sirius (8 lightyears away) 2.5 million years to reach us from the andromeda galaxy ...
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