IQ • Most changes in the appearance of the sky are caused by the Earth’s revolution. • T • F IQ • • False! “Revolution” refers to the orbital motion of the Earth about the Sun. These are “annual” changes that happen once per year. The seasonal (annual) changing of constellations depends upon revolution. Diurnal changes, for example, the transit of stars during the course of the night (or the sun during the day) are caused by the Earth’s rotation. Diurnal changes are far more obvious than annual changes IQ • Two theories that can explain the apparent (observed) motion of planets are the “geocentric” (Earth-centered) and “heliocentric” (Suncentered) models. The accepted model today is: A. Geocentric B. Heliocentric IQ • B. “Heliocentric” is the correct answer! • Ancient astronomers thought that the Earth was the center of the universe. Well, we’re not even the center of the solar system! The Sun is located at the center of our solar system. IQ • Sir Isaac Newton • When not inventing the calculus or defining gravitational force, Isaac worked as a stand-up comic across Europe. IQ – Schedule Information • Our first test is scheduled for Monday, 14 February. We are on schedule to have the test on this date. Plan on it! • On Monday, 7 February we will have a practice test to familiarize you with the type of tests you’ll see the rest of the semester. IQ • A planet moving in a circular orbit about a star experiences: • A. Good vibrations • B. Uniform motion • C. Accelerated motion • D. The Taos Hum IQ • C. Accelerated motion is correct. • The planet is in a closed orbit, therefore it is bound to the star by the force of gravity. Where there is a force, there is an acceleration. • E.g. F=ma, where F is the force on mass m resulting from acceleration a. IQ • Parallax is a direct technique to measure the distances to nearby stars by using: • A. Cepheid variables • B. The distance ladder • C. One’s thumb • D. Trigonometry IQ • The answer is D, trigonometry. • Parallax is the measurement of the apparent motion of nearby star relative to much more distant stars caused by the revolution of the Earth about the Sun. IQ • Light is one form of electromagnetic radiation. • T • F IQ • True! • Electromagnetic radiation carries to us most of the information we ever get from the universe. It is characterized by its “wavelength.” Radio waves are very long wavelength and x-rays are very short wavelength electromagnetic radiation. The wavelength of light is in between. BREAKING NEWS! • These are the primordial thermal fluctuations present at the creation of the universe 13.7 billion years ago! • The amplitude (red to blue, or hot to cold) is approximately 1 x 10-5 Kelvins.