Producers: Coast Learning Systems

The discussion of galaxies continues in this lesson by focusing on a special group of galaxies with very energetic cores called active galaxies. Different types of active galaxies are introduced, from Seyfert galaxies and blazars to quasars.

Some of the most profound questions are asked and discussed in the complex subject of cosmology. What shape is the universe? How did it begin? How will it end? Evidence is presented that supports the big bang theory, and the exciting notion of dark energy is introduced.

Opening with a survey of the solar system and an examination of the solar nebula theory that explains how our solar system was formed, this lesson also reviews how the spinning solar nebula formed a disk of dust particles that eventually became the planetesimals that formed the planets. The actual detection of planets around distant stars is given considerable coverage, with experts describing the newest techniques and the successes achieved.

Using Earth as the archetypical example, this lesson details the stages of differentiation, cratering, flooding, and surface evolution. The impact of plate tectonics is presented as the formation and evolution of Earth is detailed. Comparisons are continuously made to the other terrestrial planets.

This lesson begins with an explanation of the processes that allowed the planets in this part of the solar system to grow to such large sizes. How the gravity of Jupiter produces tidal heating of Io and Europa, causing the extensive volcanic activity on Io and a liquid ocean beneath the surface of Europa is explained. Saturn’s interior and atmosphere are compared with those of Jupiter. The formation and characteristics of the ice giants Uranus and Neptune are also discussed.

This examination of solar system “debris”: meteorites, asteroids, and comets concludes the exploration of the solar system. Astronomers explain the composition of the different types of meteorites and various theories about their origin. Images, including that of the Deep Impact Probe hitting Comet Tempel 1 in July of 2005, are used to illustrate the characteristics of comets as described by astronomers. The lesson also includes a discussion of the demise of the dinosaurs and the discovery of the crater in the Yucatán that may have been the impact site.

Scientists discuss the possibility that the early seeds of life on Earth were delivered by comet impacts and the reasons why it is believed that the first life began on the deep seafloor near hydrothermal vents. The discussion continues with a look at Europa’s subsurface ocean and the pros and cons of life forming in that hostile location. The life zone or habitable zone of a star is defined and the efforts to detect signatures of that life using future spacecraft missions are described. The efforts and difficulties of communicating with an intelligent extraterrestrial civilization are discussed.