Summary
The discussion centers on the expansion of the universe and the contrasting theories that emerged in the mid-20th century to explain this phenomenon. The Big Bang theory posits that the universe began from an initial singularity, leading to a denser and hotter past, while the steady state theory suggests that as the universe expands, new matter is continuously created to fill the void, maintaining a constant density over time. This debate was not only scientific but also philosophical, with proponents on both sides often influenced by their personal beliefs.
In the 1960s, evidence began to favor the Big Bang theory, notably through the discovery of quasars and the cosmic microwave background radiation. Quasars, which are distant and energetic celestial objects, revealed that the universe's composition has changed over time, supporting the notion that the universe was once denser and hotter. The cosmic microwave background provided further evidence of a hot, dense early universe, aligning with predictions made by the Big Bang theory.
The conversation also touches on the implications of these theories for understanding the age and fate of the universe. Calculations based on the Hubble constant suggest the universe is approximately 17 billion years old, although this estimate may be adjusted as new data emerges. The density of the universe plays a crucial role in determining its ultimate fate, whether it will continue to expand indefinitely or eventually collapse back in on itself. The ongoing exploration of these questions highlights the dynamic nature of cosmological research and the evolving understanding of the universe.
Show Notes
Frontiers/Controversies in Astrophysics (ASTR 160)Uploaded 29-09-08Professor Bailyn returns to the subject of the expansion of the universe to offer explanations that do not require belief in the Big Bang theory. One alternative is a theory that, in the past, the entire universe was reduced to an "initial singularity," in which everything was much closer, and therefore denser and hotter. Since the universe is in constant flux, however, it follows that in the future things will drift apart. The Steady State explanation for the expansion of the universe is then explained. Coined as a derogatory term meant to ridicule supporters of the Big Bang theory, Steady State purports that new energy and matter are constantly created as the universe expands, to fill in the void that results from the expansion. The discovery of quasars refuted the Steady State theory. The lecture ends with a discussion of how observing very distant objects allows us to look back in time, and also gives us a glimpse into the future of galaxies and the universe.00:00 - Chapter 1. The Expanding Universe -- Big Bang and Steady State Theories09:53 - Chapter 2. Quasars and the Rejection of the Steady State Theory32:21 - Chapter 3. Calculating the Duration of the Big Bang43:16 - Chapter 4. Calculating the Potential Future of the UniverseComplete course materials are available at the Open Yale Courses website: http://open.yale.edu/courses This course was recorded in Spring 2007. Learn more about your ad choices. Visit megaphone.fm/adchoices Learn more about your ad choices. Visit megaphone.fm/adchoices
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