The End of Everything
Class Description
Today we will try to stretch our minds as we consider the scope of the entire universe, its past, its present and its distant future.
Once it was realized that the universe is expanding, and light we see from other galaxies is coming from a distant past, astronomers developed a way of measuring their distances using a sort of ladder process called the Cosmic Distance Ladder. It utilizes geometric ways of estimating nearby stellar distances and then bootstraps out using the concept of a Standard Candle. Today they can measure distances to objects that formed shortly after the Big Bang, dating back almost 13 billion years in our past. I highly recommend viewing this video, a nice description of the Cosmic Distance Ladder measurement process.
We then shift attention to what is probably the most important cosmological discovery of the 20th century: Hubble’s Law, which is an observation that an object’s distance from us is proportional to its apparent recessional speed (using our old friend the Doppler shift) indicated by the red-shifting of its light as it travels these great distances to reach us today. The proportionality constant is called Hubble’s Constant. Its inverse is the approximate age of the Universe: 13.8 billion years.
This realization implies a beginning, and residual radiation we can still see indicates the Universe started with a very hot Big Bang. Following this moment of creation, the Universe passed through (very quickly!) some major transition points. These are illustrated in this video, which includes physicist Sean Carroll from Cal Tech who is known for popularizing fundamental physics. A key element of this video is what is called vacuum fluctuations – even in a vacuum there is a lot going on. The Heisenberg Uncertainty Principle guarantees such fluctuations. This phenomenon, as it manifested in the early Universe, is responsible for galaxies and stars and our planet as we know them today.
We conclude the class with description and discussion of possible distant futures based on extension of current evolutionary model(s) and possible variations in the components of that model, especially Dark Energy. Scenarios include the Big Crunch, the Big Rip, Heat Death, Vacuum Decay and the Big Bounce. At the end we engage in some fanciful, if not technically excluded, speculations on the behavior of a totally “empty” ever-expanding universe.
