The Big Bang and Beyond

The Big Bang and Beyond: Exploring the Early Universe
Gary Felder, PhD
Smith College
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The experience of watching this course was rather odd. First, it was taped when the COVID protocols at the Great Courses had the instructors sitting instead of standing, and always looking at one camera rather than turning from one camera to the other. Second, instructor Gary Felder has a rather odd demeanor. His quiet, measured tone projects the more of an image of Buddhist meditation instructor than a cosmologist.

But a cosmologist he is, and there is a lot of good material here. Felder goes through the basics of the big bang theory, describing the various phases of the process. The formation of the first stars, and after that the planets, solar systems, and galaxies, did not occur right away. That happened sometime between thirty million and two hundred million years after the big bang. And Felder tells us the big bang was not an explosion but simply the moment the universe started expanding. Cosmologists call this moment Planck Density, “the earliest moment we can describe with our currently known laws of physics.”

Felder explains the original theory of the big bang was pretty much accepted once Arno Penzias and Robert Wilson discovered the cosmic microwave background radiation (CMB). Before that a few cosmologists, most notably Fred Hoyle, believed the universe was a fixed, stable entity, what Hoyle and colleagues called the steady state theory. But although most scientists believed the CMB was sufficient proof of the big bang, there were several phenomena that the theory failed to account for. This is where the theory of inflation arose. Inflation posits that distances in the universe increased by a huge amount, perhaps 10^1,000,000 (that’s ten to the one million) in a fraction of a second. This explains many of the inconsistencies found in the original theory. I won’t go into them here, but Felder describes them in detail.

There are some theories that say just because the big bang happened as it did in our observable universe, it did not necessarily happen that way in the whole universe. There might be multiverses these theories say. That’s where cosmologists draw from quantum mechanics.

An open question is whether the universe will expand forever or stop expanding and collapse back into itself. That depends on the critical density of the universe. It turns out that the universe is so close to that critical density that we don’t know. At least that was the case until the discovery of dark energy. With dark energy in place the universe will expand forever. Unless dark energy decays. Then maybe it won’t.

Confusing, yes. But Gary Felder helps make all of this clear in his twelve lecture series.