Big Bang Cosmology: The Origin and Fate of the Universe

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This is the fourteenth and final lecture series of my complete online introductory undergraduate college course. This video series was used at William Paterson University and CUNY Hunter in online classes as well as to supplement in-person course material. Notes and links are present in the videos at the start of each lecture.
0:00:01 - Cosmic Homogeneity and Isotropy
0:32:18 - The Big Bang
1:23:44 - Why Does Cosmic Expansion Cause Redshift?
1:40:43 - The Cosmic Microwave Background.
2:41:44 - The First Three Minutes of the Universe
3:34:11 - Formation of Large-Scale Structure in the Universe
4:21:47 - Cosmic Inflation
5:28:37 - Dark Energy, Supernovae and the Ultimate Fate of the Universe
The Universe on the largest scales is very self-similar. It looks about the same no matter which way you look, and it’s also made up of the same stuff pretty much everywhere. This leads us to the Cosmological Principle which codifies this isotropy and homogeneity, which asserts that the universe has the same physical laws everywhere. Next, we run the clock backwards in time, and we see how, using the fundamental principles of classical physics, especially thermodynamics, that the universe was smaller and hotter ago. We see exactly what we mean by the Big Bang, and what it covers and what it does not cover. The Standard Hot Big Bang basically is a story from only about the first few billionths of a second until today. It’s just amazing what exactly we can do with classical physics and elementary general relativity. Frequently, people don't understand why expansion means that light gets redshifted. Here I link the two ideas. What causes the redshift of light, how do represent it mathematically? What exactly gets stretched? Everything is a measurable, and redshift is one of those things. As part of this, we study the expansion in great detail, outlining the Robertson Walker Metric, a solution to the Einstein Field Equations of General Relativity. The discovery of the Cosmic Microwave Background is regarded as one of the most important of all science, as it is relic radiation from its early hot, dense epochs. We see that it was a key prediction of the Big Bang, which was discovered by accident by Penzias and Wilson. By studying the microwave sky in detail, the COBE, WMAP and Planck probes of NASA and ESA have shown us that the CMB is a perfect blackbody, at the temperature 2.7 Kelvin. When we study the tiny fluctuations and anisotropies away from this near-perfect spectrum, we find that we can learn what the universe was like when it was roughly 350,000 years old. We we watch atoms combine together for the first time, letting light slip free to come to us 13.6 billion years later. This observation alone is proof of the Big Bang. The story of the universe in its infancy is actually well-known from Classical Physics. We follow the classic book by the same name on a journey back to when the universe was 180 seconds old. We find nuclear fusion in the early cosmos. Even more convincing than the cosmic microwave background, the ratio of hydrogen to helium that was fixed in these early moments is greater proof of the Big Bang. This ratio is seen in the most ancient stars, who still carry the original composition of the birth of the universe. Large-scale structure formation in the universe is the final pillar in the Hot Big Bang Standard Model. We learn why galaxy clusters have so much hot gas, and how the absorption features in distant quasars came to be. We also see how the dark matter distribution can be mapped by its effect on galaxy's light and on the shape of clusters too. The Inflationary Epoch happened when the universe was extremely young. During the Grand Unified Theory (GUT) Era, the universe became the nearly flat, critical-density Cosmos we see today. In order to understand it, we use Quantum Gravity to approximate the wild phase transitions that must have occurred in order to force the expansion of space at speeds exponentially greater than light! Oddly enough, this epoch can be observed as effects of gravitational waves on CMB. The Inflationary Epoch solves a number of problems associated with the Standard Big Bang model and raises some wild questions about the nature of the origin of the cosmos. The discovery of Dark Energy in 1998 by two teams helped us learn what will happen at the end of the Universe. Their competing studies of deceleration parameter using Type Ia supernova discovered Dark Energy, the cosmic negative pressure that’s pushing the universe apart was confirmed by WMAP and Planck. It’s possible that dark energy may, in fact, be a Phantom Energy, which will cause a Big Rip as the universe accelerates exponentially in its expansion. There could also be a grand heat death of the cosmos where it just gets larger and darker and colder for all time.

[@RajeshSingh-Bhangu]

Excellent analysis

[@edd.]

This is awesome!! Fantastic job! Thank you

[@arthurwieczorek4894]

So, is time in the universe or is the universe in time? Is there another possibility? At this level of abstraction it might be helpful to recount Lee's Elucidation: A finite number of words must be made to represent an infinite number of things and possibilities.

[@arthurwieczorek4894]

'Density is destiny' is certainly true for stars.

[@cliffferguson9024]

Very well said

[@josephshaff5194]

When do we separate from the Astronomy / Astrophysics Majors or do we ever really ? Running a dual Career.

[@kapsi]

That's a big one

[@ramlakkan9056]

Thanks 😊 😊😊😊

[@JasonKendallAstronomer]

Welcome 😊

[@deltalima6703]

5:46:00 "normal matter, and dark matter, w=0. For relativistic matter, like light or nuetrinos, w=1/3..." Confusion here. Neutrinos are dark matter. They are hot dark matter, but hot vs. cold was never mentioned. Is there a difference on w for the two? Why?

[@JasonKendallAstronomer]

Actually, neutrinos are a bad candidate for dark matter. Back in the '90s HDM was considered, but then discarded when it was understood that it would smooth out the matter density lumps and force galaxy formation to come much later....

[@kennethessenwanger268]

Jack and Jill went down a hill To fetch a pail of Hawking particles. Jack fell down and broke his gluon crown, While Jill was observing after. Jack looked up to Jill, he thought: To her he could not caper. He went to bed and wrapped his head in the singularity and black paper.

[@EKDupre]

That's a beauty💙

[@Lefejame123]

Let's gooooo

[@deltalima6703]

6:24:30 Sounds like the universe is homeopathic. No wonder scientists are mad. :D

[@deltalima6703]

For medicine you use the most powerful poisons, nightshade for example, (just like a real idiot would); but you dilute it. And the more times you dilute by half, the better the medicine works. Supposedly. End result is selling bottles of placebo in place of medicine, and it makes scientists livid.