In the spring of 2020, The Event happened. With everyone stuck at home and not being able to see anyone, online resources boomed. In an effort to keep myself sane, and to share my love of astronomy, I started to offer (mostly) weekly public talks about various astronomy-related things. I talked about the life and death of the Universe, about my research project, about where life is in the universe, what the Star of Bethlehem could’ve been, and some more complex things, like an introduction to dark matter, spiral galaxies, and a tour of the solar system.
However, while those presentations were good, they were sometimes aimed a little too high. Essentially, I was giving talks I would’ve given to a class of astronomy majors rather than the general public. The astronomy talks went on hiatus during the winter holidays so that everyone could spend safe, socially distant time with their families and so that I could recuperate from having to come up with a talk every week.
The astronomy talks have now returned in the Spring of 2021, nearly a year after The Event. This time, my goal is to rectify some of the mistakes I made the previous year. To do that, I’m calling these talks “Astronomy 101.” As the name suggests, I’m taking everything from a more basic level, spending time walking through basic mechanics, the nature of light and matter, and then moving on to the solar system and diving into stars and galaxies. Basically, walking through The Cosmic Perspective textbook.
Furthermore, in an effort to be considerate of people’s time, if someone is unable to attend the in-person virtual lecture (what a weird combination of words), I have pre-recorded each lecture and posted them to YouTube for people to watch at their leisure. I’m going to make this page a sort of landing page for those videos, keeping them updated with a summary of each (roughly) hour long video.
The first in the lecture series is titled “Introduction to the Universe.” In this talk, we cover the size and scale of the Universe, in both the space and time dimensions. We also talk about the various motions the Earth goes through: rotating on its axis, orbiting the Sun, the Sun orbiting the center of the Milky Way, as well as moving randomly with respect to the local stars, and the Milky Way moving in an expanding universe. We end with a brief mention of the human adventure of astronomy. (Presented on February 28, 2021)
The second in the series is titled “The Night Sky.” Here, we talk about how we understand the things we see in the night sky given our understanding of the Universe. We talk about the celestial sphere, why stars change depending on the time of year, and how the seasons work. We also go into detail about the phases of the Moon and how both lunar and solar eclipses work. We end by mentioning the weird apparent retrograde motion the planets go through and hint at what the Greeks attempt to solve in next week’s talk. (Presented on March 7, 2021)
As any good astronomy teacher will tell you, eventually we have to talk history. In this “The Science of Astronomy” lecture, we delve into the ancient Greek origins of astronomy, talking about the geocentric model of the universe. Then we delve into the Copernican revolution and talk about the personalities of Copernicus, Tycho, and Kepler. Especially important are Kepler’s Laws of Planetary Motion! We end with a discussion of what makes science science. (Presented on March 14, 2021)
To talk about the goings-on in the universe, it is necessary to have an understanding of “Motion, Energy, and Gravity.” Here, we talk about just that! We spend some time getting our definitions straight, before moving on to the man of the hour, Isaac Newton, and his laws of motion. We explore the deeper truths that are the conservation laws and how to apply them. Then we talk about gravity and explain how gravity works to create orbits, the tides, and Galileo’s Leaning Tower of Pisa Experiment. (Presented on March 21, 2021)
Except for a few objects, astronomers can’t go to an object and physically measure its properties. That’s why its important to understand how “Light and Matter” interact and how we can deduce the nature of an object from the light it emits or reflects. We talk just about that in this lecture, covering the types of spectra, and how we can tell the composition, temperature, and motion of an object from its light. (Presented on March 28, 2021)
Last week we talked about all of the information we can learn from light, now we need to talk about how to collect that light and that means “Telescopes!” Essentially astronomers want telescopes to be the biggest they can be to maximize light-collecting area and to minimize the angular resolution. We talk about how astronomers use those telescopes to do imaging observations, spectroscopic observations, and timing observations. We also explain the three main reasons why ground-based observing is limited and explore the wide variety of telescopes we put in space to observe the entire electromagnetic spectrum! (Presented on April 4, 2021)
We’ve finally done it! We’ve finished with the basic physics lessons and we can move on to give an “Introduction to the Solar System!” Here, we introduce the idea of comparative planetology and use it to describe the four types of basic patterns we see in the solar system. In order to do that, we go through a brief tour of the planets, the first and last time we will do that in this series. We end by describing the types of spacecraft that we use to learn about the planets and other objects in the solar system. (Presented on April 11, 2021)
We sort of ended last week on a cliffhanger, having talked about all of these large-scale patterns that we see in the solar system without explaining how they came to be. We attempt to do just that by explaining the “Formation of the Solar System.” We cover the nebular theory and how it accounts for those patterns very well. We show the pieces of evidence, both observational and computational, that support the theory as well as explaining that this wasn’t all “planetary destiny.” We end with a brief talk on radiometric dating and the age of the solar system. (Presented on April 18, 2021)
In this talk, we make our first attempt at comparative planetology by discussing the general geological processes that have shaped the “Planetary Geology” of each world and then diving into how those processes explain the features we see on each world individually. We find that Mercury and the Moon are both heavily cratered worlds with no geologic activity as of late, that Mars is slowing down in its geologic activity, and Venus and the Earth should both still be geologically active! (Presented on April 25, 2021)
After having discussed the surfaces of the terrestrial worlds, we now move to a discussion of their “Planetary Atmospheres.” Using the Earth as a template to our understanding, we discuss the basic atmospheric processes occurring on Venus, Earth, and Mars. We learn that the greenhouse effect isn’t all bad and is actually necessary for liquid water to exist on the surface of Earth. We end our discussion with a brief introduction to human-caused climate change and the consequences of inaction. (Presented on May 2, 2021)
We are now done with the terrestrial planets and we can finally move to the outer solar system and “The Jovian Planets.” This time we use Jupiter as a template to discuss the internal structures and atmospheres of each of these gas giants. Since they don’t have surfaces for us to geologize, we instead turn our attention to the plethora of moons that encircle each planet. We end with a brief discussion on their ring systems. (Presented on May 9, 2021)
This is the last talk about our solar system! We finally catch up with all the smaller things we’ve been sidestepping along the way, the “Asteroids, Comets, and Dwarf Planets!” After giving a brief history of those terms, we talk about the asteroids and comets in detail, covering both their physical properties and orbital properties. Then, we talk about the only dwarf planet we really know tons of information about: Pluto! Hopefully, I’ve illustrated just how much information New Horizons gave us when it flew by Pluto in 2015. We end by talking about impacts by asteroids and comets, including two relatively recent ones, both in Russia. (Presented on May 16, 2021)
Rounding up our large section on solar systems is all of the other “Exoplanets” in the Galaxy! The main problem with finding exoplanets is exactly that: finding them. There are three big methods that astronomers tend to use and we talk about all three of them and the biases inherent in these detection methods. We also compare the known exoplanets to the planets of our solar system and find that there are a wider variety of exoplanets than what we have in our solar system. Do we have to rethink our nebular theory of solar system formation? (Presented on May 23, 2021)
Now that we’ve ended our journey through the solar system, we’re taking a quick break from astronomy to brush up on our relativity! In “Space and Time” we talk about how Einstein’s Theory of Special Relativity says that all motion is relative, but that the speed of light is an absolute. We explore these concepts by using thought experiments, where, with two key assumptions, the results of time dilation, length contraction, and mass increase follow logically. (Presented on May 30, 2021)
Just as Einstein did after discovering special relativity, we will also generalize it to general relativity. In “Spacetime and Gravity” we leave the thought experiments behind and discuss the equivalence principle, and the multidimensional nature of spacetime. Obviously this new view of the universe has some profound effects on our understanding of it and we see how general relativity leads naturally to the idea of black holes and gravitational time dilation and redshift. But don’t take my word for it, there are several easy-to-understand experiments that verify general relativity as well! We’ll discuss them all. (Presented on June 6, 2021)