Astronomy ABCs: C is for Cepheids

Aaaaaaand we’re back. Third month in a row. Did I forget that November is Thanksgiving month and because of that I need to get a post out this week or else it won’t happen? Almost. This post is based heavily on a public talk I gave a couple of years ago, so maybe it’s cheating a little. No matter. I’m here and ready for more Astronomy ABCs. We’re on letter C, and C is for Cepheids. Cepheids have an enormous role to play in the development of extragalactic astronomy, or the study of galaxies beyond the Milky Way.

Below is the Hubble Extreme Deep Field Image. It’s a combination of two Ultra Deep Field images taken in 2002 and 2003 and the Hubble Ultra Deep Field Infrared image, taken in 2009. This image represents a tiny sliver of the sky, the equivalent area of a tenth of the area of the full moon, and it captures the light from over 5000 galaxies, some of which are so distant that we see them with the Universe was 5 percent of it’s current age.

Nearly everything in this image is a galaxy. Image credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team

When I think of the Universe, this is part of what I think of. Huge expanses of both space and time, stretching out in all directions. Entire galaxies that look like grains of sand under a microscope. This is our modern view of the Universe. It wasn’t always that way.

The Universe, before 1920 or so, was the Milky Way Galaxy and not much else. It is true that every individual star you see in the night sky is a Milky Way star. But it’s not that we couldn’t see other galaxies. Even today on a very dark night in a very dark place you can see the Andromeda Galaxy by eye in the Northern Hemisphere and the Large and Small Magellanic Clouds in the Southern Hemisphere.

As far as astronomers of the early 20th century knew, these fuzzy patches that we know as galaxies were what they called ‘spiral nebulae,’ regions in the Milky Way made up of primarily gas with a few stars. Back then we had no real way of telling how far away these objects are, and so no real way of telling how big those objects are.

Astronomers really had one method of determining distances in space, and that is the parallax method.

Parallax

Parallax takes advantage of some well known features of trigonometry and the Earth’s movement through space to measure distance of relatively nearby objects. Here’s how it works.

Let’s say, for example, that you’re riding your bike down a straight bicycle path and in the distance you see a beautiful tree standing alone in a field with a mountain in the distance. You notice at first that the tree is to the right of the mountain. Your point of view might look something like what is in that blue box.

You see the tree relative to the background mountain.

As you ride on, your perspective on the scene will change. Now your point of view will look more like what is in the yellow box. The tree and the mountain are aligned.

Your point of view has changed!

And now you’ve gone even further and your perspective changes again. Now it will look to you that the tree is on the left of the mountain.

Your point of view changes again!

You’ve probably noticed this phenomenon before. Driving down the highway, things close to the road look like they are going by extremely fast, whereas things far away move much more slowly or not at all.

This is what happens with parallax. Just replace the tree with a nearby star and the mountain with the stationary background stars. The background stars - like the mountain - are far away enough that they can be considered stationary.

OK, so how does this movement actually help us find the DISTANCE? This is where trigonometry comes in.

We can use the distance from the Earth to the Sun as a baseline, measure the resulting parallax angle, and calculate the distance.

Stellar parallax diagram, showing how the 'nearby' star appears to move against the distant 'fixed' stars when Earth is at different positions in its orbit around the Sun. Credit: Alice Hopkinson, LCO

You might be able to tell that this method of calculating distance is extremely limiting. As the object you’re trying to measure gets further and further away, the parallax angle gets smaller and smaller and gets harder and harder to measure accurately. So astronomers could use this method to measure close-by stars in the Milky Way, but it was not so useful otherwise.

So astronomers were extremely limited in their distances measurements. But they still tried, and through those efforts estimated that the Milky Way was 300,000 light years across. Which is, honestly, not a bad estimate. We know now that the Milky Way is about 100,000 light years across. Because most astronomers in the early 20th century thought that everything in the Universe was in the Milky Way, the size of the Universe was also considered to be 300,000 light years across.

Leavitt’s Law and Cepheid Variable Stars

It was in this context that Henrietta Leavitt started on her path to changing astronomy forever.

Leavitt was born on July 4, 1868 in Lancaster, MA and graduated from Radcliffe College in 1892. After she graduated she worked as a volunteer “computer” at the Harvard Observatory until she was hired officially in 1902.

There were many women working at the Harvard Observatory as so-called computers. This was their title, but really these women were astronomers. They were doing data analysis of data taken from telescopes around the world, just like astronomers do today. One of Leavitt’s fellow Harvard computers was Annie Jump Cannon - who developed the system we use today for classifying stars. Another was Williamina Fleming, who discovered the Horsehead Nebula and the first white dwarf star, which is the final stage of life for a star like our Sun. These women did complex calculations and made significant contributions to astronomy without the aid of modern technology.

When Leavitt was hired in 1902, she was assigned to work on measuring the magnitude of stars. In particular, Leavitt studied a type of star called a Cepheid variable star in the Large and Small Magellanic Clouds.

A variable star like a Cepheid is one that changes its brightness at regular periods. Cepheids were first identified in 1784, and they have a particular type of light curve, or how bright a star is over time. The light from a normal star may change a little bit with time, but not much and not on regular intervals. A Cepheid is different. A Cepheid becomes brighter and dimmer in a predictable way.

This plot shows how the brightness of the prototypical Cepheid - Delta Cephei - changes with time. The change is brightness is very regular, peaking every 5.4 days.

There are two types of Cepheid variable star: a Type I or Classical Cepheid and a Type II Cepheid. Type I Cepheids pulsate with a period of days or months and they tend to be the youngest stars, called population 1 stars. They are massive - 4 to 20 times more massive than the sun and up to 100,000 times brighter. In one pulsating cycle the radius of Type I Cepheids can change by millions of kilometers. Type II Cepheids have periods between 1 and 50 days and tend to be older, Population II stars.

Both types of Cepheids pulsate because of the same process:

• When a Cepheid is compressed, it becomes opaque. Light from inside the star cannot escape.

• Photons are now trapped inside, heating the gas and increasing its pressure.

• The high-pressure gas expands, and as it expands, it becomes transparent, meaning that light can escape from the interior of the star.

• Photons escape, the gas cools, the pressure drops.

• As the pressure drops, the Cepheid is compressed by gravity. And the process stars all over again.

Henrietta Leavitt made a couple of astonishing discoveries about Cepheid variables that would change astronomy forever. In 1908 she published her first paper on Cepheids, where the noted that the brighter Cepheids had longer pulsation periods. In 1912, Leavitt published a paper analyzing the periods and brightness of 25 Cepheids in the Small Magellanic Cloud.

She found that the average luminosity of the Cepheids - its average energy output - is linearly related to the logarithm of the period. This is called the period-luminosity relation, or more recently, Leavitt’s Law.

Plot from Leavitt's 1912 paper. The horizontal axis is the logarithm of the period of the corresponding Cepheid, and the vertical axis is its apparent magnitude. The lines drawn correspond to the stars' minimum and maximum brightness.

Above is the plot from her publication on the subject, with the horizontal axis being the period and the vertical axis as the brightness. There are two lines plotted, one represents the Cepheids at maximum brightness and one is at minimum brightness.

The modern Leavitt Law takes into account the two types of Cepheids. Plot from the lecture notes on pulsating stars from Ohio State.

Above is the modern Leavitt Law. Still basically the same, but we’ve discovered that the two types of Cepheids will give slightly different relations. But the important part of this relationship remains: You can measure the period of Cepheids and get a reliable estimate of the star’s average luminosity. Once this was calibrated, astronomers that found a new Cepheid variable star could record the period over which the star dimmed and brightened and use Leavitt’s relation to determine the star’s intrinsic brightness.

The Duel Problems of Distance and Brightness

A huge problem in astronomy was trying to figure out two things: how bright something actually is and how far away things are. How bright or dim an object looks is a function of its intrinsic properties, but it’s also a function of distance.

Illustration of the Inverse Square Law. Credit: NASA/JPL-Caltech

Every star has an intrinsic brightness, an intrinsic amount of power that it outputs, like a lightbulb. We can think of how bright a star looks as its intensity. A star has a certain intensity at the surface. It’s passing through a surface of area A. But light escapes the star in kind of a cone shape, so as the observer gets further and further away, the light must travel through a larger and larger space. If we have an observer at the star and an observer twice as far away, the star will appear 4 times fainter to the observer twice as far from the star than it would to the observer at the star, and for an observer 3 times farther away, the intensity would be 9 times fainter.

The basic physics of light really limited what astronomers could know about the stars they observed. A dim star could be a bright star that is very far away, or it could be a very dim star that is very close. Even with parallax methods, this was difficult to figure out for stars that were a moderate distance away.

Leavitt’s Law allows us to relate something that is very easy to measure - the period of a variable star - to something that is not easy to measure - the star’s intrinsic luminosity (how bright the star is close-up). If we know how bright the star *looks* and how bright the star *is,* we can calculate how far away the star is.

Cepheid variable stars are astronomy’s first so-called “standard candle,” a term coined by Henrietta Leavitt. A standard candle is something in space whose luminosity we always know.

There are other standard candles in astronomy - a particular type of supernova called a type 1a supernova comes to mind. Standard candles are an integral part of what astronomers call the cosmic distance ladder.

The Extragalactic or Cosmic Distance Ladder shows the various ways astronomers can tell how far away something is. It’s complicated!

Cosmic distance ladder is a cobbled-together mess of different methods that are valid at different distances from Earth that tell us how far away certain objects are. As you can see, there are many different methods for deterring distance. Various types of Cepheids are valid up to about a megaparsec from Earth (or 20 quintillion miles or 20 with 18 zeros).

Shapley-Curtis Debate

As Henrietta Leavitt was making her discovery, a debate is percolating. What is the scale of the Universe? The idea that there were other galaxies in the Universe was not a new one. In the 1750s, the philosopher Immanuel Kant hypothesized - with no real evidence - that spiral nebulae like Andromeda were in fact “island universes,” or galaxies like the Milky Way. This assertion stirred debate at the time, but without methods of measuring distance, it was difficult to prove one way or the other.

But by the early 1900s, there were other lines of evidence that astronomers could follow, and the debate came to a head in 1920 in something called The Great Debate, or the Shapley-Curtis debate. This was a literal debate between Harlow Shapley of the Mount Wilson Observatory and Herber D. Curtis of the Lick Observatory held at the Smithsonian Museum of Natural History. Shapley believed that the Milky Way more or less contained the entire Universe. Curtis, on the other hand, believed that spiral nebulae like Andromeda and Triangulum (another small galaxy in our Local Group) were distinct galaxies that were not encompassed by the Milky Way.

The two men had evidence to back up their ideas. Shapley, for his part, cited work done by Adriaan van Maanen in which he claims to have measured the rotational speed of the Pinwheel Galaxy, indicating that it had to be relatively close by.

Curtis noted that nova appeared at different rates inside Andromeda compared to the Milky Way. Nova are transient astronomical events where a sudden appearance of a bright star will fade over weeks or months. These are most commonly binary star system where one star steals mass from the other and temporarily becomes extremely bright. The idea is that it doesn’t make sense for Andromeda - if it was a nebula inside the Milky Way - to have more nova than other parts of the Milky Way. If Andromeda and the Milky Way were separate galaxies, this difference would make sense.

There are other details in this debate. Neither Curtis nor Shapely were right about everything, but the main question - whether or not galaxies existed outside the Milky Way - was definitively answered in 1924 by a young astronomer called Edwin Hubble.

Hubble’s Use of Leavitt’s Cepheids

Henrietta Leavitt died in 1921 when she was only 53 years old from stomach cancer. But three years after her death, her major discovery - Leavitt’s Law - was used to prove that the Universe is bigger than many astronomers at the time dared to think possible.

In 1919, Edwin Hubble was a young astronomer who had just joined the staff of the Mount Wilson Observatory near Pasadena, CA. This happened to coincide with the completion of the 100-inch diameter Hooker Telescope, which at the time was the largest telescope in the world, making it one of the best places study the universe.

And that is just what Hubble did. He decided to use Leavitt’s Law - the period-luminosity relation - to measure the distance to several nearby spiral nebula, including Andromeda and Triangulum. Using the Hooker Telescope, Hubble identified Cepheid variable stars in spiral nebulae and measured their periods. Using Leavitt’s Law, he could use these periods to determine the luminosity of the stars, and from there use the luminosity calculate their distance.

Edwin Hubble’s plate image of Andromeda. “VAR!” indicates the found a variable star in the nebula, which meant he could calculate distance using Leavitt’s Law.

Based on these measurements, Hubble estimated Andromeda to be 900,000 light years away, which is much, much farther way than the farthest reaches of the Milky Way, which, remember, was estimated to be 300,000 light years across.

By 1929, Hubble had measured the period of Cepheid variable stars in 24 other nebulae, the farthest of which was estimated to be 140 million light years away, which is REALLY beyond the accepted bounds of the Milky Way.

This put to bed the debate on whether there were other galaxies in the Universe. There were. There are. Extragalactic astronomy was born.

That was a long one, but it’s a really great story about how we all stand on each others shoulders to achieve great things. Astronomy is a team effort.

Astronomy ABCs: B is for Blackbody Radiation

Ah, hello. It is a new month and here I am, trying to fulfill the promise I made to myself to write about astronomy every month. Rather than try to come up with something very clever to write about, I decided to use the English alphabet to guide my way. Last month - the first month of this journey - was A, which of course stands for Astronomy. As is customary, B follows A, so this month let’s dig into blackbody radiation.

So…what’s a blackbody? A blackbody is an object that absorbs all light that hits it and emits thermal radiation. Atoms in the blackbody will start to heat up and vibrate faster and faster. As it heats up it will emit electromagnetic radiation - aka light - until the absorption and emission are in balance, i.e. it is in thermal equilibrium with its surroundings.

The radiation from a blackbody has three characteristics that make it useful in astronomy. Check out the plot I shamelessly stole from the OpenStax Astronomy textbook.

Blackbody radiation illustrated for several temperatures.

This plot shows the blackbody radiation curve for different temperature objects. The vertical axis is intensity - basically how many photons our objects are emitting - and the horizontal axis is wavelength.

There are a few things to notice about the blackbody radiation curve:

First, the spectrum is continuous. These blackbodies are emitting photons at all wavelengths at once (but not all equally, which is important). These blackbodies are just bundles of atoms and molecules. These atoms and molecules will vibrate and bump together at varying speeds. Some will slower than average, some will be faster than average, but most will emit energy at some average value (the peak in the plot). But it’s the spread of these energies that gives us the blackbody spectrum we see.

Second, hotter blackbodies emit more radiation at all wavelengths compared to cooler blackbodies. This is because hotter atoms and molecules vibrate and collide more often, which causes them to give off more energy.

Third, check out the peaks of each temperature blackbody. Other than the height of the curve, what jumps out at you? To me what jumps out is the shift of the peak redward as the temperature of the blackbody goes down. In other words, the peak of the blackbody moves to higher (redder) wavelengths as the temperature decreases.

How does all of this help us with astronomy? Well, it turns out that stars emit radiation like a blackbody! This means that we can use what we know about the blackbody curve to make a thermometer for stars.

There’s a nice mathematical relationship between the wavelength that has the highest intensity in a blackbody and the temperature. It’s one of those important equations that gets a name: Wien’s Law:

This says that the wavelength of maximum intensity (in nanometers) is equal to a constant divided by the temperature (in Kelvin). What this allows us to find the temperature of a star by just measuring its spectrum!

This also means that the color of a star can stand in as a rough approximation of its temperature. Light gets more energetic as its wavelength decreases, and each wavelength corresponds to a particular color. Stars with a max intensity at low wavelength will have hot temperatures, and stars with a max intensity at large wavelength will have lower temperatures. The smaller the wavelength, the bluer the light, and the longer the wavelength, the redder the light. So if we wanted to compare the temperature of a star that appears red to the temperature of a star that appears blue, we could say that the blue star is hotter than the red star just from color alone! Pretty cool!

I got this post in just under the wire for October, but I did do it. I don’t need your praise, I’ve clapped for myself. I hope you stop by next month for more ABCs of Astronomy.

Astronomy ABCs: A is for Astronomy

I used to write the way I breathe. It was effortless. I would have a thought and I would write it down, which changed very little in the distance between my head and my fingers. I haven’t written much in a while, though I’ve tried to create systems that encourage it. I really did want to learn and write a bunch about Venus, but…well. You can see how that turned out.

Part of my job is writing a monthly public science talk. Every month I choose a topic and write a roughly hour-long presentation on it. I script out every talk. I know that this isn’t necessarily “good” practice among scientists, but I do it for a couple of reasons:

1. I get really nervous when I’m speaking. A script is like a security blanket. If/when I get so nervous that I forget the point of the slide, I have something to fall back on.

2. The script is a little gift to future me. Once a talk is written, I’ll give it whenever. It’s on the schedule for a certain month but if a group wants to hear it 4 months later, who am I to say no? I write a script because I know I am forgetful. A script allows me to pick up the talk months later and know exactly what I meant to say.

3. It just helps me weave a story. The flow from slide to slide is better.

I’ve been in this position for a little over 2.5 years and I’ve written 36 individual talks, most of them hour-long public lectures. I was curious to see how much writing a year of public lectures was, so I counted up every word of each of the 12 scripts I wrote in 2024. The result: 65,491 words. A 200 page book - depending on page size and formatting - is 50,000 to 60,000 words.

Ah! No wonder I haven’t been writing more on my own! I wrote a book last year. And, since my 2025 lectures are roughly the same length as my 2024 lectures, I’m sure I’m well on my way to writing a book this year, too.

I really thought I had lost any skill I had as a writer because I couldn’t turn it on at a moment’s notice. But seeing the amount I wrote last year compiled in one place made me think that maybe I’m just trying to force myself to write about things that don’t fit into my life right now. If I may say so, the lectures I wrote are good. I think I explain complex things pretty well to a lay audience.

All of this was a long preamble before introducing a new series: Astronomy ABCs. Every month gets a letter and I will write at least one piece on an astronomical concept that begins with that letter. Why should you trust me when I have failed so many times before? I don’t know, maybe you shouldn’t. But I did spend an hour yesterday making a list of topics organized alphabetically. Do with that what you will.

The best place to start in the alphabet is the beginning, and for English that letter is A. A is for Astronomy.

And listen, I thought about this. A could have been for Accretion Disks. Or AGN. Or Asteroid. Or Airy Disk. But if I’m going to start a series of astronomy-themed posts, I thought it might be a good idea to talk about what astronomy is.

Astronomy (or astrophysics, if you prefer) is the scientific study of space and the objects and phenomena we see there. It brings together physics, math, chemistry, geology, and computer science to figure out how galaxies, planets, and the Universe itself works. There are many subfields in astronomy - cosmology, extragalactic astronomy, planetary science, exoplanet astronomy, stellar astronomy, the list goes on - but if it studies something in space, I consider it under the umbrella of astronomy.

Astronomy is also incredibly old. Early civilizations used observations of the sky to keep track of days, months, and seasons, many developing a complex mythology that encodes generational astronomical knowledge.

With a few exceptions, astronomy is an observational science. At least right now, we can’t travel to a nebula and gather a sample of cosmic dust and gas to study. We need to view our subjects from afar using telescopes that are sensitive to different wavelengths of light. The closest we can get to bringing a bucket of star back to Earth is using telescopes to gather light from far off objects as it travels in our direction.

Over the next several months I plan to write explainers on astronomical topics ranging from the small to the very, very large, from close by to very far away, from massless to massive. Some topics I’ve identified are topics I know well. Others…less so. If I do this right then we all learn something.

Next month is the letter B. What will I write about? Black holes? Blue stragglers? The Big Bang? Something else? Check back to see!

The Untitled Venus Project

I’m not a resolution person. I’m not great at planning long-term projects, which a resolution is by definition, and even worse at follow-through. So I long ago stopped trying.

And yet, this time of year does get you thinking about goals, or at least thinking about finding meaning and happiness, which are sometimes the same thing. Something I’ve missed doing is writing. Writing is both a creative outlet and the only way I can consistently think clearly. I stopped having time to write when I was getting my PhD, and things haven’t gotten better since I graduated and got a job.

I thought putting this blog page on my website would help, but I’ve had trouble feeling inspired. My mind feels muddy, and it’s felt muddy for quite some time. For me, writing is thinking. It’s been difficult to clear the water enough to form coherent thoughts, let alone develop original ideas. Even now, writing this, is not as easy as it used to be.

I realize, though, that writing is a muscle. I haven’t exercised this muscle in a while, and it’s getting weaker and weaker by the day. I want to start thinking clearly again, and I think Venus will help me.

Part of my day job as an outreach astronomer is writing a series of lectures, one a month for the entire year. Last year one of the lectures was about Venus. I’m not an expert on the Solar System, but part of what I like about my job is that I get to teach myself a bunch of stuff that I missed.

I was struck by how much we don’t know about Venus. Why are there so few craters on the surface? Why does it spin backwards? Where did its atmosphere come from? Why is it so dry? None of these questions have particularly satisfying answers. So much of what we hypothesize about Venus is based on what we know about Earth. It’s thought that Venus has the same bulk density as Earth, but the interior of Venus must be different, somehow, because it lacks a global magnetic field, which implies something different going on inside the planet. What exactly that looks like and how we got here are gaping holes in our knowledge of the Solar System.

And it’s not only the Solar System. Astronomers have found exoplanets in the “Venus Zone,” the runaway greenhouse boundary of the host star. Understanding Venus will help us understand these “exoVenuses” and these exoVenuses will help us understand what our own Venus was like in the past.

In the next decade or so, we’ll start to answer some of these question, as NASA and the European Space Agency are sending three missions to study Venus from the interior to the top of the atmosphere.

in the meantime, I want to learn as much as I can about Venus, and I want to put what I find out here. Since I don’t have a planetary science background, I expect this will involve teaching myself quite a bit of geology and chemistry. My goal is to write one piece a month on Venus’s mysteries and how we Earthlings can go about making sense of our sister planet.

I may succeed, or I may not. I’m going to try not to beat myself up if this project doesn’t quite live up to what I have in my head. I’m gonna take a year-long deep dive into something I don’t know much about and it should be interesting either way.

Paper Flowers

I went for a little afternoon walk around my neighborhood today and I saw one of the biggest dandelions I’ve ever seen. The plant was huge. The stem was huge. The flower was huge. Everything about it was huge. And it was just sitting in a patch of rocks. I didn’t get a picture of it, of course, but it was beautiful.

That got me thinking about paper flowers. For some reason, Mother’s Day brought out the ads for paper flowers in full force. Any force would have been surprising, as I had not known that this was a market until now. Then I saw an entire segment on paper flowers on Sunday Morning. These flowers are works of art. They’re gorgeous. The skill and time it must take to make them are not something I have the patience to replicate. But I couldn’t shake this one thought:

This is something I will never spend money on.

But why? On the surface it’s an extremely good deal. Expensive, but these are flowers that will never die. Never wilt. If you keep them from direct sunlight, they’ll never fade. Every week when I’m walking through the grocery store or farmer’s market I wish that I was the type of person who would buy fresh flowers for their home. But I’m not. I’m the type of person who buys fresh flowers once a year and then lets them rot in the vase for six months. These paper flowers should be a dream.

But I won’t buy paper flowers for the same reason I don’t buy silk flowers: It has all of the color, but none of the life.

I can’t smell a paper flower. Or, I can, but what would it smell like? I’m probably not going to find an ant crawling on the everlasting doppelganger. I’ll never notice them brown and whither. Never changing, eventually blending into the background so I don’t notice it at all.

Maybe I’m just mad at capitalism. If I had a friend who spent their free time crafting me a gorgeous facsimile flower, I would be over the Moon! I’d keep it forever. There’s love in that. There’s life in that.

Or, maybe I just like a mess. My home office wouldn’t certainly be evidence of that. Where I live is very…same-y. Houses look the same, yards look the same. I like a yard with very little grass in it. A yard that’s covered in native wildflowers. That’s home to gnarly shrubs and a tree or two that look a little wonky. I like it when a person can make their home a home for bees and butterflies and birds and moles. What else is that green patch of Earth for?

My family came to visit recently and noted that the town was very nice. And it is. Very well-kept.

On my way back from my walk, I walked by the ginormous dandelion. In the 20 minutes that had passed, it had been chopped down by a weedwacker. I saw the guy who did it. Just doing his job like he hadn’t cut down the most beautiful plant in the yard.

I could see the razed flower from the sidewalk. Still had all of the color, but none of the life.

You Need to See the Total Eclipse in April

In 2017, I was in Atchison, KS cursing at clouds.

It was Aug. 21, just before I was set to start my second year of graduate school at the University of Kansas. The first total solar eclipse to be visible from North America since 1979 and the first to be visible from anywhere close to where I lived since 1918. And here I was, living only an hour away from totality.

It was a big deal.

So my department chartered a couple of buses and hauled as many of us as they could cram to the campus of Benedictine College. Eclipse glasses in hand we traveled an hour northeast to hopefully see one of the rarest and breathtaking astronomical events humans can hope to see.

The clouds rolled in. Nothing leaves you feeling more powerless than when nature doesn’t follow your plans.

Because the plan was simple. It was summertime in Kansas. Hot and dry. A clear sky was not supposed to be an issue. We found ourselves on the baseball field with our lawn chairs and blankets, looking nervously up as the clouds started to pile up and get darker.

Then, a few hours before the eclipse was due to begin, the rain started.

Here we were, dozens of us, huddled in the dugouts of the Asher Sports Complex, waiting. Just waiting. And chatting. Blowing bubbles. Trying to make ourselves feel better about what was surely going to be a disappointing day. What else could we do?

Making the best of it.

——

This was my first - and so far only - eclipse. The only other time I could have possible seen an eclipse was May 10, 1994 when an annular eclipse swept across North America. I would have been 10 years old, and I have no memory of it. So whether I saw it or not, I guess I didn’t.

I have seen a couple of lunar eclipses. If a solar eclipse is when the Moon finds itself at just the right spot between Earth and the Sun, a lunar eclipse is when the Earth blocks the Sun from shining on the Moon. The Moon has no light of its own; we see the Moon because it reflects the light from the Sun. But when the Earth blocks that light, the Moon transforms its color from bright white to deep red. The Moon, rather than reflecting the light from the Sun, is reflecting back to us the light of every sunset on Earth.

In some ways, I prefer lunar eclipses to solar ones. They’re more accessible. There is not a narrow strip of Earth where a lunar eclipse is visible. If the Moon is up where you live during a lunar eclipse, you can see it. And you don’t need any special equipment to see it. You can watch it for as long as you like without fear with just your eyes.

While the blood red moon of a lunar eclipse is breathtaking, it also happens at night, often when people are sleeping. It’s an extremely ignorable event. With a solar eclipse, that’s not so.

During a solar eclipse, if you are in the path of totality, you are witness to the inescapable fact of the movement of the Universe. The temperature drops. Insects start to sing. And then when totality hits…silence. It’s a stark reminder that we are all evolved to live on this planet. Life on Earth has rhythms based on the Sun. We are dependent on it for our survival.

——

The rain came and went throughout the hours before the eclipse. I desperately wanted to lose hope. I thought the uncertainty and disappointment would be easier to deal with if I didn’t have hope. I’m not an optimist by nature, but that day, for whatever reason, I was. So I kept an eye on the weather app on my phone. This could clear, I unconvincingly said to whoever was next to me.

The eclipse started around 11:40 in the morning. The rain had stopped. The clouds were still in the way, but less so. There were pockets of sky that allowed for limited glimpses of the partial phase. Just enough to keep hope alive.

So there we were, dozens of us, out on a baseball field in the middle of the day, looking up at the silhouette of the Moon cross the disk of the Sun when the clouds would let us. All of us hoping that the clouds would break in time to see totality.

It was an excruciating 80 minutes. As the Sun approached 80 percent coverage, the air started to cool and birds and insects started to chirp. Then, the clouds parted. We could see it the Diamond Ring as the the Moon slipped right between the Earth and the Sun.

And then it was dark.

We took off our protective glasses and stared up at our completely obscured star. At 1:06 pm CDT, for 2 minutes and 19 seconds, the Sun was gone.

Those aren’t clouds! Just my terrible smartphone camera!

I’m not someone who experiences a lot of excess awe. I’ve never been moved to tears by a sunset or a painting. I didn’t expect to feel anything during totality. And that’s, maybe, what made the biggest impression. And it’s still, even years later, just a feeling. I didn’t see the eclipse. I experienced it. I had goosebumps, not just because of the temperature change, but from it was. It was unnerving and wonderful. The stress and uncertainty that came with the rain disappeared. It was just us the the sky.

The clouds rolled back in just before the last bit of partial eclipse was fading. I turned to my partner and said, “When’s the next one?”

We went to the cafeteria for lunch.

Watching totality.

——

Another eclipse crosses North America on April 8, 2024, and you should go see it in it’s path of totality if you possibly can. Not only because another total eclipse doesn’t even touch the continent until 2044, although that is true. This is a gift you can give yourself and your family and friends. It’s a chance to stop and be reminded of where you are and what that means. It’s an opportunity to feel something unexpected.

I wish I was a better writer so I could convince you that this is worth it. But go. If you can, go to totality. Take your friends and loved ones. You will never forget it.

My bike is not taking me on a weight loss journey.

I’d like to get something off my chest. It’s something I see pop up all the time regarding walkable or pedestrian- and cycling-friendly cities: This idea that you’ll be skinnier if you could just walk everywhere.

I got to thinking about this as I was reading Daniel Knowles book, Carmageddon. The title isn’t subtle, but in case you were confused, the subtitle is “How Cars Make Life Worse and What To Do About It.” So far, I’m on board.

It was an OK read; it has no notes, no bibliography, so not a book designed to help you learn more. But if you want to rip me right out of the argument that cars are bad for society, just start talking about health and weight.

Human health - what causes good and bad outcomes - is astoundingly complex. What we can say about the population at large isn’t the same as what we can say for individual people. Knowles, to his credit, doesn’t linger on health much. But I would like to quote a particular passage at length because it’s so smug and judge-y while ostensibly trying to not be smug and judge-y:

Walking and cycling are not only convenient, and often cheaper, but they are also much healthier than sitting still behind the wheel of a car. We live in increasingly sedentary societies. a 2010 survey by the Centers for Disease Control found that 38 percent of Americans say that they have not walked for more than ten minutes at a time in more than a week. At a typical walking pace, that means that more than a third of people have not walked half a mile in a week. The average Briton walks only around half a mile per day to get anywhere (so, not counting walking from the sofa to the fridge), or 181 miles a year, according to the Department of Transport. That is down by 83 miles since 1986. And so it should hardly be a surprise that we are getting fatter. Around 28 percent of Brits are clinically obese, and another 35 percent are overweight. In America, 41 percent of people are obese, a figure that is higher still in states like Texas or Iowa, where almost everybody gets around by car.

Driving everywhere is not only making out cities ugly and polluted, it is also making us fatter. It’s easy to moralize about that , but it is mostly not because people are lazy that [sic] they do not exercise enough. It is because they follow the incentives society creates. And those incentives are to drive everywhere, rather than walk. Our ancestors did not spend much time in the gym, or even eat especially healthy diets, but they stayed slim because their day-to-day habits involved walking. It would do us good to rediscover that.

Carmageddon, pp 184-185

Where do I even start? I guess start with the low-hanging fruit: that parenthetical in the first paragraph. The one about not counting the distance walking from the sofa to the fridge? Real nice. Makes the entire second paragraph look awfully disingenuous. But that’s not even the worst problem.

This is basically hand-wringing for 3/4 of a page about how fat people are. But so what? What is the harm here? I’m not going to reinvent the wheel and instead drop this episode of Maintenance Phase to get you up to speed on all things obesity, but suffice it to say that obesity doesn’t equal death. Or even guarantee bad health outcomes. It’s sloppy to equate being a certain weight with being healthy.

That is not to say that argument for more pedestrian- and cyclist-friendly streets should ignore health. Walking is good for everyone. It’s good for your heart and your muscles and your bones. There’s evidence that it supports your mental health. That’s ignoring the impact of pollution of vehicles and injuries from vehicle crashes.

I don’t meant to put this book in particular on blast. This bullshit is so common. Like a recent NPR story on NEAT, or non-exercise activity thermogenesis. The article is interesting! The gist of it is that you can’t change a lot about how your body uses calories, but if you’re active during the day - SURPRISE! - you burn more calories. Toward the end of the article they talk about other positive health outcomes, but it’s overwhelmingly about how many calories you can burn and, implicitly, how much weight you can lose.

I’m just so tired of this framing. When I lived in a walkable and bikeable city, I didn’t lose any weight, but I felt so much better. I slept better. This is anecdotal, but there are more lasting and important reasons to want to get out of your car than fitting into those size 2 jeans.

A New Blog! An Introduction

Hello. Hi. Yes. Welcome to my blog.

Put down the low rise jeans. You have not time traveled back to 2002.

I’m an astronomer, and there will almost certainly be astronomy content here. But it’s not an astronomy blog. In fact, I don’t expect it to even be a mostly-astronomy blog. Astronomy is fun, and I love helping people understand it and feel connected to it. But it’s also important to me that it not be my entire personality.

Because, look, in a lot of ways the world sucks. The effects of climate change sucks. The Supreme Court sucks. Car culture sucks. All of this suckage just puts pressure on my brain.

Writing is how I think. It’s how I process information. When I don’t write, I don’t think. At least not very well.

So what’s this blog going to be about? I don’t know. I read a book recently that I kind of like but also kind of have problems with. Maybe I’ll write about that? I also really want to learn how to make seed paper. Maybe we can go on that journey together? And I’ll write about those things that suck, but hopefully in a way that adds a little signal to the noise.

Maybe, over time, this blog will develop a theme. I’m not necessarily opposed to that. Or maybe it will peter out. Or maybe it will remain an eclectic mix of whatever is going on in my head at any given moment. That’s fine, too.

So welcome to my blog. I hope to see you again.