For her latest project, theoretical astrophysicist and science communicator Katie Mack grappled with the complexity of cosmology within a five-minute YouTube format.
As a physicist, and as a writer, I live for the deep dive.
Finding some tantalizing problem or tricky concept, digging in obsessively, and figuring out every possible angle is immensely satisfying. I have been known to chase down seemingly inconsequential details through chains of references five or six papers deep just to ensure I have fully grasped them – not necessarily for the immediate calculation, but for the context and implications as they might relate to some greater, big-picture problem. I desperately need to know, and explain, everything.
This tendency is often helpful (or even essential) in my research, and it has helped me prepare comprehensive lesson plans in my graduate teaching. It does not, however, lend itself well to short YouTube videos or Instagram reels.
A quantum science cheat sheet
Shortly after I arrived at the Perimeter Institute for Theoretical Physics to take on a joint research and outreach role, I had a discussion with the Managing Director, Paul Smith, about a recent surge of interest in quantum physics. We talked about ways that Perimeter could make use of our resources to bring some of that excitement to the public, and what I could bring to that effort.
Perimeter already had a huge database of lectures, including public talks, on all areas of theoretical physics, and regularly produced news articles and even lesson plans on scientific topics explored by our researchers. But what if someone just wants to know the basics? What is quantum physics all about, and what do all these terms flying around – entanglement, uncertainty, superposition, qubits – really mean? Could we give people some kind of cheat sheet?
This is how I found myself putting together a series of five-minute videos called Quantum 101, supported by Perimeter’s outreach group. Each one was meant to be short, punchy, and shareable, giving viewers just enough grounding in the hot topics of quantum physics to follow news articles and find a starting point for further reading.
Compressing an entire field of study that stretches across multiple years of graduate coursework into 10 bite-sized pieces is a challenge, to say the least. Especially if you happen to be speaking for one of the world’s premier research institutions and you’re trying to rope in some of their globally recognized experts for cameos. I had to learn how to tell short, informative stories that could be engaging and digestible without being inaccurate, while trying not to stress about the inevitable YouTube comments.
The complex interconnectedness of cosmology
In the end, Quantum 101 was a success – enough so that, not long after, I found myself following it up with the recently released Cosmology 101. But where Quantum 101 felt like laying the foundation for viewers to build on, writing Cosmology 101 made me feel like I was pinning index cards to a bulletin board and connecting them with string, enthusiastically insisting that it all fits together.
The problem is that cosmology is not a self-contained mathematical theory like quantum mechanics. It’s a research area that encompasses the nature, behavior, and evolution of the cosmos as a whole. While we have models and paradigms to describe a lot of the phenomena we see, we don’t have a true, fundamental, predictive theory that can be written down as a progression of methods and equations. Cosmology relies on the application of virtually every branch of theoretical physics, and patches it all together to try to make sense of our universe.
Einstein’s relativity (both special and general) describes the evolution of spacetime and how light travels through it. Newtonian gravity is what we use to talk about the growth and structure of galaxies and star systems. Thermodynamics describes the hot dense early universe, unless you go too far back, and then you need atomic, nuclear, and quantum theory.
Want to talk about how we study the most energetic objects in the cosmos? For that, radiative transfer, magnetism, and fluid dynamics rule the day. And if you’re determined to describe the very beginning, you can try quantum field theory, but you’ll eventually need a theory of quantum gravity that hasn’t even been developed yet.
Even just describing the main salient facts about the cosmos can tie you up in knots. Want to talk about galaxies? You need to have already covered the expansion of the universe, relativity, and the existence of dark matter. How do we explain dark matter? You know about galaxies already, right?
The universe absolutely refuses to separate itself into easily compartmentalized pieces.
Wandering the maze of modern science
For the video series, I did my best to tie it all together. You can watch it now: I cover the essentials of our current cosmological narrative, in all its patchwork glory, in the first five episodes, and then delve into the big mysteries (cosmic inflation, dark matter, dark energy, the end of the universe, and what comes next) in the rest. While it certainly will not answer every question you have about the cosmos, or even fully satisfy your curiosity about any one of the topics, my hope is that it can be an entry point to the warren of rabbit holes that is our ongoing exploration of the universe.
And maybe that’s the most important thing to get across: that our understanding is a work in progress, that we’re building not by neatly piling up individual bricks but by wandering that maze of knowledge and finding new paths and new connections. Some of them may be dead ends, and maybe we’ll have to dig ourselves out or abandon some promising direction. But that’s just how basic research works.
By the time any scientific result gets written up in textbooks, it generally looks like A led to B led to C, forming a neat, tidy narrative. And telling the story in that way can make a lot of sense, if what you’re aiming for is to help people build up an understanding. It’s easy to follow that kind of step-by-step logical progression, and it can definitely help with the physical intuition.
But what I learned creating Cosmology 101 is that this kind of explanation just isn’t possible if you want to share what an ongoing, incomplete research topic is really all about. I can’t give you all the answers, or even line up all the building blocks in any logical way, no matter how much I would like to make it all make perfect sense. What I can do is lead you to the corkboard covered in scribbled notes and connections, wave my hands emphatically toward the whole convoluted story, and hand you the free end of the string.
Katie Mack is the Hawking Chair in Cosmology and Science Communication at the Perimeter Institute for Theoretical Physics and the author of The End of Everything (Astrophysically Speaking). You can find her on Bluesky as @astrokatie.com, Instagram and TikTok as @astrokatiemack, and X as @AstroKatie.
