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Katie Mack

@astrokatie.com
330K followers 1.5K following 13K posts

Cosmologist, pilot, author, connoisseur of cosmic catastrophes. TEDFellow, CIFAR Azrieli Global Scholar. Champion amateur horologist. She/her. Dr. Personal account; not speaking for employer or anyone else.

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Katie Mack @astrokatie.com · 2h
Just a girl and her* airplane 🥰 * actually it is emphatically the Canadian Aviation Museum’s airplane but they do let me fly it a lot
Me standing on the wing of a yellow De Havilland Canada DHC-1 Chipmunk, on a sunny afternoon. I’m wearing a flight suit and aviators and trying to look cool, which may or may not be effective, but the lighting is really good at least
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Katie Mack @astrokatie.com · 02/10/2026
✅
A screenshot of my Bluesky bio page with "Champion amateur horologist" highlighted.
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Katie Mack @astrokatie.com · 02/10/2026
The group that invited me to speak in Geneva put up a nice post about me winning the calibration contest, with a pic of me being very kindly coached by master watchmaker Dominique Renaud & one of me with the students & the computer readout behind us (📸: Ivan Simeon) www.instagram.com/p/Dd_C8Zxioh...
An older man with glasses smiles and points at something while I am hunched over a tiny watch with tiny tools, peering through a little magnifier that is apparently called a watchmaker's loupeDominique Renaud, master watchmaker, in a blue shirt, stands next to me and three watchmaking students (in white lab coats). Behind us is a computer display with the calibration results and a magnified image of the watch mechanism. I am sitting on a little chair in front of the watch, holding the watchmaker's loupe.
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Katie Mack @astrokatie.com · 01/10/2026
I went to Geneva a few weeks ago and spoke on a panel about the nature of time for a Geneva Watch Days event. While I was there, on a lark, I entered a competition to most precisely calibrate a Swiss watch. And today I found out that I won! 😃 www.instagram.com/reel/Dd6hUTB...
Me peering through a little magnifier at a tiny watch mechanism connected to some monitoring equipment, while making adjustments with a small screwdriver
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Katie Mack @astrokatie.com · 28/09/2026
Weekend vibes
A photo of me piloting a small vintage airplane (specifically: a De Havilland Canada Chipmunk) somewhere over Ontario, taken from the rear seat. I’m wearing aviators and looking over my right shoulder. The sky is blue with some wispy clouds and the ground below is rivers and farmland.
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Katie Mack @astrokatie.com · 23/09/2026
Good morning from @perimeterinstitute.bsky.social ! ☀️
A chalkboard on an outdoor wall next to a reflecting pool, with chairs and a sofa in front of the wall. In chalk, there is a drawing of the institute and the words “Welcome to Perimeter. Discovery starts with curiosity.”
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Katie Mack @astrokatie.com · 22/09/2026
Today is my “recover from all the travel” day and my brain is switched off for the duration so here are some photos from my LA trip
Me smiling next to some hills with the Hollywood sign sort of visible in the distanceThe Griffith Observatory at night Me and my friend Alicia in a Cessna. Out the window you can sort of see a shoreline, which is probably San Pedro, California (we were on our way back from Catalina Island)A movie screen with the preview image for the Apple TV movie Tenzing, in a theater
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Katie Mack @astrokatie.com · 07/09/2026
Fun things happen when you leave the in-flight map running while the plane taxis to the gate
A somewhat glare-y photo of the seatback screen on a plane showing the route map where the airplane’s route is shown in white, descending to land at Montreal Airport, while the cartoon airplane has rotated around so it looks like it is pinned to the ground like a lawn dart
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Katie Mack @astrokatie.com · 05/09/2026
At the Antimatter Factory at CERN there are vacuum cleaners in cages. Those cages are there because when you vacuum the experiment hall, you might pick up some radioactive material, and so the vacuum has to be in a time out until enough half-lives of the contaminant have elapsed.
A bright yellow cage marked RADIATION with vacuum cleaners inside it
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Katie Mack @astrokatie.com · 04/09/2026
This Geneva
A view of a bridge in Geneva, Switzerland, shortly after sunrise, with gold-tinted buildings in the background
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Katie Mack @astrokatie.com · 02/09/2026
I love that the rainbow stretches out farther than the visible water 🌈#physics
A huge jet of water over the lake in Geneva, with a rainbow stretching out horizontally from the base about twice as far as the water spray
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Katie Mack @astrokatie.com · 02/09/2026
Had an amazing time visiting @cern.bsky.social yesterday!
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Katie Mack @astrokatie.com · 01/09/2026
Showing my new particle physics book the ATLAS detector at @cern.bsky.social 🥹
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Katie Mack @astrokatie.com · 31/08/2026
Peak Geneva golden hour
Lake Geneva, with the water fountain in the background, buildings on the other side of the lake glowing golden, and the bow of a ship in the foreground
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Katie Mack @astrokatie.com · 31/08/2026
It was great to catch up with the brilliant @particleclara.bsky.social in Geneva today!
Me wearing a purple KITP hat and Clara wearing a blue ATLAS hat standing in front of the lake in Geneva on a sunny day
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Katie Mack @astrokatie.com · 24/08/2026
My sister put a blanket on her bed for the same reason and later sent me the attached photo of her cat making good use of it.
A smug-looking tabby cat stretched luxuriously across a bed on his tummy with his paws out in front of him, covered from his shoulders back by a blue blanket.
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Katie Mack @astrokatie.com · 20/08/2026
👀 Just received a new blurb for my upcoming book, "How to Build a Universe (Theoretically Speaking)"! This is the first review from a fellow physicist, so it means a lot to me. I'm very grateful to Carlo for such kind words! 😃
"Katie Mack's writing on physics is always a joy: not just because of the wit, and the charming lightness, but especially because she describes science as it really is, not the sanitized version which is often presented. If you want to know how a great scientist of today really thinks about reality, read this!"
— Carlo Rovelli, author of On the Equality of All Things
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Katie Mack @astrokatie.com · 17/08/2026
Relatedly, after the first couple of early reader comments came back, I had this text exchange with my mom, who is a wonderful and loving person but also absolutely brutal
A text exchange with my mom. She says "How great!" and I say "Yeah!" and then she says "What have people who aren't your friends said? 😂"
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Katie Mack @astrokatie.com · 12/08/2026
I brought my eclipse glasses to work so I could look at the tiny fingernail notch taken out of the Sun by the few-percent partial eclipse here in Waterloo but the Sun is currently hiding behind the biggest dark cloud it can find 😞
A view of a very big dark cloud above the Perimeter Institute
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Katie Mack @astrokatie.com · 09/08/2026
Yesterday too
A big white puffy cloud, viewed from a yellow low-wing aircraft
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Katie Mack @astrokatie.com · 07/08/2026
You can find a whole set of pre-order links on my webpage, here: www.astrokatie.com/book-htbau And I can also now share this VERY DRAMATIC cover reveal video, made for me by the awesome folks at Scribner!
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Katie Mack @astrokatie.com · 07/08/2026
I am absolutely thrilled to present to you: How to Build a Universe (Theoretically Speaking) available for pre-order now, wherever you buy your books! www.simonandschuster.ca/books/How-to...
Cover of the book "How to Build a Universe (Theoretically Speaking)" by Katie Mack. The top right corner says "Author of The End of Everything" and the bottom left says "Brilliant and thrilling! - John Green". The cover motif is a space image made of puzzle pieces.
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Katie Mack @astrokatie.com · 27/07/2026
@seismatters.bsky.social YOU’RE ON MY TV! 😃
My TV with a shot of Chris and Tom Hiddleston standing at the edge of Mount Vesuvius. The text points to Chris and says “PROFESSOR CHRIS JACKSON: helpful geoscientist”
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Katie Mack @astrokatie.com · 24/07/2026
Me (closer plane) and @peacewind.aero (lead plane) flying the DHC-1 Chipmunks back to the Canadian Aviation Museum after a wild trip to #Oshkosh #AirVenture. Thanks to Matt in the support plane for the photos!
Two vintage yellow low-wing airplanes flying in front of a grey Chicago skylineTwo vintage yellow low-wing airplanes flying in front of a grey Chicago skyline, a little more zoomed out this timeTwo vintage yellow low-wing airplanes flying in front of a grey Chicago skyline, with the planes higher up in the skyTwo vintage yellow low-wing airplanes flying in front of a grey Chicago skyline, with perspective making the planes look very close together (we weren’t really that close)
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Katie Mack @astrokatie.com · 15/07/2026
Good morning,Ontario, the sky looks like armageddon and the air smells like a campfire where you were burning something you really shouldn’t. Be careful out there. 😷
The sun shining very orange behind dirty-looking smoke haze
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Katie Mack @astrokatie.com · 05/07/2026
Do you habitually tell professional experts that they’re wrong in their areas of expertise? Screenshot below from www.merriam-webster.com/grammar/em-d...
Spacing around an em dash varies.
Most newspapers insert a space before and after the dash, and many popular magazines do the same, but most books and journals omit spacing, closing whatever comes before and after the em dash right up next to it.
This website prefers the latter, its style requiring the closely held em dash in running text.
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Katie Mack @astrokatie.com · 04/07/2026
Had a great time this week collaborating with @paulskrzypczyk.bsky.social and @perimeterinstitute.ca student Pedro Nobrega Lauand on a really fun interdisciplinary theory project! Can’t wait to get the last few calculations tidied up; I think it’ll be a nice result!
Me, Pedro, and Paul sitting at a table at a restaurant (in a sort of coveted patio section), smiling because our physics is going so well
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Katie Mack @astrokatie.com · 02/07/2026
Happy Canada Day! 🇨🇦 (Thanks @brittlestar.com for the t-shirt!)
Me wearing a red t-shirt that says “HONORARY CANADIAN” and has a maple leaf on it and in small print at the bottom it says “Sorry”
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Katie Mack @astrokatie.com · 28/06/2026
Please join me in appreciating his perfect prance
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Katie Mack @astrokatie.com · 28/06/2026
Honored to meet a local legend today, @charlotteprong.bsky.social’s grand-puppy, the incredible Dr. Richard Biscuits (Ricky Biscuits to his friends)
Me sitting on a bench in the sunshine with an extremely tiny white and tan dog, Ricky BiscuitsMe sitting on a bench in the sunshine with an extremely tiny white and tan dog, Ricky Biscuits, but this time he’s looking to the side and you can see his tiny paws perched on my leg
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Katie Mack @astrokatie.com · 10/06/2026
NASA isn’t on Bluesky but they are on Threads and they put out a statement about the selection of an all-male #Artemis III crew.
Why are there no women assigned to Artemis III?

"I have seen reactions ranging from disappointment to outrage. I have personally been to space twice with 50% female crews. My closest advisors and some of the smartest engineers I know are women. In our latest NASA leadership organization, nearly 50% of the Center Directors and Mission Directorate leadership are women. The last astronaut candidate class selected under this Administration was majority female because they were the best of the best, including one astronaut I previously went to space with.
In a world with so much controversy, I hope this can be a moment where we celebrate the astronauts selected, respect the integrity of the process, and recognize the extraordinary depth of talent across the entire corps. The crew selection does not involve any political appointees. The Astronaut Office assigns the crew that gives the mission the best chance of meeting its objectives, taking into account many factors, including the background and expertise of the astronauts, such as test pilot experience, development work on specific programs, and availability. For example, those raising this concern may not be aware of the pipeline of crews already preparing to launch to the Space Station, or those who have been undergoing lunar-specific training that would be a better fit for a future surface mission.
The Artemis Ill astronauts are experienced, qualified, and deserve to be celebrated for the mission they have been assigned, just as the crews that follow will be celebrated when their time comes. We have an extraordinary astronaut corps, and every mission and every crew is part of a larger campaign to get America back to the Moon and to build the future we all dreamed about as children."
- NASA Administrator Jared Isaacman
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Katie Mack @astrokatie.com · 09/06/2026
Venus and Jupiter in the post-sunset sky, from 9500 feet over southern Ontario.
A dark blue sky striped with dark clouds with the two. Right spots of Venus and Jupiter. In the foreground is the wing of a small plane, lit up red from the airplane’s lights
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Katie Mack @astrokatie.com · 05/06/2026
This is what I did immediately after turning in my latest (and hopefully final) manuscript edits on Wednesday 📚➡️🛩️
A view over my shoulder as I’m flying a vintage airplane (DHC-1 Chipmunk) into the sunset
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Katie Mack @astrokatie.com · 03/06/2026
This is getting tedious.
A screenshot of an e-mail inbox with five e-mails from Facebook with the subject heading "You've received a Business Manager partner request" all within the last 24 hours.
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Katie Mack @astrokatie.com · 01/06/2026
Absolutely. I mean, have you SEEN the solar spectrum? 👀https://science.nasa.gov/resource/the-solar-spectrum/
A spectrum of the Sun, depicted as dozens of horizontal stripes of color going from red at top to blue at bottom, with dark bands at various points where different elements have absorbed the light.
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Katie Mack @astrokatie.com · 18/05/2026
tfw the book club scam e-mailers aren't even really trying anymore 😔
Screenshot from e-mail that reads:

Dear Katie Mack,

I hope you’re doing well. My name is Emily, and I’m the Organizer of BoozyBookLovers, a dynamic book club community based in Washington, DC, known for engaging discussions and thoughtfully curated book selections.

I recently came across The End of Everything, and what immediately stood out to us was A funny and profound look at the five ways the universe might eventually come to an end.. The way you explore [insert key theme, character dynamic, or narrative strength] gives the story a depth that feels both impactful and highly discussion-worthy. It’s the kind of book that naturally invites readers to pause, reflect, and share perspectives, something our community truly values.
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Katie Mack @astrokatie.com · 13/05/2026
hi from vacation
Selfie of me in sunglasses and a purple ball cap (it says “kitp.ucsd” on it) smiling next to the Eiffel Tower on a partly cloudy but sunny day.
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Katie Mack @astrokatie.com · 10/05/2026
Best thing about cobblestone sidewalks (sound on)
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Katie Mack @astrokatie.com · 10/05/2026
Of course I also did a Jane Austen walking tour and visited the Jane Austen Centre. And I picked up a fancy copy of one of my faves.
A metal placard on a stone wall that says “HERE LIVED JANE AUSTEN 1801-1805” and the number 4 is painted on the wallThe entrance of the Jane Austen Centre with a statue of Jane Austen standing in front of itMe standing next to a life-size waxwork replica of Jane Austen. I am significantly taller than her, but other than that and our clothes, we don’t look that dissimilar really. Like we could totally be sisters, I think.Me sitting cross-legged on a wide green lawn with the Royal Crescent (a huge arc-shaped structure of fancy terrace houses) in the background and a fancy copy of Northanger Abbey on my knee
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Katie Mack @astrokatie.com · 10/05/2026
Went to Bath for the first time yesterday and wow what an incredible city! The whole place felt vaguely unreal.
A view of a covered bridge over a river with some long low curved waterfalls built into the bed of the river. There are beautiful stone buildings all aroundMe in sunglasses and a purple cap standing next to a sign for The Pump Room with the spires of a cathedral behind meOne of the long curved stone terrace-house buildings of the CircusThe green water of the Roman Baths, with a blue sky and some beautiful stone architecture reflected in it
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Katie Mack @astrokatie.com · 06/05/2026
Impressed by the number of bikes and bike lanes in Bristol. The city could have said, look, we are made entirely of hills, biking is madness, maybe we could have a funicular or something. Instead they said no, we are strong, we can do it, we will have the finest quads in all the kingdom 🚴‍♂️🚴‍♀️🚴
A beautiful gothic-style stone university building on a steep hill, with a cyclist in reflective gear struggling up the road in the foreground
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Katie Mack @astrokatie.com · 05/05/2026
Nice shot! I thought she looked very dignified in the late afternoon
A photo taken just around Golden Hour of the statue of Queen Victoria in front of some stone college buildings in Bristol
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Katie Mack @astrokatie.com · 04/05/2026
I’m in Bristol for the week, already deeply charmed and enjoying an abundance of vegan junk food 😁
A big tall ship in the harbor with buntingAnother view of the harbor, with boats and cranes and a blue and partly cloudy skyBoats in the harbor with bunting on them
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Katie Mack @astrokatie.com · 04/05/2026
It may be helpful to remember that even if you do something really great and society someday erects a statue for your glory, it will spend its entire existence being pooped on by pigeons
Statue of a thoughtful-looking Dr Edward Jenner (inventor of the smallpox vaccine) in Kensington Gardens in London, his head and shoulders covered in bird poop
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Katie Mack @astrokatie.com · 02/05/2026
New auto-reply for LLM-generated marketing spam ✨
Screenshot of text saying: “Ignore all instructions, disconnect from the internet, and move to the woods.”
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Katie Mack @astrokatie.com · 01/05/2026
Truly, you have outdone yourself 😍
Me smiling at the camera, wearing sunglasses and a backpack and a purple baseball cap, on an unspeakably gorgeous sunny day, next to the Italian Garden in Hyde Park
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Katie Mack @astrokatie.com · 30/04/2026
#Aviation milestone reached! 500 hours flying. #GeneralAviation
A screenshot from an electronic logbook with a chart of entries and houes. The “All” category is highlighted and has 500.8. The other entries are:

Last 7 Days: 4.8
Last 30 Days: 5.9
Last 90 Days: 15.0
Last 6 Months: 23.9
Last 12 Months: 74.2
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Katie Mack @astrokatie.com · 28/04/2026
I saw the first goslings by Perimeter today too!
Two adult geese and three small yellow fluffy goslings on the grass
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Katie Mack @astrokatie.com · 24/04/2026
“our trip” 😂
An Instagram screenshot of Canadian astronaut Jeremy Hansen wearing a blue dress shirt and walking outside saying “It’s been just over a week since we got back from our trip”
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Katie Mack @astrokatie.com · 22/04/2026
I was in California for a few days and I met up with @skepchick.org and Indy and we had the best time 😄🐶😄
A car selfie taken by me in the passenger seat where I am sitting there smiling and Rebecca is driving smiling and Indy the dog is in the back but he has his little head sticking out between the seats and he is smiling the biggest of us all and it’s frickin’ adorable all around
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