Katie Mack Profile picture
Cosmologist, writer, connoisseur of cosmic catastrophes. @TEDFellow. Author: "The End of Everything (Astrophysically Speaking)". Personal account. She/her. Dr.
Jeffrey Rubinoff Profile picture Jean-Marc Cavedon Profile picture Maureen Albertson Profile picture Stuart Profile picture Mary Waggener Profile picture 12 added to My Authors
5 May
As of Monday, I am officially a PILOT! 👩‍✈️🛩️

After three delays due to weather, I finally had my checkride (the final step for getting a pilot license, which consists of an oral exam and a practical test). Here's a picture of me, the examiner, and my certificate after the flight! Me standing outside a build...
Learning to fly has been AMAZING and I'm thrilled I've been able to do it during the pandemic. My flight school (@Fly7B2) has been good about masks etc during lessons & indoors. It's just a hobby for me, but I'm now obsessed with aviation and can't wait to see where it takes me! Me piloting an airplane wit...
For those interested, here's the track log from my checkride. Lots of maneuvers, almost two hours of flying. The examiner was very thorough, as he should be! Flight actually started at Northampton, but I had the GPS off for the first bit for navigation by pilotage/dead reckoning. A track log showing an airp...
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20 Apr
Nice article by @uncertainquark for @exploreplanets about why terraforming Mars is probably a lot harder than you've been led to believe planetary.org/articles/can-w…
The problem with Mars isn't that it's dry, or even that it's cold. The problem is it has very little air and that air is mostly CO2, and is, incidentally, being slowly sheared off by the solar wind (for lack of a magnetic field). Just heating the planet doesn't solve any of that.
There's actually a decent amount of water (as ice) at/near the surface. But even if you made the planet warmer, above what we consider freezing, that ice will turn right into vapor because there's too little air pressure for liquid water to exist. The atmosphere is a challenge.
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8 Apr
I want to expand on this a little... it's an issue that makes the POSSIBLE NEW PHYSICS announcement today a bit more complicated/caveat-y...
Both the measurement and the theory prediction for this experiment require INCREDIBLE precision. And the calculations are HARD. You have to account for how every particle known to science might interact with a muon, hypothetically, and exactly how that would affect its motion. 😳
One way to do this calculation is called the "data-driven" approach, which relies on generalizing from other precise measurements. The other is a new approach using supercomputers doing "lattice QCD" -- solving lots of very difficult equations on a very tight grid.
Read 5 tweets
7 Apr
I've been tweeting a bunch of articles and threads about the #gminus2 result -- a possible indication of ✨ NEW PHYSICS ✨ coming from @Fermilab! Check my timeline for details, but I'll give a very brief and simplified summary here...
An experiment at @Fermilab is measuring a property of muons -- subatomic particles similar to electrons, but heavier -- to try to determine if our current understanding of particle physics is correct or not. The experiment hinges on the fact that muons are a tiny bit magnetic 🧲
The "Muon g-2" experiment measures how muons spin around and how that spin wobbles when they're sent around a circular track in the presence of strong magnetic and electric fields. That depends on how the muon spins and its "g-factor", related to its magnetism.
Read 11 tweets
8 Mar
New guidelines from the CDC for what might be okay for fully vaccinated people: cdc.gov/coronavirus/20…

Note: Dr. @RWalensky emphasized during the White House press conference that this is the best guidance RIGHT NOW but may change as conditions change and the science develops.
New CDC guidance:

"Fully vaccinated" (FV) = at least 2 weeks after final vaccine dose

* FV people can hang out in small groups with each other without masks

* FV people can hang out in small groups with LOW RISK unvaccinated people

* Non-essential travel still discouraged
The reason they're not saying fully vaccinated people can "just go out and do whatever" is partly because vaccines aren't 100% effective and partly because being vaccinated might not always prevent you from carrying the disease to others. (This is still being studied.)
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5 Mar
This is an amazing optical illusion — caused by atmospheric conditions over the water bending light rays to make it look like the ship is above it. This video has a nice explanation (especially the bit starting around 1:20) . #FataMorgana
The proper term for this is “superior mirage” or “superior looming mirage” but I have seen the term “fata morgana” used for a similar phenomenon also caused by weird kinds of light bending over the ocean.
More on superior mirages from @iansample. theguardian.com/science/2021/m…

Rather than "optical illusion" it might be better to call this an "optics illusion." Your brain is processing visual information correctly, it's just that the light deflection makes that information unreliable!
Read 5 tweets
4 Mar
Here’s a long-ish excerpt from my book where I talk about THE BIG RIP, one possibility for the end of the universe. (More likely is a Heat Death, caused by endless accelerated expansion, which *doesn’t* rip things apart. But a Big Rip would be fun too.) americanscientist.org/article/tearin…
I just saw a clip of Neil deGrasse Tyson on the Late Show saying that the Big Rip is likely coming and that it’s the necessary result of endless accelerated expansion, neither of which is true! So, see above for clarification.
If you’re interested in reading about what cosmologists are discovering now about how the universe might end, check out my book, “The End of Everything (Astrophysically Speaking)”! It’s accessible and comprehensive and has lots of funny footnotes astrokatie.com/book
Read 4 tweets
19 Feb
A thing a lot of people don't seem to be aware of is that the proportion of astronomers who believe there is alien life of some sort in the universe is almost 100%. It's just the proportion who think they've *dropped by* that's almost 0.
I had a radio interview recently where the host started out all challenging saying "It's UNTHINKABLE there isn't other life out there in the cosmos!" and I was like, "yeah, pretty much" and I think he was not really prepared for that
What we know is that we find life in just about every environment we look for it on Earth, wherever there's some amount of liquid water -- sometimes even just ice. And we know there is water on other worlds. And there are a LOT of other worlds. So: life seems likely to be common!
Read 4 tweets
7 Feb
Watching the snow fall outside and thinking about terminal velocity, and how much less peaceful this whole scene would look without air resistance. ❄️💥
Terminal velocity is the final speed something reaches when falling through a fluid (like air). The force of gravity accelerates the thing, and air resistance slows it down (in proportion to the square of the speed), so at some point those things balance and it stops speeding up.
Terminal velocity for a raindrop is around 9 meters/second. For a snowflake it’s generally closer to 2 meters/second, depending on the size and fluffiness of the flake. (Some formulae here hyperphysics.phy-astr.gsu.edu/hbase/airfri2.…)
Read 4 tweets
1 Feb
Reporting on non-mainstream ideas in science is often skewed on either side, presenting them as either rare/revolutionary or totally suppressed.

In practice, there are a ton of people working on ideas their colleagues look at & say "eh, a bit niche" that might/might not pan out.
We don't invest en masse in the fringe ideas unless they pass enough rigorous tests to become the new consensus, but no one is saying "you can't publish on that." The vast majority of papers on ALL topics are ignored; the more extraordinary the claim, the more evidence it needs.
Not sure why I’m going on about this so much lately. I just think it’s important for people to know that in between all the big flashy results there are a bunch of us just chugging along trying all different things (and getting excited or not) and that’s good and normal science.
Read 5 tweets
30 Jan
Love it when people come into my mentions to tell me their personal criticisms of modern cosmology theory like I’m soliciting product reviews and will relay their complaints to the physics manager.
I’m sorry you find the current cosmological consensus around dark energy to be aesthetically unpleasing but telling me that is not going to upend the paradigm and replace it with one you like better.
I promise we have good reasons for favoring the theories we do, and I do try to explain those reasons from time to time! The reasons are not “we are too lazy to come up with something else” or even “we accept the first idea we find and stick with it despite its obvious problems.”
Read 4 tweets
12 Dec 20
Vaccines are combat training for your immune system. They show it what to expect from a virus/bacteria so your cells can build a better defense when the actual pathogen arrives.
Usually, a vaccine gives your immune system dead or weakened pathogens so it can mount a specialized defense. Say an invading army is coming and you capture some soldiers and their weapons. You'll be in a much better position to repel the invasion than if caught by surprise!
mRNA vaccines, like Moderna & Pfizer/BioNTech's, work differently. They give your cells the blueprints for a piece of the virus, so your cells can build that piece (which, on its own, can't hurt you), study it, & be ready to attack it & the virus it's attached to when it shows up
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9 Dec 20
SpaceX #Starship launch attempt scheduled to start in five minutes or so... #SN8
This is the rescheduled launch attempt after the last-second abort yesterday:
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9 Dec 20
If you give my book as a gift you can write on the card "I will love you until the end of the universe"! It's really a very romantic kind of present!!
"Unlike the Higgs vacuum, my love for you will never decay"
"The cosmos may succumb to a Heat Death due to the second law of thermodynamics, but the first law of MY HEART is that I love you"
Read 6 tweets
8 Dec 20
SpaceX is about to do a high-altitude test flight of its Starship prototype, in about two minutes theverge.com/2020/12/8/2216… spacex.com/vehicles/stars…
Or... not. Abort. Alas.
The #Starship prototype did not launch but it ALSO did not explode so I think this is a "successful failure" situation and the data will be helpful to the engineers as they set up for the next try. #SN8
Read 4 tweets
7 Dec 20
I keep thinking about how the public and government response to COVID might be different if (sensible) patient privacy rules and safety concerns didn't prevent TV crews from constantly broadcasting close-up dispatches from inside the ICU front lines.
Comparing US fatalities from COVID-19 with those from wars makes it clear it's not because the pandemic is less deadly that so little is being done on a national level. I think it's partly because we mostly don't actually see it happen.
Note: I'm NOT saying we SHOULD put TV cameras in patient rooms. I don't think that's a good or simple solution. I'm just thinking about the implications of this all being behind closed doors.
Read 4 tweets
26 Nov 20
Hello everyone just letting you know I am going to attempt to bake a pecan pie
This is the pecan pie recipe I’m using: thebigmansworld.com/wprm_print/351… It requires a high-speed blender, which I don’t have!!, so this will be an interesting experiment in adaptation! I’m using a mini food processor instead. It’s, um, trying very hard.
Pie update: Pie crust with brown pecan-pie filling in it. Mostly not tooPie crust with brown pecan pie filling plus pecan halves on
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23 Nov 20
Just my two cents but if schools are closing because some threshold level of community transmission has been reached the correct response is not "we should have decided to keep schools open no matter what" it is "we should have closed other things so schools could stay open."
(this tweet brought to you by yet another morning yelling at The Daily podcast)
Yes, be mad at the mayor for the fact that schools are closing while bars and restaurants are not. But not because it's UNFAIR that bars and restaurants can stay open and schools can't, but because bars and restaurants staying open is WHY schools had to close.
Read 4 tweets
5 Nov 20
In quantum mechanics, there's uncertainty built into every physical process. Let's say an electron could go left or right at a junction. Before you check, you can't know where the electron is: you say the result is a superposition of electron-going-left and electron-going right.
When you measure the electron's position, you'll find it either went left or right, and depending on how you set up the experiment, it might be that half the time you do it, you'll find left-electron, half the time right-electron. How does each electron "decide" which way to go?
That question is what different interpretations of quantum mechanics try to answer. How do we go from probabilities to single answers? You start with a "wavefunction" that contains all possibilities and end with a data point: you could say the wavefunction collapsed to one result
Read 6 tweets
1 Nov 20
You're never too young to learn about the ultimate fate of the cosmos!! 🤩 #EndOfEverythingBook
Update: I have been informed that 7 might be too young to learn about the ultimate fate of the cosmos. Please use the usual parental judgment when discussing cosmic apocalypses with your children.
My 3.5-year-old babynieces are pretty tough, though. I’m sure they can take it. Two 3.5-year-old girls in white sweaters and denim skirts si
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4 Oct 20
I took this photo of the Moon and Mars last night with my phone. It might not be the best photo but believe me when I say they were both GORGEOUS. Or better yet: don’t believe me — go out tonight and see for yourself! A very dark fuzzy image of the nearly full Moon rising over
Now is a great time to look at Mars. It’s unusually close to Earth in its orbit and (for the same reason) pretty much directly opposite the Sun. It’s as though it’s doing its best to be a mirror for the Sun shining back at us, so it’s very very bright. This is called #opposition.
Here’s a diagram of the positions of the planets right now from theplanetstoday.com. You can see that both the Moon and Mars are in the opposite direction as the Sun, so the Moon is close to full & Mars is bright and close. #MarsOpposition A diagram of the Solar System showing the Sun (labeled Sol),
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