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Katie Mack Profile picture
@AstroKatie
Sep 15, 2017 • 7 tweets • 3 min read • Read on X
What does @CassiniSaturn mean to me? It's more than an instrument for observations. It's a traveller, visiting another place, an alien world
Very few of us humans will ever leave Earth. But missions like @CassiniSaturn give us a taste of that freedom, & let us reach out & explore.

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More from @AstroKatie

Katie Mack Profile picture
Sep 21, 2018
I want to make you dizzy
I want to make you look up into the sky and comprehend, maybe for the first time, the darkness that lies beyond the evanescent wisp of the atmosphere, the endless depths of the cosmos, a desolation by degrees
I want the Earth to turn beneath you and knock your balance off, carry you eastward at a thousand miles an hour, into the light, and the dark, and the light again. I want you to watch the Earth rising you up to meet the rays of the morning sun
Read 14 tweets
Katie Mack Profile picture
Sep 7, 2018
In The Hitchhiker's Guide to the Galaxy, Douglas Adams wrote that the trick to flying is to "throw yourself at the ground and miss." It turns out that from a physics viewpoint, this is very nearly correct.
The trick is to actually throw yourself really fast *sideways* such that when you fall, you miss, and keep falling, and keep missing.
Newton drew a picture of this in Principia. Imagine you fire a cannonball so fast that by the time it falls to the ground, it has gone so far that the curvature of the Earth means that the ground is farther away. A planet with an unrealistically tall mountain on it. There are trajectories drawn from the mountain top, of projectiles fired at different speeds. The slow ones fall close to the base of the mountain. The faster ones go further around the Earth. The fastest goes all the way around. There are also some higher orbits depicted in the image.
Read 5 tweets
Katie Mack Profile picture
Sep 1, 2018
It is Friday night and I feel the need to tell you a thing about being stardust
Yes, you are made of stars. Yes, you, in particular.

Mostly.

All that carbon, oxygen, nitrogen, etc — that was all made in stars. Most of your body is made of that stuff: atoms that a star forged inside itself or at the moment of its unimaginably violent death.
So, yes, you are stardust. But only if you count by mass. If you count the number of atoms in you, most of those?

Hydrogen.

Never part of a star at all.

Most of your atoms have been in the Universe for 13.8 billion years.

Most of your atoms were forged in the Big Bang itself.
Read 5 tweets
Katie Mack Profile picture
Aug 21, 2018
I was contacted by a journalist about this today because someone in Turkey with almost a million followers tweeted out a version of this meme that somehow manages to be even more wrong
The confusion evidently comes from a New Scientist article that makes somewhat misleading claims based on a 2007 study whose speculative results have been disputed in the literature several times since then. And then someone stuck an image of a dark nebula to it, for fun.
The more-wrong version includes the irrelevant dark nebula pic, but adds spooky dark tendrils to it. 🙄
Read 6 tweets
Katie Mack Profile picture
Jul 26, 2018
Friends, we need to talk about The Future. It is no longer acceptable to complain about not having jetpacks and flying cars. Old TV shows have created a generation of people doing sci-fi-future envy wrong. Thread begins here.
JETPACKS exist. They’ve been around for decades. No one uses them because they are expensive, inefficient, extremely loud, and fantastically dangerous. Want to get somewhere fast? In many cities you can now walk down the street and rent an electric scooter with your phone. Enjoy.
FLYING CARS are a terrible idea. Traffic is chaotic enough in two dimensions. Being in an ordinary car is more likely to kill you than almost anything else you do. And you wanna put *rockets* on that thing?? Go get a helicopter license and stay away from the roads.
Read 15 tweets
Katie Mack Profile picture
May 11, 2018
I want to tell you a short story about #DarkMatter and how the search for it sometimes leads us to beautiful and surprising things. (thread)
One of the ways we look for (invisible) dark matter is through "self-annihilation." Idea is: when two dark matter particles love each other very much, they might (with some small probability) annihilate and create stuff we can see.
We haven't (yet) found conclusive evidence for dark matter annihilation. But we're searching! The main way to search is to try to find weird signals of light or cosmic rays that are hard to explain with what we know of astrophysics.
Read 13 tweets

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