Katie Mack Answers Your Many, Many Astrophysics Questions on JoCo Cruise 2019
Channel: Angela Brett
Date: 2019-04-04

Description from https://jococruise2019.sched.com/event/L9Ti/katie-mack-answers-your-many-many-astrophysics-questions

We know you have, like, hundreds of questions about astrophysics. Well, you're in luck, because Katie Mack is an astrophysicist, and she's here to answer every single one of them! (time permitting)

Description from me:
Katie Mack is a cosmologist, which means she studies the universe from the smallest to the largest scales, from the beginning to the end, and she was asked to give a Q&A with a short introduction about the universe.

We live in a galaxy. The universe is full of galaxies (including that one weird one in the Hubble Deep Field. You know who you are.) Each of them has millions or billions of stars. But most of the universe is entirely invisible, made of dark matter, which is almost, but not quite, entirely unlike The Force. Hey, if you want a transcript of exactly what she said, contribute improvements to the automatically-generated closed captions — I think community captions should be turned on. There’s also dark energy, which adds extra possibilities for the end of the universe. The universe is being weird, but eventually we won’t be able to see any of it, so 🤷🏻‍♀️. There isn’t time to discuss the other possibilities — the universe isn’t going to be around forever, you know!

Now that Katie Mack has introduced us to 95% of the universe, Paul Sabourin comes out to introduce her. Then she takes questions.

When were we first aware of a star going nova/supernova? (We sing ‘Haaaaa…’ to the questioner because of https://youtu.be/sW43Q7BbSAc)
Was all the matter in this room in a single star in the past? We are star stuff, but we’re also Big Bang debris.
We’re on a boat! Why can’t we see more stars?
Can you talk about how black holes manipulate time?
Are you a fan of science fiction, and if so, what science fiction annoys you the least, as a professional?
What science is science fiction really missing out on? What science would you like to see more fiction tapping into? Relativistic effects!
Why is there matter that didn’t annihilate, after matter and antimatter were created in equal parts? Is it due to some kind of asymmetry, or did the matter and antimatter fly away from each other very fast, and when they meet they will disappear? Baryogenesis! Something was weird in the early universe, and there’s nothing particularly weird in any particular direction (e.g. a region of antimatter, not like that galaxy that was called out earlier), so it’s the first thing.
What would be happening to Lorentz transformation equations if the speed were higher than the speed of light? It would violate causality! (I missed a bit of the answer to this one because I reached the 4GB file size limit and had to restart the recording)
Do you think dark matter is something in the Standard Model, or is there new physics there? It would be really really hard to get dark matter to fit within the Standard Model.
Is time a regular dimension like the other ones, such that the future already exists in some sense, or is it that it doesn’t exist and is actually created? Well, there’s this idea called the block universe, which is not the universe that Nathan Sawaya lives in but rather that first thing the questioner mentioned. But also, time is different in that it has a direction, because disorder increases with time.
If nothing can escape from black holes, how come pulsars and quasars emit radiation? Pulsars are spinning neutron stars, not black holes, so they’re not really relevant. Quasars are powered by black holes, and the twisted magnetic fields of the black holes accelerate particles and shoot them off into space. The particles are coming from the vicinity of the black holes, but not coming out of the black holes themselves.
What other ways could the universe end, other than heat death? You should go get her book, The End of Everything, if it’s out by the time you watch this video.
How do you wrap your head around how in relativity, from one reference frame time for one thing is going slower, while from the other reference frame, time for other thing is going slower?
What if spacetime itself has a weight, and that causes dark matter, or if light dilates differently and that gives an illusion of the acceleration of the expansion of the universe? The ‘tired light’ hypothesis doesn’t fit the data.