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Welcome to another installment of our LBS
physics deep dive.

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After exploring the world of experimental
physics at CERN in our first video

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documentary in episode 93, we'll stay in
Geneva for this one, but this time we'll

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dive into theoretical physics.

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We'll explore mysterious components of the
universe, like dark matter and dark

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energy.

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We'll also see how the study of gravity
intersects.

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with the study of particle physics,
especially when considering black holes

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and the early universe.

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Even crazier, we'll see that there are
actual experiments and observational

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projects going on to answer these
fundamental questions.

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Our guide for this episode is Valérie
Dormcke, permanent research staff member

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at CERN who did her PhD in Hamburg,
Germany, and postdocs in Trieste and

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Paris.

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When she's not trying to decipher the
mysteries of the universe, Valérie can be

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found on

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she's a big sailing fan.

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This is Learning Vagin Statistics, episode
95, recorded September 6, 2023.

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Hello my dear Vagins!

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Some of you have reached out for advice
and coaching in parallel to my online

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courses on intuitivevagin.com.

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So, to help you, I have started something
new.

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If you go to

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You can pair your online course with my
15-hour or 20-hour coaching packages to

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get a fully premium learning path.

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Each week, we'll get on a one-to-one call
and we'll walk through any questions,

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difficulties, or roadblocks that you may
have to jumpstart your learning even more.

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Again, that's topmate.io slash Alex
underscore and Dora.

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And now, let's talk theoretical physics
with Valerie Donka.

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I'll show you how to be a good peasy and
change your predictions.

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Valérie Damke, welcome to Learning Asian
Statistics.

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Glad to be here.

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Yeah.

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Thank you for taking the time.

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I am really happy to have you on the show.

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Again, a physics-packed episode.

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I'm really, really happy about that and I
have a lot of questions for you.

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I think you're the first theoretical
physicist to come on the show.

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That's cool.

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We're going to talk about topics.

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a bit different than those we talk about
when we have experimental physicists on

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the show.

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So that's cool, more diversity for the
listeners.

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And also, when that episode is going to
air, by the magic of time travel, episode

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93 will have been published.

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So that's the one at CERN.

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So the very special video documentary I
did at CERN with Kevin Kaif.

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So if listeners haven't checked it out
yet, I highly recommend it.

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And that one, of course, I recommend
mainly watching the YouTube video because

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I recorded and edited it firstly for video
format.

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You have access to the audio format also,
but I'm telling you, it's going to be

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funnier in video.

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So now to actually complete what we talked
about in episode 93.

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where Kevin does a lot of fun experiments
at CERN, today we are going to talk about

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another part of physics that's done at
CERN, thanks to you, Valerie.

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But first, before doing that, let's start
with your origin story.

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How did you come to the world of
theoretical physics, and how sinuous of a

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path was it?

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It was, it was more of a path that I kind
of ended up on without honestly thinking

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about it too much.

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It's kind of been a topic that has
fascinated me since I was quite young,

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reading science fiction books and the
like.

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And I basically, we just kind of following
my interests, taking the course of the

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university that interests me most without
thinking too much about where that would

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lead me in the end.

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And it was basically only when I was doing
my PhD that I realized, wow, I'm actually

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working on cosmology and kind of these big
open questions of the universe, which is

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something I was dreaming about as a kid.

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And somehow I got there without, somehow
without too much planning, but just

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following what I thought was kind of the
most interesting thing for me to do at

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every step.

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Oh yeah, so it's really like the call of
passion for you.

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In a sense, in a sense.

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Yeah, that's really cool.

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I mean, and that's also one of the cool
things of this kind of job, right?

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In physics or I don't know, airplane
pilots or firefighters.

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You can dream about them already as you're
a kid and then make that your job.

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I personally love my job, but...

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I'm afraid I cannot say that I dreamed
about patient statistics when I was a kid.

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Like I never told when I was five years
old, oh, I want to be a patient

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statistician.

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You know, that's not how it works,
unfortunately.

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Really?

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Yeah, no, I know, I know that must be
quite disappointing to a lot of people,

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but I had to burst that bubble because I
get a lot of questions about that, yeah.

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So.

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I would also say that you kind of have to
really...

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dream about or be enthusiastic about it,
because doing science, you always

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encounter moments when nothing works.

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Yeah.

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And if you're not passionate about
actually solving the problem, it's, you're

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just going to get stuck.

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Yeah.

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No, definitely.

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That's a very good point.

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And that's where actually statistics get
back in the, in the mix, because that's, I

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would say that's the same for

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programming and the kind of statistics at
least I do where you are going to get a

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lot of bumps along the way.

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And I always say to beginners that models
never work, only the last iteration of a

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model is going to work.

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And even then, you just have to be
satisfied with good enough.

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So that's a field where you have to become
comfortable failing all the time.

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First, be comfortable with making mistakes
and failing.

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And also where you need to be driven by
passion because if you don't have that

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inherent passion, you're not going to
still be driven to solve those numerous

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data analysis issues and bugs and stuff
like that.

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So now, I'd like to talk about what you do
actually, what you're doing nowadays,

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because we know you dreamt about doing
that since you were a child.

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But how would you define the work you're
doing nowadays and what are the topics

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that you are particularly interested in?

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Right, I think there's probably two parts
to that question, right?

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One is kind of how does an everyday day
actually look like?

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And the other one is, okay, what are the
big topics I'm interested in?

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Yeah.

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So to start with the format, so what my
day does not look like is that I kind of

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sit in my office all by myself, waiting
for the fantastic idea that is going to

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win me a Nobel Prize.

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That's kind of the image I had maybe as a
kid of how a theoretical thesis would

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work.

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But that's not at all what my day looks
like.

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Right.

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So I'm it's a lot discussing with people,
listening to talks, going to conferences,

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reading papers, discussing over coffee on
a blackboard over lunch.

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And then progress comes bit by bit.

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But it does kind of, there's never a lack
of things to work on.

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There's never a lack of interesting
questions.

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There's only always a lack of time to
decide what is the most interesting

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question of all the questions to work on.

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Because there's really a lot of things
that we don't understand.

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And that brings me a bit to the
overarching team of my research.

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So I work on the intersection of particle
physics and cosmology.

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So

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meaning kind of the physics of the very,
very smallest particles, the fundamental

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building blocks of nature.

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And at the same time, the physics of the
very largest scales, so the largest scales

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we can observe in our universe, and how
the latter can teach us something about

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the former.

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So how kind of from astrophysical or
cosmological observations, we can learn

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something about what is really the nature
of the fundamental building blocks of

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nature.

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Yeah, so small topics, fundamental
building blocks of nature.

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Yeah, thanks.

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That's interesting.

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I'm actually curious.

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So of course, we're going to talk about
the projects you work on a day to day a

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bit more.

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But also I'm curious now that you brought
up basically what your days look like

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concretely.

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Yeah.

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What's the part of basically solitary work
with pen and paper?

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What's the proportion of that in
comparison to, as you were saying,

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collaboration with people, exchange of
ideas and things like that?

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Because I think when you tell people
you're a theoretical physicist, and that's

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definitely the case when you tell people
you're a statistician, most of the people

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doing math on a blackboard.

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So most of the time, which is not true if
you're a statistician.

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So yeah, I'm curious how it is on your
slide.

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Yeah, it's probably similar.

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I mean, if I get one or two hours on block
to actually sit down and do a calculation,

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that's rather the exception than the rule.

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So it is, of course, part of my job, and I
enjoy it a lot.

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Sometimes just to have time just to think.

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really thoroughly about a problem, either
analytically, so pen and paper, or coding.

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But it's usually not like very long
stretches at a time because then you

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either you hit a problem, right?

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Or you hit a solution.

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And in either case, that's the point to
reach out to your collaborators and

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discuss the next steps.

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Yeah.

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I mean, that's interesting because for me,
now I'm using more and more the

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excuse of teaching to dive deep in a topic
and a project because, well, I have to be

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able to explain it properly to students.

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So that's actually, these are actually the
good occasions and rare, quite rare

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occasions where I can just be myself
working on the computer or sometimes with

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a pen and paper and really understand
deeply.

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a topic that I need and want to understand
because otherwise, yeah, you have so many

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other projects and solicitations that can
be hard to actually take the time just for

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yourself and focus on these.

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So I'm the same.

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I do appreciate these solitary moments,
although I'm happy that they are not 90%

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of the work, I have to say.

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Yeah, same here.

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And actually, Sue, you...

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You're a very math savvy person.

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So of course you know about patient stats,
but I'm curious if you were introduced to

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Bayesian methods actually, you know, in
your graduate studies or before, and if

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you use them from time to time in your own
work.

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No, so I never received any.

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any type of formal or informal training.

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So it's, of course, it's something we need
to know in the sense that we deal with

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empirical data.

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Even if I myself don't usually deal
directly with the empirical data, but I

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kind of deal with the processed empirical
data, or I deal with the publications that

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people have written on the data, and then
I need to evaluate, interpret, and kind of

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continue to work from there.

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But for that, of course, I need to kind of
understand the significance of certain

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experimental results.

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So I would say, okay, I mean, I have a
fundamental understanding of them, right.

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But it's, it's not something that actually
kind of on a on a day to day basis, I

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really am like deep in the in the details
of it.

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Yeah, because I'm more work at the kind of
one level.

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away, right?

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So kind of that I that I kind of take, I
need to understand what is the

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significance of that result, right?

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But once I've understood that, I can
basically work directly with the result

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without having going to back to the data
at every step.

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Which is quite a luxury, I have to say.

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I'm a bit jealous.

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I'm very, very happy that there's people
who do the work that I don't need to do.

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Yeah, that's, that's a very good point.

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I like that.

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And if you go listen to episode 93, you'll
see the difference between basically that

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kind of work that Valery does and the
experimental physics work where statistics

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is way more present and of course, patient
statistics is extremely helpful.

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So I find that super interesting to
notice.

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Just because you don't use patient stats,
Valery doesn't mean that your work is not

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interesting.

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I have to put that out there.

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On the contrary, I find it fascinating.

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So let's dive in because one of your areas
of interest is to go beyond the standard

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model phenomenology to kind of probe it,
if I understood correctly.

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So can you tell us what that means and
maybe first define the standard model for

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us?

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Right.

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So the standard model basically reflects
our current understanding of these

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fundamental building blocks of nature.

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So it kind of contains what we think are
kind of elementary particles, which are no

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longer further dividable into even smaller
particles.

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And there's not many of them.

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There's basically a handful of them,
depending how you count.

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00:15:37,952 --> 00:15:40,413
And we think that these...

233
00:15:40,470 --> 00:15:46,851
fundamental particles together with the
interactions between these particles that

234
00:15:46,851 --> 00:15:53,673
they explain all of kind of nature, the
way it surrounds us, right?

235
00:15:53,673 --> 00:15:59,155
So all, all everything that we can, we can
grasp, grasp or experience here on earth.

236
00:16:01,816 --> 00:16:03,736
And the standard model describes basically
this.

237
00:16:03,736 --> 00:16:07,817
So it describes kind of which building
blocks are there and how do they interact

238
00:16:08,097 --> 00:16:09,037
with each other.

239
00:16:10,350 --> 00:16:15,873
And now going beyond the standard model,
because a model is always a model, right?

240
00:16:15,873 --> 00:16:20,756
So it means that it describes kind of
nature to the best of our knowledge.

241
00:16:20,997 --> 00:16:24,079
But most models are incomplete at some
level, right?

242
00:16:24,079 --> 00:16:27,681
Because because it's kind of only a way
that we describe nature, not actually the

243
00:16:27,681 --> 00:16:29,262
fundamental theory of nature.

244
00:16:29,963 --> 00:16:34,366
And for this, the standard model of
particle physics, in particular, it, it

245
00:16:34,366 --> 00:16:39,729
does extremely well in many respects, one
could even say,

246
00:16:40,214 --> 00:16:45,496
frustratingly well, because like in all
our searches of looking for new

247
00:16:45,496 --> 00:16:50,297
interactions, looking for new particles
here at CERN at the Large Hadron Collider,

248
00:16:51,018 --> 00:16:56,040
we always keep confirming the predictions
that the standard model makes with

249
00:16:56,040 --> 00:16:57,380
incredible accuracy.

250
00:16:58,381 --> 00:17:00,002
But we still know the model is not
complete.

251
00:17:00,002 --> 00:17:03,283
And the reason we know that the model is
not complete basically comes from

252
00:17:03,283 --> 00:17:04,323
cosmology.

253
00:17:04,544 --> 00:17:09,305
So there's observations that we make about
the dynamics of the universe.

254
00:17:10,046 --> 00:17:15,850
or properties of the universe, which are
simply in contradiction with this model,

255
00:17:16,051 --> 00:17:19,453
which tells us that there's ingredients
missing.

256
00:17:19,914 --> 00:17:22,796
And we have a rough idea of what these
ingredients are.

257
00:17:23,537 --> 00:17:29,201
Or rather, maybe, instead of one rough
idea, we have 100 rough ideas.

258
00:17:29,342 --> 00:17:32,684
And the big question is, which one of
these is correct?

259
00:17:32,684 --> 00:17:34,125
Is any one of these correct?

260
00:17:34,606 --> 00:17:39,329
And how can we make progress in
understanding these missing parts better?

261
00:17:39,766 --> 00:17:45,327
So to give you some keywords, things like
dark energy, dark matter, those are some

262
00:17:45,327 --> 00:17:46,587
of the open questions.

263
00:17:47,428 --> 00:17:51,509
Yeah, because we know basically you say
they are open because first we cannot

264
00:17:51,509 --> 00:17:57,970
really explain them fully for now, as we
said in episode 93, but also we know that

265
00:17:57,970 --> 00:18:07,033
the standard model breaks down at those
points and cannot explain them.

266
00:18:07,393 --> 00:18:09,734
So that's basically what you're trying to
understand.

267
00:18:09,734 --> 00:18:14,476
Why does the standard model fail here and
how can we actually explain these

268
00:18:14,476 --> 00:18:14,836
phenomena?

269
00:18:14,836 --> 00:18:17,678
Correct.

270
00:18:17,678 --> 00:18:19,218
I see.

271
00:18:19,218 --> 00:18:21,979
So concretely, what does that research
look like?

272
00:18:22,400 --> 00:18:26,822
Maybe could you share an example of a
discovery or theoretical development in

273
00:18:26,822 --> 00:18:33,025
this field that has the potential to
reshape our understanding of particle

274
00:18:33,025 --> 00:18:33,805
physics?

275
00:18:35,154 --> 00:18:39,257
You mean like a discovery in the past that
did that or a discovery, potential

276
00:18:39,257 --> 00:18:41,098
discovery in the future that...

277
00:18:41,618 --> 00:18:42,399
I would say both.

278
00:18:42,399 --> 00:18:46,762
Yeah, both if you can.

279
00:18:46,762 --> 00:18:48,343
Let's start with the past.

280
00:18:50,265 --> 00:18:58,591
So one observation, for example, was
rotation curves of galaxies.

281
00:18:58,851 --> 00:19:02,213
So people were looking at galaxies in the
sky.

282
00:19:02,690 --> 00:19:09,715
And they were they were looking at kind of
how fast the stars were rotating, which

283
00:19:09,715 --> 00:19:12,717
you can do by measuring the redshift of
the stars.

284
00:19:12,718 --> 00:19:17,041
Because as they move away from us, the
light gets slightly red as they move

285
00:19:17,041 --> 00:19:19,003
towards us, the light gets slightly bluer.

286
00:19:20,204 --> 00:19:25,088
And if you know, like if you have an
object on a stationary orbit, and you

287
00:19:25,088 --> 00:19:28,830
know, you know, the orbit, you know, the
velocity.

288
00:19:29,471 --> 00:19:32,533
I mean, actually, even knowing the orbit
and the mass of stars enough.

289
00:19:33,314 --> 00:19:37,737
Then you can estimate how much mass you
need in a center in order to make that a

290
00:19:37,737 --> 00:19:39,598
stable orbit.

291
00:19:39,598 --> 00:19:44,141
And so that's just Newton dynamics, high
school physics.

292
00:19:44,401 --> 00:19:49,425
And what people observed is that the mass
that you needed in the center in order to

293
00:19:49,425 --> 00:19:53,988
put these stars on the orbits that were
being observed was much, much bigger than

294
00:19:53,988 --> 00:19:57,030
the mass you would have inferred just by
counting stars.

295
00:19:57,791 --> 00:20:00,132
And now you can say, OK, well, counting
stars is obviously not enough, right?

296
00:20:00,132 --> 00:20:01,113
Because there's going to be planets.

297
00:20:01,113 --> 00:20:02,513
Planets are not luminous.

298
00:20:03,086 --> 00:20:06,967
So there's going to be a bit of an offset,
but you would have expected that counting

299
00:20:06,967 --> 00:20:08,887
stars would give you a good estimate.

300
00:20:09,167 --> 00:20:10,688
And it turned out it was completely off.

301
00:20:10,688 --> 00:20:16,749
So it turned out it was kind of a big
amount of something that has an attractive

302
00:20:17,130 --> 00:20:22,311
gravitational force in the center of the
galaxies, or like in a halo around the

303
00:20:22,311 --> 00:20:26,172
galaxies, which was invisible to our
telescopes.

304
00:20:26,972 --> 00:20:31,973
And that is basically what I'm coined the
term dark matter.

305
00:20:32,054 --> 00:20:39,037
because it kind of has a gravitational
pull of matter, just like everything else.

306
00:20:39,037 --> 00:20:40,538
But it's dark, meaning we can't see it.

307
00:20:40,538 --> 00:20:45,781
And not seeing it means like not only kind
of we don't pick it up with telescopes,

308
00:20:45,781 --> 00:20:51,044
but kind of also all other type of
experiment that we've performed to date,

309
00:20:51,044 --> 00:20:53,245
trying to find this stuff.

310
00:20:53,245 --> 00:20:54,746
And this stuff should be around
everywhere, right?

311
00:20:54,746 --> 00:20:56,686
So it's not that there's none of it on
Earth.

312
00:20:57,727 --> 00:21:01,549
It's just that it's so incredibly weakly
interacting with...

313
00:21:01,549 --> 00:21:02,054
Yeah.

314
00:21:02,054 --> 00:21:05,975
all the instruments that we build, that
it's very difficult to see.

315
00:21:06,876 --> 00:21:10,777
And then observations, I mean, more
observations, particularly cosmological

316
00:21:10,777 --> 00:21:16,840
observations, reveal that there's actually
five times more of this dark matter than

317
00:21:16,840 --> 00:21:18,681
there is of what we call ordinary matter.

318
00:21:18,681 --> 00:21:22,962
So ordinary matter is everything that we
know of on Earth and everything that we

319
00:21:22,962 --> 00:21:25,523
can describe with our standard model of
part of the physics.

320
00:21:26,464 --> 00:21:30,545
Meaning that there's really a lot of stuff
out there that we don't know.

321
00:21:30,830 --> 00:21:32,531
That's just one example.

322
00:21:33,172 --> 00:21:35,774
And that kind of gave very clear
indication that the Sonop model of

323
00:21:35,774 --> 00:21:36,915
particle physics is incomplete.

324
00:21:36,915 --> 00:21:40,918
And that we're not only missing a little
bit, but that we're actually missing a

325
00:21:40,918 --> 00:21:45,962
very big bit of the picture.

326
00:21:45,962 --> 00:21:48,704
And along the same line of thought, you
know, what would really be a

327
00:21:48,704 --> 00:21:56,331
groundbreaking discovery if one of the
many experiments looking for such a dark

328
00:21:56,331 --> 00:22:00,033
matter particle, if they would actually
find something.

329
00:22:00,110 --> 00:22:03,672
I mean, even if they don't find anything,
if a particular experiment doesn't find

330
00:22:03,672 --> 00:22:07,214
anything, then okay, you still learn
something because you can probably exclude

331
00:22:07,214 --> 00:22:08,555
some class of models.

332
00:22:10,036 --> 00:22:14,480
But if one of them actually made a
discovery, and we would have kind of a

333
00:22:14,480 --> 00:22:20,864
very clear indication of which direction
to go in when we're kind of trying to

334
00:22:20,864 --> 00:22:28,029
describe these dark matter particles, that
would be a complete game changer.

335
00:22:28,309 --> 00:22:29,190
Yeah, for sure.

336
00:22:29,190 --> 00:22:35,772
And so these kinds of experiments are
underway at CERN in particular, right?

337
00:22:36,513 --> 00:22:38,534
Yeah, at CERN and across the world.

338
00:22:38,534 --> 00:22:45,536
I mean, it's something you can look for
when in a collider because you can always

339
00:22:45,536 --> 00:22:49,178
hope that as your collider reaches higher
and higher energy, or you have just more

340
00:22:49,178 --> 00:22:52,980
and more particles that you're colliding,
you'll eventually kind of reach the

341
00:22:52,980 --> 00:22:55,020
threshold for producing these particles.

342
00:22:55,401 --> 00:22:57,601
And then you can find indirect traces of
them.

343
00:22:58,258 --> 00:23:05,342
in the K channels, or you basically have
some sort of, not a collider, but

344
00:23:05,342 --> 00:23:09,325
basically just a very big detector volume
somewhere.

345
00:23:09,325 --> 00:23:16,149
So a very big amount of an noble gas, for
example, even water.

346
00:23:16,849 --> 00:23:20,572
And then you wait basically for a dark,
you like have to shield it very well

347
00:23:20,572 --> 00:23:21,412
against everything else.

348
00:23:21,412 --> 00:23:23,913
And then you wait for some dark matter
particle.

349
00:23:24,002 --> 00:23:28,205
to have one of these very rare
interactions with one of the atoms of your

350
00:23:28,205 --> 00:23:29,126
detector.

351
00:23:29,606 --> 00:23:31,327
And you're looking for that interaction.

352
00:23:31,348 --> 00:23:35,772
And there's a there's a range of
experiments underway, looking for very

353
00:23:35,772 --> 00:23:39,014
different types of these dark matter
candidates.

354
00:23:40,696 --> 00:23:46,801
Yeah, so but we've been we've been hoping
that we'll find it any day now.

355
00:23:47,041 --> 00:23:50,864
Basically, since I don't know, I mean,
basically, since I do physics.

356
00:23:52,926 --> 00:23:53,466
So we don't know.

357
00:23:53,466 --> 00:23:56,968
It could be around the corner or it could
be very well hidden.

358
00:23:57,749 --> 00:23:58,469
Yeah.

359
00:23:58,469 --> 00:24:04,352
I mean, these kinds of experiments, I
think I would not be able to work on them

360
00:24:04,352 --> 00:24:05,873
at least full time, you know, that's
awful.

361
00:24:05,873 --> 00:24:09,255
Like you're just waiting for something and
you cannot control anything.

362
00:24:10,896 --> 00:24:12,677
Oh, there's plenty of stuff to do.

363
00:24:12,677 --> 00:24:13,978
You're not just waiting, right?

364
00:24:13,978 --> 00:24:18,200
I mean, because you're basically
constantly fighting to reduce noise,

365
00:24:18,200 --> 00:24:21,138
reduce background, understand noise.

366
00:24:21,138 --> 00:24:26,261
understand background, argue with somebody
who's making noise in the building next

367
00:24:26,261 --> 00:24:27,082
door, right?

368
00:24:27,082 --> 00:24:28,683
And disrupting your experiments.

369
00:24:28,683 --> 00:24:33,726
So, Yeah, yeah, no, for sure.

370
00:24:33,726 --> 00:24:39,390
That's, yeah, that's something you have to
deal with all the time, I guess.

371
00:24:39,390 --> 00:24:44,053
But yeah, I mean, I would be also, you
know, incredibly stressed out.

372
00:24:44,053 --> 00:24:49,077
Like, so did the, I think a lot of them
are helium pools, right?

373
00:24:49,077 --> 00:24:50,277
Or something like that.

374
00:24:51,010 --> 00:24:54,691
Did the helium pool move tonight or not?

375
00:24:54,691 --> 00:24:58,432
I would be incredibly stressed out.

376
00:24:59,832 --> 00:25:01,332
Yeah, so thanks a lot.

377
00:25:01,693 --> 00:25:07,754
That's actually very interesting to hear
about that because I find this kind of

378
00:25:07,754 --> 00:25:11,495
experiment absolutely fascinating.

379
00:25:11,495 --> 00:25:15,756
And where does your work come into that
picture?

380
00:25:20,354 --> 00:25:22,835
So you're part of these big teams, right,
in physics.

381
00:25:22,835 --> 00:25:27,877
Like you see a physics paper, it's like
most of the time a lot of people, because

382
00:25:27,877 --> 00:25:32,579
a lot of you are very, like many of you
are very specialized in what they do.

383
00:25:32,579 --> 00:25:35,580
And so you bring one of the brick to the
paper.

384
00:25:35,580 --> 00:25:38,421
So you in this kind of work, what do you
do?

385
00:25:38,421 --> 00:25:41,003
What do you bring?

386
00:25:41,003 --> 00:25:45,765
So the papers really with like the many
hundreds of authors, they're usually the

387
00:25:45,765 --> 00:25:47,685
experimental collaborations.

388
00:25:47,685 --> 00:25:48,325
So.

389
00:25:48,414 --> 00:25:54,657
As a theorist, you know, I usually have
whatever, two, three, four, co-authors on

390
00:25:54,657 --> 00:25:54,858
a paper.

391
00:25:54,858 --> 00:25:55,678
That's a lot.

392
00:25:56,118 --> 00:25:56,359
Right.

393
00:25:56,359 --> 00:26:01,422
So we build, of course, very heavily on
the results of these big collaboration

394
00:26:01,422 --> 00:26:02,282
papers.

395
00:26:03,423 --> 00:26:08,926
But largely, the work that I concretely do
is with much smaller groups of people.

396
00:26:09,587 --> 00:26:13,769
So, yeah, I basically have two...

397
00:26:14,242 --> 00:26:16,442
two main approaches to this.

398
00:26:16,442 --> 00:26:21,184
One is kind of starting from really
standard model of particle physics, and

399
00:26:21,184 --> 00:26:26,947
trying to come up with possible extensions
of that, which kind of makes sense within

400
00:26:26,947 --> 00:26:29,268
the framework that the standard model is
written in.

401
00:26:29,268 --> 00:26:33,209
So it makes sense within the symmetries
that they are, makes sense within the

402
00:26:33,209 --> 00:26:38,031
framework of quantum field theory, and
address some of these open problems that

403
00:26:38,031 --> 00:26:39,652
we have in cosmology.

404
00:26:40,132 --> 00:26:43,393
And then the question is, okay, once
you've kind of constructed

405
00:26:44,250 --> 00:26:50,873
such an inherently consistent model, what
sort of implications might that have in

406
00:26:50,873 --> 00:26:52,253
various types of experiments?

407
00:26:52,253 --> 00:26:52,473
Right.

408
00:26:52,473 --> 00:26:56,575
So that can be experiments like the chart
Hadron Collider.

409
00:26:56,715 --> 00:26:59,977
It can also be some astrophysical
observations, or it can be some

410
00:26:59,977 --> 00:27:01,077
cosmological observations.

411
00:27:01,077 --> 00:27:08,740
So that's kind of one approach, and coming
kind of more from the fundamental

412
00:27:08,740 --> 00:27:10,301
mathematical theory of it.

413
00:27:11,486 --> 00:27:16,770
My other approach is more the lamppost
approach, meaning, well, you, you look

414
00:27:16,770 --> 00:27:19,532
where you can look right, and you hope
that nature is kind.

415
00:27:20,813 --> 00:27:26,978
And they're kind of the my approach is to
say, okay, what types of probes do we have

416
00:27:26,978 --> 00:27:30,681
of the universe of astrophysical
processes?

417
00:27:31,862 --> 00:27:37,147
Try and understand as much as possible
about those, and then see what type of

418
00:27:37,147 --> 00:27:40,709
models or what kind of types of building
blocks of models.

419
00:27:40,874 --> 00:27:44,735
you could test with these types of
observations.

420
00:27:44,735 --> 00:27:50,796
And there, for example, the new big player
in the game are gravitational waves.

421
00:27:52,117 --> 00:27:58,078
Because now since the first discovery with
LIGO and now a tentative discovery in a

422
00:27:58,078 --> 00:28:03,580
different frequency range this year with
the pulse of timing arrays, that's kind of

423
00:28:03,580 --> 00:28:07,041
opening up a completely new way of
observing our universe.

424
00:28:07,901 --> 00:28:10,041
And so there's the potential for...

425
00:28:10,798 --> 00:28:13,199
for big excitement in that field.

426
00:28:13,199 --> 00:28:20,423
So I'm also just involved in trying to
understand as much as possible about how

427
00:28:20,423 --> 00:28:24,525
gravitational waves can reveal something
about the universe.

428
00:28:25,866 --> 00:28:26,186
Oh, yeah.

429
00:28:26,186 --> 00:28:29,007
So that's actually fascinating.

430
00:28:29,007 --> 00:28:32,069
So yeah, talk to us a bit more about that,
basically.

431
00:28:32,589 --> 00:28:36,632
What can gravitational waves tell us about
the universe?

432
00:28:36,632 --> 00:28:40,578
And maybe redefine quickly what
gravitational waves

433
00:28:40,578 --> 00:28:42,219
waves are for listeners?

434
00:28:42,219 --> 00:28:48,883
Right, so gravitational waves are, we
think of them as perturbations of the

435
00:28:48,883 --> 00:28:51,805
metric, so perturbations of space-time.

436
00:28:52,046 --> 00:28:59,370
So the type of gravitational waves that
we've already seen with LIGO and Virgo,

437
00:29:00,071 --> 00:29:03,573
which are big Michelson interferometers,
so the type of

438
00:29:09,398 --> 00:29:12,878
which are circling each other and then
finally merging.

439
00:29:12,898 --> 00:29:15,319
So these are like extremely massive
objects.

440
00:29:15,319 --> 00:29:21,821
And as you might know, a massive object
kind of creates if you want a dent in

441
00:29:21,821 --> 00:29:22,801
space-time.

442
00:29:23,381 --> 00:29:26,782
And if you have two of them, just kind of
their dance around each other really like

443
00:29:26,782 --> 00:29:32,544
sends out ripples of this kind of
space-time perturbations out into the

444
00:29:32,544 --> 00:29:33,444
universe.

445
00:29:34,144 --> 00:29:37,985
If you're very close to a black hole,
right, these ripples will be quite

446
00:29:37,985 --> 00:29:38,858
significant.

447
00:29:38,858 --> 00:29:40,699
But then you'd also have all sorts of
other problems, right?

448
00:29:40,699 --> 00:29:45,242
Because if you're really close to black
hole, I mean, then you have a lot of

449
00:29:45,242 --> 00:29:46,122
problems.

450
00:29:47,003 --> 00:29:53,207
So, by the time these gravitational waves
reach us, they've kind of spread out very

451
00:29:53,207 --> 00:29:57,089
far, meaning the amplitude is very much
decreased.

452
00:29:57,089 --> 00:30:00,972
So, by the time they reach us, these are
typically very, very small, like tiny

453
00:30:00,972 --> 00:30:03,813
perturbations in space time.

454
00:30:04,230 --> 00:30:07,290
So it's not something we have to worry
about in everyday life, rather we need to

455
00:30:07,290 --> 00:30:10,771
build an extremely sensitive detector to
even pick them up.

456
00:30:11,212 --> 00:30:16,773
And so, so far, the observations that
we've made are this type of observation.

457
00:30:16,773 --> 00:30:25,715
So observations of these black holes
merging, which happened, I mean, still at

458
00:30:26,316 --> 00:30:30,737
the distance of megaparsecs or gigaparsecs
from here, right?

459
00:30:30,737 --> 00:30:32,817
So it kind of...

460
00:30:34,506 --> 00:30:37,788
Yeah, quite far away on cosmological
scales.

461
00:30:39,229 --> 00:30:44,832
But nevertheless, compared to the lifespan
of the universe, these are still fairly

462
00:30:44,832 --> 00:30:45,632
recent events.

463
00:30:45,632 --> 00:30:52,156
So at the moment, we're using this to
learn, as a new way to learn about the

464
00:30:52,156 --> 00:30:57,218
universe surrounding us or the more recent
universe or the relatively recent

465
00:30:57,218 --> 00:30:58,098
universe.

466
00:31:03,446 --> 00:31:07,869
Because these gravitational waves are so
weakly interacting with everything, in

467
00:31:07,869 --> 00:31:11,212
principle, even gravitational waves
generated in the very, very early

468
00:31:11,212 --> 00:31:15,676
universe, when the universe was not yet
transparent to photons, when kind of no

469
00:31:15,676 --> 00:31:19,138
other messenger could escape this
primordial soup.

470
00:31:19,479 --> 00:31:20,940
Gravitational waves could.

471
00:31:20,940 --> 00:31:25,804
So in principle, if we detected them
today, they could reveal information about

472
00:31:25,804 --> 00:31:29,887
extremely early times in the universe,
when the temperatures in the universe were

473
00:31:29,887 --> 00:31:32,566
extremely high, when all the fundamental
particles.

474
00:31:32,566 --> 00:31:35,187
kind of existed as fundamental particles.

475
00:31:35,308 --> 00:31:40,211
And when we can really kind of probe these
constituents of the standard model or of

476
00:31:40,211 --> 00:31:41,952
any model beyond the standard model.

477
00:31:42,313 --> 00:31:44,975
So that's the ultimate hope.

478
00:31:47,117 --> 00:31:51,340
But it's challenging because we don't know
what is the amplitude of these gravitation

479
00:31:51,340 --> 00:31:53,001
waves from the very early universe.

480
00:31:53,141 --> 00:31:58,325
And so we first need to understand the
gravitation waves generated in the late

481
00:31:58,325 --> 00:31:59,205
universe.

482
00:32:00,070 --> 00:32:04,012
Make sure we fully understand that before
we kind of look for a fainter signal.

483
00:32:04,012 --> 00:32:06,753
Very similar to with photons, right?

484
00:32:06,753 --> 00:32:10,796
You basically first need to kind of
understand all the light kind of coming

485
00:32:10,796 --> 00:32:13,077
from the nearby universe, coming from the
galaxy.

486
00:32:13,637 --> 00:32:16,299
And only when you have a very good
understanding of your foregrounds, can you

487
00:32:16,299 --> 00:32:21,401
go and can you look for fainter light that
is coming from earlier times.

488
00:32:23,443 --> 00:32:25,183
Yeah, yeah, that makes sense.

489
00:32:25,183 --> 00:32:29,342
Because also those waves are like so much
weaker that...

490
00:32:29,342 --> 00:32:34,804
Also, I'm guessing you have to be a bit
more aware of what you're looking for,

491
00:32:35,344 --> 00:32:37,465
because otherwise it's even harder.

492
00:32:38,085 --> 00:32:42,507
And to understand, do we know if...

493
00:32:43,868 --> 00:32:45,288
Just one black hole, for instance?

494
00:32:45,288 --> 00:32:52,151
So for instance, the back hole at the
center of our galaxy, is it emitting also

495
00:32:52,151 --> 00:32:56,653
gravitational waves, but since it's not
orbiting another one, at least that we

496
00:32:56,653 --> 00:32:57,473
know of,

497
00:32:57,782 --> 00:33:00,943
the gravitational waves are weaker so we
cannot see them?

498
00:33:00,943 --> 00:33:06,266
Or do we know that, no, you have to have
the collision of two massive objects to

499
00:33:06,266 --> 00:33:08,267
get those gravitational waves?

500
00:33:08,788 --> 00:33:14,331
Yeah, so a single black hole won't do it
because anything that is perfect spherical

501
00:33:14,331 --> 00:33:16,732
symmetry won't do it.

502
00:33:18,353 --> 00:33:21,795
That has to do with the fact that these
gravitational waves are tensor modes,

503
00:33:21,795 --> 00:33:21,955
right?

504
00:33:21,955 --> 00:33:26,477
So they have two Lorentz indices and
something that's spherical symmetric.

505
00:33:27,018 --> 00:33:28,378
is a scalar quantity.

506
00:33:28,418 --> 00:33:30,499
So a single black hole won't do it.

507
00:33:30,679 --> 00:33:35,981
So you need two, or you need a black hole
and another massive object, so you have a

508
00:33:35,981 --> 00:33:36,862
black hole and a neutron star.

509
00:33:36,862 --> 00:33:36,982
Okay.

510
00:33:36,982 --> 00:33:41,164
Or anything else that breaks spherical
symmetry, right?

511
00:33:41,164 --> 00:33:43,825
So kind of, I don't know, you dancing
around, right?

512
00:33:43,825 --> 00:33:46,106
That will in principle generate
gravitational waves.

513
00:33:46,106 --> 00:33:49,587
They're just very, very small.

514
00:33:50,127 --> 00:33:50,508
Thank you.

515
00:33:50,508 --> 00:33:55,629
I'm flattered.

516
00:33:55,766 --> 00:33:56,346
Yeah, I see.

517
00:33:56,346 --> 00:33:56,646
Okay.

518
00:33:56,646 --> 00:34:03,890
Yeah, so it's very like, it's really the
density of the objects that count.

519
00:34:03,890 --> 00:34:05,651
Yeah, again, you can imagine that.

520
00:34:05,651 --> 00:34:09,913
A large concentration of mass and in some
asymmetric way.

521
00:34:09,913 --> 00:34:15,376
So some sort of violent process, which is
condensing a lot of energy, a lot of mass.

522
00:34:15,496 --> 00:34:16,116
Yeah.

523
00:34:16,357 --> 00:34:19,918
But in some way that is moving in a bit of
a non-trivial way.

524
00:34:21,179 --> 00:34:22,960
Yeah, that makes sense.

525
00:34:23,601 --> 00:34:25,621
Even though I...

526
00:34:25,638 --> 00:34:30,640
I like thinking about these things because
it's so hard to imagine.

527
00:34:31,061 --> 00:34:36,444
Like the power of these collisions must be
just incredibly devastating.

528
00:34:36,444 --> 00:34:43,809
I would love to see that in a way, but
that's so like, it's really impressive and

529
00:34:43,809 --> 00:34:46,550
at the same time, really frightening.

530
00:34:46,550 --> 00:34:47,231
Yeah.

531
00:34:47,231 --> 00:34:51,913
So the, the gravitational waves that we
saw.

532
00:34:52,170 --> 00:34:57,933
with LIGO, there we think it's something
like two black holes, roughly after the

533
00:34:57,933 --> 00:35:03,877
mass, like roughly 10 solar masses each
colliding, a bit more.

534
00:35:03,877 --> 00:35:08,140
And the energy that is just the energy
that is released into gravitational waves

535
00:35:08,140 --> 00:35:10,721
corresponds roughly to the mass of our
sun.

536
00:35:11,422 --> 00:35:13,263
So it's a huge amount of energy.

537
00:35:13,263 --> 00:35:16,885
And now the gravitational waves that we
think we might have seen with these pulsar

538
00:35:16,885 --> 00:35:17,945
timing arrays.

539
00:35:17,974 --> 00:35:19,594
These are even more massive objects.

540
00:35:19,594 --> 00:35:22,736
These are really the large black holes,
right, like the one in the center of a

541
00:35:22,736 --> 00:35:25,157
galaxy that we think we see colliding.

542
00:35:25,157 --> 00:35:31,940
So this is two far away galaxies, each
with their big, massive 10 to the 6 solar

543
00:35:31,940 --> 00:35:33,780
mass black hole in the center.

544
00:35:34,101 --> 00:35:38,403
And when they collide, that's the signal
that we expect.

545
00:35:39,183 --> 00:35:41,044
So that's a massive event, right?

546
00:35:41,044 --> 00:35:43,445
I mean, two galaxies colliding.

547
00:35:45,554 --> 00:35:48,275
Yeah, you don't want to be close to
witness that.

548
00:35:48,915 --> 00:35:55,057
Yeah, no, that's for sure.

549
00:35:55,558 --> 00:36:03,401
These are absolutely fascinating topics
and I'm wondering what are the main

550
00:36:03,401 --> 00:36:12,545
challenges in understanding these topics
right now and how do you folks as

551
00:36:12,545 --> 00:36:14,585
researchers in this field...

552
00:36:14,886 --> 00:36:17,167
address them.

553
00:36:17,167 --> 00:36:20,168
That's, that's a broad question, right?

554
00:36:20,248 --> 00:36:26,030
I mean, there's different levels of
challenges, right?

555
00:36:26,030 --> 00:36:30,612
So when it comes down, for example, to
let's say something, something concrete,

556
00:36:30,612 --> 00:36:35,514
like understanding these signals that we
think might be from gravitational waves,

557
00:36:36,114 --> 00:36:39,676
then I mean, a lot of the problems boil
down to, you know, making sure this is a

558
00:36:39,676 --> 00:36:43,497
signal and not a background or a noise
source.

559
00:36:43,717 --> 00:36:44,277
So

560
00:36:44,534 --> 00:36:52,076
That means, of course, building
experiments that are extremely precise

561
00:36:52,177 --> 00:36:53,537
measurement devices.

562
00:36:54,678 --> 00:37:01,941
It also means a lot of modeling of the
various components that go in, and kind of

563
00:37:01,941 --> 00:37:04,942
both on from the theoretical side and also
from the experimental side.

564
00:37:06,023 --> 00:37:11,905
And then when you get the data, again, to
cross-check, is this really the type of

565
00:37:11,905 --> 00:37:13,206
signal that we have kind of...

566
00:37:13,206 --> 00:37:17,447
Do we have a way, a robust way to
distinguish what we call a signal from

567
00:37:17,447 --> 00:37:19,147
something that we call a background?

568
00:37:19,647 --> 00:37:23,008
Take it into account that we might not
have thought of every possible background,

569
00:37:23,008 --> 00:37:23,188
right?

570
00:37:23,188 --> 00:37:28,170
So do we kind of really have a telltale
signal of what we think the signal would

571
00:37:28,170 --> 00:37:28,930
look like, right?

572
00:37:28,930 --> 00:37:31,771
And typically all these analysis are done
as blind analysis, right?

573
00:37:31,771 --> 00:37:35,672
So you think about what signal you need to
see in order to be convinced that this is

574
00:37:35,672 --> 00:37:40,153
what you're looking for before you open
the box and look at your data.

575
00:37:41,513 --> 00:37:42,993
So that's one challenge.

576
00:37:43,038 --> 00:37:47,960
more kind of on the data analysis or
experimental side.

577
00:37:51,783 --> 00:37:55,485
The other challenge may be more on the
theory side.

578
00:37:55,485 --> 00:38:00,127
So when you're kind of building models,
which extend to standard model of particle

579
00:38:00,127 --> 00:38:06,211
physics, there's many, many options, and
you need some sort of guiding principle.

580
00:38:06,211 --> 00:38:10,674
And I mean, if you're lucky, you have data
to guide you, you have some sort of

581
00:38:10,674 --> 00:38:14,757
anomaly, something you feel like, okay,
here's the weak point, right?

582
00:38:14,757 --> 00:38:18,339
Here's kind of where you need to poke,
where you need to extend.

583
00:38:19,261 --> 00:38:21,583
Sometimes you have things like simplicity,
right?

584
00:38:21,583 --> 00:38:24,465
Which you kind of hope is a good
principle, though, of course, you never

585
00:38:24,465 --> 00:38:25,566
know that that's a good principle.

586
00:38:25,566 --> 00:38:26,766
Yeah.

587
00:38:28,568 --> 00:38:34,033
And recently, that's really been a bit of
a challenge, precisely because the

588
00:38:34,033 --> 00:38:37,976
standout model works as well as it does.

589
00:38:38,557 --> 00:38:39,617
There's no...

590
00:38:40,010 --> 00:38:41,950
I mean, sure, we know we need to explain
dark matter, right?

591
00:38:41,950 --> 00:38:45,351
But there's many, many possible options
how that dark matter could or could not

592
00:38:45,351 --> 00:38:46,991
tie into the standard model.

593
00:38:47,232 --> 00:38:53,813
And there's no very obvious way, like,
there's no obvious weak point at the

594
00:38:53,813 --> 00:38:54,934
standard model.

595
00:38:54,934 --> 00:38:56,114
It is not precise weak point.

596
00:38:56,114 --> 00:38:59,615
I mean, there's a global weakness, things
that cannot explain, but it's kind of not

597
00:38:59,615 --> 00:39:06,037
quite clear where exactly it needs to be
refined or extended.

598
00:39:07,037 --> 00:39:08,597
And that I think for

599
00:39:08,886 --> 00:39:11,927
In the past, it was more clear, or people
had pretty clear ideas, right?

600
00:39:11,927 --> 00:39:14,508
And then there was pretty obvious things
that needed to be checked, right?

601
00:39:14,508 --> 00:39:17,329
So we needed to find the Higgs particle,
right?

602
00:39:17,329 --> 00:39:19,950
So the last missing particle of this then
our model.

603
00:39:20,010 --> 00:39:23,812
And then we also thought, because the, I
mean, the Higgs particle has certain

604
00:39:23,812 --> 00:39:27,513
properties, which kind of led us to
believe that we thought, okay, once we

605
00:39:27,513 --> 00:39:32,115
find the Higgs particle, we should also be
finding other particles somehow related to

606
00:39:32,115 --> 00:39:37,957
this particle that would naturally explain
certain open challenges.

607
00:39:38,486 --> 00:39:43,127
But the fact that we haven't found them
and that we're just kind of testing with

608
00:39:43,127 --> 00:39:46,688
higher and higher accuracy, and we're just
kind of getting the prediction of the

609
00:39:46,688 --> 00:39:49,329
standard model or confirming the
prediction of the standard model without

610
00:39:49,329 --> 00:39:56,111
finding any small deviations is making it
very hard to kind of decide a bit.

611
00:39:57,051 --> 00:40:00,332
What's yeah, how, how should the extension
work?

612
00:40:00,332 --> 00:40:00,672
Right?

613
00:40:00,672 --> 00:40:04,993
And how should the extension like is, is
the extension in such a way that we can

614
00:40:04,993 --> 00:40:05,994
actually test it with.

615
00:40:05,994 --> 00:40:07,175
with the tools that we have, right?

616
00:40:07,175 --> 00:40:09,637
Or do we need to think differently?

617
00:40:09,637 --> 00:40:13,760
I mean, either different types of
experiments, but also maybe different

618
00:40:14,021 --> 00:40:20,467
theoretical concepts, because so far, most
extensions of the standard model kind of

619
00:40:20,467 --> 00:40:24,130
rely on the same theoretical framework
point of view theory.

620
00:40:24,911 --> 00:40:27,914
And then they kind of within that
framework, you try different things.

621
00:40:28,735 --> 00:40:32,077
But the fact that kind of we haven't had a
real breakthrough there.

622
00:40:33,914 --> 00:40:37,856
maybe indicating, okay, whatever, you
know, it's just at higher energies, which

623
00:40:37,856 --> 00:40:43,499
we can't reach, what may be indicating the
framework we're thinking in is maybe not

624
00:40:43,499 --> 00:40:44,379
the best.

625
00:40:44,739 --> 00:40:51,103
So yeah, there's many, many questions,
many levels of questions that can be

626
00:40:51,103 --> 00:40:51,923
addressed.

627
00:40:52,504 --> 00:40:54,644
Yeah, that's really interesting.

628
00:40:56,806 --> 00:41:01,008
I'm curious, basically, what would you
like to be true?

629
00:41:03,934 --> 00:41:10,375
something that at some point nature will
tell you, what would you like to see and

630
00:41:10,375 --> 00:41:15,517
to observe and the kind of consequences it
would have on our understanding of how the

631
00:41:15,517 --> 00:41:17,517
universe works?

632
00:41:18,258 --> 00:41:22,799
Well, I would mainly like nature to
produce something that we can, like give

633
00:41:22,799 --> 00:41:23,999
us something to work with.

634
00:41:23,999 --> 00:41:28,141
I would like nature to be kind enough to
produce some sort of signal, be it in dark

635
00:41:28,141 --> 00:41:30,741
matter, be it in gravitational waves, be
it at a collider.

636
00:41:31,862 --> 00:41:35,983
that actually gives us something which is
accessible with the two worlds, the

637
00:41:35,983 --> 00:41:38,183
experiments that we have at the moment.

638
00:41:38,823 --> 00:41:45,045
Because it could simply be that all these
completions of the standard model live at

639
00:41:45,045 --> 00:41:49,826
an extremely high energy scale, which is
simply inaccessible to any type of

640
00:41:49,826 --> 00:41:51,247
collider we can build on Earth.

641
00:41:51,247 --> 00:41:58,909
And that'll make it not impossible, but
very, very much harder to actually unravel

642
00:41:58,909 --> 00:41:59,949
these questions.

643
00:42:02,770 --> 00:42:04,730
Yeah, yeah, for sure.

644
00:42:04,910 --> 00:42:12,534
And that, I mean, so that's one part of
the work you're doing.

645
00:42:12,534 --> 00:42:17,596
I told that work around gravitational
waves, which are of course related to

646
00:42:17,596 --> 00:42:21,298
gravity, in case people didn't understand.

647
00:42:21,298 --> 00:42:28,021
Oh, and by the way, on the podcast, I had
another researcher called Laura Mansfield

648
00:42:28,021 --> 00:42:30,461
and she's working on gravity waves.

649
00:42:30,646 --> 00:42:33,627
which are not the same as gravitational
waves.

650
00:42:34,508 --> 00:42:41,612
That's quite confusing, but yeah, that's
also actually very interesting field of

651
00:42:41,612 --> 00:42:46,994
research, basically gravity waves and the
relationship with climate.

652
00:42:47,215 --> 00:42:49,236
That's all here on Earth.

653
00:42:49,636 --> 00:42:54,119
But that's also related to gravitational
waves in a way, in the sense that it's big

654
00:42:54,119 --> 00:42:56,019
objects basically on Earth.

655
00:42:56,400 --> 00:42:59,821
Like the Everest or the Mont Blanc or all
these big

656
00:42:59,902 --> 00:43:07,486
massive mountains which actually distort a
bit the gravitational field around them

657
00:43:07,486 --> 00:43:10,668
and that has impact on the climate.

658
00:43:10,668 --> 00:43:12,228
How do you model that?

659
00:43:12,809 --> 00:43:18,552
Basian modeling gets here because that's
really useful because you don't have a lot

660
00:43:18,552 --> 00:43:20,073
of sample size.

661
00:43:20,073 --> 00:43:23,635
I recommend listening to Episode 64.

662
00:43:23,635 --> 00:43:26,077
I put that in the show notes.

663
00:43:27,546 --> 00:43:33,750
Yeah, I was fascinated by the fact that
gravity, you can study it here on Earth,

664
00:43:33,750 --> 00:43:39,974
but also it has incredible effects in the
universe and at masses that we cannot even

665
00:43:39,974 --> 00:43:44,817
imagine, right, with the collisions of
black holes and collisions of neuron

666
00:43:44,817 --> 00:43:48,700
stars, so that's really something I find
fascinating.

667
00:43:49,140 --> 00:43:57,005
And actually, can you make the distinction
between a neuron star and a black hole

668
00:43:57,342 --> 00:44:02,424
listeners and yeah, so that they
understand a bit the difference between

669
00:44:02,424 --> 00:44:02,664
both.

670
00:44:02,664 --> 00:44:02,924
Right.

671
00:44:02,924 --> 00:44:13,388
So a neutron star is made of neutrons,
meaning kind of it's a very, very densely

672
00:44:13,648 --> 00:44:17,990
packed environment of nuclear matter.

673
00:44:19,270 --> 00:44:22,292
And a black hole is even more denser,
right?

674
00:44:22,292 --> 00:44:26,153
So a black hole is really the densest
object that we can imagine.

675
00:44:27,218 --> 00:44:32,982
where kind of matter has really any type
of matter has really just collapsed into

676
00:44:32,982 --> 00:44:37,086
this object, and you don't care any much
anymore kind of what it was initially made

677
00:44:37,086 --> 00:44:37,546
out of, right?

678
00:44:37,546 --> 00:44:39,708
If we just has one property.

679
00:44:39,708 --> 00:44:44,071
Of course, it can also spin, but
basically, it only has one property, which

680
00:44:44,071 --> 00:44:45,493
has which is its mass, right?

681
00:44:45,493 --> 00:44:48,114
And then it may also have spin if it's if
it's rotating.

682
00:44:49,236 --> 00:44:52,098
But it doesn't it doesn't matter anymore
what it was made out of.

683
00:44:52,098 --> 00:44:56,601
So one, one consequence of that is that if
you have two

684
00:44:57,138 --> 00:45:01,119
neutron stars merging as they get very
close to each other, their gravitational

685
00:45:01,119 --> 00:45:03,640
force will slightly distort them.

686
00:45:03,640 --> 00:45:06,882
So they can be a little bit deformed
because despite that they are very, very

687
00:45:06,882 --> 00:45:12,124
compact, and very dense, they can still be
kind of slightly deformed as they get very

688
00:45:12,124 --> 00:45:17,427
close to each other, whereas two black
holes will really stay perfectly spherical

689
00:45:17,427 --> 00:45:19,527
as they as they approach each other.

690
00:45:19,648 --> 00:45:24,129
So you can tell the difference between the
two by looking at

691
00:45:24,642 --> 00:45:29,037
details of the gravitational wave signal
as you approach this merger event.

692
00:45:32,110 --> 00:45:32,970
Okay.

693
00:45:34,150 --> 00:45:40,652
I didn't know that black hole stayed
spherical even as they approach each

694
00:45:40,652 --> 00:45:41,232
other.

695
00:45:41,232 --> 00:45:44,873
Is that because they are so dense that
they cannot be deformed?

696
00:45:45,554 --> 00:45:48,274
Yeah, it's basically because they are so
dense.

697
00:45:49,535 --> 00:45:53,376
And because they, I mean, in some sense,
despite that they are physical objects in

698
00:45:53,376 --> 00:45:58,177
our universe, in some sense, they kind of
become a rather mathematical object.

699
00:45:59,866 --> 00:46:07,408
Yeah, like a perfect sphere that you
cannot deform or do anything on.

700
00:46:07,408 --> 00:46:07,868
It's really weird.

701
00:46:07,868 --> 00:46:08,448
Yeah.

702
00:46:10,489 --> 00:46:13,469
And it's crazy that we're actually seeing
them, right?

703
00:46:13,469 --> 00:46:18,311
I mean, both in these gravitation wave
signals as also then with direct

704
00:46:18,311 --> 00:46:21,952
observations with optical telescopes.

705
00:46:22,552 --> 00:46:26,813
That's like this first picture of the
black hole in our galaxy and the

706
00:46:26,813 --> 00:46:28,033
neighboring galaxy.

707
00:46:28,293 --> 00:46:28,746
Yeah.

708
00:46:28,746 --> 00:46:31,827
Yeah.

709
00:46:31,827 --> 00:46:40,390
And so your work on gravity, I'm curious
to understand it because here, obviously

710
00:46:40,390 --> 00:46:47,213
when we talk about gravity, gravity is so
weak that you have to have so massive

711
00:46:47,213 --> 00:46:52,475
objects to really see its effects and also
it needs a lot of time.

712
00:46:52,475 --> 00:46:58,617
So obviously here we're dealing with the
largest scales of the universe.

713
00:46:59,498 --> 00:47:02,899
But you also work on particle physics, as
you were saying, and you work at CERN,

714
00:47:02,899 --> 00:47:06,700
where particle physics is one of the
biggest fields.

715
00:47:06,700 --> 00:47:13,621
So I'm curious, how does that study of
gravity intersect with the study of

716
00:47:13,621 --> 00:47:19,843
particle physics, especially when we
consider the phenomena you work on, so

717
00:47:19,843 --> 00:47:24,564
especially black holes and or the early
universe?

718
00:47:25,585 --> 00:47:27,465
Right.

719
00:47:28,638 --> 00:47:32,821
Well, I mean, anybody, you know, who's, I
don't know, fallen down the stairs, right,

720
00:47:32,821 --> 00:47:34,702
will not say gravity is a weak force.

721
00:47:35,163 --> 00:47:41,388
But indeed, right on Earth, right, when we
compare the force of gravity to the other

722
00:47:41,388 --> 00:47:46,472
forces that we have, so the forces that
bind atoms together, things like that,

723
00:47:47,313 --> 00:47:48,514
gravity is extremely weak.

724
00:47:48,514 --> 00:47:53,138
So when we perform any particle physics
experiment on Earth, we just completely

725
00:47:53,138 --> 00:47:57,120
neglect gravity, and we're not introducing
any error in our estimations.

726
00:47:58,098 --> 00:48:02,519
Now, gravity can become important, as you
say, either if you have some very massive

727
00:48:02,519 --> 00:48:08,601
objects like black holes, or if you have
very far distances, because here on Earth,

728
00:48:08,601 --> 00:48:13,542
kind of, okay, we have so much matter
interacting so strongly that we don't care

729
00:48:13,542 --> 00:48:14,642
about gravity.

730
00:48:14,682 --> 00:48:17,343
But the universe as a whole is actually
pretty empty.

731
00:48:17,443 --> 00:48:20,384
So in most of the universe, there's just
nothing.

732
00:48:20,864 --> 00:48:22,245
What leading order, there's nothing.

733
00:48:22,245 --> 00:48:25,558
And that means that on those scales,
because there's no matter which

734
00:48:25,558 --> 00:48:30,660
has any interactions that are stronger on
those large scales, it's really gravity

735
00:48:30,660 --> 00:48:34,842
that is describing the dynamics of the
universe.

736
00:48:35,343 --> 00:48:39,785
And so if we want to understand both kind
of the dynamics of the universe today, but

737
00:48:39,785 --> 00:48:43,207
also extrapolating back in past, if we
want to understand the evolution of the

738
00:48:43,207 --> 00:48:48,390
universe, the birth of the universe, then
we need to understand gravity.

739
00:48:50,151 --> 00:48:54,673
And one of the big puzzles, for example,
is

740
00:48:55,366 --> 00:49:01,607
that at the moment observations tell us
that we are in a phase of the universe

741
00:49:01,607 --> 00:49:07,249
where the universe is not only expanding,
but expanding in an accelerated way.

742
00:49:07,749 --> 00:49:12,431
And that's pretty weird because normally
you think if you just have a bunch of

743
00:49:12,431 --> 00:49:15,391
matter, right, a bunch of galaxies, you
think, well, they're going to have

744
00:49:15,391 --> 00:49:17,692
gravitational interactions between each
other.

745
00:49:17,852 --> 00:49:21,413
So even if you somehow gave them some
initial velocity, you would think, okay,

746
00:49:21,413 --> 00:49:23,153
well, they're going to kind of slow down.

747
00:49:23,262 --> 00:49:26,504
and eventually crunch back together again,
because on those large scales, it's only

748
00:49:26,504 --> 00:49:28,386
gravity that is important.

749
00:49:28,386 --> 00:49:33,970
So on those large scales, you think you
can you can either have things collapsing,

750
00:49:33,970 --> 00:49:36,693
or you can have kind of things, at least
if they're expanding, they should be

751
00:49:36,693 --> 00:49:37,713
slowing down.

752
00:49:37,874 --> 00:49:39,195
What we observe is the opposite, right?

753
00:49:39,195 --> 00:49:43,738
What we observe is really, things are
deferred, things are away from us, the

754
00:49:43,738 --> 00:49:45,420
faster they are moving away.

755
00:49:45,420 --> 00:49:49,623
So we're in a universe which is expanding
faster and faster.

756
00:49:50,464 --> 00:49:52,825
And that is also gravity driving that.

757
00:49:54,782 --> 00:49:59,383
It's just not the usual form of gravity
that we know on Earth, that gravity is

758
00:49:59,383 --> 00:50:00,383
attractive.

759
00:50:00,564 --> 00:50:05,445
But in some sense, you can call it a
repulsive force of gravity, or it's a part

760
00:50:05,445 --> 00:50:11,227
of gravity that acts as a pressure that
drives the universe apart.

761
00:50:11,647 --> 00:50:14,247
And that is what we call in dark energy.

762
00:50:14,988 --> 00:50:19,789
So again, the term dark just implies we
don't really understand and we can't see

763
00:50:19,789 --> 00:50:20,349
it.

764
00:50:21,650 --> 00:50:26,574
And energy basically comes from
observations that it has this effect of

765
00:50:26,574 --> 00:50:29,856
driving the energy of driving the universe
apart.

766
00:50:30,537 --> 00:50:37,302
So it acts as a type of energy in the
expansion history of our universe and

767
00:50:37,543 --> 00:50:38,904
concretely today.

768
00:50:39,585 --> 00:50:45,210
But we don't really so we can model it,
but we can't we don't really fundamentally

769
00:50:45,210 --> 00:50:46,550
understand what it is.

770
00:50:47,532 --> 00:50:50,086
So understanding that and understanding
kind of.

771
00:50:50,086 --> 00:50:53,668
how the universe evolved, not only today,
but in the past.

772
00:50:54,729 --> 00:50:59,313
That then immediately ties back into
particle physics, because going back in

773
00:50:59,313 --> 00:51:04,437
time in an expanding universe means you go
to a smaller universe where everything was

774
00:51:04,437 --> 00:51:06,258
much more dense, much more hot.

775
00:51:06,299 --> 00:51:09,721
You end up in this primordial soup of
particles.

776
00:51:10,002 --> 00:51:13,405
So you're looking at particles at high
temperatures, particles when they're

777
00:51:13,405 --> 00:51:16,988
really kind of not bound in atoms and
molecules, but when they exist really in

778
00:51:16,988 --> 00:51:18,068
their fundamental

779
00:51:20,374 --> 00:51:23,376
basically a lab to study particle physics.

780
00:51:23,376 --> 00:51:27,519
So that's how the connection works between
these very large scales of the universe

781
00:51:28,381 --> 00:51:30,623
and then the very smallest particles that
we study in that way.

782
00:51:30,623 --> 00:51:33,304
I see.

783
00:51:33,385 --> 00:51:39,490
Yeah, it's because then it's because
you're going back to the early universe

784
00:51:39,490 --> 00:51:45,476
where basically the structure that we have
today of the universe didn't apply because

785
00:51:45,476 --> 00:51:47,297
it didn't exist yet.

786
00:51:47,297 --> 00:51:47,778
Correct.

787
00:51:47,778 --> 00:51:48,018
Correct.

788
00:51:48,018 --> 00:51:52,119
We go back to when everything was really
kind of just this hot primordial soup of

789
00:51:52,119 --> 00:51:53,500
fundamental particles.

790
00:51:54,420 --> 00:52:00,483
We tried to understand kind of how
different properties of the soup, meaning

791
00:52:00,483 --> 00:52:05,145
different possible extensions of the
standard model, would kind of leave traces

792
00:52:05,145 --> 00:52:06,706
in the evolution of the universe.

793
00:52:06,706 --> 00:52:10,007
So would leave traces in kind of
astrophysical and cosmological

794
00:52:10,007 --> 00:52:11,228
observations that we can make today.

795
00:52:11,228 --> 00:52:12,328
I see.

796
00:52:14,809 --> 00:52:15,669
And...

797
00:52:16,762 --> 00:52:25,369
these days, what's a specific experiment
or project that you're involved in, in

798
00:52:25,369 --> 00:52:30,793
this film, and what would be the main
question that this project is trying to

799
00:52:30,793 --> 00:52:31,553
answer?

800
00:52:33,162 --> 00:52:33,362
Right.

801
00:52:33,362 --> 00:52:36,703
So a big, big project I'm involved in,
right?

802
00:52:36,703 --> 00:52:42,445
So this is a, you know, many hundreds,
thousands of people working together is

803
00:52:42,445 --> 00:52:43,906
the LISA project.

804
00:52:43,906 --> 00:52:50,188
So that's a future space-based
gravitational wave observatory.

805
00:52:50,609 --> 00:52:52,469
It's going to be an ESA mission.

806
00:52:53,210 --> 00:52:59,852
The idea is to have three satellites
circling around the sun on an orbit

807
00:52:59,852 --> 00:53:01,293
similar to the Earth.

808
00:53:01,393 --> 00:53:02,770
So following Earth.

809
00:53:02,770 --> 00:53:04,250
on an orbit around the sun.

810
00:53:04,891 --> 00:53:08,933
The satellites will be two and a half
million kilometers apart.

811
00:53:10,234 --> 00:53:13,376
They will exchange laser links.

812
00:53:13,376 --> 00:53:17,458
So they will be shooting, there will be
lasers going between all combinations of

813
00:53:17,458 --> 00:53:18,498
the satellites.

814
00:53:19,399 --> 00:53:23,982
And using these lasers, the idea is to
measure very precisely distance between

815
00:53:23,982 --> 00:53:26,223
these satellites as they orbit the sun.

816
00:53:26,803 --> 00:53:30,965
And the idea is that if a gravitational
wave comes, since it's a

817
00:53:31,274 --> 00:53:36,095
little ripple in space-time, it will
change very slightly the distance between

818
00:53:36,095 --> 00:53:37,215
the satellites.

819
00:53:38,676 --> 00:53:44,797
And so by kind of looking for this,
looking for these little variations in the

820
00:53:44,797 --> 00:53:49,359
distance between the satellites, the goal
is to look for gravitational waves.

821
00:53:49,659 --> 00:53:53,620
And being in space has the big advantage
that a lot of the noise that you have to

822
00:53:53,620 --> 00:53:56,441
deal with on Earth is not there.

823
00:53:56,981 --> 00:53:58,981
So the idea is that you can

824
00:53:59,998 --> 00:54:05,100
much better sensitivities than you could
on Earth.

825
00:54:05,100 --> 00:54:06,720
Yeah, that makes sense.

826
00:54:06,720 --> 00:54:10,762
Also, although I'm guessing the sun can be
noisier at times.

827
00:54:11,783 --> 00:54:13,784
Right, but it's all a question of
frequency, right?

828
00:54:13,784 --> 00:54:17,405
So you need to kind of find a frequency
band which is clean.

829
00:54:18,246 --> 00:54:23,628
But yeah, I mean, there's obviously huge
technological challenges in implementing a

830
00:54:23,628 --> 00:54:26,469
mission like this and many things that can
go wrong.

831
00:54:28,338 --> 00:54:32,559
This is why you need a lot of people with
a lot of different expertise coming

832
00:54:32,559 --> 00:54:36,921
together and also a lot of money to build
an instrument like that.

833
00:54:37,241 --> 00:54:37,762
Yeah.

834
00:54:37,762 --> 00:54:43,104
I mean, just the engineering part of it is
you have to launch three satellites.

835
00:54:43,104 --> 00:54:45,185
First, that's already hard.

836
00:54:45,185 --> 00:54:48,606
And then you have to put them in orbit
around the sun and that they still can

837
00:54:48,606 --> 00:54:50,627
communicate with each other.

838
00:54:50,987 --> 00:54:54,229
It's just, and they are extremely far
apart from each other.

839
00:54:54,229 --> 00:54:56,626
So just that part is...

840
00:54:56,626 --> 00:54:59,127
absolutely incredible that we can do that.

841
00:55:00,529 --> 00:55:01,409
Knock, knock, right?

842
00:55:01,409 --> 00:55:03,291
I mean, we hope we can do it.

843
00:55:03,651 --> 00:55:07,914
Yeah, I mean, that's just incredibly
fascinating.

844
00:55:08,315 --> 00:55:11,778
And so what's the ETA on this mission?

845
00:55:11,778 --> 00:55:16,221
When will the satellites go up
theoretically?

846
00:55:16,642 --> 00:55:16,882
Right.

847
00:55:16,882 --> 00:55:24,828
So the hope is to launch in the early
2030s, which seems a long way from now,

848
00:55:24,828 --> 00:55:26,629
but it's really not.

849
00:55:27,730 --> 00:55:32,972
Because, yeah, I mean, it takes a while to
build a satellite.

850
00:55:33,812 --> 00:55:39,615
And also to develop all the kind of the
data analysis pipelines that you need.

851
00:55:40,255 --> 00:55:44,677
Make sure you have all the sensors on
board that you might need to perform

852
00:55:44,677 --> 00:55:46,357
whatever type of cross checks.

853
00:55:46,478 --> 00:55:51,580
Yeah, make sure you didn't put anything on
board, which generates a bunch of noise.

854
00:55:52,500 --> 00:55:54,641
Because once it's up there, it's up there,
right?

855
00:55:54,641 --> 00:55:55,341
You can't.

856
00:55:55,341 --> 00:55:56,021
Yeah.

857
00:55:56,178 --> 00:55:59,820
Yeah, I mean, it's not in the orbit,
right?

858
00:55:59,820 --> 00:56:00,180
Exactly.

859
00:56:00,180 --> 00:56:01,962
You cannot find it, send anybody to repair
it, right?

860
00:56:01,962 --> 00:56:03,482
So once it's up there, it's up there.

861
00:56:03,963 --> 00:56:10,527
So you really have to think of every
possible complication beforehand.

862
00:56:10,527 --> 00:56:13,409
Yeah, which is quite daunting.

863
00:56:13,990 --> 00:56:18,133
I have to do that for my own statistical
model, you know, where I probe them and

864
00:56:18,133 --> 00:56:20,374
I'm like, okay, where can the model fail?

865
00:56:21,115 --> 00:56:23,656
What could be the potential issues?

866
00:56:23,776 --> 00:56:24,717
It's already...

867
00:56:25,598 --> 00:56:29,100
stressing me out, but then if you have to
do that for something you cannot go back

868
00:56:29,100 --> 00:56:33,203
to, that's just incredibly daunting.

869
00:56:33,203 --> 00:56:37,105
If you think a code release is stressful,
then imagine this.

870
00:56:37,305 --> 00:56:37,846
Oh, yeah.

871
00:56:37,846 --> 00:56:39,166
Oh my God.

872
00:56:40,087 --> 00:56:41,928
But so fascinating.

873
00:56:43,970 --> 00:56:48,393
Personally, what's your part in this
project, for instance, in the Lisa

874
00:56:48,393 --> 00:56:49,253
project?

875
00:56:49,714 --> 00:56:50,254
Right.

876
00:56:50,254 --> 00:56:55,277
I'm in charge of coordinating research on
what we call

877
00:56:55,850 --> 00:56:57,410
the stochastic backgrounds.

878
00:56:59,772 --> 00:57:03,795
So the signals we've talked about so far,
and predicted the ones we see by LIGO, are

879
00:57:03,795 --> 00:57:08,379
what we call transient signals, meaning
most of the time the detector actually

880
00:57:08,379 --> 00:57:09,559
sees nothing, just noise.

881
00:57:09,559 --> 00:57:13,662
And then from time to time, you have a
rather relatively strong signal.

882
00:57:14,363 --> 00:57:16,124
You see it, then it's gone.

883
00:57:16,925 --> 00:57:22,629
So if that's your data analysis challenge,
then you can calibrate your detector in

884
00:57:22,629 --> 00:57:23,990
the signal-free moments.

885
00:57:23,990 --> 00:57:27,452
You can learn all about your properties of
the noise and you can have a good noise

886
00:57:27,452 --> 00:57:27,932
model.

887
00:57:27,932 --> 00:57:31,755
And then when you get a signal, you can
kind of do a pretty good signal to noise

888
00:57:31,755 --> 00:57:32,896
discrimination.

889
00:57:33,616 --> 00:57:39,521
Now with Lisa, the situation is going to
be very different because we're going to

890
00:57:39,521 --> 00:57:44,024
have, because it's such a sensitive
instrument, we're going to have lots and

891
00:57:44,024 --> 00:57:45,725
lots of stuff going on all the time.

892
00:57:45,725 --> 00:57:49,948
So we're basically not going to have
signal free time.

893
00:57:50,869 --> 00:57:51,938
So we're kind of.

894
00:57:51,938 --> 00:57:55,660
dealing with kind of measuring all these
different signals and the noise at the

895
00:57:55,660 --> 00:57:56,680
same time.

896
00:57:56,940 --> 00:58:00,442
And at the same time, the idea is that we
might have stochastic backgrounds.

897
00:58:00,442 --> 00:58:03,964
So stochastic backgrounds could, they're
not transient signals, but there's kind of

898
00:58:03,964 --> 00:58:07,546
more like a white noise, which is there at
all times.

899
00:58:07,987 --> 00:58:13,009
They could be coming from unresolved
astrophysical sources, so unresolved black

900
00:58:13,009 --> 00:58:16,491
or black or merges that are kind of out of
the range of our detector.

901
00:58:16,491 --> 00:58:19,633
So we can't individually detect them, but
they just kind of contribute to some

902
00:58:19,633 --> 00:58:20,793
confusion noise.

903
00:58:21,670 --> 00:58:24,372
Or they could be these signals from the
very early universe, which is, of course,

904
00:58:24,372 --> 00:58:26,233
the ones that I'm actually after.

905
00:58:26,573 --> 00:58:32,137
But so you have to kind of dig them out
between all these loud transient signals,

906
00:58:32,917 --> 00:58:38,861
between these possible astrophysical noise
like signals, which look very, very

907
00:58:38,861 --> 00:58:43,124
similar to the kind of cosmological noise
like signal that you will be looking for.

908
00:58:43,525 --> 00:58:46,787
And of course, the words are very, very
similar to instrument noise that you might

909
00:58:46,787 --> 00:58:50,049
have mismodeled or misunderstood.

910
00:58:50,049 --> 00:58:50,789
So.

911
00:58:51,298 --> 00:58:57,761
And what I'm working on is okay, a on on,
okay, understanding the possible models

912
00:58:57,761 --> 00:59:01,323
for these for these different components,
in particular for the cosmological

913
00:59:01,323 --> 00:59:08,927
sources, but also trying to understand how
could we if we you know, actually get some

914
00:59:08,927 --> 00:59:14,110
actual data, how can we actually
disentangle all of these components?

915
00:59:14,110 --> 00:59:18,473
And how can we really kind of make the
most of the of the mission, extract as

916
00:59:18,473 --> 00:59:20,113
much information as possible?

917
00:59:21,626 --> 00:59:27,688
which with all these kind of overlapping
signals and challenges.

918
00:59:27,688 --> 00:59:30,288
Yeah, yeah.

919
00:59:30,648 --> 00:59:38,211
And I'm guessing that having to do that,
not in a few months is something you

920
00:59:38,211 --> 00:59:40,451
appreciate.

921
00:59:41,712 --> 00:59:42,252
Yes.

922
00:59:42,252 --> 00:59:45,573
Yes, yes, yes.

923
00:59:45,993 --> 00:59:48,593
Yeah, so there's many challenges out
there.

924
00:59:48,810 --> 00:59:52,332
Obviously, many people working on it.

925
00:59:52,332 --> 00:59:56,074
And I mean, luckily, as you say, luckily,
we don't have to solve this in a couple of

926
00:59:56,074 --> 00:59:56,614
months, right?

927
00:59:56,614 --> 01:00:02,157
Because we're basically also counting on
things like computing power, and so on,

928
01:00:03,118 --> 01:00:06,539
increasing new methods becoming available.

929
01:00:07,660 --> 01:00:12,643
But, but yeah, so it's, but still, I mean,
the development has to happen now.

930
01:00:13,464 --> 01:00:16,885
Because if we kind of figure, okay, we
need a certain type of

931
01:00:18,354 --> 01:00:21,895
sensor or some certain type of output data
that would help us to discriminate these

932
01:00:21,895 --> 01:00:23,055
different signals.

933
01:00:23,196 --> 01:00:26,377
We can't come along with that when the
mission is already built or even worse,

934
01:00:26,377 --> 01:00:27,257
already launched.

935
01:00:27,257 --> 01:00:31,259
So you can't wait till you see the data to
decide how you're going to do the

936
01:00:31,259 --> 01:00:32,160
analysis.

937
01:00:32,160 --> 01:00:36,782
You at least have to have a very good idea
of how you're going to do the analysis

938
01:00:36,782 --> 01:00:37,682
before you see the data.

939
01:00:37,682 --> 01:00:40,463
And then maybe you can refine once you see
the data.

940
01:00:42,024 --> 01:00:43,604
Yeah, definitely.

941
01:00:47,442 --> 01:00:52,926
Actually, this kind of work that you do in
theoretical physics or that kind of

942
01:00:52,926 --> 01:01:00,511
project you just described, it really
involves the development of models, of

943
01:01:00,511 --> 01:01:12,480
hypotheses, and I'm curious if you have
some favorite hypotheses or models or the

944
01:01:12,480 --> 01:01:14,934
most intriguing theoretical ideas.

945
01:01:14,934 --> 01:01:20,641
that you've encountered in your field and
that you'd like to see tested.

946
01:01:20,641 --> 01:01:24,725
And if we could actually test them right
now with our current technology.

947
01:01:29,094 --> 01:01:29,654
Good question.

948
01:01:29,654 --> 01:01:34,055
I must say, I don't have a particularly
favorite model.

949
01:01:34,055 --> 01:01:39,757
I don't feel, I don't know, protective
ownership of any particular idea.

950
01:01:39,757 --> 01:01:42,557
I'm more the type of person who I start
working on something because I find it

951
01:01:42,557 --> 01:01:42,977
interesting.

952
01:01:42,977 --> 01:01:47,879
And then once I've understood it to a
certain degree, I move on to the next

953
01:01:47,879 --> 01:01:48,679
topic.

954
01:01:50,800 --> 01:01:57,321
But I think there are a couple of kind of
big overarching...

955
01:01:57,902 --> 01:01:58,942
questions, right?

956
01:01:58,942 --> 01:02:05,628
So kind of, yeah, understanding, getting
some experimental input on what on what

957
01:02:05,628 --> 01:02:10,432
dark matter is, would really help a lot on
the on the theory development side.

958
01:02:12,153 --> 01:02:15,436
As I mentioned, when we also have issues
understanding the Higgs particle,

959
01:02:15,436 --> 01:02:22,042
understanding in particular mass of the
Higgs particle, which is potentially

960
01:02:22,042 --> 01:02:24,584
indicating there's something we don't
understand properly about quantum field

961
01:02:24,584 --> 01:02:25,544
theory about

962
01:02:28,058 --> 01:02:33,761
that I find is incredibly exciting,
because it would really mean kind of,

963
01:02:33,761 --> 01:02:38,864
okay, not an add on, you know, not a small
extension of our existing model, but

964
01:02:38,864 --> 01:02:43,166
really, completely revolution and how we
think about things.

965
01:02:43,326 --> 01:02:46,428
Yeah, of course, it also makes it much
more difficult, right?

966
01:02:46,428 --> 01:02:49,790
Because you don't even have the framework.

967
01:02:49,790 --> 01:02:52,631
Maybe we don't even have the mathematical
framework to think about this.

968
01:02:54,192 --> 01:02:56,813
It's a huge step to take.

969
01:02:57,334 --> 01:03:01,955
So I would, I mean, that's what would be a
big step, right?

970
01:03:01,955 --> 01:03:05,596
So I'm not sure if and how that's going to
happen.

971
01:03:05,596 --> 01:03:06,596
If it's even necessary, right?

972
01:03:06,596 --> 01:03:10,017
Maybe the current framework is totally
fine, but that would definitely be a

973
01:03:10,017 --> 01:03:15,679
development that on just on the pure
theory side, that would be very exciting

974
01:03:15,679 --> 01:03:16,759
to see happening.

975
01:03:17,119 --> 01:03:17,599
Yeah.

976
01:03:17,599 --> 01:03:19,740
Yeah, for sure.

977
01:03:19,740 --> 01:03:20,260
Definitely.

978
01:03:20,260 --> 01:03:25,081
I kind of, I'm also really curious about
that.

979
01:03:27,654 --> 01:03:35,401
Actually, is there one big question that
you would like to see answered before you

980
01:03:35,401 --> 01:03:35,701
die?

981
01:03:35,701 --> 01:03:41,026
Your one big question that you'd really
like the answer to.

982
01:03:41,026 --> 01:03:43,908
I think I really would like to know the
answer to Dark Matter.

983
01:03:44,409 --> 01:03:45,789
Just because that-

984
01:03:48,934 --> 01:03:57,037
It's well, there's this we have many, we
have many very reasonable models, which

985
01:03:57,037 --> 01:03:59,798
can be tested and which are being tested.

986
01:03:59,798 --> 01:04:05,121
So we could still be unlucky and nature
could choose not one of these nice and

987
01:04:05,121 --> 01:04:07,461
reasonable models, right, but something
completely different.

988
01:04:09,963 --> 01:04:15,805
But that that's a field where there are
some very good suggestions and they can be

989
01:04:15,805 --> 01:04:16,542
tested.

990
01:04:16,542 --> 01:04:19,764
Now, unfortunately, there was one
excellent suggestion, right, which was

991
01:04:20,805 --> 01:04:25,009
supersymmetry and the dark matter particle
that comes with supersymmetry would have

992
01:04:25,009 --> 01:04:30,613
solved, was mathematically beautiful,
would have solved a ton of questions, was

993
01:04:30,613 --> 01:04:33,696
in many ways the perfect theory, right?

994
01:04:33,696 --> 01:04:35,237
Unfortunately, we didn't find it.

995
01:04:35,538 --> 01:04:41,142
So it could still be out there, but kind
of not as a solution to all of the

996
01:04:41,142 --> 01:04:42,644
problems that we hoped it would solve.

997
01:04:42,644 --> 01:04:45,345
Because if that were the case, we should
already have seen it.

998
01:04:46,238 --> 01:04:52,943
Yeah, so something kind of being the ideal
theory from our point of view, doesn't

999
01:04:52,943 --> 01:04:54,343
mean nature actually cares, right?

1000
01:04:54,343 --> 01:04:55,224
Yeah, for sure.

1001
01:04:55,224 --> 01:04:56,525
And does it that way.

1002
01:04:58,126 --> 01:05:04,090
But yeah, so Dark Matter, I think it
really has the potential that we could

1003
01:05:04,090 --> 01:05:05,171
actually find it.

1004
01:05:05,171 --> 01:05:10,795
And if we find it, that could really be a
starting point of a whole new exploration

1005
01:05:10,795 --> 01:05:13,216
of questions.

1006
01:05:13,216 --> 01:05:15,057
Yeah, definitely.

1007
01:05:15,870 --> 01:05:22,575
And that's interesting that you mentioned
dark matter too, because Kevin Clive, I

1008
01:05:22,575 --> 01:05:26,498
asked him the same question and he
answered dark matter too.

1009
01:05:26,498 --> 01:05:30,662
So that's interesting to see that it's
really something that's picking up in the

1010
01:05:30,662 --> 01:05:38,628
physics space these days where it seems
like we're less, let's say we're more

1011
01:05:38,628 --> 01:05:45,398
hopeful that we can actually start making
sense of it and probing

1012
01:05:45,398 --> 01:05:50,339
the universe in a way that will give us
some answers, at least to this mystery.

1013
01:05:50,799 --> 01:05:54,500
Whereas dark energy, from what I
understand, we understand way less about

1014
01:05:54,500 --> 01:05:57,921
dark energy than we understand about dark
matter for now, right?

1015
01:05:57,921 --> 01:05:59,221
Yeah.

1016
01:05:59,221 --> 01:05:59,821
That's correct.

1017
01:05:59,821 --> 01:06:06,283
And also there we have much less, I mean,
we see what it does on large scales,

1018
01:06:06,283 --> 01:06:06,563
right?

1019
01:06:06,563 --> 01:06:14,185
But we have also much less of an idea how
to make progress.

1020
01:06:14,518 --> 01:06:19,641
Both on the theory side, there's kind of
not these kind of clear cut models that

1021
01:06:19,641 --> 01:06:23,783
kind of say, okay, here's a good theory of
why it is how it is, and here's how you go

1022
01:06:23,783 --> 01:06:25,764
test it, right?

1023
01:06:25,764 --> 01:06:26,905
For Dark Energy, we have neither.

1024
01:06:26,905 --> 01:06:31,307
Neither a clear cut theory that kind of
says, okay, here's a good explanation, nor

1025
01:06:31,307 --> 01:06:33,769
any way of probing them really.

1026
01:06:34,429 --> 01:06:37,551
So it's a much, it's much more in the
blur.

1027
01:06:37,551 --> 01:06:38,151
Yeah.

1028
01:06:40,753 --> 01:06:41,813
So hopefully.

1029
01:06:41,886 --> 01:06:47,211
In 10 days, you'll come back to the show
and we'll talk about Dark Energy and the

1030
01:06:47,211 --> 01:06:51,294
latest progresses.

1031
01:06:51,354 --> 01:06:56,199
Valerie, I think I have so many more
questions, but you've been already very

1032
01:06:56,199 --> 01:06:57,820
generous with your time.

1033
01:06:58,701 --> 01:07:03,085
Before closing up, is there any topic I
didn't ask you about and that you'd like

1034
01:07:03,085 --> 01:07:03,905
to mention?

1035
01:07:05,786 --> 01:07:10,170
I think we covered a lot, but nothing
particular comes to my mind.

1036
01:07:10,170 --> 01:07:11,552
Okay.

1037
01:07:11,552 --> 01:07:18,819
Well, then I think we can call it a show,
but as usual, before I think you go, I'm

1038
01:07:18,819 --> 01:07:23,163
going to ask you the last two questions I
ask every guest at the end of the show.

1039
01:07:23,484 --> 01:07:28,729
First one, if you had unlimited time and
resources, which problem would you try to

1040
01:07:28,729 --> 01:07:29,569
solve?

1041
01:07:32,883 --> 01:07:38,732
Yeah, that's as I said, that's actually a
really tricky question because we are in

1042
01:07:38,732 --> 01:07:45,221
this in this situation that I find it very
hard to pinpoint.

1043
01:07:47,734 --> 01:07:49,495
where is the weak point of the standard
model?

1044
01:07:49,495 --> 01:07:51,376
Where should we poke it?

1045
01:07:51,376 --> 01:07:51,596
Right?

1046
01:07:51,596 --> 01:08:01,121
So from the pure theory side, without any
experimental input, I feel like if I had

1047
01:08:01,121 --> 01:08:06,184
unlimited time and resources, I wouldn't
engage on a single project right now.

1048
01:08:08,365 --> 01:08:15,189
But I would basically just try and, you
know, gather as broad as possible

1049
01:08:15,189 --> 01:08:16,609
understanding of

1050
01:08:17,042 --> 01:08:23,643
as many concepts as possible and hope that
we will eventually get some sort of data,

1051
01:08:23,643 --> 01:08:26,764
which points us in the direction we need
to explore.

1052
01:08:26,764 --> 01:08:31,105
I don't at the moment really have a clear
cut avenue where I say this is where I

1053
01:08:31,105 --> 01:08:32,366
would put all my money.

1054
01:08:35,487 --> 01:08:37,107
Yeah.

1055
01:08:37,107 --> 01:08:43,469
So wise answer where you don't put your
eggs in the same basket.

1056
01:08:43,469 --> 01:08:45,610
And second question, if you could have
dinner.

1057
01:08:45,610 --> 01:08:51,975
with any great scientific mind, dead,
alive or fictional, who would it be?

1058
01:08:51,975 --> 01:08:54,677
Yeah, I think, well, we'd go for somebody
dead, right?

1059
01:08:54,677 --> 01:08:58,360
Just because that's a chance you don't get
on a regular conference dinner.

1060
01:08:59,761 --> 01:09:05,586
So I'd be really curious to talk with some
of the people involved in the discovery of

1061
01:09:05,586 --> 01:09:06,927
quantum mechanics.

1062
01:09:07,127 --> 01:09:09,689
So say Heisenberg or somebody like that.

1063
01:09:10,290 --> 01:09:14,873
Because I feel like they were kind of...

1064
01:09:15,558 --> 01:09:21,723
at the core of the field, when the field
was also in a situation where it was kind

1065
01:09:21,723 --> 01:09:26,567
of not so clear cut, at that time, not
even clear cut that it was a need to kind

1066
01:09:26,567 --> 01:09:30,851
of extend the current understanding
because classical physics was well

1067
01:09:30,851 --> 01:09:31,631
understood, right?

1068
01:09:31,631 --> 01:09:35,875
And nearly all phenomena were very well
understood.

1069
01:09:35,875 --> 01:09:39,238
And people were thinking, okay, you know,
physics, it's done, you know, we

1070
01:09:39,238 --> 01:09:40,418
understand nature.

1071
01:09:41,439 --> 01:09:44,014
And it was just kind of very small.

1072
01:09:44,014 --> 01:09:47,035
tweaks here and there, right, that kind of
were a bit confusing.

1073
01:09:48,316 --> 01:09:52,558
So one could have easily believed
everything is done and understood, go

1074
01:09:52,558 --> 01:09:53,919
study something else.

1075
01:09:54,720 --> 01:09:58,482
But they kind of opened the door to the
world of quantum physics.

1076
01:09:59,202 --> 01:10:04,345
And with that then came quantum field
theory, with that came kind of elementary

1077
01:10:04,345 --> 01:10:08,908
particle physics, with that came kind of
all the questions that we have today.

1078
01:10:09,488 --> 01:10:12,149
So actually, from today's point of view,

1079
01:10:12,522 --> 01:10:14,803
we would say, well, they understood very
little, right?

1080
01:10:14,803 --> 01:10:20,006
It was a whole bunch of new physics that
was kind of not known to them, but they

1081
01:10:20,006 --> 01:10:22,807
didn't even know that it was not known to
them, because there was kind of no glaring

1082
01:10:22,807 --> 01:10:23,888
open question.

1083
01:10:24,828 --> 01:10:30,512
So I'd really be curious to know how they
perceived that situation and how they got

1084
01:10:30,512 --> 01:10:34,574
to the point of opening the door to the
quantum world and taking up that

1085
01:10:34,574 --> 01:10:34,954
challenge.

1086
01:10:34,954 --> 01:10:37,275
Yeah, yeah, yeah.

1087
01:10:37,275 --> 01:10:40,997
Yeah, definitely sounds like a very fine
dinner.

1088
01:10:41,602 --> 01:10:44,502
Please invite me.

1089
01:10:44,502 --> 01:10:46,003
So, well, awesome.

1090
01:10:46,003 --> 01:10:48,123
Thanks a lot, Varyry.

1091
01:10:48,123 --> 01:10:50,564
That was absolutely fascinating.

1092
01:10:51,084 --> 01:10:54,685
We didn't talk a lot about stats, but I
love doing these episodes from time to

1093
01:10:54,685 --> 01:11:00,527
time, you know, where we de-zoom a bit
from stats and just talk about fascinating

1094
01:11:00,527 --> 01:11:02,148
science in general.

1095
01:11:02,808 --> 01:11:08,529
I think it's very interesting and also
quite important to put more rigorous

1096
01:11:09,338 --> 01:11:12,741
pedagogical scientific content out there
in the world.

1097
01:11:12,781 --> 01:11:14,402
We've seen that in the recent years.

1098
01:11:14,402 --> 01:11:19,046
So thanks a lot for doing this for us,
Valérie.

1099
01:11:20,027 --> 01:11:23,690
I will put a link to your website in the
show notes for those who want to dig

1100
01:11:23,690 --> 01:11:24,570
deeper.

1101
01:11:24,631 --> 01:11:30,676
Also feel free to add any link to cool
papers or experiments or videos that you

1102
01:11:30,676 --> 01:11:32,998
think listeners will appreciate.

1103
01:11:33,298 --> 01:11:37,621
And thank you again, Valérie, for taking
the time and being on this show.

1104
01:11:38,582 --> 01:11:39,462
Thank you.

1105
01:11:39,542 --> 01:11:44,684
And rest assured that stats is still at
the basis of all this, despite that we

1106
01:11:44,684 --> 01:11:48,025
took a more high-level approach in this
discussion.

1107
01:11:48,345 --> 01:11:50,486
Yeah, for sure.

1108
01:11:50,486 --> 01:11:56,788
Well, thanks a lot, Valerie, and see you
soon on the show.