Lucian:

This is the second episode of the third season of the Meridian, and we are once again recording at Lund Observatory, Sweden. Crossing our local Meridian today, we are lucky to have Ruth Pötgen who works here at the Department of Physics.  

She studies those fundamental particles that make up the Universe, and more specifically, she is on a quest to find that elusive dark metal particle.  After Ruth's interview we will be bringing you some Cosmic Curiosities.  

“What are cosmic curiosities?” I hear you asking. Well, these are some ideas, events or trivia from astronomic history. Yes, history has become legend and legend has become myth and some things that should have not been forgotten will now be rediscovered in our Cosmic Curiosities. More about that later.

 

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The intro scene includes background music and 24 high school students saying astronomical words like “Space missions”,  "Solar wind", "The big dipper", "Galactic dynamics", "Gravitational waves", "Exoplanets", "Black holes", "Betelgeuse", "Dark energy", "Near earth asteroids", "Jupiter", "Ground based telescopes" and more.  Slowly it fades to everyone saying “The Meridian”.      

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Nic:   

Wait a minute. Who was that?

Rebecca:

Well, so you know... you weren't here yesterday because you were a bit sick. So we kind of had to improvise. And I figured ‘Let's bring. Lucian in’.  So that was Lucian, who is a master student here at the observatory.

Nic:   

Yeah, I know him quite well.

Rebecca:

Yeah, he's in your research group. Studying exoplanets.  So thanks a lot Lucian and thank you for coming on with the Cosmic curiosities that we have more about later.

Nic:   

Yeah, you absolutely did a great job at introducing everything.

Rebecca:

Yes. Brilliant. Brilliant. Nice. Well, I figured:  Last week we sort of catched up with what I did on this whole year offer, especially what I did at ESO. But I'm curious what did you? Do Nick tell me. All about what you did when I was away.  Cause I've seen you've been a bit of a globetrotter.

Nic:   

I was going to say not much, but yeah. So I guess you remembered my whole diary on La Palma from season two?  

Rebecca:

Yes. Amazing.

Nic:   

Yeah, yeah. Except for the fact that I didn't get any data.

Rebecca:

You got to see a volcano.

Nic:   

Yeah. Life changing experience. No data. I think it was a fair trade. But anyway, I got the time back. So I went back to La Palma and... Well, there was no. Volcano erupting. And not only that, we almost got two perfect nights of data. So yeah, so I was so over the moon. The the night astronomer that was helping me was also quite impressed, too.

Rebecca:

That's amazing. What is a night astronomer?

Nic:   

So a night astronomer is someone who works at a telescope to assist you in your observation run. So almost every main telescope will have one of these, and they just... they're the ones that know the ins and outs of how the telescope is working and can tell you and help you to fix problems a lot faster than you might be able to do by yourself.  

Rebecca:

Which is great.

Nic:   

So yeah, the NOT has a great programme where it trains masters students on the telescope, so they get actually get to incorporate part of their education.  

Rebecca:

That is really great. Also what an experience to have, as a master student working at like a big telescope like that. On a Canary Island.

Nic:   

Yeah, exactly. Yeah, I know. In Paradise, pretty much so, yeah.  

Rebecca:

I'm glad you got the data.

Nic:   

Thank you. Thank you. So yeah, I did that and then I decided to fly back to Australia for a friend's wedding and then. So I went to Hawaii. To do some more observing. So I got some time on the Keck telescope, which is the really big...

Rebecca:

Yeah. Kick is like one of the. Really, really, really big ones, right?

Nic:   

Yes. So I submitted a proposal thinking, hey, like, what's the worst that can happen? And the best happened again so.

Rebecca:

That's amazing.

Nic:   

Yeah. So I was so shocked to be in that observing room.  So many scientists want to be here. Like you know, you imagine my childhood dream of becoming an astronomer. I was basically living that dream. I was also so nervous.

Rebecca:

It's amazing. Oh, so actually...  Cause for the Nordic optical telescope, you really sort of get to sit and, you know: Manage the telescope yourself. Is it the same with the Keck, like you actually sit in the control room?

Nic:   

So it's a little bit different. So the night astronomer has more control over the scope. You basically set up when to observe and what to observe? But they just make sure everything is going smoothly.  

So I had a I had a lot of help and once again it was a perfect night and I got great data. So I got my ducks lined up in a row. Someone's looking down on me. I'm really happy.  

So on top of that, I also went to quite a few different conferences. Well, not quite a few, a couple. So I went to Las Vegas. Not to gamble, but to actually but to see Exoplanets Four, where all the exoplanet experts congregate...

Rebecca:

Including you.

Nic:   

Including me. So you think that astronomers are a quirky bunch?  Imagine if you get like a small group of them. Yeah. So we all think exoplanets cool. So we all got along really well. And I also went to a really big conference with a lot of European astronomers. So I think it's on the order of, I think, 2000 people. There. So it was crowded as a lot of stuff.

Rebecca:

Oh yeah. I actually do remember that conference from my ESO visit because all of a sudden all of the ESO PhD students weren't there for a week.

Nic:   

It was fun. It was like half the department was with us, so it was quite good.  

And I also have submitted my first paper.

Rebecca:

Yes, yeah, this is great. This is like a huge thing. I'm very proud of you.

Nic:   

Yeah, I'm really excited. And you're actually a co-author on it too, so it's... It makes it even more exciting.

Rebecca:

I know I was very happy that you invited me.  Because you sort of invited me on the aspect of... Well, I guess I shouldn’t spoil your paper, but you have discovered very heavy elements in your paper. And I’m sort of like the in-house experts on heavy elements. So you invited me to, and I was very happy.

Nic:   

Yeah. And you had some really interesting insights, which were great and I think it sort of helped make the paper shine even better than it already had.

Rebecca:

Thank you.

Nic:   

Has also, on a personal note, I got engaged.

Rebecca:

This is amazing. I'm very happy. Congratulations.

Nic:   

Thank you. Yeah, yeah.

Rebecca:

So nice. Well, the wedding take place here I or in Australia.

Nic:   

In Australia.  

Rebecca:

Oh boy.

Nic:  

Yeah. We may try to do some hybrid thing in Sweden as well, cause she  is Swedish, but yeah, the the plans are up in the air at the moment. So, we're trying to figure things out.

Rebecca:

I'm very happy for you. Really. Congratulations, man.

Nic:   

Thank you so much. Yeah, thank you so.

Rebecca:

It also goes to show, you know, we have life outside of telescopes and papers.

Nic:   

And science? Yeah, exactly. Yeah. Enough to convince people were interesting enough to be married. Yeah, but I guess that's all about me.

Rebecca:

Perhaps we should introduce our guest.  

Nic:   

Yes, we should.

Rebecca:

Yeah. Who is Ruth Pötgen, who works across the street on finding dark matter.

Nic:   

Ohh really? Looking forward to that.

 

---------------------- Scene change with music.      

 

Rebecca:

And now I'd like to welcome to the podcast Ruth Pötken who is a partclie physicist here at the university.  

Ruth:   

Thanks.  

Rebecca:

So welcome. I think we kick it off. Could do you like tell us a bit about yourself and what made you end up here at Lund University.  

Ruth:   

I can try.   Yes.  So for me to come to Lund, I think was. There was a lot of luck involved. And sort of, you know. Stars lining up, in a way.  

So it was at the the end of my first postdoc, so one and a half years after I graduated with my PhD and there was this position announced, which was about going new ways in looking for dark matter. To a large extent.  In combination with something that I had been doing before.

The description of what this position was supposed to be fit me perfectly. But then I thought - it said something very intimidating in the title. Something like  ‘Associate, senior lecturer‘ or something like that and I was like, oh, that doesn't sound like somebody can apply for this two years after their PhD.

Rebecca:

Yeah, yeah.

Ruth:   

So I was actually sending this around to sort of senior colleagues and friends. I was like, ‘don't you want to apply for this?’ And they were like, ‘no, no, maybe not. But you should’. And yeah, so I hesitated for a long time because I I thought I would never have a shot at this. But then in the end I figured trying can't hurt.  

So I applied and we was invited to an interview and in the end I got the position.

Rebecca:

Well, that's very nice.

Ruth:   

Yeah, it was, was incredible. So this was really a sort of a, you know, it was. Just an opportunity. That popped up and I was very lucky.

Rebecca:

Yeah, but I guess being in academia, you sort of learned that it's. It's a bit about like as well.

Ruth:   

It is very much that.  Luch and timing.  The the right things have to happen at the right time. Like if this had come out half a year earlier, I wouldn't have applied. Yeah, sure. I wasn't looking for for jobs back then. Yeah, it's ...

Rebecca:

So you did your. PhD at CERN if I'm correct, right? What did you do there so there?

Ruth:   

I also worked on. Dark matter? I guess we will come to this again.

Rebecca:

Well, we'll come back to dark matter many times, I think.

Ruth:   

So this was one part of my project and the the other one, which was why I actually was at CERN, was a more hardware related project. So CERN has this technical doctoral student programme where you are actually employed by a certain and and you work on something that's a bit more technical.  More hardware.  And for me it was what is called the central trigger of the Atlas experiment.  

Rebecca:

OK.

Ruth:   

Atlas is one of the big experiments at the Large Hadron Collider and a very important task we have to do when we take data with this experiment is what we call triggering.  Because we get lots and lots of collisions, we get collisions 40 million times per second, roughly, and we cannot record all of this.  

But we also don't have to record all of this because most of it is not the things we're interested in, but we have to filter out the things we're interested in. And this is what what we do at the trigger level.  

And there the central trigger is sort of the first stage, so we have we have several stages where we take more and more informed decisions.  And at the first level it's just - we have to be very quick and very efficient.  And it's actually an impressively small piace of hardware.

So it's a box that is like, I don't know, half a metre wide and 30 centimetres large or something. And there are a couple of electronics boarda in there.  And they do some very simple algorithms because this system has to be very reliable and stable and easy to debug.

Rebecca:

So lets see if I understand.  This is about sorting which data to use and save , ‘cause there’s a lot of data.

Ruth:   

Exactly.  There's a lot of data and we only need a small fraction of it.

Rebecca:

Yeah, yeah, yeah. And you need to figure out which one you need.

Ruth:   

Exactly. Yeah. And so this is the the component that does the first step of this selection. And I was part of the team.   It's about, it varies a bit, but five to 10 people.  And we were responsible round the clock for keeping this thing working, because otherwise Atlas can't take any data.

Rebecca:

Sure. OK. There's a lot of like things that comes in my head. I wanna ask you, but I guess backing up a bit. So when you say collisions, what are you colliding in, CERN?  Or in the hadron collider, I guess.

Ruth:   

Yeah. So. the the Large Hadron Collider mostly, what it does is to collide protons and protons.  

It also has a couple of weeks every year where it collides protons with heavy ions. So lead mostly. Or even lead lead nuclei.  

Rebecca:  

Wow. Yeah,  

Ruth:

This is not so much for the Atlas experiment. I mean, Atlas also takes this data. But this is for another experiment that's called Alice. Which focuses on these heavy ion collisions.  

So sometimes we say that the LHC was built to imitate The Big Bang and to study conditions shortly after The Big Bang. And it's really, this experiment that does it, because if you collide these heavy nuclei at very high energies, you break them apart and you form – or at least it's believed that you form -  a new state of matter that's called the quark gluon plasma.

So all the building blocks of the the protons and neutrons in the nuclei are sort of broken. Well, they are separated and you get the soup of of quarks and gluons. Like it could have been after The Big Bang and. Then you can you can measure this in its behaviour.

Rebecca:

How long does - this might be a super silly question - but how long does that state of the quark- gluon plasma last? Is it even possible to answer that or... ?

Ruth:   

OK, so I'm not a heavy iron physicist

Rebecca:

Sorry.R

uth:   

But it's it's. I mean, it's really short. It's. Yeah. So we, I mean, well, this collision happens not quite as often, but it's on the time scale of I guess nanoseconds or something.

Rebecca:

Oh yes. So I think it's.

Ruth:   

Or, or even less than.

Rebecca:

That I think it's very impressive that we have humans in a way, have managed to build a machine that can mimic the conditions that was like seconds after really Big Bang. That's very impressive.

Ruth:   

Yeah, I I think so. And it, yeah. It continues to blow my mind.

Rebecca:

So I want to ask the questions here.  So particle physics. What more is there to discover? Like, don't we already know? You know, you talk about the protons, you talk about the quarks. And don't we already know about the particles? What more is there to study?

Ruth:   

Very good question. And I I forget who it was, but there was a famous physicist who sort of said exactly this. Maybe a bit more than like 100 years ago or so.  He said like ‘We're we're done. Physics is complete. We have discovered everything.’

Rebecca:

We're done!

Ruth:   

And then people started discovering more and more particles.  Like, exotic particles. And then we we realised that there was actually more than, you know, protons and neutrons and electrons.

Nowadays it's - so you are right in that we have we've come very far in describing the ordinary matter. The matter that everything around us is made-up of. So this is all the stable mater and then there are some, you know, unstable particles that you can create, for example in an accelerator. But all of this is described in what we call the standard model.  Which is our theory, and it works very, very well and it, you know it can explain. Yeah, pretty much all the normal matter.

Rebecca:

Sure, everything we see around us, yes.

Ruth:   

Yeah. But one of the big open questions that the standard model doesn't answer is Dark Matter.

Rebecca:

Right.

Ruth:

So this is something that we know from cosmological observations where we see that. Essentially you - I mean you can do this in different ways and at different scales - but essentially you always see that the gravitational effects you observe cannot be explained by the visible matter.  

Rebecca:

Yeah.

Ruth:  

So you infer that there must be some kind of invisible or Dark Matter.

Rebecca:

Sure, there's more. There's more mass there that we can see.

 

 

 

 
 

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