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  • NATURE PODCAST

Podcast: Free-floating DNA in cancers, an ancient molluscs relative, and can the Arctic's ice be regrown?

This week, free-floating DNA in cancers, an ancient relative of molluscs and can the Arctic's ice be regrown?

In this episode:

00:36 Vanishing icescape

The Arctic is losing its sea ice, but could it one day be regrown? Feature: After the ice goes; Earth’s Future research paper: Newton et al.

06:49 Deviant DNA

Unpicking the role of free-floating DNA in cancer. Research paper: Turner et al.

13:53 Research Highlights

Building a bat-bot; and gene therapy for deaf mice. Research Highlight: A robot that flies like a bat; Research Highlight: Gene therapy restores hearing

16:16 Missing mollusc

A slug-like fossil sheds light on the mollusc family tree. Research paper: Vinther et al.

22:59 News Chat

What’s next for the world’s gravitational wave observatories? News: Underdog lab is ready to roll; Book review: The wave catchers

Never miss an episode: Subscribe to the Nature Podcast on Apple Podcasts, Google Podcasts, Spotify or your favourite podcast app. Head here for the Nature Podcast RSS feed.

doi: https://doi.org/10.1038/d41586-019-02159-6

Transcript

This week, free-floating DNA in cancers, an ancient relative of molluscs and can the Arctic's ice be regrown?

Interviewer: Kerri Smith

Coming up: how a slug-like fossil is shedding light on the mollusc family tree.

Interviewee: Luke Parry

So, it sort of ends this palaeontological mystery.

Interviewer: Adam Levy

And, the Arctic is melting but is that the end of the story for its ice?

Interviewee: Stephanie Pfirman

If we were able to reduce the temperatures then the ice would come back.

Interviewer: Kerri Smith

Plus, how free floating DNA could impact on how cancers evolve. This is the Nature Podcastfor February the 9th2017. I’m Kerri Smith.

Interviewer: Adam Levy

And I’m Adam Levy.

[Jingle]

Interviewer: Kerri Smith

The Arctic is losing its sea ice, and fast. The ice has thinned and retreated, leaving behind just a quarter of what was there only thirty years ago. Adam takes a look at why that matters and whether one day we might be able to grow it back.

[Music]

Interviewer: Adam Levy

Researcher, Dirk Notz, has a very personal relationship with the ice at the top of the world.

Interviewee – Dirk Notz

I think as a kid I was just fascinated by anything adventurous, and obviously, explorers trying to reach the North Pole or the South Pole were the stories that I read as a kid.

[Music]

When I was studying meteorology here in Hamburg suddenly the opportunity arose to spend a year and study up there and I immediately fell in love with that landscape. Whenever I take photos up there and I come home and show those to my kids, knowing that by the time that they’ve reached my age all that might be gone, actually creates a very real sadness of seeing something disappear in front of our eyes and knowing that it’s our responsibility.

[Music]

Interviewer – Adam Levy

The globe is warming but the Arctic is burning up. In fact, the Arctic is heating about twice as fast as the global average. As the sea ice melts, it reveals the dark ocean beneath. In a vicious circle, more and more sunlight is absorbed, amplifying the warming process. Many scientists now see Arctic summers free of ice as a question of when, not if. Scientists can work out roughly how much CO2 we can emit before the last of the sea ice melts away. And considering the scale of global emissions, the figure is uncomfortably small.

Interviewee – Dirk Notz

At current emission rates that number will be reached within twenty to thirty years.

Interviewer – Adam Levy

The loss of this ice will have direct impacts on the people and wildlife that rely on it. But sea ice researcher, Stephanie Pfirman, explains that we all have reason to care about the vanishing Arctic.

Interviewee - Stephanie Pfirman

The world needs an Arctic that is along the lines of what it is today. So, the Arctic provides services to the rest of the globe; it provides a sea-level-stabilisation service because it keeps the ice frozen on Greenland. The cold Arctic atmosphere keeps our weather system stable because the whole weather system is driven by the gradient between the tropics and the poles. So, the changes in the Arctic can affect billions of people around the globe.

Interviewer – Adam Levy

With the stakes so high, the Arctic has become the poster child for tackling Global Warming. Many scientists are increasingly pessimistic about its chances but Stefanie is refusing to be defeated so easily.

Interviewee - Stephanie Pfirman

What’s interesting is that a lot of people have been focusing on the ice loss but when you cool the Arctic – if we were able to reduce the temperatures then the ice would come back.

Interviewer – Adam Levy

In Stephanie’s future Arctic the loss of ice isn’t the end of the story. She suggests that even after Arctic sea ice has disappeared during summers and all that’s left is miles of blue sea, cooling the earthcould allow it to eventually regrow.

Interviewee - Stephanie Pfirman

It could be an area where people have gotten used to this mainly blue Arctic and then if we are successful in addressing Global Warming through our actions and we are successful in turning temperature around then the ice would come back to this blue Arctic.

Interviewer – Adam Levy

But cooling the world is easier said than done. It’s not going to be enough to just stop producing emissions; we’re going to have to take carbon dioxide out of the atmosphere. Many Climate Change policies, including the Paris agreement may rely on these negative emissions technologies to achieve their targets. But Dirk is unsure whether these will work in practice.

Interviewee - Dirk Notz

In order to regrow massive amounts of sea ice in the Arctic we would have to remove CO2 at a very large scale from the atmosphere, and so far I haven’t seen a single method that would not only extract CO2 from the atmosphere but would also allow for its storage for very, very long time periods.

Interviewer – Adam Levy

There are alternatives to extracting and storing CO2. Other approaches might be able to cool just the Arctic, say, by using brightly coloured particles to reflect away the sun’s rays once again. But geoengineering the Arctic in this way could come with unforeseen consequences and many think that CO2 capture and storage is the only viable option to lower temperatures. Removing such vast amounts of CO2 is a daunting task. Even so, Stephanie wonders if economics might be able to turn it into a reality.

Interviewee - Stephanie Pfirman

I’m optimistic because this is new technology, it’s jobs. I think that having people focus on trying to tackle this problem and trying to resolve it is something that we might be able to achieve.

[Music]

Interviewer: Adam Levy

No-one knows for sure whether we’ll be able to develop the technology to remove CO2 on these huge scales and so no-one ever knows for sure whether we would be able to return the Arctic to its former glory. So for Dirk, to protect the Arctic, and indeed the planet, it’s far safer to avoid the warming in the first place.

Interviewee: Dirk Notz

From my personal perspective it really seems most efficient to emit less CO2 rather than having to extract the CO2 from the atmosphere later on.

[Music]

Interviewer: Adam Levy

That was Dirk Notz who’s at the Max Planck Institute for Meteorology in Hamburg, Germany. Before Dirk, you heard from Stephanie Pfirman of Barnard College at Columbia in the US. For more on the ice loss and possibility of regrowth in the Arctic, check out the Feature in this week’s Nature. Find it at www.nature.com/news.

Interviewer: Kerri Smith

Next up, Noah has been investigating how DNA found outside chromosomes could be impacting how cancer evolves.

Interviewer: Noah Baker

How do cancers evolve? It’s a hot topic in medicine and one that Paul Mischel from the Ludwig Institute of Cancer Research in San Diego, US, wants to know more about.

Interviewee: Paul Mischel

Cancers become more aggressive as time goes on, and more and more difficult to treat: they evolve.

Interviewer: Noah Baker

And cancer cells don’t always evolve slowly and steadily.

Interviewee: Paul Mischel

Recent data suggests that it isn’t a straight linear process but it’s almost as if there are bursts of genome instability. Alterations of copy number, focal amplification, seem to be very important in this.

Interviewer: Noah Baker

One culprit that could be making genomes unstable is a type of gene called an oncogene. Paul and his team know that there are way too many copies of these genes in cancer cells but where do the copies actually live in the cell?

Interviewee: Paul Mischel

When we began to think about this and to talk with colleagues and to survey the literature – about where are those copy number alterations, where are those focal amplifications localised in the cell? – it was very unclear. Nobody actually knew.

Interviewer: Noah Baker

So, Paul and his team went back to basics and looked at how DNA is stored.

Interviewee: Paul Mischel

One of the first things people learn when they study Biology is that prokaryotes – things like bacteria – have their DNA on a circle, a small circular chromosome, and small circular plasmas. In contrast, linear DNA is the rule for eukaryotes including vertebrate animals and humans.

Interviewer: Noah Baker

In eukaryotes like us, this DNA is stored in chromosomes but we have some DNA outside of our chromosomes too.

Interviewee: Paul Mischel

There was an observation that was made in the ‘70s to ‘80s when people looked at cancer chromosomes, they noticed these little dots. But at that time it was hard to know what was on those dots.

Interviewer: Noah Baker

It turns out that these dots were free-floating, circular DNA, known as extra-chromosomal DNA elements.

Interviewee: Paul Mischel

So what we did was we took a pretty wide swab and this included a wide variety of cancer types: cancers of the brain, the colon, the lung, melanoma, ovary, pancreas. I think there were about seventeen different cancer types. And then we also looked at normal cells so we would be able to ask the first question: what’s the scope? What’s the frequency of these extra-chromosomal DNA elements in cells? And what became absolutely clear is that this is an exceedingly rare event in normal cells but in cancer it’s incredibly common; nearly half of cancers have this.

Interviewer: Noah Baker

Paul and his team wanted to find out what was on these extra-chromosomal DNA elements so he started sequencing them along with the rest of the genomes of these cancer cells.

Interviewee: Paul Mischel

And in the whole genome sequencing what we found is the spectrum of amplifications in these cells was really identical to the spectrum of amplifications that one normally sees in the large cancer genome studies.

Interviewer: Noah Baker

They saw the same spectrum of oncogenes being amplified as other studies had seen. The kicker though, came when they looked at where these oncogenes were located.

Interviewee: Paul Mischel

We were in for a bit of a surprise which was that the most common oncogenes all are on extra-chromosomal DNA and/or extra-chromosomal DNA jumping onto abnormal places on the chromosome, to abnormal locations on the chromosome.

Interviewer: Noah Baker

Those cancers which had extra-chromosomal DNA associated with them also seemed to be putting their oncogenes there. The question is, why?

Interviewee: Paul Mischel

It occurred to us it all goes back to Charles Darwin and Gregor Mendel, in the following sense… Circular DNA is really designed, in a way, for variation, whereas linear DNA, for fidelity.

Interviewer: Noah Baker

Paul and his team argued that this circular extra-chromosomal DNA, chock-full with oncogenes, helps tumours to evolve more rapidly. He explained, starting with how oncogenes on normal chromosomes are copied during cell division.

Interviewee: Paul Mischel

So let’s just take an example. Let’s just say an oncogene had 3 copies that were sitting on chromosomes. When that cell was getting ready to divide it would make six copies and those chromosomes would be passed equally to daughter cells, 3 and 3. If, in contrast, that oncogene were amplified and extra-chromosomal DNA all mixed in, when that cell was getting ready to divide it would make 6 copies, but those 6 copies aren’t parcelled equally to daughter cells being on chromosomes. They can actually be randomly segregated, so you could get 6 and 0, you could get 5 and 1, you could get 4 and 2, or you could get 3 and 3 to daughter cells. And if you look at that, what that implies are two features: 1. The copy number goes up very rapidly; the second thing that it implies is the variance is enormous because you’ve got not just 3 and 3 now, you’ve got a range that goes from 6 to 0. And, going back to Darwin’s principles of natural selection, variation is really a critical component of that and so this provides effectively, the fuel for selection. It’s quite likely that under any variety of conditions there’s a tumour cell that has the optimal amount of that particular gene to thrive under that particular circumstance.

Interviewer: Noah Baker

Essentially, if a cancer cell’s oncogenes are on its chromosomes, then when the cell divides, the two daughter cells will get an exact copy of the parent’s oncogenes and the number of copies of the gene stay the same. But, if the oncogenes are on free-floating extra-chromosomal DNA, then the daughter cells could get an endlessly varying mixture of different oncogenes and different copy numbers. By mixing everything up, the cancer helps the process of natural selection find a foothold. This theory has been supported by computer modelling and appears consistent with clinical data. Paul thinks that this could go some way to explaining why some cancers see bursts of severity and grow so rapidly.

Interviewee: Paul Mischel

In all of these cancers that patients present very aggressive, high-grade tumours, we tend to see that those cancers have a lot of extra-chromosomal DNA elements: glioblastoma, pancreas, ovarian cancer: those sorts of things.

Interviewer: Noah Baker

If this is the case, Paul hopes it could lead to new treatments.

Interviewee: Paul Mischel

If we figure out rules that govern this process, perhaps that can be stopped, perhaps there’s a vulnerability that can be targeted because if cancer cells can’t engage this mechanism, they won’t be able to adapt or evolve as quickly. And if that’s the case we may be much more capable of intervening therapeutically in a way that actually works and have a higher success rate in our cancer cells.

Interviewer: Kerri Smith

That was Paul Mischel from the Ludwig Institute for Cancer Research in the US. Read more at nature.com/nature.

Interviewer: Adam Levy

Still to come, in the News Chat, it’s a year since the LIGO team announced that they had detected gravitational waves. But physicists are not the type to sit back and stop looking. Our reporter Davide Castelvecchi will be here to tell us what they’re planning next. But now though, it’s the best research in bite size form; it’s the Research Highlights read by Corie Lok.

[Jingle]

Interviewee: Corie Lok

Bats are capable of some amazing aerial feats. And now researchers have built a bat-like robot that can do many of the same manoeuvres. The device, called Bat-Bot, weighs 93 grams. Each wing has 9 joints and is covered by a stretchy silicon skin. This allows the wings to fold, extend and move independently of each other. Bat-Bot can fly straight, dive and even do banked turns. Previous bat inspired robots could not even get off the ground. Now the researchers say they can use Bat-Bot to learn more about the mechanics of bat flight. You can find the study in the journal Science Robotics.

[Jingle]

Gene therapy has allowed deaf mice to hear again. Researchers studied new-born mice with genetic mutations that cause Usher syndrome, a genetic disease that causes deafness, blindness, and balance problems in people. The scientists injected a synthetic virus into the ears of the deaf mice. The virus carried a healthy version of the mutated gene. The team found that the new gene was incorporated into the sound sensing cells in the ear and this restored hearing. The animals could respond to sounds as quiet as a whisper. With further testing, gene therapy could one day be used to treat certain genetic forms of deafness. They study was published in the journal Nature Biotechnology.

[Jingle]

Interviewer: Kerri Smith

We love getting your reviews by email and on iTunes, like the one we got from Sam Rajabi who emailed us from Iran to say that we make the Tehran commute more bearable for him. And to chemical engineer Richard O. who’s been listening for the past four years.

Interviewer: Adam Levy

We’re less happy to hear that reviewer ‘Dads53’ thought this month’s Backchat was vacuous. Sorry ‘Dads’. Though it is worth pointing out that vacuums are very interesting indeed so maybe he meant it as a compliment?

Interviewer: Kerri Smith

If you’ve got thoughts on the show, you can email us…

Interviewer: Adam Levy

Podcast@nature.com

Interviewer: Kerri Smith

Or find us on Twitter…

Interviewer: Adam Levy

@NaturePodcast

Interviewer: Kerri Smith

Or leave us a review on iTunes or your podcasting software of choice which will hopefully help others find the show. Now, Adam, what do mussels and squid have in common? Apart from the fact that they’re both delicious.

Interviewer: Adam Levy

Well, unless you’re a vegetarian.

Interviewer: Kerri Smith

Ah, unless you’re a vegetarian.

Interviewer: Adam Levy

Or keep Kosher.

Interviewer: Kerri Smith

Okay, sure. But aside from that, delicious or not, they’re also both molluscs which means at some point, way back when, the tentacle-y, shell-less squid and the two-shelled mussel shared a common ancestor. Shamini Bundell set off across the city to find out what it might have looked like.

[Background noise at the National History Museum]

Interviewer: Shamini Bundell

If you’re in London and want to find out about molluscs and their relatives, the place to head is the Natural History Museum. They’ve got your common or garden molluscs like slugs and snails, your marine molluscs like clams and squid, and molluscs you’ve never even heard of, including some that look like worms and other that look like woodlice or pill bugs. And that’s just the modern molluscs. In order to get a proper idea of the mollusc family tree, you need fossils. Fortunately, the Natural History Museum has plenty of these too. I fought my way through the school trip crowds into a back office to find Luke Parry from the University of Bristol. He’s been working here during his PhD which involves studying a 478 million year old fossil mollusc.

Hi Luke.

Interviewee: Luke Parry

Hi.

Interviewer: Shamini Bundell

We’re talking a lot about molluscs today. They’re not the most glamorous of creatures. What’s so great about molluscs?

Interviewee: Luke Parry

So, I think the most interesting thing about molluscs is that they’re incredibly diverse today and they also have a number of disparate body plans. They span the range from things that are really complicated and really intelligent, like octopuses that use tools, to then really simple things like clams and garden snails.

Interviewer: Shamini Bundell

So there are loads of different types of molluscs even living in the world today. How did they all evolve?

Interviewee: Luke Parry

So if we look at the family tree of molluscs there are two main groups. So there’s what are called the conchiferan molluscs; so those are things like snails, octopuses, and clams. And then if we look at the other main lineage of molluscs, I actually have – so this is a chiton here –so these are things that have these 8 shells that lie across the top of their body. And then –

Interviewer: Shamini Bundell

They look a bit like pill bugs.

Interviewee: Luke Parry

They do look a little bit like pill bugs. And then you have these really weird things, see these worm molluscs.

Interviewer: Shamini Bundell

And there were some sort of mystery organisms that were found that for a long time people didn’t know where they fit in.

Interviewee: Luke Parry

Yes, so one of the things people have been discussing is Halkieria. So, this is from the early Cambrian of Greenland.

Interviewer: Shamini Bundell

So you’ve got a fossil here which looks like a vaguely flat slug-shape.

Interviewee: Luke Parry

Yeah, so it’s a spiny slug and it has a shell at either end of its body and then the rest of its body is covered in this really complicated arrangement of little mineralised spines and spicules. It’s got a few weird characteristics.

Interviewer: Shamini Bundell

Why was this particular fossil so mysterious?

Interviewee: Luke Parry

It doesn’t really look like anything that’s alive today so people have debated whether or not it could be closely related to molluscs or lie within molluscs. And people have also debated whether or not it could be an ancestor of things called brachiopods or ‘lamp shells’.

Interviewer: Shamini Bundell

So we didn’t even know if this was a mollusc or not.

Interviewee: Luke Parry

Yeah, indeed, yeah.

Interviewer: Shamini Bundell

And that brings us onto a new find which is what the paper’s about: this new creature.

Interviewee: Luke Parry

Yeah, so our new fossil is from the Ordovician of Morocco. This thing is quite substantially younger than a lot of the fossils that we’ve talked about.

Interviewer: Shamini Bundell

What are we calling this new creature?

Interviewee: Luke Parry

So this thing is called a Calvapilosa Kroegeri. So it’s named after –

Interviewer: Shamini Bundell

You don’t make it easy do you?

Interviewee: Luke Parry

No! So the name Calvapilosa means like ‘shaggy head’ because it’s got this one shell that sits at the front that’s covered in all these hairy, thin spines.

Interviewer: Shamini Bundell

And we’ve got some pictures of the fossil here and we’ve also got a recreation that I’m not sure I want to touch because it’s kind of spiky looking.

Interviewee: Luke Parry

So what you can see here, is you’ve got the main body which is covered in all these tiny little spiny sclerites. They would have been mineralised in calcium carbonate so they would have been really, really hard. And they also extend over the shell as well. The shell would have actually been peeking out from underneath them.

Interviewer: Shamini Bundell

I feel like I know why limpets have shells, and I know why snails have shells: so they can hide in them.

Interviewee: Luke Parry

Yeah.

Interviewer: Shamini Bundell

This guy just has a sort of little shell on his head. Is that useful for it?

Interviewee: Luke Parry

Yeah, so this is covering what’s called a radula which is this tooth tongue that they use for rasping up food, and it’s actually the radula that’s the big new discovery.

Interviewer: Shamini Bundell

And why is the fact that it has this spiky radula tongue so important?

Interviewee: Luke Parry

You can see that this animal has a lot of similarities with Halkieria – so that two-shelled thing that we saw earlier – in that it has this body covered by these mineralised sclerites and in this case only this one shell on the head. And the radula is a really, really important morphological feature because although not all molluscs have a radula, a radula is not known from any other group of organisms. So, because we can see a radula in this fossil, we know absolutely that is must belong to molluscs.

Interviewer: Shamini Bundell

So we found ourselves a mollusc and that also tells us about that other fossil, the Halkieria.

Interviewee: Luke Parry

Yeah, so it sort of ends this paleontological mystery. It ends the debate about where Halkieria sits in the tree of life; because we see in this very, very similar looking fossil, we can also say that a lot of other weird looking things that we have from the Cambrian are probably also molluscs and also would have had this radula.

Interviewer: Shamini Bundell

So how many mysteries does this one specimen solve?

Interviewee: Luke Parry

So there are a number of different things from the Cambrian. There’s obviously Halkieria, so this thing from Greenland, and then there are a few things which are known just from their shells or just from their spines which are actually some of the earliest known mollusc fossils that we have.

Interviewer: Shamini Bundell

And does this help us solve the question we were asking at the beginning which is: where do the molluscs come from? What were the first molluscs like?

Interviewee: Luke Parry

Yeah, so, in our analysis of the family tree of molluscs, we find that these armoured, spiny, slug things, so things like Halkieria and Calvapilosa, our new discovery, lie on the lineage leading to these pill bug like molluscs (the chitons and the worm molluscs, the aplacophorans). And because those two groups are very different from each other, so there’s no shell on one side and many shells on the other side, we now know that that group evolved from an ancestor that only had a single shell, very much like our new discovery.

And then if you look at the other major groups of molluscs, so, things like snails and squids and octopuses and clams and so forth, it seems like those also evolved from a single-shelled ancestor. So, from that information we can infer that only one shell, a single shell, was present in the last common ancestor of molluscs. We can also say that associated with this single shell was some sort of covering of spines. So it tells us that things which are really, really, complicated like octopuses and squids, evolved from some sort of very, very simple, single-shelled, spiny ancestor along with all of the other groups that we see today.

Interviewer: Kerri Smith

That was Luke Parry of the University of Bristol showing various mollusc fossils and models to Shamini Bundell. The paper on Calvapilosa Kroegeri is out this week and can be found at nature.com/nature.

Interviewer: Adam Levy

You definitely didn’t sound like you were just making that up.

Interviewer: Kerri Smith

What, nature.com/nature? No, it’s been like that for ages.

Interviewer: Adam Levy

[Laughs]No, the other bit! The Calva… Oh, I can’t even… I can’t even try.

Interviewer: Kerri Smith

Let’s just leave this to Shamini in future.

[Jingle]

Interviewer: Kerri Smith

It’s time for the News now and reporter Davide Castelvecchi joins me in the studio here in London. Davide, hello.

Interviewee: Davide Castelvecchi

Hello Kerri.

Interviewee: Davide Castelvecchi

Your favourite topic, it’s probably true still to say, is gravitational waves, is it not?

Interviewee: Davide Castelvecchi

I guess I have that reputation by now.

Interviewer: Kerri Smith

And the LIGO discovery was announced a year ago now.

Yes, it was the 11thof February when your podcast colleague, Adam Levy, and I were both in Washington DC and our colleague, Alex Witze. So, we did full coverage.

Interviewer: Kerri Smith

And the coverage did not stop after the announcement was made. You’re bringing it right up to date this week.

Interviewee: Davide Castelvecchi

Yes, so this week is interesting, not only because it’s the first anniversary of this big announcement, but also because a sort of underdog instrument or observatory which is in Pisa, Italy, is getting ready to start after a long overhaul, having been shut down for 5 years. This is an instrument that has already, just like LIGO, has already looked for gravitational waves in the past and now there’s high expectations for what they can do together.

Interviewer: Kerri Smith

So this is kind of a twin, or at least it’s very similar to LIGO. This apparatus is called Virgo. What’s the aim of Virgo? Is it exactly the same as what LIGO’s been doing or are there any differences in what they’re actually looking for?

Interviewee: Davide Castelvecchi

It is practically the same. So, what they do is they bounce laser beams between mirrors and each of these interferometer has two arms and then they compare the lengths over time and they look for the signs of passing gravitational waves. All these experiments pool their data together; they analyse the data together and they publish together. So, when LIGO made its announcement, it was really the LIGO-Virgo team.

Interviewer: Kerri Smith

And because they pool all their data and they collaborate on the analysis, they didn’t feel, at Virgo, as if they’d been scooped in any way?

Interviewee: Davide Castelvecchi

Well, some of them privately did. There was excitement because they felt validated that this entire field of research which – it wasn’t clear at all that this was going to work – has been validated, on one hand. On the other hand there was also a sense of ‘we missed the big party, we missed the first big detection’.

Interviewer: Kerri Smith

Your story this week looks at when they get their detector back up and running, the kinds of things that they could work together with LIGO to improve upon. What are some of the ways in which the two facilities – or three if we count LIGO as two and Virgo as one – could work together to improve our knowledge of gravitational waves.

Interviewee: Davide Castelvecchi

One thing is that gravitational waves – when there’s some event, some cosmic cataclysm, like two black holes merge – the waves come from that direction and depending what direction they come from, LIGO can be more or less sensitive to them. And Virgo, which is geographically in a different hemisphere, and also it’s oriented differently in respect to the waves, will help to tease apart some of these details about the intricate physics of these waves. And the other thing is that the timing of arrival of these signals – because there’s a few milliseconds of difference – can be used for instance between the signals as they arrive at the two LIGO locations and at Virgo. From these three timings, they can use trigonometry and narrow down the direction; they can actually figure out where in the sky it came from.

Interviewer: Kerri Smith

I love it when people say words that I remember from maths GCSE.

Interviewee: Davide Castelvecchi

And it is – it’s definitely high school level trigonometry they use.

Interviewer: Kerri Smith

And are there more facilities like this on the horizon, given that it takes a long time to build one of these things?

Interviewee: Davide Castelvecchi

Yeah, this is very exciting. There is one next year; 2018 is to be the opening of KAGRA, which is a Japanese detector which is kind of similar to LIGO and Virgo except that it’s underground and also it will be cryogenic. Its mirrors, its optics, will be kept 20 degrees above absolute zero to reduce thermal fluctuations in the noise.

Interviewer: Kerri Smith

Let’s just wind back from this very forward looking article that you’ve just written to an article that you wrote last week – it’s actually a book review – and it also has to do with LIGO. So cast your minds back, listeners, to when the gravitational wave announcement was made, that was February, but of course since September of the previous year it had been known about. And for all of this time, and for the previous few decades, Harry Collins who’s a sociologist was embedded with the team at LIGO and he’s written a book about the finding, hasn’t he?

Interviewee: Davide Castelvecchi

It’s indeed a very exciting book to read. It’s the first book that tells the inside story of the discovery and how the researchers went about first of all convincing themselves that they didn’t have just a fluke, to deciding how they would go about letting the world know and convincing their peers that they’d saw it.

Interviewer: Kerri Smith

Tell us a little bit about Harry Collins because as I mentioned in the intro, he’s basically a member of the family at LIGO, isn’t he, at this point?

Interviewee: Davide Castelvecchi

Yes, this is his fourth book by my count about LIGO. He doesn’t spend all his time there but he keeps in touch. He gets all the internal emails and he visits the lab periodically. He’s interested in: how do scientists know that they know something? How do they go from seeing some data that looks interesting to actually realising that the data constitutes a discovery? And this is actually a very interesting process. It’s not a ‘eureka moment’ as it’s often described.

Interviewer: Kerri Smith

And in this latest – this is an extreme example isn’t it, LIGO, of the way the discovery was made, the amount of people who were needed to make that discovery and then finally announce it.

Interviewee: Davide Castelvecchi

Absolutely, and a lot of what the book focuses on is the issue of transparency. He disagrees strongly with the way that LIGO and Virgo went about trying to keep it a secret. Their official line was always, ‘we cannot comment on our data analysis, we are studying our data and we will make an announcement when we can. Meanwhile, journalists such as myself were frantically trying to piece together what was happening from rumours and things that were being said. And this is also something that figures prominently in the book. I should say, for full disclosure, I am mentioned in the book because one of the people I kept calling to ask for comments was the author, Harry Collins, himself.

Interviewer: Kerri Smith

Do you reach the same conclusions in your position as a journalist phoning around, trying to make sure, trying to establish whether the rumours are true or not – do you agree with him that they were not transparent enough?

Interviewee: Davide Castelvecchi

Well he certainly makes a very, very eloquent and noble case for science to be an exemplar, kind of a beacon of intellectual honesty. I just don’t know that scientists necessarily need to release or tell everyone what they know as soon as they know it. Before coming out with a claim they wanted to be really sure.

Interviewer: Kerri Smith

Davide, thank you very much for coming in. You can find Davide’s book review and the News story on Virgo at nature.com/news.

Interviewer: Adam Levy

That’s all we’ve got time for this week, but there’s more where that came from. There’s a sci-fi short story just out on the podcast feed and soon we are re-broadcasting the penultimate episode of Nature Pastcast, our history of science show. If you’re a subscriber you’ll get it automatically. Or, if you’re listening to this episode but haven’t subscribed, do consider finding us on your favourite podcasting app. I’m Adam Levy.

Interviewer: Kerri Smith

And I’m Kerri Smith

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