NATURE PODCAST

Podcast: Galileo and the science deniers, and physicists probe the mysterious pion

Tune in for the latest from the world of science, with Shamini Bundell and Nick Howe.

This week, a new way to study elusive subatomic particles called pions, and the relevance of Galileo in a time of modern science denialism.

In this episode:

00:46 Probing pions

Pions are incredibly unstable and difficult-to-study subatomic particles. Now researchers have come up with a clever way to examine them - by sticking them into helium atoms. Research Article: Hori et al.

08:28 Research Highlights

A colourful way to cool buildings, and the rapid expansion of cities. Research Highlight: A rainbow of layered paints could help buildings to keep their cool; Research Highlight: Urban sprawl overspreads Earth at an unprecedented speed

10:46 The life of Galileo

A new biography of Galileo Galilei examines some of the myths about his life and draws parallels with problems facing scientists today. Books and Arts: Galileo’s story is always relevant

16:42 Pick of the Briefing

We pick our highlights from the Nature Briefing, including botanical graffiti, and rock-eating bacteria. The Guardian: 'Not just weeds': how rebel botanists are using graffiti to name forgotten flora; Scientific American: Scientists Waited Two and a Half Years to See whether Bacteria Can Eat Rock

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Transcript

This week, a new way to study elusive subatomic particles called pions, and the relevance of Galileo in a time of modern science denialism.

Host: Nick Howe

Welcome back to the Nature Podcast. This week, observing the strange subatomic particles called pions…

Host: Shamini Bundell

And the life of Galileo Galilei. I’m Shamini Bundell.

Host: Nick Howe

And I’m Nick Howe.

[Jingle]

Host: Nick Howe

First up on the show – pions. Pions are subatomic particles you might not have heard of even though they stream down from the atmosphere all the time. Like protons, they’re made up of quarks. But while protons have three quarks, pions have just two, and that makes them both super unstable and reactive. On their own in a vacuum, a negatively charged pion might live for a few billionths of a second. But attempt to capture one in a material to study it, and it reacts, disappearing in mere trillionths of a second. This week in Nature, scientists have used an ingenious method to keep pions around a little longer – by sticking them into helium atoms. Though hypothesised to exist, the creation of pionic helium has never been verified until now. Aside from being a bit weird, pionic helium is useful because it keeps the troublesome pions alive long enough to measure them using spectroscopy, and that could open up whole new avenues for research into this elusive particle. Reporter Lizzie Gibney called up lead author Masaki Hori to find out more and started by asking about why physicists thought pionic helium could be created in the first place.

Interviewee: Masaki Hori

So, in the 1960s, people studied pions using devices called bubble chambers. These were big tanks filled with liquid helium that was almost boiling. When pions were allowed to run through this helium, they would make small tracks of bubbles. These bubbles would be photographed with analogue camera and film – that was what was available at that time – and when looking at the developed photographs, there was an anomaly which seemed to suggest that a small fraction of these pions were surviving longer than a trillionth of a second. So, a scientist named George Condo of Tennessee University in 1964 devised a theory which said maybe there is this long-lived pionic helium atom being produced inside this chamber. The normal helium atom that fills a child’s balloon – this is composed of an atomic nucleus and two electrons. In this new pionic helium atom that we have verified, one of these electrons is replaced by a pion, so we have an atom, an artificially produced atom, where a pion and an electron both orbit the normal helium nucleus.

Interviewer: Lizzie Gibney

So, if physicists suspected that this pionic helium existed back in the 1960s, why has it taken so long to actually create it?

Interviewee: Masaki Hori

Presumably, the atom was previously produced by, for example, accident in previous experiments. There was just no way to technologically verify that. The smoking gun proof would be to carry out what’s called optical spectroscopy. Each atom that exists in nature has several characteristic atomic frequencies that means the atoms can absorb or emit light of certain wavelengths. These wavelengths are the atom’s fingerprint, if you want. But this new pionic helium atom’s lifetime is so incredibly short that it doesn’t live long enough to emit light and provide this fingerprint to us. If it doesn’t emit light, we can’t see it, and therefore we can’t detect that it exists. But there is another more modern way. If we place these atoms within a very powerful beam of laser light at the correct wavelength, then we can possibly make the atom resonate within its short lifetime, so this is what we did.

Interviewer: Lizzie Gibney

And what kind of kit do you need then to create the pionic helium and then actually detect them?

Interviewee: Masaki Hori

We needed to have a really powerful laser and also produce a large sample of these atoms, relatively speaking. So, for this, we went to the world’s most powerful pion source – that is located in the Paul Scherrer Institute in Switzerland. The way our experiment was designed, we could only expect to see two or three atoms per hour resonating with the laser and producing a signal. There was a background of spurious events, which was 1,000 times bigger than this signal we were looking at, so we had to just tune our laser and run the experiment 24 hours a day before we could say, ‘Okay, there might be some interesting signal.’ But even after we saw the first indication, it took more than a month to collect enough data, running 24 hours, to be sure.

Interviewee: Masaki Hori

It sounds like it was such an enormous slog. You’ve got to produce billions of your atoms and then filter them and get rid of the contamination and then make sure you’re actually hitting that crucial fingerprint wavelength. Once you’ve done all that and you’ve got your handful of pionic helium left, what do you do with those atoms? What can we learn about pions?

Interviewer: Lizzie Gibney

We can possible determine the pion’s mass with a precision of perhaps 8 or 9 digits, hopefully. This would be 100 times even more precise than in previous experimental methods. Also, if there exists particles that are beyond the standard model, that interact with pions in unexpected ways, perhaps we can set upper limits to the possible existence of those kind of particles.

Interviewer: Lizzie Gibney

And what do you hope to do next? Is there another kind of particle that you’re planning to put in a helium atom?

Interviewee: Masaki Hori

This is a dream. We want to do it with kaons. So far, all the particles that we have talked about here today – protons, pions, neutrons – they are made of up and down quarks. But nature provides, in fact, six quarks. The next quark in line is called the strange quark, and the strange quark can make a new kind of meson called a K meson – kaon, it’s called. And this would be very exciting because if we can study kaons using laser spectroscopy, we would be able to study the characteristics perhaps of the particle that includes a strange quark to a higher precision than before. But of course, this experiment will be even more challenging than the pion case, so this is, for now, a dream.

Host: Nick Howe

That was Masaki Hori from the Max Planck Institute. You can find a link to his paper over in the show notes.

Host: Shamini Bundell

Before we get on with the rest of the show, you might have heard we have been nominated for a Webby Award. We’re shortlisted in the Science and Education Best Individual Episode category for an episode which included the science of foot callouses, protein-based archaeology and an on-location report about the Ebola outbreak in the DRC.

Host: Nick Howe

This episode is also up for a People’s Choice Award – in other words, a public vote in which we are currently sitting in second place. I’m just casually mentioning this, of course, in case any of you fancy voting for us. It only takes a couple of minutes, and voting closes at midnight Pacific Time on Thursday 7th May. You can click on the link in the show notes and we’d very much appreciate your support.

Host: Shamini Bundell

Coming up, we’ll be hearing about everyone’s favourite heliocentric astronomer, Galileo. Right now, though, it’s time for the Research Highlights, read to you this week by Benjamin Thompson.

[Jingle]

Benjamin Thompson

Painting buildings white could help keep interiors cool and reduce the need for air conditioning by reflecting the Sun’s energy. But what are your options if you don’t want a white building? Well, a team of researchers in China and the US have now shown a way to add a splash of colour to buildings without sacrificing cooling capabilities. Their solution involves painting a colourful topcoat less than 100 micrometres thick on top of a white undercoat. The near-infrared portion of sunlight, which carries about 50% of the light’s heat, passes through the eye-catching topcoat but is then reflected by the white layer underneath. The team suggests that this approach represents a cost-effective, scalable way to achieve both colour and cooling. Brush up on that research over at Science Advances.

[Jingle]

Benjamin Thompson

Given that over half the world’s population lives in urban areas, it’s not so surprising that cities have expanded in size in recent decades. But new research suggests that this expansion has happened much faster than previously thought. To study how cities have changed over time, a team of researchers studied satellite images taken between 1985 and 2015 and looked at how land use altered during this period. Their results show that urban areas expanded by 80% and that each year, an average of more than 10,000 square kilometres of land – an area bigger than New York City – converted from non-urban to urban uses, a rate of expansion much greater than previous estimates. This rapid urbanisation is also substantially higher than the global rate of population growth, with the authors suggesting that many urban areas were not used for housing but for other purposes like commercial or industrial use. The team hope their results will help inform sustainable urban planning and research into the effects of city expansion on biodiversity loss. Read that research, perhaps from your urban abode, over at Nature Sustainability.

[Jingle]

Host: Shamini Bundell

Galileo is regarded as the founder of modern astronomy and the father of modern science, as well as a symbol of the fight for intellectual freedom. Astrophysicist Mario Livio has written a new biography of Galileo’s life, which analyses the mythos of the man and looks at the parallels between Galileo’s experiences and modern science and even with the science denialism that we see today. Anand Jagatia caught up with Mario and started by unpicking one of the most famous stories of Galileo’s life.

Interviewer: Anand Jagatia

There’s this story about Galileo that he stood at the top of the Leaning Tower of Pisa and dropped these two heavy weights to show that they would hit the ground at the same time. Is that a real experiment? Do we know if that actually happened?

Interviewee: Mario Livio

Well, no, he did experiments, but I don’t think he did it from the Leaning Tower of Pisa. As far as I could tell and as much as I researched it, that appears to be a legend. But there were people who dropped balls from the Tower of Pisa. Galileo did drop balls from various heights, but he never mentions having done that from the leaning tower of Pisa. He found a way to sort of dilute gravity, if you like, by rolling balls down inclined planes instead of making them simply fall, so this was truly an incredible insight on his part to understand that at some level even freefall can be regarded as sort of an extreme case when the inclined plane is perpendicular to the ground.

Interviewer: Anand Jagatia

Galileo’s approach was revolutionary, really, at the time, so how did it differ from people that came before him?

Interviewee: Mario Livio

So, yeah, the ancient Greeks thought that to discover facts about nature, all you need is to sit down and think about those. Galileo is the person who introduced this revolutionary way of thinking that the only way to discover things about nature is by experiments, observations and then reasoning based on the results of those experiments and observations. So, in that sense, he really started the modern way of doing physics and science in general.

Interviewer: Anand Jagatia

You then write about how Galileo turned his attention to the skies and used telescopes to observe objects in the heavens, and the first thing he observed was the Moon. Can you tell us about what he saw there?

Interviewee: Mario Livio

Galileo actually used his artistic education. He had learnt how to draw and he understood light and shadow, so he very quickly understood that what he was observing was a rugged surface with craters and mountains, and this was really revolutionary in the sense that celestial objects were supposed to be perfect and not look like the surface of the Earth.

Interviewer: Anand Jagatia

Galileo, of course, went on to make many more astronomical observations, leading him to put the Sun at the centre of the Solar System rather than the Earth, which went against what many scientists and the Church said was the case. Infamously, this culminated in him being put on trial by the Holy Inquisition and in 1633 being forced to denounce his entire life’s work on his knees. And reading your account of what happened, today it is actually still quite shocking.

Interviewee: Mario Livio

Indeed, yes. I mean this is one of the most humiliating stories in our intellectual history, and the point that I make in the book is that even if Galileo were completely wrong in his model for the Solar System, the Church had really no authority to put him on trial and find him guilty for having an opinion. For that to have been convicted and made to abjure and put on house arrest for the rest of his life, it really remains as a shameful incident in the history of science.

Interviewer: Anand Jagatia

There’s another story that as he left the court, he muttered under his breath to himself, ‘And yet it moves,’ in Italian, basically saying that in spite of what you believe, the facts are that the Earth does move around the Sun in this way. Did that actually happen?

Interviewee: Mario Livio

Of course, he didn’t say it in front of the inquisition. That would just have been simply insane.

Interviewer: Anand Jagatia

But that phrase, ‘And yet it moves,’ has become a symbol of intellectual defiance, and you mention in the book that perhaps today, phrases like that are having to be used a bit more often than they should be, so can we draw parallels between what happened then in the 1600s and science denial today?

Interviewee: Mario Livio

Oh, absolutely, and this is one of the main reasons why I also decided to write the book. We see science denial all over the place today, and this is starting, of course, with denial of climate change from people in the highest positions, and in just this latest COVID-19 pandemic. The early denial of the reality of this pandemic was very, very costly.

Interviewer: Anand Jagatia

Do you think that there are any lessons that can be learned?

Interviewee: Mario Livio

Well, the real lesson is: believe in science. It’s not that science is always right, but science has this ability to self-correct, so we have to believe in science and we have to put the science first and before any kind of political considerations, conservatism, religious beliefs and things like that. I mean this is the big lesson.

Host: Shamini Bundell

That was Mario Livio. His new book is called Galileo and the Science Deniers and you’ll find a link to a review of the book in the show notes.

Host: Nick Howe

Finally on the show, you may have heard of the Nature Briefing, Nature’s daily pick of science news and stories delivered directly to your inbox. Well, Shamini and I have been looking through it to bring you some non-corona science news. Shamini, what’s on the agenda this week?

Host: Shamini Bundell

Okay, so my favourite Briefing pick this week is a story that just made me unreasonably happy when I read it. It’s about graffiti, but graffiti with a sort of science communication cause, and it’s basically people who have been chalking the names of plants and trees and shrubs on pavements around, well, Europe.

Host: Nick Howe

And what’s the hope of these guys? What are they trying to accomplish by writing down the names of species?

Host: Shamini Bundell

Well, I think this is just getting people connected to the wildlife that is all around us. So, this is a lovely Guardian article with some pictures, and these are just tiny little plants growing up just through cracks in the pavements or on the edges of streets that you would just walk past. And seeing their common names, so there’s like here’s a daisy, here’s herb Robert – I didn’t even know there was a herb called Robert – but it’s great to get people aware of the wildlife that’s around them, I think. Although I should note that in the UK, chalking on the pavements or anywhere like that is actually illegal, so the Guardian article actually starts with the opening sentence: ‘A rising international force of rebel botanists.’ So, the Nature Podcast does not condone the illegal graffiti-ing, but I personally think it’s wonderful. I also kind of hope that there’s some kid out there who’s going to be looking at this and going, ‘I want to grow up to be an international force of rebel botanists.’

Host: Nick Howe

Laughs.

Host: Shamini Bundell

What a cool career that is.

Host: Nick Howe

I mean that is an excellent career, becoming a rebel botanist.

Host: Shamini Bundell

I know, right. What have you got this week?

Host: Nick Howe

So, my story that I found in the Briefing this week is how rock becomes dirt or soil.

Host: Shamini Bundell

Oh, how very glamorous.

Host: Nick Howe

Oh, so, so glamorous. So, scientists basically understand that rocks become soil through weathering, but that’s made of several different components and that’s like rain and erosion and things but also, it’s been thought for a long time that there’ll be a biological component – specifically a bacterial or fungal component.

Host: Shamini Bundell

So, some sort of bacteria or fungus is physically turning rock into tiny pieces that become part of soil.

Host: Nick Howe

Yeah, that’s what’s been thought, and it’s been shown to be theoretically possible, but this seems to happen at such a slow rate that no one’s ever observed it. No one’s ever proven it experimentally.

Host: Shamini Bundell

I hope you’re going to say, ‘Until now…’

Host: Nick Howe

Until now because what scientists have done is they have been looking for rocks that weather very, very quickly – ones that can be observed in sort of, well, in time to publish a paper, basically. And they found a rock called Rio Blanco Quartz, which weathers very, very quickly, and they thought this will be a good rock to test.

Host: Shamini Bundell

So, they watched the rock for a while.

Host: Nick Howe

What they did is they drilled down to bedrock where this rock was and found like the transition layer where the rock was turning into soil, took a little sample of that and assumed that what was happening there was involving bacteria of fungi, and then they took a few samples of these rocks, and on some they put this transitional zone and on others they didn’t, and then they left it for 30 months to see what happened. As I said, very, very glamorous.

Host: Shamini Bundell

Oh, so there was something in that layer that was actually helping the breakdown of rock.

Host: Nick Howe

Well, that’s what they were hoping to find out, and what they did, is after the 30 months they saw what had happened and in the ones where they had added this transitional layer, the rock was sort of like rough and had like pits and holes in it as if it had been, essentially, eaten.

Host: Shamini Bundell

What, and what was eating it?

Host: Nick Howe

So, they did a DNA analysis and they also looked for something called ATP, which you might remember from school biology, which is like sort of an energetic resource that is produced by life, and what they found with the DNA analysis is there was bacteria present there, and because there was this ATP as well, they hypothesised that this was actually bacteria breaking down the rock.

Host: Shamini Bundell

But given that it’s super slow and in their experiment it didn’t even manage to break down a whole rock, is this rock-eating bacteria actually useful at all?

Host: Nick Howe

I don’t know about useful. It probably forms a component of weathering but probably not the biggest part of it. This happens over a long time and this rock in particular was a rock that was really, really easy to break down, so for other rocks it may only be playing a very, very small role, but it’s still interesting to know and finally have confirmation of the fact that bacteria is involved in the breakdown of rock.

Host: Shamini Bundell

Good to know. Good science, thanks Nick.

Host: Nick Howe

Yeah, it is some good science, and that was published in PNAS and the article I read was in Scientific American if you want a slightly snappier version. But yeah, there’s some more interesting articles and if you listeners are interested in getting more bite-sized bits of science then make sure you check out the Nature Briefing, and we’ll put a link to that in the show notes.

Host: Shamini Bundell

Well, that is all that we’ve got time for this week, but if you are listening to this episode before Thursday 7th May then don’t forget you can vote for us in the Webbys. Let’s try and get the Nature Podcast to number one. Thanks very much. I’m Shamini Bundell.

Host: Nick Howe

And I’m Nick Howe. Thanks for listening.