Podcast: Mighty magnets, and aerosols in the atmosphere

Host: Nick Howe

Welcome back to the Nature Podcast. This week, we’ll be finding out about a mighty magnet…

Host: Benjamin Thompson

And hearing about aerosols’ effects in the atmosphere. I’m Benjamin Thompson.

Host: Nick Howe

And I’m Nick Howe.

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Interviewer: Benjamin Thompson

Listeners, for our first story today, I want to talk about magnets, but not the ones you might have attached to your fridge at home. Oh no, I want to talk about some monstrously powerful magnets. For many years, researchers have been creating stronger and stronger magnetic fields for use in things like MRI scanners, particle accelerators and nuclear fusion experiments. This week in Nature, a team have beaten the current world record for a particular type of magnet, using techniques that could usher in a route to even stronger magnets being made in the future. Now, magnetic fields are measured in units called teslas. A fridge magnet has a strength of a maybe a few millitesla, but this new one can produce a field tens of thousands of times stronger, at 45.5 tesla. To get an idea of how the team managed it, let’s find out a bit about the magnets involved, and these are electromagnets – ones that require power and can be switched on and off. Now, broadly speaking, these fit into two categories, as Damian Hampshire, who researches powerful magnets at Durham University here in the UK, explains.

Interviewee: Damian Hampshire

One is we can make magnets in the way that we did traditionally for electrical applications like transformers, where you take a wire – generally a copper wire – and you wind it into a coil and then you can just drive a current through the copper wire and produce the large magnetic field that way. The problem with that is that once you get above a few tesla, you have to have very large power supplies. If you look at the high field labs around the world that use that sort of approach, they’re putting megawatts, tens of megawatts, into these magnets to drive them.

Interviewer: Benjamin Thompson

When you put a large amount of power into these so-called resistive magnets, they get hot, and without proper cooling, they could melt. The other category of electromagnet also requires cooling, but for rather different reasons.

Interviewee: Damian Hampshire

Now, the second technology is to use superconducting materials. The advantage that superconducting materials have is they have no resistance, so now you don’t need a large power supply. You can basically use a sophisticated car battery to drive the current through this very low-resistance superconducting material. The drawback is that you have to cool things down. You have to cool the magnet down to low temperatures in order for it to go into the superconducting state and achieve this zero resistance.

Interviewer: Benjamin Thompson

For superconductors to work properly, they need to be mighty cold, and the coils in these magnets are often cooled using liquid helium to only a few kelvin above absolute zero. As superconducting materials has no electrical resistance, none of the power fed into these magnets is lost to heat, which makes them more efficient. However, you can only push them so far, as at high magnetic fields, the coils within the magnet can lose their superconductivity. So, there are the two types of electromagnet and they have their strengths and weaknesses. They’re both capable of making really strong magnetic fields, but putting one type inside the other – to make a hybrid magnet – combines their fields, giving the strongest outputs. Until now, the strongest direct-current, or DC, magnetic field in the world was created by a hybrid found at the National High Magnetic Field Laboratory at Florida State University in Tallahassee in the US. It’s a big old thing, says David Labalestier, who works at the lab.

Interviewee: David Larbalestier

If you went to see the hybrid magnet, what you would see is a huge physical plant that is many metres in diameter and many metres high, and it’s a very large superconducting magnet, about 2 metres outside diameter and about 2 metres high, and inside this is a small resistive magnet, and that magnet has been very reliable. It’s been operating since 2000 and it has scientists from all over the world using it.

Interviewer: Benjamin Thompson

The combined output of this superconducting/resistive hybrid magnet is a magnetic field of 45 tesla, which for a few decades has been the record, but now David and his colleagues have made a hybrid that tops it, producing 45.5 tesla – a new world record for a direct-current magnetic field. Central to this achievement is the makeup of the superconducting magnet, which in this case is found on the inside, rather than the outside, of the hybrid. Instead of using traditional low-temperature superconducting material to make the magnet’s coils, the team used an incredibly thin tape containing a high-temperature superconducting material wrapped many, many times around the magnet’s core. These high-temperature superconductors still require temperatures way below zero degrees Celsius to work, but David and his team have been cooling them a lot more than that.

Interviewee: David Larbalestier

So, the advantage of a high-temperature superconductor is actually not that we’re using it at high temperatures – we’re using it at exactly the same temperature as we use a low-temperature superconductor – but the meaning is that actually it has a much more robust superconductivity in it and this superconductivity exists to much, much higher fields, so we can generate here twice the magnetic field that is possible with any low-temperature superconductor.

Interviewer: Benjamin Thompson

Using this setup means that the new hybrid magnet is more compact, it’s more energy efficient and the researchers are able to pump more current through the superconducting section.

Interviewee: David Larbalestier

I mean it’s like a car, right? I mean the more power you can have in the engine, the more torque you can add to the wheels, the faster it will go, and it’s exactly the same thing here – the more current you can put into the windings, the higher the magnetic field. It’s just directly proportional.

Interviewer: Benjamin Thompson

So, there’s a new champion in the field of magnetic fields. Damian Hampshire, who you heard from earlier, and who wasn’t part of the new study, is impressed with what’s been achieved.

Interviewee: Damian Hampshire

Well, of course, this is an important step forward in the field because they have achieved – as far as I can see – the highest DC field yet, so that is a fabulous piece of work, so they should be applauded. But, as they mentioned in the paper, this is not a route yet for commercial ultrahigh-field magnets because the magnet itself is largely damaged at the end of the experiment, but this is the nature of research and this is the nature of development in this field.

Interviewer: Benjamin Thompson

Setting a world record took its toll on the setup. The coils of the superconducting magnet were damaged in places by the stresses caused by the high magnetic field. David suggests that tiny defects in the superconducting tape were the cause of this, but he’s confident that this is something that can be overcome in future. On the face of it, moving from 45 to 45.5 tesla might not seem like a big leap, but David explained to me that this really is a proof-of-principle test, not designed for a particular application, and really, it’s about paving the way for even more powerful magnets to be made in future.

Interviewee: Damian Hampshire

In raw numbers, it isn’t a huge leap but it’s a huge leap because the technology used to develop it opens the route towards 60 tesla or even higher. The limits now are not in the superconductor – the limits are in managing the genie in the bottle and the genie in the bottle is the stored magnetic energy which is very, very large.

Interviewer: Benjamin Thompson

That was David Larbalestier from the National High Magnetic Field Laboratory of Florida State University in the US. You can read his paper over at nature.com. You also heard from Damian Hampshire from Durham University in the UK.

Host: Nick Howe

Later in the show, we’ll be hearing about another researcher wanting to use CRISPR to edit human embryos – that’s coming up in the News Chat. Now though, it’s time for the Research Highlights, read this week by Anna Nagle.

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Anna Nagle

Monkeys may not have a brain for music, according to new research from the US. By scanning the brains of humans and macaques while they were listening to sounds, scientists were able to show that human brains had a strong response to harmony and pitch – key components of music and speech. Macaques don’t tend to spend much time listening to Jay-Z on a lazy Sunday afternoon though, so the researchers wondered whether music just wasn’t relevant to monkeys. To check this, the researchers did the same experiment, but this time with macaque noises. Even then, when harmonic sounds were present, human brains showed a stronger response than the macaques. The authors believe that these differences are due to the importance of speech and music to humans. Harmonise with that research over at Nature Neuroscience.

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Anna Nagle

I just want to say one word to you: plastics. Today, plastics are truly everywhere. Recently, there’s been research into microplastics – tiny specks of plastic – and their effects on marine life. It may not only be the residents of Neptune’s kingdom that are exposed to these puny, plastic particles though – humans may be too. By taking data from 26 studies and looking at around 15% of Americans’ food intake, scientists from Canada were able to estimate that humans take in between 74,000 and 121,000 microplastic particles a year. People could also be exposed to an additional 90,000 particles a year if they only drink water from plastic bottles rather than from the tap. At the moment, it’s unclear what the health effects might be of microplastics on human, but the researchers suggest that plastics are pervasive. Find that study over at Environmental Science and Technology.

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Interviewer: Nick Howe

Next up, I’ve been looking into how aerosols affect the climate.

Host: Benjamin Thompson

Well, hang on a minute, don’t we already know that? Aerosols are bad for the climate, aren’t they?

Interviewer: Nick Howe

Well, that’s the thing – we don’t really know. There’s a lot of uncertainty about… Hang on, are you thinking of aerosol sprays like the ones for your armpits?

Host: Benjamin Thompson

Yeah, absolutely. That’s why I only use roll-ons, right? Smelling good without the guilt.

Interviewer: Nick Howe

Right, well, that’s actually a common misconception. Back in the 80s and 90s when the hole in the ozone layer was all over the news, there were spray cans that released chlorofluorocarbons (CFCs) into the air, which cause damage to the ozone layer. Damage to the ozone layer is also not really about climate change, which is what we’re talking about here. Anyway, the media often refer to those spray cans as aerosols, but that’s not typically what scientists mean when they use the word.

Host: Benjamin Thompson

Ah, I see – well, what do scientists mean when they say aerosols?

Interviewer: Nick Howe

Well, that’s a good question, and it’s the first thing I asked Joyce Penner, a climate scientist from the University of Michigan, who’s written a Comment in this week’s Nature about aerosols’ unclear effects on the climate.

Interviewee: Joyce Penner

We’re talking about just particles, very small particles, usually less than a micron, you know, like the dust in the air that you see.

Interviewer: Nick Howe

So, what are some types of aerosols and where are they coming from?

Interviewee: Joyce Penner

So, the aerosols come from a variety of sources. When you’re burning coal, coal has sulphur embedded in it and that’s released into the atmosphere as SO₂, which goes through some chemical reactions to form sulphate, which condenses as an aerosol. But dust is just blown by wind action into the atmosphere, soot is… any kind of burning produces some amount of soot, and sea salt is also a source that is put into the atmosphere by winds.

Interviewer: Nick Howe

So, what is our current understanding of how aerosols affect the climate?

Interviewee: Joyce Penner

Well, we think in general they cool, so they are actually hiding the effects of CO₂ and the other greenhouse gases by being present in the atmosphere. Aerosol particles themselves can scatter solar radiation, so instead of absorbing that radiation at the surface of the Earth and warming the Earth, it’s scattered out. And the other way is they act as seeds for cloud drops and ice particles and when they do that, at least in warm clouds, they tend to make more cloud particles and that allows the cloud to be more reflective of sunlight as well, but the extent to which they do that is not very well known.

Interviewer: Nick Howe

So, what are the challenges in trying to understand that?

Interviewee: Joyce Penner

Well, particularly for the cloud issue, one of the things that has been difficult to pin down was whether changes to the clouds are occurring because of the aerosols or just because of meteorology. So, the clouds are changing day by day, and is that what we see when we go out and look at experiments or is it actually the aerosols?

Interviewer: Nick Howe

What is the cost to not knowing, what is the cost of not understanding aerosols properly?

Interviewee: Joyce Penner

Right now, we have projections, if we keep burning fossil fuels as we have been, that by 2100, the Earth may warm but the range of warming is quite large, so that range, I think, could be narrowed if we knew the aerosol forcing much better.

Interviewer: Nick Howe

So, what are the things we need to do in order to understand aerosols?

Interviewee: Joyce Penner

We need to establish what the aerosol properties are and because aerosols have a fairly short lifetime, like 5-10 days in the atmosphere, that means that in different source regions, their properties are different. So, you’ll see mainly dust aerosols coming off of the Sahara and maybe organics and sulphates coming off of China and areas like that and we need to know what the properties of these aerosols are in terms of the mixing and that means we have to get out there with aeroplanes to determine those properties, as well as the size of the aerosol, which determines how much reflection of solar radiation takes place.

Interviewer: Nick Howe

If I was to give you an infinite amount of money to better understand how aerosols are affecting climate change, what would you spend it on?

Interviewee: Joyce Penner

I think that the biggest part of the uncertainty has to do with the way that aerosols affect clouds. So, if we can get the community to use particular meteorological conditions to study in observations how clouds respond to aerosols and then make sure that the models can reproduce that behaviour, that would be a big step forward.

Interviewer: Nick Howe

Is there a degree to which there always will be some uncertainty about aerosols’ impact on the climate?

Interviewee: Joyce Penner

I hope not. I’m very certain that if we can beat down the uncertainties then we can also beat down uncertainties in how the climate is going to change in the future, but I think what it will take to do that is a concerted effort by the community at large.

Interviewer: Nick Howe

That was Joyce Penner from the University of Michigan in the US. You can check out the Comment article she wrote unpacking some of the uncertainties about aerosols over at nature.com/opinion.

Interviewer: Benjamin Thompson

Finally then, as always on the show, it’s time for the News Chat and joining me here in the studio is Davide Castelvecchi, senior reporter here at Nature. Davide, hi.

Interviewee: Davide Castelvecchi

Hi, Ben.

Interviewer: Benjamin Thompson

For our first story today, Davide, we’re going to be talking about X-rays, but maybe not in a hospital context.

Interviewee: Davide Castelvecchi

No, this is astrophysics. It’s high-energy photons from space and it’s a new space observatory which will launch later this month.

Interviewer: Benjamin Thompson

Right, well who’s making this observatory then Davide?

Interviewee: Davide Castelvecchi

It’s a joint Russian and German mission and it will carry actually two separate instruments, both of which are X-ray telescopes and they will look at the same part of the sky at the same time and they will scan the sky continuously for four years to produce a full sky map at these very high-energy X-rays.

Interviewer: Benjamin Thompson

So, why then do we want an X-ray map of the sky? What can it tell us that just a regular sort of observatory or regular telescope can’t?

Interviewee: Davide Castelvecchi

It’s just like when you use filters on your camera and you can see the world in different ways, different colours. X-rays are produced by different phenomena than visible light and different wavelengths within the general category of X-rays can give us this different information. So, for example, plasma – which is interstellar matter that is very feeble and thin but is present almost everywhere – you would think it’s invisible and transparent, but it glows in X-ray wavelengths.

Interviewer: Benjamin Thompson

So, it will be telling us stuff then about the universe that we didn’t know before?

Interviewee: Davide Castelvecchi

Yes, well the main goal of this mission is to do a map of galaxy clusters. So, these are the largest structures we know in the universe that can be made by thousands of galaxies and sometimes we can’t even see the individual galaxies but these instruments will see the glow of the intergalactic gas from these clusters.

Interviewer: Benjamin Thompson

Right, and well, something you and I have talked about before, Davide, is dark matter. Is this observatory designed to maybe hunt this kind of mysterious stuff that’s out there in the universe?

Interviewee: Davide Castelvecchi

So, it will trace the effects of dark matter on the formation of these gigantic structures, and also there is a hope that it might see more directly the decay of dark matter. Kind of like how radioactive matter decays, perhaps particles of dark matter also decay and give off X-rays.

Interviewer: Benjamin Thompson

Well, on this one then, Davide, I understand that this mission has been quite a long time in the making.

Interviewee: Davide Castelvecchi

The roots of this mission stretch back to the 1980s under Gorbachev’s rule and there were different proposals at the time and then the Soviet Union collapsed and the Russian economy went down with it and for a long time, the Russian space programme and Russian science were troubled also by brain drain and so on, so especially the Russian side of the collaboration hopes that this will represent kind of a comeback, specifically for astrophysics.

Interviewer: Benjamin Thompson

Well, last one on this one, Davide, so the launch of this is next week. How excited are the researchers behind it?

Interviewee: Davide Castelvecchi

For Rashid Sunyaev, one of the Russian astrophysicists I interviewed, it’s an especially significant mission because he is rather old and he has been dreaming of such a mission since the 1980s. When I was interviewing him, he kept knocking on wood saying if all goes well we will do this and that. There’s always risks in any launch, in any space mission – things can go wrong and you can lose the spacecraft – so there was a feeling that there was a lot at stake.

Interviewer: Benjamin Thompson

Well, Davide, let’s stay in Russia for our next story, and it’s a story that we’ve covered a bunch on the News Chat, but it just seems to have so many twists and turns, and this is a story which began in November last year about the CRISPR editing of two baby girls in China. But as I say, we’re in Russia now. What’s going on here?

Interviewee: Davide Castelvecchi

We have revelations that a molecular biologist in Moscow called Denis Rebrikov is planning to do something similar to what was done in China by He Jiankui – the story that you mentioned from last year – which of course rose huge controversy.

Interviewer: Benjamin Thompson

So, Nature had the exclusive on this one – that Rebrikov is considering implanting gene-edited embryos into women. Davide, why does he want to do this?

Interviewee: Davide Castelvecchi

So, Rebrikov, his goal is the same – to prevent the transmission of HIV from parent to child. Now, in the case of He Jiankui, it was an attempt to prevent transmission from the father, and here instead it would be to prevent HIV-positive mothers from passing on the virus to the children.

Interviewer: Benjamin Thompson

And how is Rebrikov planning to do this then?

Interviewee: Davide Castelvecchi

He wants to target the same gene. It’s a gene called CCR5, which controls a protein which may or may not prevent HIV viruses from entering human cells. Now, the technique he wants to use is CRISPR, which of course has become hugely successful and powerful in all biology, but it has yet to be proven to be safe in humans.

Interviewer: Benjamin Thompson

Well, a couple of weeks ago we had a story in the News Chat about China potentially changing their laws in response to what happened back in November, and there’s been calls across the world for a sort of moratorium on this. Is Rebrikov able to do this in Russia? What’s the sort of legal framework? Is this something he’s just able to go ahead and work on?

Interviewee: Davide Castelvecchi

It seems that there’s a grey area legally, so it’s unclear whether what he wants to do is legal according to current Russian law. He is applying for permits to carry out his experiments, so we’ll see what happens.

Interviewer: Benjamin Thompson

Well, ethicists and biologists had a lot of opinions on the last time this was attempted, and none of them were positive, as far as I’m aware. What are people saying this time about this potential sort of second go?

Interviewee: Davide Castelvecchi

The issues are always the same. It’s unclear whether this will be effective, it’s unclear whether it’s needed and there’s also potential side effects. Rebrikov claims that he can avoid them but whenever you use this kind of technique, which is based on enzymes editing DNA, there’s always a risk of mutations happening in unintended parts of the genome where you could have consequences that you can’t predict.

Interviewer: Benjamin Thompson

At least Rebrikov has announced ahead of time that he’s thinking about doing this, I suppose, which is more than the world got last time. Has he given any idea of what his plans actually are?

Interviewee: Davide Castelvecchi

He’s hoping to start within a few months but it also depends on how fast he will be able to get the permits from the Russian authorities.

Interviewer: Benjamin Thompson

Or if he gets them at all. Davide, definitely one for us to keep a close eye on here. Listeners, for more on both of these stories, head over to nature.com/news.

Host: Nick Howe

That’s all we’ve got for this week. There’s just time to let you know that we’re now on Spotify, so if that’s your go-to destination for podcasts, you can find this and all our previous episodes over there. I’m Nick Howe.

Host: Benjamin Thompson

And I’m Benjamin Thompson. See you next time.