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Interviewer: Shamini Bundell
Hello and welcome to the Nature Podcast. This week we’re finding out how a quantum trick could help measure even fainter gravitational waves.
Interviewer: Adam Levy
Plus we’re looking at an early sign of autism and taking steps to assess exercise.
Interviewer: Shamini Bundell
This is the Nature Podcastfor July the 13th2017. I’m Shamini Bundell
Interviewer: Adam Levy
And I’m Adam Levy.
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Interviewer: Adam Levy
In 2015, scientists detected gravitational waves for the first time: tiny ripples in space time caused by the violent collision of two massive black holes. Since then they’ve seen two more similar collisions. But they want to see even fainter events, even further away. To do that they need to navigate limits imposed by the fuzzy world of quantum mechanics. Reporter Lizzie Gibney investigates.
Interviewer: Lizzie Gibney
When massive black holes collide billions of light-years away, they emit gravitational waves – tiny ripples in space time. Remarkably, we can see these on earth in the way that these waves subtly shrink and stretch space time as they pass by. Scientists at LIGO, the US based advanced Laser Interferometer Gravitational Wave Observatory, pick up these waves. They send laser beams down two 4 kilometre tunnels which bounce back off mirrors at either end. If a passing wave has stretched and squeezed space time, the distance between the free-moving mirrors changes. To detect these subtle changes, detectors are already sensitive to tiny changes in distance around one ten thousandth of the width of a photon, but they want to get even more sensitive. Nergis Mavalvala, a physicist at the Massachusetts Institute of Technology and a member of the LIGO experiment, explains why.
Interviewee: Nergis Mavalvala
Yes, so, the amplitude of the gravitational wave scales with how far the source is. So if you can make a more sensitive detector you can actually see the same kind of source to greater distances which is really important as we try to map out what’s out there is the sky at greater and greater distances. It’s probably one of the most magnificent thing about distance – is the farther you look out, the further back in time you’re looking so it also tells us about the history of the universe and how these systems evolved and so there’s a lot of excitement to be able to look farther out, which means you need more sensitive detectors and that’s what we’re trying to do.
Interviewer: Lizzie Gibney
Engineers already protect the equipment from noise that could mask or emulate a passing wave but eventually they hit a pretty solid road block: a fundamental limit on how accurate measurements can be, imposed by quantum mechanics.
Interviewee: Nergis Mavalvala
Quantum noise comes from the fact that light is quantised. We know that light comes in packets called photons and what we do when we make the measurement is we’re counting the number of photons. And so that process of counting the number of photons has quantum uncertainty on it, and that’s in the end, the fundamental limit to the sensitivity of the detectors that we’ve built so far.
Interviewer: Lizzie Gibney
The problem is that as soon as you’ve tried to measure something on the quantum scale, the measurement itself introduces an uncertainty. This is because to figure out how the passing waves affect space time, the researchers measure a distance between the mirrors with photons, but each time the photon hits the mirror, it nudges it, gives it a little kick of momentum which slightly changes that distance, and as the photons fluctuate in number, so does this disturbance – a phenomenon known as back action. Nergis and her colleagues have been studying for decades how it might be possible to get around this fundamental fuzziness in LIGO’s measurements and they plan to employ a few tricks in the detector’s next upgrade. But a different team, publishing in Naturethis week, have devised a new way to measure changes in distance that evades this quantum limit. The idea is to cancel out the effect of the photon’s momentum kicks: the back action. They do this by taking measurements from the point of view of a different system which experiences an equal but opposite effect. To do this, a team led by Eugene Polzik, of the Niels Bohr Institute in Copenhagen, brought in something unusual: a cloud of atoms. This cloud of atoms is special because it’s been artificially primed by the researchers so that when it’s hit by the proton beam, its only option is to switch to a lower rather than higher energy state. Imagine the photon is a ball, says Eugene. Throw it at a mirror and it makes the mirror accelerate away. Bizarrely, for the cloud of atoms it’s the opposite. When the ball hits, it’s as though the cloud accelerates back towards you, mathematically at least.
Interviewee: Eugene Polzik
In principle, this eliminates the back action completely and practically it means that we can improve the sensitivity by as much as we wish. But this is always difficult in real life. There are always imperfections and losses and for example, in the paper we demonstrate the reduction of this back action by only 30%.
Interviewer: Lizzie Gibney
It’s early days but Eugene reckons that using this technique, detectors like LIGO could increase their sensitivity by a factor of two or maybe three. Nergis is also optimistic.
Interviewee: Nergis Mavalvala
The early thinking is that this could be very useful but we really have to be careful and do the detailed calculations before we can be sure. If these kinds of schemes could be applied to these long kilometre scale gravitational wave detectors, what we would hope for its that they would have improved sensitivity and therefore could see either fainter objects that are nearby or see farther out into the universe.
Interviewer: Lizzie Gibney
It seems like the technique could prove pretty useful, but for Eugene it’s about more than that.
Interviewee: Eugene Polzik
Well, the general curiosity of course, simply to see how we can fool around, so to say, with quantum mechanical restrictions. What we’re trying to do is to demonstrate that the naively and usually assumed limitations of quantum mechanics, they actually can be overcome if you think of this measurement in a special reference frame.
Interviewer: Adam Levy
That was Eugene Polzik, of the Niels Bohr Institute in Copenhagen. You also heard from Nergis Mavalvala from MIT. Thank you to reporter Lizzie Gibney for explaining the quantum fuzziness in as un-fuzzy a way as possible. You can read her news story on the study online at nature.com/news, where you’ll also find a link to Eugene’s research paper.
Interviewer: Shamini Bundell
Stay tuned for the Research Highlights where we’re looking for protected areas that aren’t great at protecting animals, and boosts to children’s maths skills. Now though, what determines how much you walk each day? Reporter Anand Jagatia has been taking steps to find out.
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Interviewer: Anand Jagatia
I’m currently walking to the station as part of my daily commute and I’m enjoying the last bit of fresh air and sunshine that I can before I have to descend into the hot, stuffy bowels of the London Underground, but thanks to an app that uses my smart phone’s accelerometer, I can see exactly how many steps I’ve taken so far today and right now I’m on 3,596… 97, 98, 99… Millions of people around the world have apps like this one recording their daily activity and this week scientists have analysed the data from over 700, 000 of them.
Interviewee: Jure Leskovec
We took the data collected by that app and had for over a two year time period, physical activity of the individuals.
Interviewer: Anand Jagatia
That’s study author Jure Leskovec, a computer scientist at Stamford University.
Interviewer: Jure Leskovec
Of course this was all anonymous but what was nice was that we had the precise measurement of their daily physical activity together with their gender, age, location and because we also have their weight we can computer what is called the Body Mass Index, which is whether the person is obese or not.
Interviewer: Anand Jagatia
Jure wanted to study the relationship between a country’s activity and its levels of obesity but somewhat surprisingly, if you take a country’s average activity, there isn’t a very strong link with its obesity. Instead…
Interviewee: Jure Leskovec
What is very important is how is activity distributed among the population? And what we found out is the measure of inequality of how the activity is spread through the population is very well associated with the amount of obesity in a given country, right? So it’s not about what is the average; it’s about how many people are activity poor.
Interviewer: Anand Jagatia
This concept of activity inequality is a bit like the economic measure of income inequality. So what’s going on here? Why is more activity inequality linked to higher levels of obesity?
Interviewee: Jure Leskovec
What we find is that it’s the gender gap that causes activity inequality. So basically in countries with low activity inequality like Japan and China, men and women are about equally active. But in countries with big gaps between high activity and low activity people, so, for example, Saudi Arabia or the United States – there it’s actually women who are in some sense the vulnerable population that is getting much less active. What we then find is that women are more sensitive to the decrease in activity so if you decrease the activity of a man and a woman by the same amount, the fraction of obese people will increase faster in women than in men.
Interviewer: Anand Jagatia
The study also looked at whether people’s activity was influenced by the walkability of the city that they live in which is a metric that tries to measure how easy it is to get around on foot.
Interviewee: Jure Leskovec
There is a very strong association between walkability of the city and how much people in that city walk. But the interesting thing is that we see this gap in activity also over the weekends. So even over the weekends, in more walkable cities, people tend to be more active actually throughout the day, and we were careful to make sure that these results were not results of climate, so that walkable cities have nice climates, friendly to be outside. We also made sure that it’s not about socio-economic status, that rich cities are walkable but poor cities are not. This seems to be true regardless of climate or socio-economic status.
Interviewer: Anand Jagatia
You might be thinking, ‘derrrr’, obviously people will walk more in more walkable places. But having actual data on people’s behaviour in the real world could enable us to design cities that are better for our health and using activity inequality could help scientists identify which people in a population are activity poor and could benefit most from any changes. But, on a more fundamental level, the study also shows how useful smartphones can be for gathering data on people’s behaviour and not just on how many steps they take.
Interviewee: Jure Leskovec
These devices are with us all the time and they know us better than our doctor does. They can be used to monitor food intake, they can be used to monitor exercising, heart rate, to measure sleep, but there is also a lot of work to be done to make sure that we understand how we are measuring, what is this thing really measuring, how is it biased, skewed, distorted and so on?
Interviewer: Shamini Bundell
That was Jure Leskovec from Stamford University talking with Anand Jagatia. Check out the paper in the usual place.
Interviewer: Adam Levy
Interviewer: Shamini Bundell
And I’d like to take this opportunity to out self-professed closet science fan John McKee who’s been enjoying his holiday by listening to the podcast, and observing insect behaviours.
Interviewer: Adam Levy
To get in touch with us, drop us a tweet @NaturePodcast, an email, podcast@nature.com, or an iTunes review, right? Now back to the science.
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Interviewer: Adam Levy
About one in a hundred people are affected by autism but there’s still lots we don’t know about the condition. A lot of what we do know is about how the disorder appears, for example it most often becomes apparent in the second year of life and it makes it hard for a child to socialise with others.
Interviewee: John Constantino
And it’s not that children don’t want to engage in those relationships, but they have a great deal of difficulty navigating them and maintaining, for example, friendships.
Interviewer: Adam Levy
This is John Constantino who researches social development disorders in children. It’s known that autism has strong genetic links and John is interested in getting to the bottom of them. In a paper out this week, John and collaborators have been taking a closer look at an early indicator of autism: where infants spend their time looking. I called John up to find out what’s been missing from our understanding of autism so far.
Interviewee: John Constantino
Historically it’s been very difficult to see the earliest signs of the autistic syndrome, so in other words very young babies appear to look normal for a very long time over the first year to year and a half of life and that becomes impairing as that child ages into their second and third year of life.
Interviewer: Adam Levy
And in this study out this week, you were actually looking at something which might show signs of autism earlier in life.
Interviewee: John Constantino
We capitalised on two important discoveries of the last 10 or 15 years in autism, the first being that it is highly genetically influenced, and the second, that children’s attention to the eyes and faces of others in their environment was in decline in young children at risk for autism, beginning as early as 2 months of age. So this offered an opportunity to identify a predictor for how the condition actually occurs or arises in a child.
Interviewer: Adam Levy
How do you actually test where a child is looking and whether they’re more or less interested in looking at other people’s faces?
Interviewee: John Constantino
A young child – a baby – is seated in front of a screen that is showing them a video of a person either talking to them or a video of individuals interacting with one another. So we had a way to distil from those experiments, the total proportion of time oriented to eyes and faces and then we could also then look at the actual eye movements on a tens-of-milliseconds time scale.
Interviewer: Adam Levy
So we already know that where the infants look is a strong indicator of the disorder. We know that autism has strong genetic roots but in this study you were aiming to put those facts together.
Interviewee: John Constantino
We wanted to know to what extent do individual differences in that capacity to orient visually to social cues, how is that driven by genetic factors? So to do this we recruited an epidemiologic of young twins and twins are particularly useful for disentangling of nature and nurture because identical twins share 100% of their genetic variation and non-identical twins only share on average half of their genetic variation.
Interviewer: Adam Levy
And by doing these tests with twins – with identical and non-identical twins – what do you end up finding?
Interviewee: John Constantino
What we found was that those particular aspects of a child’s unique development were nearly identical among identical twins and very much different among non-identical twins, so the estimates of inheritance playing a role in individual differences among the twins was over 90%.
Interviewer: Adam Levy
So these experiments indicate that behind where a child looks and how a child engages with faces, there’s this kind of genetic under-pining. What does that actually tell us?
Interviewee: John Constantino
The importance of linking this particular trait to genetic factors is that if it is not influenced by genetic factors, it would be very difficult to say that that is a cause of autism because we know that autism is so heavily influenced by genes, by genetic factors, but this particular predictor has now been linked strongly to genetic factors and so we can recognise this predictor, not only as a developmental predictor, but as one that is linked to the genetic causes of autism and that alone may not cause autism, but in combination with other genetic liabilities, may incur liability to the condition.
Interviewer: Adam Levy
Does this work help us with interventions that might help people with autism lead easier lives?
Interviewee: John Constantino
Even if we use just the types of intervention that we already have for young children with autism spectrum conditions, rarely are those kinds of interventions applied earlier than 18 months of life and so moving those interventions earlier and designing them for younger infants may give us an opportunity to have a higher level of impact on the developmental course of a child at risk of autism.
Interviewer: Adam Levy
That was John Constantino who’s at the Washington University School of Medicine in Missouri.
Interviewer: Shamini Bundell
It’s almost time for this week’s News Chat where we’re looking at the lack of science staff in the White House, and, fake space dust. Now though we’ve got a special guest reading the Research Highlights. It’s Adam Levy. Oh wait that’s you.
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Interviewer: Adam Levy
Protected areas are set up to support animal species living within them. Now, a study has found that they’re often not up to scratch. It seems like areas aren’t set aside because they’re the best spaces to protect animals but because they’re not particularly useful for farming. In the last decade or so, 3 million square kilometres have been protected. The land set aside has helped protect 84 vertebrate species. Not bad but the same area could have protected 3,500 species if it had been chosen more tactically. That paper is in Conservation Biology. Now over to Shamini Bundell.
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Interviewer: Shamini Bundell
Playing games may be the best way to start a career as a mathematician. Researchers played one of two games with preschool kids – one relating to maths concepts like numbers and shapes and the other with no maths, instead relating to social interactions. The kids that played the mathsy games ended up being better in maths tests. For example, it boosted the children’s intuition about numbers, like their ability to estimate quantities. In some cases this brain boost lasted as long as the study – a full 15 months after the games were completed. Find that paper in Science.
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Interviewer: Adam Levy
Time now for this week’s News Chat, and Lauren Morello joins us from the other side of the Atlantic in Washington DC. Hi Lauren.
Interviewee: Lauren Morello
Hi Adam.
Interviewer: Adam Levy
Now, first up we have an update on the Trump administration or rather, kind of, a lack of an update. What’s going on in the White House regarding science?
Interviewee: Lauren Morello
So, this is about the White House Office of Science and Technology Policy which sounds like a boring thing but is actually a really important thing. It’s the office in the White House that is run normally by the presidential science advisor and tries to co-ordinate science priorities across all of the government agencies that do science.
Interviewer: Adam Levy
And what’s unusual about Trump’s Office for Science and Technology Policy?
Interviewee: Lauren Morello
OSTP, if you want. So, I guess the first thing to mention is that president Trump hasn’t nominated a science advisor yet and he’s later than many recent presidents have been with this but George W. Bush didn’t announce who he wanted until June, so Trump is right there with the last Republican to hold the White House, but more importantly, Trump just hasn’t filled a lot of positions in the White House Science Office. Under Obama there were about 130 people on staff at any one given time and Trump, right now, only has 35 of those jobs filled.
Interviewer: Adam Levy
But I know that Obama was actively very keen on science and didn’t he actually expand the office?
Interviewee: Lauren Morello
For a long time it had four divisions and what Obama did was he created a chief technology officer and that person had his own office. So he made one extra division. But this is taking things back further than that and it’s still somewhat hard to tell whether this is just Trump being very slow filling positions – he’s been very slow filling positions across the government – or whether he doesn’t intend to fill some of these positions at all which is also possible because he’s repeatedly said that he wants to shrink the government.
Interviewer: Adam Levy
Well, given that promise is this just a part of Trump’s pledge to shrink the government, or is what’s happening with science somehow unusual?
Interviewee: Lauren Morello
Well it seems like science is one of the first areas where this is really visible and some of the events last week kind of shed light on what might be going on here. Four employees left the science office on Friday and a few of them tweeted about it and revealed there are no staff members left in the science division or the technology division of the science office, which remember, has science and technology in its name and the White House initially denied those reports but initially what they said was, there are nobody in those divisions but we have 12 people who work on science in the office. And the White House told one of our reporters that they thought that under Obama the science office was very siloed that seems to suggest that they want to rearrange the office and that some of these unfilled positions are intentional.
Interviewer: Adam Levy
Given that there are so many fewer people around – how’s this affecting existing, on-going projects?
Interviewee: Lauren Morello
There’s a lot of uncertainty in the science office right now. You know, from the top down, there’s an acting director, somebody who’s been on staff since 2011 but people who have worked in the science office under Trump told us that it’s not clear that the acting director is running things. There’s a mid-level Trump appointee who is attending the daily meetings of the White House senior staff, filling the spot that would normally be filled by the science advisor. In the meantime a lot of mid and lower level staff working on various programs are just at a standstill. They’re not getting clear direction.
Interviewer: Adam Levy
So can big projects that were set up during the Obama administration be kept alive or is this a real problem?
Interviewee: Lauren Morello
It really depends on what project you’re talking about. President Obama started the brain initiative to understand the inner workings of the brain and that is mature enough now that the three agencies that participate in that programme are pretty much okay running their chunks of it and things are normal. But for the staff at the science office who work on climate change for example… Trump’s positions on climate change are radically different to Obama’s and they’re not really getting any direction from the Trump White House on what they want so those people are basically twiddling their thumbs.
Interviewer: Adam Levy
Let’s move onto our second story which is a bit more tangible a problem; it’s a problem with artificial space dirt. Before I looked at this story I didn’t know that artificial space dirt was even a thing, so what’s it actually useful for?
Interviewee: Lauren Morello
Space scientists and space agencies need to test things like drills and rovers before they send spacecraft and landers and rovers and drills into space, so since we really only have limited samples of rocks and soil from the moon’s surface and we don’t have samples from an asteroid or from Mars, space agencies or companies that they do business with make fake space dirt. It’s more properly known as simulant.
Interviewer: Adam Levy
So, what’s the problem with this simulant?
Interviewee: Lauren Morello
It’s really hard to make. Even with fake moon dirt we don’t really have that much of the real stuff: we can’t replicate it perfectly. So the first decision you have to make if you’re a scientist is you decide what properties of the real stuff you want to mimic. And then beyond that the demand isn’t necessarily constant. So, over the past few decades, the companies who make this stuff have not really managed to stay in the business.
Interviewer: Adam Levy
How much could this actually mess up people’s experiments?
Interviewee: Lauren Morello
Our reporter talked to a team at the European Space Agency, that’s working on a drill. They want to hunt for buried ice on the moon and they ordered half a tonne of fake moon dirt from a commercial supplier, but when that fake dirt was delivered, they found that it didn’t behave the way that they wanted it to behave. When they tried to drill into it, it just broke apart too easily. So, you know, that didn’t really allow them to test their drill very efficiently. So those are the kinds of problems that you can run into.
Interviewer: Adam Levy
And how are space agencies looking to get a handle on this problem? Are they planning on fixing it in some way?
Interviewee: Lauren Morello
So NASA has just recently started to try to address this problem. They put together a team of scientists in June among the people who work at its research centres and they’re trying to analyse the physical properties and the availability of the existing fake space dirt and the hope is to put together a kind of catalogue that tells scientists what each type of fake dirt is good for, how it’s best used and just let people know what’s out there. There’s more than 30 different kinds of fake moon dirt and so it’s really hard for scientists to get a handle on which fake dirt is appropriate for the experiments that they want to do.
Interviewer: Adam Levy
I really love stories like this where there’s actually a really big problem in an area that I didn’t even know existed.
Interviewee: Lauren Morello
I didn’t know that this stuff existed either before our reporter brought me this idea, and then there’s the bonus of being able to say that I got the phrase ‘fake space dirt’ into a headline in Nature, which – I will remember that for a long time.
Interviewer: Adam Levy
Thank you Lauren Morello. For more on space dirt and the dirt on science in the White House, head to the usual place. Nature.com/news.
Interviewer: Shamini Bundell
That’s all for this week but make sure to keep your eyes peeled for our latest Nature Videoall about organised, tower-building ants. That’s at youtube.com/NatureVideoChannel. I’m Shamini Bundell.
Interviewer: Adam Levy
And I’m Adam Levy.
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