CrowdScience BBC World Service

The CrowdScience team like a challenge. And listeners Jenny and Kai in the UK have come to us with a big one. They want to know how many flies have ever existed.
Flies first appeared around 270 million years ago, so presenter Caroline Steel prepares herself to calculate a very, very large number indeed. She enlists the help of Dr Erica McAlister, Curator of Flies at the Natural History Museum in London. As Erica introduces her to specimens from the Museum’s collection of over 30 million insects, they start with the basics. Like... how do you define a fly in the first place?
Caroline also explores the incredible diversity of flies… from fast-moving predators like robber flies which catch other insects on the wing to midges which are a vital part of chocolate-production; and from blood-sucking mosquitoes which transmit fatal diseases to the housefly buzzing lazily around a room.
And that leads to another fly-related question. Listener Brendan in Colombia wonders why they always fly in circles around a particular area of his apartment. For an explanation we turn to Prof. Jochen Zeil from the Australian National University who reveals that this apparently aimless behaviour is, in fact, a battle for sex.
And Collin in Barbados has e-mailed to ask how flies and mosquitoes benefit us. He’s had first-hand experience of their negative effects through contracting the disease chikungunya from a mosquito bite so he’s wondering if these insects are anything other than a nuisance. However, passionate fly advocate Erica McAlister is ready with plenty of reasons that we should be extremely grateful for them!
Contributors:
Dr Erica McAlister, Natural History Museum, London
Dr David Yeates, Director, Australian National Insect Collection
Prof. Jochen Zeil, Australian National University
Prof. Jo Lines, London School of Hygiene and Tropical Medicine
Presenter: Caroline Steel
Producer: Jeremy Grange
Editor: Cathy Edwards
Production Co-ordinator: Ishmael Soriano
Studio Manager: Sarah Hockley
(Image: Close-up of insect on leaf, Kageshwori Manohara,Bagmati Province,Nepal. Credit: Aashish Shrestha)

It’s hard to imagine something as mind-bogglingly small as an atom.
But CrowdScience listener Alan has been attempting to do just that. All things in nature appear to be different and unique; like trees and snowflakes, could it be that no two atoms are ever the same?
Alan isn’t the first person to wonder this. Philosopher and scientist Gottfried Leibnitz had a similar idea in the 17th century; in this episode, philosopher of physics Eleanor Knox helps us unpick the very idea of uniqueness.
And with the help of physicist Andrew Pontzen, presenter Anand Jagatia zooms into the nucleus of an atom in search of answers. Listener Alan has a hunch that the constant movement of electrons means no atom is exactly the same at any given moment in time. Is that hunch right? We discover that the world of tiny subatomic particles is even stranger than it might seem once you get into quantum realms.
Can we pinpoint where uniqueness begins? And if the universe is infinite, is uniqueness even possible?
In the podcast edition of this show, we peer into that expansive universe, as we discover that the quantum world of hydrogen - the tiniest and most abundant of all atoms - allows us to observe galaxies far, far away.

Featuring:
Dr Eleanor Knox – King’s College London
Prof Andrew Pontzen – University College London
Dr Sarah Blyth – University of Cape Town
Dr Lucia Marchetti – University of Cape Town
Presented by Anand Jagatia
Produced by Florian Bohr
Editor: Cathy Edwards
Production Coordinators: Ishmael Soriano and Liz Tuohy
Studio Manager: Emma Harth
(Photo: Twelve snow crystals photographed under a microscope, circa 1935. Credit: Herbert/Archive Photos/Getty Images)

Listener Julie lives close to the coast in New Zealand and wants to know why the water that washes up on the beach isn't fresh. How exactly does all that salt get into the world's oceans?
In India, a country where salt became symbolic of much more than well-seasoned food, host Chhavi Sachdev visits coastal salt farms and a research institute dedicated to studying all things saline, to better understand our relationship with salty seas.
The team also ventures to a very briny lake on the other side of the globe in Salt Lake City, Utah, to learn how salt makes its way into water bodies.
Speaking to an expert in deep sea exploration, we learn how hydrothermal vents may play a role in regulating ocean saltiness, and how much the field still has to explore.
Meanwhile, listener Will wants to know how much melting ice sheets are affecting ocean salinity. But ice melt isn’t the only thing affecting salt levels when it comes to the impacts of climate change.
And... how many teaspoons of salt are in a kilogram of sea water anyway? We do the rigorous science to answer all these salient saline questions.
Featuring:
Deepika - small scale salt farmer
Mark Radwin - PhD candidate in geology and geophysics at the University of Utah
Brenda Bowen - Geology & Geophysics, Atmospheric Sciences, University of Utah
Chris German - Geology & Geophysics, Woods Hole Oceanographic Institution
Prasan Khemka - Chandan Salt Works
Paul Durack - Lawrence Livermore National Laboratory
Bhoomi Andharia - Central Salt & Marine Chemicals Research Institute
Presenter: Chhavi Sachdev
Producer: Sam Baker
Editor: Cathy Edwards
Production Coordinator: Liz Tuohy
Studio Manager: Sarah Hockley
(Photo: Shiv Salt Works, Bhavnagar, Gujarat in India. Credit: Chhavi Sachdev, BBC)

CrowdScience listener Eleanor was lying in bed one rainy evening, listening to the radio. She lives in New Zealand, but happened to hear a weather forecast that told her it was raining in the UK too.
She started wondering: could it be the same rain falling there and outside her window in New Zealand? Can a raindrop really travel all the way around the world?
There are a number of routes the droplet could take, including traveling as moisture in the air. Presenter Caroline Steel meets meteorologist Kei Yoshimura, who puts his powerful weather simulation to work plotting the raindrop’s journey through the sky.
What if the raindrop falls along the way and gets trapped? Where might it end up? Hydrologist Marc Bierkens talks Caroline through the detours it could take, ranging from short stop-offs in plant stems to extremely long delays in deep groundwater.
Finally, could the drop of water make it to New Zealand by circulating through the world’s ocean currents? Oceanographer Kathy Gunn maps the droplet’s path through the ocean – and explains how climate change might affect its journey.
Featuring:
Prof. Kei Yoshimura, Professor of Isotope Meteorology, University of Tokyo
Prof. Marc Bierkens, Professor of Earth Surface Hydrology at Utrecht University
Dr. Kathy Gunn, Lecturer in Climate Sciences at the University of Southampton
Presenter: Caroline Steel
Producer: Phil Sansom
Editor: Cathy Edwards
Production Co-ordinator: Liz Tuohy
Studio Manager: Tim Heffer
Additional recording: Knut Heinatz
(Photo: Textures of rain on the surface of the ocean. Credit: Philip Thurston/Getty Images)

It’s often said that fine wine gets better with time, and this week’s oenophile listener Jeremy has a cellar full of dust-covered bottles. He is curious whether chemistry can account for the range of flavours that develop as wine matures, but also wonders why some of it tastes like vinegar if you leave it too long?

We head off to the Bordeaux region of France, where vines were planted almost 2,000 years ago. Here, winemakers are joining forces with scientists to better understand wine ageing, a process so subtle and intricate that even the scientists refer to it as magic.

In the world-famous vineyards of Chateau Margaux, presenter Marnie Chesterton learns that the key ingredient for good grapes is a sandy soil type; and that in this part of France, the warming climate is actually having a positive effect on the vines, which need very little water to thrive. Over in the lab, we meet the chemist mapping the molecules responsible for aromas associated with a well-aged Bordeaux.

Featuring:
Philippe Bascaules, Chateau Margaux
Prof Cornelis van Leeuwen, Bordeaux Sciences Agro
Dr Stephanie Marchand-Marion, ISVV
Alexandre Pons, ISVV

Presented by Marnie Chesterton
Producer – Marijke Peters
Editor – Cathy Edwards
Production Co-ordinator – Liz Tuohy
Studio Manager – Sarah Hockley
(Photo: Aged bottles on wine racks in a cellar. Credit: Morsa Images/Getty Images)

The Blue Ridge Parkway is 469 miles of beautiful vistas, a mountainous road that winds from Virginia to North Carolina in the USA. The route is peppered with elevation signs, telling you how many metres above sea level you are. Which has CrowdScience listener Beth wondering: as we are told that sea level is rising, will all the elevation signs need repainting?
It’s a task she’s passed over to the CrowdScience team, who like a difficult challenge. The height of an enormous pile of rock like Ben Nevis, or Mount Everest feels unchangeable. But we measure them relative to the nearest patch of sea, which is where our story becomes complicated. Unlike water in a bath, sea level is not equal around the world. The east coast of America has a different sea level to its west coast. And as host Marnie Chesterton discovers in Finland, in some parts of the world the land is being pushed up, so sea level is actually falling.
In fact, when nothing on earth - not the sea, the shore or the mountains - seems to be stable or constant, the question of what you measure from and to becomes incredibly tricky. But that hasn’t stopped oceanography and geography scientists risking life and fingers to use an ever-evolving array of technologies to find answers. In this show we find out why they care so much, and why we should too.
Featuring:
Dr Paul Bell – National Oceanography Centre, Liverpool, UK
Dr Severine Fournier – NASA Jet Propulsion Laboratory / California Institute of Technology
Dr Jani Särkkä – Finnish Meteorological Institute
Khimlal Gautam – Mountaineer and Chief Survey Officer, Government of Nepal
Dr Derek van Westrum – National Oceanic and Atmospheric Administration, USA
Presented and produced by Marnie Chesterton
Editor – Cathy Edwards
Production Co-ordinator – Liz Tuohy
Studio Manager – Steve Greenwood
(Photo: Sea Level Elevation Sign in Death Valley, California. Credit: Mitch Diamond/Getty Images)