That May Q&A!

07 May 2019
Presented by Izzie Clarke
Production by Izzie Clarke.


A germinating seedling


It’s Q&A time… We’ve got a panel of scientists ready and waiting to tackle the questions you’ve been sending in. Izzie Clarke was joined by plant ecologist Howard Giffiths, chemist and writer Kit Chapman, reproductive physiologist Bill Colledge, and physicist Ben McAllister.

In this episode

A large astronomical telescope against a dark starry sky.

04:24 - Are scientists looking for alien life?

And if so, how? Physicist Ben McAllister explains all...

Are scientists looking for alien life?

Dan on Twitter wants to know if scientists are looking for alien life. Izzie Clarke was joined by physicist Ben McAllister from the University of Western Australia who tackled the topic... 

Ben - I love this question. The answer is a resounding yes! We've been doing it for a very long time, at least as early as the 1900s, the very early 1900s, and probably much earlier than that - in terms of people just looking up into space and hoping that they see something. But in terms of concentrated efforts using good technology, we'll have started around the beginning of the 1900s, and really kicked into high gear in the late 70s, early 80s timeframe.

Broadly, searches for extraterrestrial intelligence, as they are known, fall under the umbrella term SETI, perhaps you've heard of it, and there's a few different institutions around the world that adopt that name to describe the things they do. There are two main types of SETI search. The probably more traditional one is to essentially get a big radio telescope - kind of like a satellite dish that you would have on the roof of your house - to try and point into space and pick up radio waves coming in that could be signals from alien civilisations. We humans are putting radio waves out all the time, so it's not a stretch to imagine that alien civilisations might be doing something similar.

Although there have been no detections just yet, there was at least one really interesting period in 1977 at the University of Ohio, I believe. They have this telescope called The Big Ear and it received what is widely considered to be the strongest candidate signal from space for an alien message. It's called the Wow! signal. It's basically just an extremely powerful radio signal that hit the telescope once. It lasted about 70 seconds or something like that, some short period of time, and has never been observed again. No one's been able to explain any source for it, so it's widely considered to be the closest thing to an alien communication we may have observed.

Izzie - So what are people actually looking for? Is it predominantly just signals or is there anything more to it than that?

Ben - Okay. The ones with radio telescopes and stuff typically are looking for radio waves from outer space. But there are other ways you could think about searching for extraterrestrial life and these typically revolve around looking for what are called alien megastructures. Yeah, this is getting a little bit more sci-fi, but it is extremely cool.

We theorise basically that any advanced civilisation will constantly be increasing its demands for energy, until you reach a point where you basically require all of the energy output by a given star. Our star that we orbit around - the Sun - we don't come close to harnessing even all the energy from it that hits the Earth, let alone all the energy puts out in all directions at all times. But a super advanced alien civilisation might want to do that, and if they were going to do that they would want to build something that we have called a Dyson sphere, which is named after this guy called Freeman Dyson. He was a physicist - he has nothing to do with the vacuums.

Izzie - That was my next question.

Ben - I thought that as well. I was like, “oh wow”, but definitely not. So the idea behind a  Dyson sphere, you basically create some giant structure that encapsulates a star and sucks all the energy out of it, like an array of solar panels or something. Maybe instead of having one big rigid structure, you would have a whole bunch of little satellites that orbit the star in rings and stuff, and just absorb all the solar energy that way, and then you could have it for whatever purpose you want. And if that was the case, you might be able to see signatures of these things, like Dyson swarms they're called, these swarms of satellites moving around distant stars.

So pretty much every time we see a distant star with a weird dimming pattern or something, like there's something weird about the sunlight coming off it, some people get pretty excited about the fact that it might be a Dyson sphere, or a Dyson swarm, or something. But so far there have been no confirmed reports.

Two ash trees in a park

08:08 - How do tall trees stay hydrated?

And how does water get all the way to the top?

How do tall trees stay hydrated?

This tall order came into our Facebook inbox. Izzie Clarke asked Howard Griffiths, plant ecologist from the University of Cambridge, to dig up an answer.

Howard -  Well that's a really great question. And it's one that's puzzled physiologists for many years and we think we have an answer. Basically, we recognise that trees can be up to 120 m high, that's taller than the St Pauls Cathedral dome, for instance. And the reason that water can move up from the soil right through that trunk of the tree and then be lost through evaporation through the leaves is because of the amazing powers of water. It's got this most amazing tensile strength which... well it's remarkable, have you noticed how water remains a liquid exactly between nought and a hundred degrees? But within that range that's basically why water supports life on earth but it's also that hydrogen bonding which holds the water molecules together which gives it an amazing strength. Then the water rises up capillaries, due to two properties known as cohesion and adhesion.

Izzie -  Are they just almost like little tubes that run up and down a tree, essentially?

Howard - They're tiny tubes. Most of them are around the diameter of a human hair, okay, but they act like little capillaries. They're only maybe less than a centimetre, often only a couple of millimetres in length and so water moves through those tubules. And you can visualise those tubules; they're in the tissues that we call the xylem, which forms the heart wood trees. And if you take a cross-section through a tree, if you look through a fence post, you can often see the annual rings which make up the new increments of growth of the xylem that we get every year.

So the water is drawn up through that xylem, held by that tensile strength, and then what actually causes it to come right to the top of the tree is the dryness of the air at the surface at the top. Because there's such a change in energy between the free energy of water vapour and the liquid water that's being drawn up through the moist tissues,  that when the liquid evaporates into the moist cavities of the leaf and then leaves the leaves to the atmosphere, that draws up more water through those micro capillaries to that site of evaporation within those cells of the leaves.

Izzie - And even as a tree gets older, does that process diminish? Trees obviously can keep going for so long, how can they repair that system if something were to happen to it?

Howard - Ah well, that's another good question. Partly because they grow new xylem every year. New annual rings represent the new growth and clearly some very very old trees don't make very much growth. But what's been intriguing scientists over the last 20 years or so is what happens if those water columns snap? And you can actually hear them clicking sometimes. Now it's not often you see plant physiologists sticking their ear to the tree but you can, with a microphone, pick up the sound of those water columns snapping. And we think there are some mechanisms which may help trees, and particularly shrubs and so on repair those water columns overnight.

Izzie - How much water does a tree actually need? If you've got your plants in the garden, you’re like ‘I've got to make sure I look after them and they don't die’, but how does it work for trees?

Howard - Well, for a big tree like a big beech tree that you might see in a park, they might use something like let's say 400 litres of water. So if you imagine 200 large bottles of fizzy drink, that's the amount of water they need every day.

Shirts drying on a washing line

11:53 - How can you remove body odour from clothes?

Kit Chapman sniffs out an answer to this chemical query...

How can you remove body odour from clothes?

Izzie Clarke received this chemical query from Europan Ocean on The Naked Scientists Forum, which also inspired fellow panellist Bill Colledge to chip in. It was over to chemist and writer, Kit Chapman, to sniff out an answer for them...

Kit - Well, you could set the material on fire, that will certainly get rid of everything. But assuming you want to keep your clothes, let's have a look at what body odour is. Your body will naturally release all kinds of secretions, sweat is a great example, and the natural bacteria that live on your skin, and everyone has it it's perfectly normal, they will start breaking those down and release molecules that stink. And they'll react with your nose sensors and that's how your find out that you're a bit wiffy.

So when things dry on your clothes, what can you do? One thing is to wash them. Water is fantastic for getting rid of those horrible smells and also you can use a detergent. Now, detergents are fantastically shaped molecules because they have what we call a hydrophobic tail.

Izzie - Now, that means that they are essentially afraid of water?

Kit - Exactly. The tail is afraid of water, but the head loves water. So it sticks the tail in those fats, it breaks things up and gets rid of them, and that's how we get rid of dirt, and that's why you use washing-up liquid to clean your plates, same kind of principle. So you can get rid of stenches that way.

The other thing you can do is try and neutralise them. One thing that works very well is actually using white vinegar in a bowl of water and that will absorb the smells from the room and neutralise them.

Izzie  - And so why is it that combining that with water, that white vinegar, gets rid of it?

Kit - It's not necessarily combining it with the water, it's just making sure that the white vinegar is actually going around the room essentially. It's because of an acid-base reaction. It's very very basic chemistry.

Speaking of basic chemistry another thing, and other brands are available, but Febreze is a great example of how you can actually trap these smells. Febreze has a structure in it called a cyclodextrin and that's shaped like a donut. It has a big hole in the middle, it's a sort of a circular molecule. And what it'll do is it will get those molecules in there that are causing the horrible smells inside that circle and trap them. You can't smell it and the molecules are still there, but the BO's gone.

Izzie - Oh Bill, you've got a question.

Bill - Yeah. I know some people use sodium bicarbonate to put in the microwave to eliminate smells. How does that work?

Kit - We're going exactly the same kind of route as the vinegar. Sodium bicarbonate is a great version of a base and it will cause that same kind of reaction. So it depends really what the smells are as to how you get rid of them. But sodium bicarbonate - fantastic for cleaning products and these things are really really cheap. Everyone thinks that you need to go for really expensive cleaning product, but actually white vinegar, sodium bicarbonate, things that we've used for over a hundred years now are just terrific.

A man and woman holding hands

14:41 - Why can fertile people struggle to conceive?

Why are some people fertile but can't produce offspring with their partner?

Why can fertile people struggle to conceive?

Lindsay posted this question about fertility and compatibility on the forum. Izzie Clarke asked reproductive physiologist Bill Colledge to explain why some fertile couples struggle to conceive. 

Bill - Occasionally this does happen. I think one of the reasons is that fertility can be affected by a huge range of different factors. So you might have a couple where they're both slightly subfertile so that together that's a compound problem -  they can't conceive. And then if they split up and they find another partner, the new partner is completely fertile and their subfertility isn't such a problem, so that's one of the possible reasons.

Another reason is that in very rare conditions, maybe about 4% of the time, it is known that a woman can make antibodies that will specifically recognise the partner's sperm. So they make antibodies which are released into the vagina when they have sex, the sperm are attacked by the antibodies and it causes the sperm to clump and coagulate and that prevents the sperm from reaching the egg.

Izzie - And so essentially they are rejecting it?

Bill - They are rejecting it, yes. I mean I don't think that they have been primed against it or anything like that, it's just that there's this incompatibility which is unfortunate for that particular couple.

Izzie - Would there be anything to get around that issue?

Bill - Oh, yes. There are ways of getting around that if that is the problem. You can obviously take the egg from the woman and you can fertilise it using in-vitro fertilisation in a dish, and then you can take the fertilised egg and you can implant it back in the woman. That means that there's no antibodies in the dish so it should work fine.

Izzie -  And Kit, did you have a question?

Kit - Yeah. I'm just curious as to whether or not someone would be attacking every sperm, or is it just a specific person’s sperm, or is it a specific group of people's sperm?

Bill - It's related to a person's sperm. So if they have this problem that they make antibodies against a particular sperm, it'll be all of the sperm from that person and it necessarily won't be from another person, so it's not selective, it'll be all of the sperm that are attacked.

Izzie - And how important are hormones when it comes to fertility?

Bill - Hormones are very important in fertility. In males, for example, testosterone is absolutely crucial for fertility. When you go through puberty, your testosterone level rises and that's required to start making sperm at puberty. And anything that reduces your testosterone after puberty is going to impact on your ability to make sperm and there are a lot things that could impact on your testosterone levels. One thing is that if you are overweight and you have a lot of fat tissue, then testosterone is lipophilic, it likes lipids, which fat tissue is, it'll tend to get sequestered into the fat tissue which can result in lower levels of testosterone in the bloodstream which can have an effect on how well you make sperm.

Izzie - I see. Now Howard, how about plants? What determines how many seeds a plant makes?

Howard - Oh, well. That's a big question. Well, it depends what sort of flower it makes. Sometimes plants make a single flower if they have a kind of determinate structure, what we call their inflorescence. Sometimes when they start flowering at the bottom and they just keep flowering, like wallflowers at the moment, that's just called indeterminant so they can have lots and lots of seed pods and so on. That's partly the condition.

It also depends on whether they've got enough water and nutrients. Plants can adjust their structure, the number of branches they might have, the number and size of the flowers they have, if they've got plenty of resources and that's all controlled by similar substances to the animal hormones - we call them plant growth substances.

And then finally, it decides whether they need to allocate reproductive effort into seeds or sometimes you might have other storage organs. So take the potato for instance, we know that they store a lot of resources underground because they reproduce from that vegetative structure. It depends really how you're going to produce your generation in the following year, whether it's from a seed or whether it's from a vegetative structure.

Long exposure image of a question mark in neon lights

19:42 - De-bunking that suspicious science...

Our panel unravel the science behind common mythconceptions.

De-bunking that suspicious science...
with Ben McAllister, University of Western Australia, Kit Chapman, Chemistry World, Bill Colledge & Howard Griffiths, University of Cambridge

The Naked Scientists love chatting about mythconceptions; the common myths that can be de-bunked by science! Izzie Clarke is joined by physicist Ben McAllister, plant ecologist Howard Griffiths, chemist Kit Chapman and reproductive physiologist Bill Colledge who all brought in their own myths.

Ben - Right. Mine’s actually more of a science history myth than a science myth itself. I figured given that I’m here to represent the physical sciences I might confront a common myth about one of the most famous physicists of all time. You may have heard the idea that Albert Einstein supposedly failed some maths tests in school or maybe it was in university or something. And yeah, that’s not really true. He was something of an unconventional student, there is a bit of truth in that. He didn’t get along with his teachers, he didn’t like the way things were normally taught, he had a tendency to sort of not pay attention in school. But all signs point to him doing maths quite well at all times which probably makes a fair amount of sense if you think about the career he went on to have. But the origin of the myth is that when he did try and get into university he did fail his entrance exams, but it was not because he failed the maths section, it was because he failed the botany, zoology and language sections. So perhaps someone here on the panel could have helped him out there but yes, in the mean time, he was alone.

Izzie - Do we know where it came from or is it just one of those ones that just floating about?

Ben - Yeah, I think probably just spawned out of that, the fact that somebody read somewhere he failed is entrance exam into university and then wanted to create some kind of pseudo-inspirational myth surrounding it, which is a nice story. “Albert Einstein, one of the greatest physicists of all time, failed his maths, so if you're bad maths you might be good later,” I guess is the message. I don't know but yeah, something like that.

Izzie - If anything, he went on to be a very, very important person for the world of physics and maths. Howard, what are you putting down as a mythconception?

Howard - Okay. What really gets me wild is when I hear regularly on TV and radio programmes that the rainforests are the lungs of the Earth. Now don't get me wrong, I think trees are absolutely vital. I want to plant more trees. I want to stop people cutting down forests because forests are absorbing carbon, they're protecting us against climate change.

But, when that phrase is used, it's often used to infer that the oxygen we breathe is being produced at this minute by the forests. And what you've got to remember are that forests are really giant compost heaps. There's as much rotting, degrading and material just being respiring and consuming oxygen as there are in the photosynthetic leaves above which are producing oxygen, so there's roughly a net balance.

Izzie - Okay. So do you know where the majority of our oxygen comes from?

Howard - Well, it did come from plants. It's come from plants both in the marine system and on land over the last 2.4 billion years and gradually, organic carbon made by plants has been buried either underground in the sediments, turned into rocks and so on, and that’s trapped carbon. Some of its turned into fossil fuels which, of course, we're now burning and releasing CO2 back to the atmosphere. But that's where the carbon went and that allowed the oxygen to gradually increase in the atmosphere.

Izzie - Thanks very much Howard. Now Kit, what are you putting down as something that gets on your nerves?

Kit - This myth that you can’t turn lead into gold. You absolutely can do that. You don't want to do that, but you can do it.

Izzie - How would you do that?

Kit - Well, in 1980 there was a very famous chemist called Glenn Seaborg and he was a nuclear chemist. And what he did was he got a particle accelerator and he fired carbon and neon atoms at a piece of lead and chipped off some protons, and protons decide what element you have and he bashed it way back down into gold.

Izzie - Right. Why aren't we all trying to make gold then?

Kit - This is the problem. To fire up a particle accelerator is a bit expensive. It cost him around $120,000 a day to do it.

Izzie - A day... wow.

Kit - So he worked out that to make one ounce of gold would cost one quadrillion dollars.

Izzie - Come on guys, we can put that down together, no?

Ben - It's definitely something we could scale as well. Maybe it cost that much today, but we’ll push that down in time if we all put enough effort into it.

Izzie - Bill, how about you?

Bill - Well this is a sort of myth that I’d like to debunk which is aimed at couples that are trying to conceive. And people are told that if you’re trying to conceive there’s a window of fertility which is the best time around the time of ovulation for the woman, and if you’re having sex around that time you should have intervals. You should have sex every other day. And it was thought that this is to allow the sperm to build back up to increase your chance of conception.

And actually, it’s completely not true. The best way to conceive during this window of fertility, the window of opportunity, is to have sex as often as you can, provided you’re up to it of course. And the reason that we now know it’s best to just have sex frequently comes from IVF clinics where men have gone in, they’ve given a sperm sample and then they’ve taken another sperm sample two hours later, and often the second sperm sample has more sperm than the first. So basically, you can have just have sex as often as you want during this fertile period and that will improve your chances of conception.

Izzie - Do we know why that happens that a few hours later there is a higher sperm count?

Bill - Well, we make a lot of sperm very, very rapidly. I think that we’re making 5,000 sperm every second - well we are, I’m afraid you’re not. But men are making 5,000 sperm or so every second so we’re making millions of sperm over a few hours. And I think what happens is that the first time you make sperm there maybe some there that has been sitting around for a while, whereas two hours later it’s sort of fresh stuff so they’re much more virile and much more potent.

Izzie - We talk about this ovulation period, the golden opportunity, six or so days a month, can a woman get pregnant outside of that period?

Bill - There is a reproductive window during which a female is likely to get pregnant and it lasts for about six days. The reason it is such a short window during the whole of the cycle is that an egg is only viable for about 12 to 24 hours once it's released. Sperm cells are a bit more robust, they can be viable in the reproductive tract for up to 5 days. So if you put these two together you've got a window of about six days when you're more likely to conceive, and outside this window you're ultimately much less likely to conceive and women often use this natural sort of rhythm method to monitor when they're going to ovulate and to make sure that they don't have sex close to that period.

Izzie - We're going to get to contraceptives later but is that a reliable method of contraception?

Bill - It's not the most reliable method of contraception. I think if you use that method you have to be prepared for failure some of the time. There are more reliable methods.

Graphic of planets in the solar system

How old are the planets?

Izzie Clarke found this question from Hans on The Naked Scientists Forum. Physicist Ben McAllister, from the University of Western Australia, was able to shed some light on the matter...

Ben - This is another great question and the answer is yep, pretty much within a narrow window within the degree of confidence we have in saying a date for any of these things. We're pretty sure that the entire solar system, the sun, the earth, all the planets are something like 4.6 billion years old, again, give or take a few million years. This is a very large large number type problem that we're dealing with here.

The easiest one, the first thing that we can do is just basically date rocks on earth. We can use geological processes and radioactive decays in order to figure out how old rocks are on earth, and that's easy to do because we have rocks on earth kicking around all over the place. So how you might do that is if you pick up a rock that you think is one of the older rocks on earth, maybe it's deep down in the core. I'm not entirely sure where the oldest rocks on earth actually come from, but if you were to find one of these older rocks on earth you could look at the relative populations of these different what are called radioactive isotopes inside them. There are these natural chemicals that undergo this process called radioactive decay; we were hearing a little bit about it before turning one element into another element by stripping off a few protons. There are things like uranium which break down into smaller things and they do this with a characteristic time associated with them. There's a bit of variation, it's a bit random, but for a very large population of say uranium there's going to be a certain amount of time with which about half of that uranium breaks down.

So if you look at a bit of rock, and you can figure out how much uranium is in there. And also look at, for example, how much of the stuff that uranium breaks down into is in the rock, you can figure out how long ago that decay started happening by knowing how much uranium there was originally and how long it takes to break down, and then you can date the rock.

We can do a similar process with rocks from the Moon because been there. We can do a similar process with bits of rock that have landed on Earth that we are pretty sure have come from Mars at some point in the past.
So basically, we've got Earth, the Moon, Mars that we can, very directly, access and then you can look at the other planets and you have to do a slightly different process to figure out how old they are because we don't have any rocks from Jupiter for anything.

Izzie - So how does that work?

Ben - One of the best methods that people use to figure out how old something like Jupiter is, is basically looking at the surface of Jupiter and counting how many craters there are. Because one thing that we are pretty sure about is that the number of stray bodies moving through our solar system that collide with the planets has been constant over a really long period of time - billions of years. So if we know how many craters there are on something like the Earth or the Moon that we're pretty confident in how old it is, and we can compare that with how many craters there are and Jupiter just because we can be sure that the relative rate with which their being struck by stuff is the same, we can infer the age something like Jupiter or one of the other planets in the solar system.

Izzie - Hans there you have it. I guess it also depends on what you are using as a reference of a year because someone who is 30 in earth terms is also 120 years on Mercury or 2 1/2 on Jupiter, so we’ll say earth years. 

Ben - Yeah. Also if you use the kind of uncertainty that we have in dating planets they might be a million years old or they might not have been born.

A germinating seedling

29:57 - What is a weed?

Is it as simple as "anything I don't want growing there"?

What is a weed?

We received this question from SooYeah on The Naked Scientists Forum. Izzie Clarke asked Howard Griffiths from the University of Cambridge to dig out an answer as well as take on panellist Bill Colledge's own question.

Howard - Well, I think you've really answered your own question. But just to explain: beauty really is in the eye of the beholder. And if you're a naturalist and wandering through the countryside, many of the natural plants you see would be classed as weeds if you found them growing in a cultivated border. Equally so, you might see plants like invasive aliens, like Japanese knotweed, or a giant hogweed, or something like that, and you might think that's a weed of the countryside, we need to get rid of that one.

It really does depend where those particular plants are. I do remember as a child being told a joke, which I don't think is a very good joke, but it asked, how could you tell whether a plant is a weed or a border plant is: you pull them all up, and the ones that regrow are the weeds.

Izzie - Very true. Of course, they're really hard to get rid of. You can spend so much time pulling them out and thinking great, got that one done, and then give it a couple of days it's back again, so how can you actually get rid of them?

Howard - Well, I'm not a great believer in using chemicals and sprays although, of course, you can use those very selectively and very carefully if you paint them onto individual plants, and some of them will be taken down into the plant and kill the actual deep roots, that are the ones from which the plant will regrow. I'm a great believer in weeding, and hoeing, and using rather traditional methods of weed control.

Izzie - And speaking of annoying things in the garden…

As a bit of a follow-up - it seems to be on everyone’s mind at the moment - Emma has also got in touch to say

Q - How on earth do mealybugs/other bugs grow on plants? Where do they come from?

Are these those small green bugs that we see on plants, that we actually don’t want there?

Howard - Mealybugs are a kind of a scale insect. They're rather similar to aphids, they are a slightly different class of organisms, but they have similar penetrating mouthparts. We talked earlier about the water conducting system of plants, this is
the sugar conducting system of plants. So they dip into the phloem and they feed on that. And that's why they often exude droplets of honeydew, aphid honeydew, which you may hear of.

So where do they come from? Well, they overwinter in cracks and crevices, or in the soil, or they may be laid down as packets of little eggs from which the new instars will germinate once the cold weather has gone away.

Izzie - Are they a problem for plants?

Howard - They're a real problem for plants. Not only because they're feeding on some of the sugars that the plants are trying to supply to some of its growing areas, but they also transmit lots of diseases: lots of viruses are transmitted through these sap-sucking insects. And there's some very interesting science being done by my colleagues which shows how even the viruses change the behaviour of the insects in order to make them move on and move to another plant and so on.

Izzie - My goodness! Is there anything you can do to get rid of them?

Howard - Well, again, I'm all in favour of using warm soapy water to wash them off, or gently going along and squiging the blackfly on my broad beans with my fingers. I'm afraid it's a bit messy. But you can use safe sprays that are available from garden centres and so on.

Izzie - Bill, what would you like to ask?

Bill - When I was doing biology at school, my biology teacher told me a story and I just like to know if this is true. Scientists wanted to know what the composition of the sap was from the phloem and you mentioned the aphids tapping into it. And he said that what the scientists did was they took aphids and they chopped off effectively their head and left the bit that was in the sap, and they collected the droplets of sap coming out and they analysed it and that's how they did it. Is that correct?

Howard - There's some fascinating videos available on YouTube which can show scientists excising aphid stylets and collecting the sap as it drips out. The very clever trick that aphids have learnt to do is to is to plumb into the phloem without it blocking. If you artificially try to put a needle into the phloem, it will automatically coagulate and block and prevent the sap from flowing, but the aphids have learnt how to circumvent that problem.


35:48 - Quiz: Battle of the Sciences

We put our panel to the ultimate test. Who will win Big Brain of the Month?

Quiz: Battle of the Sciences

Izzie - It’s now QUIZ time! As promised we have a little quiz for our panel, please do play along at home. Don’t look so worried everyone, it’s going to be OK.

Team 1 is Ben and Howard

Team 2 is Kit and Bill


There are three rounds - round one is More or Less…

Team 1 - Ben and Howard

Q1: Does a Bee hummingbird weigh more or less than a 1p coin?

Ben - A Bee Hummingbird. Now that’s interesting. I would think they would certainly be types of hummingbirds that weigh more than a 1p coin.

Howard - But I think from the sound the bee hummingbird. I mean to be or not to be that is the question. I would say could weigh less.

Ben - It’s a trick question. I’m a colonial I must say, so I have not got a lot of experience with 1p coins but can you really fathom a bird that weighs less than that?

Izzie - I’m going to have to hurry you.

Howard - I’d would say yes.

Ben - Okay. I’ll go with the biologist, let’s go with less then.

Izzie - Congratulations.

A: Less - a 1p coin weighs 3.56g, a bee hummingbird - found in Cuba - on average weighs just 1.8g

Ben - Wow.

Team 2 - Kit and Bill

Izzie -  How do you feel in quizzes, are we good at them?

Kit - Well I was in the worst scoring University Challenge team of all time. So no!

Bill - I did win a quiz at school once.

Q2: Is the height of the Elizabeth Tower, home to Big Ben in London, more or less than the height of the tallest Redwood tree in california?

Kit - Wow. I mean, The redwood trees grow pretty big.

Bill - Yeah. My gut instinct here would be to say the tree’s bigger.

Kit - Yeah. I think the biggest tree is called the General Sherman. I might be wrong with that and it’s a fair old size, so I think the tree is probably bigger.

Izzie - So you're saying that redwoods are bigger?

Kit - Bigger, yes.

Izzie - Correct. Less: Redwoods are the tallest trees in the world, the tallest being 116 m tall, that’s 380 ft. The Elizabeth tower that’s home to Big Ben is just 96m.

Round Two - Animal magic…

Team 1 - Ben and Howard

Q3: What do you call a group of flamingos?

  A - A fiend
  B - A flamboyance
  C - A fortune

Ben - I feel like any of them are appropriate but I might have said something like a festival of flamingos if it was up to me. I like flamboyance.

Howard - Yes. It sounds reasonable to me. I'll go with that.

Ben - Unless, do you have any leaning?

Howard - No, I have no idea whatsoever so I'll go with you.

Ben - I'm going to go with the flamboyance of flamingos.

Izzie - Bill, you can’t give a thumbs up to help you’re supposed to be on the other team.

Bill - He’d already got the right answer!

Izzie - Well, let’s hear it. Correct.

Team 2 - Kit and Bill

Izzie - Similar question…

Q4: What do you call a group of ferrets?

A - A bulk
B - A band
C - A business 

Kit - Well, I think I know this one.

Bill - Oh great. Well you were on University challenge so I'll let you make the decision.

Kit - Oh don't say that now. What were you going to go for?

Bill - I've no idea. Probably the last one.

Kit - I think it is a business of ferrets.

Izzie - Well very well done. It is indeed.

We had a lot of fun in the office exploring this.. You can also have a conspiracy of lemurs, a smack of jellyfish, a kaleidoscope of butterflies, a leap of leopards - but I digress…

Round three - true or false?

All to play for on this round

Team 1 - Ben and Howard

Q5: There are more people that have lived on the International Space Station than there are elements in the periodic table?

Ben - Okay. That's a great question. I was going to say ‘The International Space Station, there's not that many’ - but there's also not that many elements - it's like 100 and something and change

Howard - About 170, 120 is it? Hmm.

Ben - I would think there haven't been that many people living on the ISS.

Howard -  Yeah. I would imagine because they tend to stay there for quite a long time. Once they've been put up into orbit and they've had a limited number of shuttles that have been able to deliver them and bring them back, so shall we go for less?

Ben  - Yeah. Less ISS than elements in the periodic table. Yeah, let's go for it.

Howard - Yeah, yeah.

Ben. That’s false.

Izzie - Very well done.

A: False. There are 118 elements in the periodic table but only 109 people have lived on the international space station. 

Izzie -I was hoping to catch you out with that one!

Team 2 - Kit and Bill - True or False?

Q6: The total length of blood vessels from the average person is enough to go around the world two and a half times

Kit - What do you think.

Bill - You're looking at me right.

Kit - I'm absolutely looking at you as the physiologist.

Bill - This is like watching a penalty shootout isn't it? There are a lot of blood vessels. Okay I'm going to have a guess - I think it's true.

Izzie - It is true.

A: True - An average human has 100,000km of blood vessels and the Earth’s circumference is 40,000km

Izzie - Right so that means it’s over to a tiebreaker, closest wins.

Q: How many patents did Thomas Edison get in the US?

All - *whispering*

Izzie - Team 1, have you got an answer do you think?

Ben - We're going to guess 175.

Izzie - 175. Team two?

Kit - Shall we go 176?

Bill - Let's go higher.

Kit - 400?

Bill - 402.

Izzie - Well, I can announce that team 2 are the winners. But you are quite far off.

A: 1093. He had 512 worldwide patents, but over a thousand in the US. Shunpei Yamazaki has over 5000 patents in the US!

Congratulations team 2. You are our big brains of the month.

Kit, you didn’t do the best on University Challenge but you’ve won our monthly quiz.

Ben - A much higher prize.

Image of a firey explosion

42:38 - What causes chemical explosions?

Where is that energy coming from? Chemistry World's Kit Chapman explains...

What causes chemical explosions?

Izzie Clarke asked Chemistry World's Kit Chapman to tackle this explosive question from James on Facebook.

Kit - Well, the energy isn't actually coming from anywhere. We don't make energy. If you know how to make energy, contact me, we'll win the Nobel prize, it'll be fantastic. Energy is just transferred. What's happening here is we're transferring it from the chemicals themselves out into the atmosphere. When you have a chemical reaction this is what we call an exothermic reaction, so something that gives off heat, and what you're doing is breaking up the bonds. So, if you think about it, you've got your molecule, that's atoms attached to each other with bonds, those bonds have to be broken and reformed to make whatever you're making. And so when you break those bonds you're releasing the energy there. When you're reforming the bonds, that takes up less energy usually and so that means that there is energy left over, and that's given away as heat.

Image of contraceptive pills and packets on a wooden table

43:44 - Is there a male contraceptive?

And how does the pill work? It's over to reproductive physiologist, Bill Colledge...

Is there a male contraceptive?

Izzie Clarke received this question from listener Sophie. Reproductive physiologist Bill Colledge, from the University of Cambridge, started by explaining how the pill works...

Bill - The modern pill that females take actually prevents pregnancy in two ways. It contains two hormones usually. It's a synthetic oestrogen which is a female hormone and also a synthetic progesterone and they work in different ways. So the oestrogen component, what that does is it causes a thickening of mucus within the reproductive system and that makes it more difficult for the sperm to reach the egg. The progesterone part of it acts slightly differently, what that does is it suppresses the reproductive axIs and prevents ovulation, so there's this dual effect. You could get by just with oestrogen only, you don't have to have progesterone. But it's a bit like belt and braces, you've got both actions which will make the contraceptive much more effective.

But it's been a lot more difficult to make a male contraceptive. And the reason for this is just the way in which the body works and the difference between men and women. So if you think about women, they go through cycles and they produce an egg once throughout a 28 day period. Whereas men are making sperm continuously and it's much more easy to suppress one egg being released at one point in the cycle than it is to suppress the millions of sperm that are being made continuously by the men.

Izzie - So have we got to a stage that we can now have something similar that would work for men?

Bill - There's developments that are going on. Ideally what you want is an oral contraception for men, just like for the woman. The woman takes the pill and it gets into the body. Theoretically, you could give men analogues of testosterone and increase the testosterone levels which, eventually, would suppress sperm production. The problem with that is you can't take it orally. You ingest testosterone and most of it gets inactivated in the liver straight away, so you have to inject it which means that every week you have to have an injection of high level of testosterone and most people wouldn’t use that as a contraceptive. So that's how it would work but it's not possible to take it orally at this stage.

Izzie - And do you think there will be developments to get something like that or are we still not quite there yet?

Bill - There are developments aimed at having an oral contraception. One of the problems, of course, is that it has to be reversible. If someone stops taking it and then wants to conceive there's no point in having all of your germ cells dead in your testes, so it has to be reversible.

Image of nuclear power station on a sunny day

47:55 - What is nuclear power?

And what are the advantages and disadvantages of using nuclear power?

What is nuclear power?

Sam wants to know about the pros and cons of nuclear power. Izzie Clarke asked physicist Ben McAllister, from the University of Western Australia, to start by explaining what nuclear power is...

Ben - Okay. There are two primary types of nuclear power. I'll very quickly run through both of them. We already heard from Kit before that we can’t just create energy out of anywhere, we have to get it from somewhere else. In the context of nuclear power we are making use of a very famous relationship that was first, I guess you'd say discovered, by a person I mentioned before - Albert Einstein with this very famous equation e = mc squared, which tells you that the energy that a given thing has is essentially equal to its mass times a constant, the speed of light squared, which is really just a way of saying that mass, how heavy something is if you like, is just another form of energy. So, if you can change a thing’s mass then you can harness some energy by breaking off a little bit of mass and converting it into energy, and the amount of energy you can get out is really really really big.

In the context of nuclear power what we're doing is essentially taking - well I mentioned it as well before with uranium and elements that can break down and become other elements - you're taking something, for example, big like uranium, and it has a certain mass. So a uranium atom has a certain mass, it breaks down into two smaller atoms, but when you look at the mass of those two atoms combined, it doesn't quite add up to as much as the uranium atom that you started with.

Izzie - So you've lost a bit?

Ben - Well, you haven't lost it, it's just converted into energy and it’s radiated away. And that's sort of the fundamental principle of what's called nuclear fission power and that's what goes on in all nuclear power plants that actually generate energy in the world today. You could also, theoretically, make use of another nuclear process that works in a similar way, which is called nuclear fusion and that's what the Sun does when it wants to make energy. So what you would do with nuclear fusion is you take a light thing like hydrogen - the lightest element - and you’d smash a bunch of hydrogens together until you got a helium, which is the next lightest element. But, again, the mass of that helium atom is going to be slightly less than the mass of all the hydrogen that you put in so you get a bit of energy released.

And the pros and cons of these things? Well, if you're talking about nuclear fission which is the one that we know how to do, again there are no fusion plants on earth yet, although we're getting there, the Sun is an example of one. You take a nuclear fission reactor and you break down stuff like uranium. The great thing is you don't produce a lot of carbon dioxide, you don't produce a lot of other harmful greenhouse gases and it is pretty good for the environment in that way.

The cons are you can produce a lot of radioactive waste. Personally, I actually think the amount of radioactive waste that you produce is pretty acceptable from modern plants compared to the kind of toxic stuff you put out from every other kind of energy production that we use. You've got to put something out. And the other con is that there is the possibility for, essentially, huge disasters. Like you may have heard of the Chernobyl reactor meltdown, there was Fukushima in Japan a few years ago, where the reactors essentially 'run away'. They generate so much energy and they create what’s called this chain reaction that runs away and you can’t control it,and they just keep putting out so much energy and they melt down.

Izzie - Looking at nuclear fusion though, are we close to getting anywhere near getting to dod that process?

Ben - Nuclear fusion is difficult because you essentially need to create conditions similar to the Sun which means you need very very high temperatures. You need to have things very very close to each other, very condensed, very high pressures. We have been able to make nuclear fusion reactions happen on earth, it’s just that we haven’t been able to do it in such a way that we’re getting out more energy than we’re putting in, and we’re able to keep them sustained for a really long time, which is what we would want to do if we were going to build a reactor, essentially build a small sun. If we could do it would be great because nuclear fusion will get around basically the two biggest problems associated with nuclear fission, whilst also still producing no CO2.

The first one being that there’s no toxic waste or a very very small amount of waste produced. The main byproduct from a nuclear fusion reactor is helium, which is really inert, it’s not going to do anything to the environment and in fact, we actually need it to do other science. It’s a thing that we need and that we’re actually running out of. So if we could make a bunch of it as a byproduct of creating energy, that would be kind of cool. The other thing is it’s very very hard for a fusion reactor to melt down so we can reduce the danger there as well.

Image of daffodils wilting in a field

52:21 - Why don't daffodils last?

Plant ecologist Howard Griffiths answered this blossoming question from listener Sarah

Why don't daffodils last?

Izzie Clarke asked plant ecologist Howard Griffiths, from the University of Cambridge, to provide a blossoming answer for listener Sarah.

Howard - Well, it just shows what clever things plants are because they always find a time and a place to be able to flower and produce seeds. And so the key thing to do is to wait and they'll come back next year because what they're doing at the moment with the leaves is they're now making reserves that they’re storing and putting back into the bulbs that will sit out and allow the plants to last right the way through maybe a hot dry summer in the Mediterranean or maybe a summer here, or maybe the shade of a forest canopy over and above when we are talking about bluebells for instance.

Bluebells are just about to start flowering, they have a similar response. These plants are called vernalised plants because they flower in the spring. And sometimes we have equivalent ones that flower in the autumn, the autumn crocus for instance. So they avoid competition from either environmental conditions or shade by flowering out of synchronisation with the main growing season for other plants, so they're vernalised plants. But one thing I would council is when your daffodils have finished flowering don't cut the leaves off.

Izzie - And why's that?

Howard - Because those leaves need to be carrying on making sugars to store to put back into the bulb for next year.

this is a picture of children walking through wet sand

Are kids experiencing puberty earlier in life?

Charles sent this question into The Naked Scientists on Facebook. Izzie Clarke was joined by reproductive physiologist Bill Colledge, from the University of Cambridge, who took us through the history of puberty.

Bill - Yes, they are. If you look historically at the age at which, particularly girls, first start going through puberty - and usually this is measured by their first period - in 1850, let's go back to 1850, it was about 17 years old. By 2010 it’s 12 years old. So there's definitely been a decrease in the age at which children go through puberty.

Izzie - And do we know why that is?

Bill - Well, partly this is caused by better nutrition, so people are better fed now. Certainly from 1850 onwards we've got better nutrition. And what is happening is people are growing more rapidly, they're gaining a critical body mass, and you have to achieve a critical body mass to go through puberty. But importantly, is not just about how much you weigh, it's about how much fat you carry in your body. And it's thought you have to have about 17% of your total body mass as fat to go through puberty, and you've got to have about 22% of your total body mass as fat to maintain fertility, and if you fall below those you either won't go through puberty or you will become sub-fertile. Top athletes that have less than 5% body fat, the females often don't cycle, they don't menstruate, they're infertile, because they have less body fat.

So what we think is happening with the Western diet of course, children are perhaps becoming obese, they're carrying a lot of body fat at a much earlier age, and this means they're actually going through puberty at an earlier age.

Izzie - Does that impact your life later on?

Bill - It can do, yes. It can increase the risk of developing certain types of cancer - ovarian cancers - because as soon as you go through puberty you start making all the various female hormones, and you are having a longer exposure to those over your lifetime. So it does increase the risk of some types of cancer.

Image of a pile of gold ingots

55:55 - Why is printer ink more expensive than gold?

Kit Chapman from Chemistry World took on this chemical query from listener David.

Why is printer ink more expensive than gold?

Kit Chapman from Chemistry World took on this chemical query from listener David. He explained to Izzie Clarke why this is indeed true...

Kit - Well, it is true, but bare in mind that gold is a really dense and heavy thing. So if you think about a pound of lead and a pound of feathers, a pound of feathers is going to take up far more space. But gold is not the most dense element, that's actually osmium, but it is dense so it takes up very, very, little space and that's why printer ink seems to be more because you get far more bang for your buck.

But printer ink is not the most expensive substance on Earth, that's a common misconception. The most expensive is californium, and this goes back to what we were talking about earlier with nuclear reactors and making things. What we actually do is we stick rods into our nuclear reactors; there are two of them that can make californium on earth - ones in Russia, ones in Oak Ridge in Tennessee in America, and it undergoes a series of what we call neutron capture reactions. A neutron gets turned into a proton and that moves it one place up the periodic table. Eventually we get to californium and that's really useful for things like space probes and exploring Mars.


The last thing our overcrowded world needs is more fertility but that is what we are getting. There are so many historical and current implications in all of that.

The P word never gets mentioned does it! (That's P for population...)

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