Time: It's all relative

We take some time, to look at the science of time
25 February 2020
Presented by Chris Smith, Adam Murphy
Production by Adam Murphy.


an old style alarm clock, faded with time


With the leap year upon us, and the rare appearance of Feb 29th, we’re “marking time” to find out how time works: from why time seems to go faster when we’re older, to the mind-bending warping of time around black holes. Plus, in the news, scientists develop a way to produce electricity from thin air, how old mattresses are feeding refugees, and why bringing back beavers might solve some of our flooding problems...

In this episode

A lightning bolt in the sky

Energy from thin air
Derek Lovley, University of Massachusetts Amherst

Engineers and microbiologists have collaborated to invent a device that generates electricity out of - literally - thin air. They call this incredible bit of tech, published in Nature, the Air-gen, and it relies on tiny strands of protein farmed from bacteria. These so-called ‘protein nanowires’ absorb trace amounts of humidity in the air and produce electricity. At the moment, the Air-gen can power only small electronic devices, but its inventors, from the University of Massachusetts Amherst, have big plans to scale it up. Phil Sansom spoke to one of them, Derek Lovley, to find out how it works...

Derek - We've developed a new type of sustainable electricity production. We don't require sunlight, we don't require wind. We can make power 24/7 from the humidity in air.

Phil - I've got to be honest, it sounds like science fiction.

Derek - I know. And that was our initial thought too! And we spent many months trying to discredit the idea, but it all checks out and remarkably we can make electricity literally from thin air.

Phil - So how does it work?

Derek - It's a very simple device with two electrodes and a new type of electronic material called protein nanowires. And those wires absorb moisture from the air and generate a voltage and current.

Phil - What am I picturing here? Are there two bits of metal and then something in between them?

Derek - That's correct. Basically a sandwich with the protein nanowires in between two electrodes.

Phil - What is a protein nanowire?

Derek - It is a filament, three nanometers in diameter, 10 to 20 microns long, comprised of protein that we produce with a microorganism called Geobacter. Geobacter is a common constituent of soils and sediments. It produces those wires to make electrical connections with its environment.

Phil - So it's little molecules that are around the edge of this bacteria?

Derek - Little molecules produced inside the bacteria. It assembles them into the wire and as the wire is produced, it pushes it out of the cell. So the cell looks hairy, basically. It has hairs extending all from it. Those are the protein nano wires.

Phil - Are you farming these bacteria and then shaving them like sheep?

Derek - Absolutely. That's exactly what we're doing.

Phil - How physically do you deal with them? Because they must be too small to tweezer off, right?

Derek - Absolutely. But it's quite a simple process. We throw them into a blender, which will sheer the wires off of the cell and then we collect the wires on a filter.

Phil - And so how many do you get at once?

Derek - Billions and billions, but of course they're so small it's only micrograms from a relatively large number of microbes.

Phil - Wow. And then do you attach them to the metal?

Derek - Actually, we just suspend them in water, put a drop of that water on the electrode and let the water dry off.

Phil - Once you've done that, what's the point of all this? What are they doing once they're actually on the electrode?

Derek - They start making electricity. I mean, and this was a very surprising result to us, we were actually working with the protein nanowires to make wearable electronic sensors. And then even without applying any electricity to the system, it was generating electricity itself.

Phil - Oh, this was almost an accidental discovery?

Derek - Absolutely serendipitous.

Phil - So do you know how it works then?

Derek - We think we know! As long as it works, right? Okay. Of course we certainly are trying to uncover more of the basic mechanisms and what we do know so far is that a film of the protein wires absorbs moisture from the atmosphere and creates a gradient of water because only the top is exposed to the atmosphere.

Phil - And then how does that water then translate into electric charge?

Derek - The protein nanowires have charges associated with them and are exchanging protons. So it's basically setting up a gradient of protons within that film.

Phil - So is the cool part how tiny these wires are, or is it the way that the charges work on the wires themselves?

Derek - I think it's both. You need to have tiny wires with tiny pores in between the wires. But they also have to have this charge in order to get the voltage gradient.

Phil - And how much electricity can you actually get out?

Derek - Right now, we're making small amounts of power and the reason for that is the initial devices were quite small. This was because we could not produce a large quantity of wires with Geobacter. We've now constructed a new microbe, a strain of E-Coli, which is very easy to grow, can be grown in large quantities so we can mass produce the wires.

Phil - And once they're mass produced, what's the potential? How much power can you get out of this?

Derek - Everything that I'm going to say next is theoretical because we've only made the small devices, but with continued scaling a device, say the size of a refrigerator, could in theory generate enough electrical power to power, say a small home.

Phil - And does it matter if you're in a really, really humid environment? Do you have to be in the rainforest for example?

Derek - No, that is another fantastic part of this process. It can work over a wide range of humidity, say even as low as you would find in the Sahara desert.

Rose blooms

06:37 - Unearthing new Neanderthals

What can new remains tell us about our distant cousins?

Unearthing new Neanderthals
Emma Pomeroy, University of Cambridge

Have you got your trowel ready? Let's dig into some archaeology! Because one of the most complete Neanderthal skeletons discovered to date has been unearthed in the foothills of Iraqi Kurdistan, at a place called Shanidar Cave. This new finding, published in Antiquity, is an exciting insight into how Neanderthals lived, and - crucially - what they did with their dead. Cambridge University's Emma Pomeroy is part of the project, and joined Chris Smith and Adam Murphy to tell them about it...

Emma - So the Neanderthals are basically our closest evolutionary cousins. They evolved in Europe about 350,000 years ago, the same time we evolved in Africa. And they spread across into central Asia. But went extinct about 40,000 years ago, soon after we spread from Africa into Europe.

Adam - And then can you tell us a little bit about what it is you found?

Emma - So what we've found is the upper body, so from about the waist, upwards of an older adult Neanderthal. We're not sure if it was a man or a woman yet, and the bones are articulated, so that means they're in their original anatomical positions. So that's very exciting, because it's also in the place where it was placed soon after death. And we can look at, for example, what was done with the body and what that might tell us about how the other Neanderthals thought.

Adam - So on that, what was done with the body?

Emma - Well, what our evidence is suggesting is that the body was placed into a purposefully dug depression, and that it was probably covered over with soil quite quickly. And that there may also have been plant remains placed into the grave or placed in around the body as well.

Adam - That sounds like it's not a million miles away from how we treat a lot of our dead now.

Emma - Yeah, it sounds very familiar, but it's actually been very controversial. So right next to where this individual is, in 1960 the American archeologist Ralph Solecki found another Neanderthal known as Shanidar IV, and in soil samples from around the bones they found clusters of pollen. And they argued that that was evidence of flowers having been put with the body. But it's been really, really controversial over the years.

Adam - So then what does this tell us definitively about what the Neanderthals used to do with their dead?

Emma - So it does seem to be that they have intentionally buried this individual. It's also intriguing, we're still analyzing some of the evidence, but one of the counter arguments for the flower burial was that the pollen was all modern contamination or had been dragged in by borrowing rodents. But, because we can actually see that we've got mineralized plant material, so ancient plant material with the bones, that's actually very suggestive that the plant material could genuinely be old.

Adam - And you mentioned that you'd found the top half of the body. What happened to the bottom half?

Emma - When they found this other individual, the flower burial Shanidar IV in 1960, the bones were very, very delicate. So when they uncovered them, they decided they would cut out a whole block of soil and remove it all in one big block to the museum in Baghdad so that they could excavate it under much more controlled conditions. What they didn't realise was that there were other individuals directly underneath and to the side of that individual. So in cutting out that block, unfortunately they cut off the bottom half, but they didn't discover that until a couple of years later when they excavated it in the museum in Baghdad. And the team never got to go back and excavate the site.

Chris - I bet there were sorry about that, weren't they? But if this is Neanderthals burying their dead, and obviously this is speculative, what do we know about their contemporaries that were anatomically modern humans? Our direct ancestors, homo sapiens, from the same time? Were they doing the same sort of thing, or did it take longer for us to embrace similar sorts of behaviours?

Emma - Well, that's a really good question and actually it's around this same time that we do see some similar behaviours. They do date back a little earlier actually in modern humans, but it's significant because when treatment of the body involves some degree of symbolism that suggests a kind of level of abstract thought, and it was argued for a long time that Neanderthals just weren't capable of that kind of complex thought. So this evidence would help build that argument that actually they weren't so cognitively different from ourselves.

Chris - Lee Berger from South Africa was on this programme when he discovered Homo Naledi. This is a small brained ancestor. He suggested that these individuals were burying their dead. So does this suggest something about the way in which we have evolved? We naturally tend to embrace these sorts of behaviours. It doesn't matter whether you're Neanderthal, anatomically modern human, or a much smaller brained ancestor like Homo Naledi?

Emma - We don't have a great deal of evidence for intentional treatment of the dead prior to the advent of Neanderthals and modern humans. We do have some other evidence from another site in Spain called Sima de los Huesos , where they seem to have been putting whole individuals into a cave, as well. And that dates to over 400,000 years ago. But these seem to be very isolated incidents. Whereas when we get modern humans and Neanderthals, we see these patterns recurring. So we have examples of Neanderthal probable burials from also France and other parts of the world, but also evidence that they did other things with the bodies. So in some cases, we know they de-fleshed the bodies and perhaps even consumed some of the remains, as did some of their contemporary modern humans.

A germinating seedling

Growing crops in old mattresses
Tony Ryan, University of Sheffield

The horror of the war in Syria - and the consequences for those affected - have been in the news a great deal recently. More than half of the Syrian population have been displaced and many have ended up in makeshift shelters. But, on a happier note, the University of Sheffield have found a way to make life a bit more bearable in at least one refugee camp. They’re repurposing the foam from used mattresses to make hydroponic grow beds. Chemist Tony Ryan had previously done research using foam to grow plants on roofs, so he was perfectly positioned to spot the opportunity when it came along, as he explained to Katie Haylor...

Tony - Zaatari refugee camp is 12 kilometres from the Syrian border; there are 80,000 refugees in six square kilometres, and most of them were farmers before they had to leave their homes. Once the mattress has been given out, those people either move on, or the mattress gets changed; then the UN are stuck with this mattress that to them is dirty, and there's nothing they can do with it. They didn't know how to dispose of them even. So they showed me a warehouse full of mattresses, and I sent the most excited text message back to Sheffield university to say, "I know what we can do. We can give every refugee family a garden in an old mattress." So our task really was to convince them that they could grow things in foam, because where they were currently living was in the desert and nothing will really grow in the desert. Once we'd done that, they showed each other how to do it and then showed us how to do it even better.

Katie - The process involves filling waste containers with the foam and a nutrient solution. Seedlings are then placed into the foam, which supports the roots of the plants as they grow.

Tony - So for hydroponic horticulture all you need the soil to do is hold the plants up, because actually you provide everything for the plant in the nutrient solution that's delivered. Nitrogen, phosphorus, and potassium, the three main macronutrients, and depending on the plants that are being grown, the micronutrients are selenium, iron, magnesium...

Katie - What kinds of plants have people been growing? Is this for recreation? Is it for food? Is it both?

Tony - You won't be able to grow your main food calories this way. This is about quality of life. We've grown onions, radishes, cucumbers, lettuces, tomatoes, cauliflowers, squash, chillies, mint, coriander, and lots of other herbs; I got a WhatsApp message the other day with people harvesting strawberries from a collection of yogurt pots in a greenhouse; couple of hundred lettuces...

Katie - For experienced farmers who are used to growing in soil, was it quite hard to convince people to give it a go?

Tony - The key to getting Syrian farmers to change to something new is to get another Syrian farmer to explain it to them and be an advocate. We have a guy called Moaed Al Meselmani who's actually a Syrian refugee, he was a cereal researcher back in Syria. He helped enormously because he knows hydroponics can can speak Arabic. He convinced Abu Wisam, a 50-something Syrian engineer; he showed him and got him going, so he was the green-hand man that kept our hydroponic greenhouse working. You're far more likely to believe it if a Syrian farmer's telling you as opposed to some crazy English professor. And when you ask Maya, the young lady who works on the program, what she enjoys best about it, she says it's the smiles on the old ladies' faces because they can grow things again and they can see the color green. It gives people hope.

Katie - What have you learned from their experience of using this set-up?

Tony - So we have a research program in Sheffield on hydroponic horticulture and we've learned lots of little tricks about how to start plants growing, what the right watering regimes would be in an arid place. Lots of little technological tricks as well, and little inventions. So one guy turned up and he'd been growing herbs in a yoghurt pot that was full of foam, and then he put that yoghurt pot inside a bigger pot and used a repurposed pump from a soap dispenser. So every time he took a piece of mint to make his mint tea he recirculated the nutrient solution.

Katie - Do you think that would be the potential to make this system self-sustaining? I'm just wondering, is it always going to be reliant on the nutrient solution being provided? Or could it be sourced locally?

Tony - It wouldn't be difficult in terms of technology to go out of the refugee camp into commercial production. We'd like to take it into a business so that the refugees, as they move out into the community, if they don't get to go home, can actually generate a livelihood from being hydroponic farmers in a very water-deprived country. It would be competitive with growing things in polytunnels because you get better water usage, so you'd need less water in a very water-deprived place; and actually you get more efficient usage of the nutrient fertiliser solutions. The reason we're currently fundraising is to take it to every other UN refugee camp. They always have people with time on their hands. We know that growing things improves people's wellbeing and mental health. They always have dirty mattresses, and they nearly always have farmers. So it's a really positive thing. It turns two potential problems, a waste disposal problem and an idle hands problem, into something that gives people an awful lot of satisfaction.

Cartoon of nerve cells (neurones) affected by Alzheimer's Disease with beta-amyloid plaques and neurofibrillary tangles

Inflammation's role in Alzheimer's Disease
Clare Bryant, University of Cambridge

New insights into why people with Alzheimer's Disease lose their memory, and what causes the disease in the first place, have emerged thanks to a new study from Cambridge University, published in Communications Biology. In Alzheimer’s, a chemical called beta-amyloid builds up in the brain, and appears to “poison” nerve cells, although we didn’t know exactly how. But now immunologist Clare Bryant has discovered that this beta-amyloid can trigger an immune pathway in exposed brain cells. This, her experiments show, causes inflammation, deactivates the ability of nerve cells to store memories, and ultimately kills them, and she joined Chris Smith, to give him the details...

Clare - Yeah, Chris, it was very interesting. We had with Dave Klenerman in the Department of Chemistry a discipline-hopping grant from Alzheimer's Research UK, for Dave and I to look at our pathways in consistency. So what Dave does is measures how proteins clump; and amyloid beta or Abeta is a protein that's made naturally within the brain, but what it can do under disease conditions when it folds up incorrectly, it can form these kinds of clumps. So what Dave did was worked out how big the clumps were, and then I took clumps of different sizes, we put them on immune cells, and we looked to see whether or not they generate an inflammation-type response.

Chris - Just immune cells? Or brain cells more broadly?

Clare - Initially just the immune cells. And what we found when we did that was that actually the clumps of beta amyloid of a particular size would trigger a receptor that normally only responds to bacteria, called Toll-like receptor 4, and that then triggers inflammation.

Chris - Now are the particles then fooling the cells into thinking they're seeing sort of an infection almost? They're actually activating a pathway that you'd normally detonate when there's an infection? And that would normally be there quite naturally to ramp up inflammation and get rid of an invading organism, but in this case it's just something that's naturally and accidentally there.

Clare - Yeah, sort of. It's slightly different though. When a bacteria comes in contact with Toll-like receptor 4, it's like nuclear warfare, it's a massive response. But actually with the amyloid beta, what happens is you trigger the response, but it's a real slow burn. And that's really interesting because it comes on over a series of a few days, which means that you could potentially, if you were to inhibit or block this receptor, you might only need to block it every other day or every few days to actually prevent the beta amyloid-driven inflammation.

Chris - So if it's not ultimately killing the cells outright or detonating a nuclear war outright - it's just causing a low grade level of, almost tickling the cells - what consequences are there for them?

Clare - So the responses are really on the bystander cells, so to speak. The immune cells in the brain will trigger this inflammation and the production of this inflammation then kills neurons. And that's the key problem in the Alzheimer's response.

Chris - But does it have to kill them straight away? Because one of the other points you raised in the paper is that it also causes a memory deficit. And that comes earlier in Alzheimer's. People don't immediately present with a rotted-out brain, they present often with low grade symptoms of memory loss first.

Clare - Yeah. And this was the big surprise really. And so what actually happens is you can see in a brain slice - if you stimulate it you can measure something called long-term potentiation which is a measure of memory, and our collaborator Kai did this - but what was really surprising was we know that if you put amyloid beta into this preparation, you can see a drop in the development of long-term potentiation. If you put a TLR4 antagonist there, or a TLR4 blocker, you actually completely block this amyloid beta-driven suppression of the memory response, which is really interesting as well.

Chris - That's telling you two things then. One is that it doesn't have to just kill the cell initially, it can affect the ability of the cell to have this long-term potentiation, which is how we think memories are stored. So it could erode your memory circuits without actually killing the cell to start with. The second is - and this is tantalising - you're saying you can put a blocker drug on there and minimise the effects. So does this mean this is a new way potentially then to attack Alzheimer's?

Clare - Yeah, we think it might be. And that's very exciting. And as a consequence of all this work, we've been funded by Apollo Therapeutics to do exactly that, to develop new TLR4 blockers that can go into the brain and potentially interfere without the development of Alzheimer's disease at a number of different levels. And it speaks to the neuroinflammatory hypothesis - i.e., this is a hypothesis whereby inflammation in the brain is absolutely central to the development of Alzheimer's...

Chris - And that fits with other observations we've made already about Alzheimer's disease, which is that people say low levels of aspirin, for instance, seem to reduce the risk. Aspirins - anti-inflammatory. So that would fit with that. Certain dietary things like curcumin, which is in turmeric - antioxidant, which appears to be anti-inflammatory in the brain. It kind of fits then with what you're finding.

Clare - It does indeed, yes. It really underpins the importance of inflammation in the brain and the pathogenesis of diseases like Alzheimer's. And also it's true for Parkinson's as well, actually. And we see this as a really new, exciting therapeutic opportunity.


A beaver chewing on a twig in water

Beavers back in British rivers
Alan Puttock, Devon Wildlife Trust

The UK has seen widespread flooding this month following the arrival of storm Dennis and his sidekicks. The deluge has totally overwhelmed flood defences in many places. These defences are often necessary because poor land stewardship has drastically reduced the ability of the ground to store water. Until they were hunted to extinction, beavers were the UK’s land managers: their building projects helped to control how water moved through the terrain. So might one solution be to bring them back? Well, for the first time in four hundred years, they are swimming wild again, at least in one river in England. And - in the words of one correspondent, their impact has been “dam impressive”. Megan McGregor spoke to Alan Puttock, who’s one of the researchers keeping an eye on them...

Megan - Beavers are staging a comeback in a corner of southwestern England. Some accidental escapees into the River Otter provided scientists at the University of Exeter and Devon Wildlife Trust with an opportunity - to figure out if the beaver can still thrive in modern UK landscapes. And five years later the results are looking positive.

Alan - Beavers were able to thrive in our modern British landscapes, the population increased from two families to thirteen families over the course of five years and we found that overall beavers had a positive impact. This was in terms of holding back water and reducing flood risk, a massive increase in wetland habitat and biodiversity and also some other more social benefits, such as ecotourism. For instance, there were local villages that benefited from increased visitor numbers with people who wanted to come and see these wild animals.

Megan - Since beavers went extinct, we humans have created a lot of concrete paved cities and compacted farmland. These landscapes drain water very quickly and can contribute to increased flooding. Luckily beaver dams have a rather handy side effect for humans.

Alan - By building dams within the landscape, beavers increase water storage, but also the roughness of the landscape. So they slow the flow of water. So when you get heavy rain events, rather than water rushing off the land and flooding, for instance, downstream communities, you get this slower release of water from a beaver impacted sight. Beavers aren't the sole solution to flooding. They are part of the solution. We're not saying that you should take away these flood defenses that currently exist. What beavers can do is increase the resilience of flood defenses, so by reducing flooding a little bit you might not see, say, flood walls overtopped during flooding.

Megan - The beavers have such an impact on their environment because, like humans, they're what's known as ecosystem engineers - animals that change the landscape to their liking, rather than adapting to the landscape as they find it. And when two ecosystem engineers clash, a little bit of ingenuity is required for them to get along.

Alan - There were some negatives or management issues, such as localised inundation of farmland. If you have dams that are flooding land to what's deemed an unacceptable level, you can use something called a beaver deceiver. It's essentially a pipe to artificially lower the level of a dam. You essentially fool the beaver. The beaver thinks the dam's still there, but you can use this pipe to control the water level. So you still get much of the benefits of the dam, for instance, holding water back. You've got this habitat created, but you can lower the water level down to what's deemed an acceptable level, say for a neighbouring farmer.

Megan - So the beaver benefits can be big, but they require management to keep clashes with humans to a minimum. Luckily those hoping to bring the beaver back can learn from other successful examples of re-introduction, such as the programme in Bavaria in Germany,

Alan - Beaver re-introduction happened there a couple of decades ago. They probably have around thirty, forty thousand beavers there and they've introduced a very pragmatic management strategy where you have a couple of regional beaver advisers who are government funded, but then a whole team of volunteers within the farmer and land-owner community who can keep them updated and do easy tasks such as protection of trees or removing of dams if they're in a undesirable location.

Megan - And what does the future hold for British beavers?

Alan - We have now reported to government and we've provided them with all of our findings and they've extended the trial in River Otter by six months, which is to give them a chance to assess all the evidence and make a decision both upon the River Otter beavers and also beavers nationally.

Megan - If the government rules against the beavers, they'll have to be trapped and sent to a zoo.

Alan - I think we've shown that beavers can bring a whole range of benefits. I really hope that under appropriate management strategies we'll be able to expand beaver populations throughout Great Britain.

A close up of an open pocket watch

The ticking of the Trinity Clock
Hugh Hunt, University of Cambridge

How do we measure time? Adam Murphy went to see engineer Hugh Hunt, and a very large clock in Trinity College Cambridge, the setting for a scene in Chariots of Fire, to find out...

Adam - What you're hearing right now is the clock at Trinity College at the University of Cambridge heard from the inside, from within the clock tower. It's not just any clock, it's also the clock from Chariots of Fire. We're in the film. Students have to run around the whole of the Great Court of Trinity before the 12th strike of the bells. I was lucky enough to get up close to the mechanism of the Trinity College clock with Hugh Hunt who looks after it as we stopped to chat on the roof overlooking the Great Court, so I could learn some history.

Hugh - Well, this clock was installed in 1910. It's the third clock that's been in this tower. The first clock, from 1610, was actually not a bad clock for its time, but in 1726 the new master of the college wanted his own fancy clock and that turned out not to be a great clock at all. Fortunately, we got a new clock at a time when clocks were at their zenith, that mechanical clocks were at their very best. There's a pendulum, Isaac Newton would have told you that the period of a pendulum is relative to its length, and you can get very accurate time keeping with a pendulum. Then there are some weights that go down the height of the tower. They go down about seven metres. It takes about a week for them to fall the distance, so the clock needs winding once a week. Those weights keep the pendulum going. They give the pendulum a little nudge through a thing called the escapement. Now the clever part is the mechanism that links the pendulum to the weights to the escapement, to make it just go steadily, reliably, day after day, week after week, month after month. Then there's an extra part which rings the bells and that's kind of an added extra.

Adam - And having stood right beside those bells I can say that it's really something. But how good is the rest of the clock?

Hugh - This clock is accurate, at its best, to maybe a second a month. And I find that absolutely astonishing because most people's wristwatch, if you've got a quartz crystal wristwatch, that's accurate to a second a day if you're lucky. The more accurately you measure things, the more funny things you find. That's what science is all about, you know, you answer one question and you find five more riddles. We discovered that when the sun is shining, we find that the clock tends to slow down. We're trying to figure out, well why is that? Turns out that the sun shining on the south-facing wall of the tower, by thermal expansion, causes the tower to tilt over. It's a couple of millimetres of movement at the top of the tower, but that then means the pendulum is no longer swinging in a vertical plane anymore. It means that the pendulum is slightly leaning over and that means that the pendulum starts to twist because it's moving in a bit of a curve rather than a straight line.

Adam - So it's a well-maintained, really incredible piece of history that still might have some secrets to offer up. But it's amazing just how simply things can get in the way.

Hugh - You might hear in the background up here that there are some birds flying around. Some of those birds are pigeons. They are a bit of a nuisance because they love to sit on the minute hand when the sun is shining on a lovely warm morning, just to bask in the sun. Now at about a quarter to the hour when the minute hand is horizontal, a couple of pigeons standing on the hand is enough to stop the clock. The weight of the pigeons. I was looking at some documents in the library from about sixty, seventy years ago where the people, who were looking after the clock then, were complaining that the clock kept on stopping and they had to get the clockmakers to come and fix the clock. And they said the clock stopped at 7:43 again today. Aaah, it always stopped at about a quarter to! So sixty years ago, I'm certain they were having problems with the pigeons but they didn't figure it out. So now what we've got is a wire on the minute hand, which is stretched across the minute hand, so that the pigeons can't stand on the minute hand anymore. Problem solved. So this kind of sixty, eighty year old problem now, in fact, it's probably been like that ever since the clock was put in! It's just great. Love it.

Ocean and an island

Solving the Longitude Problem
Josh Nall, University of Cambridge

Time doesn’t just change over the course of a day. It changes as you go east or west. And as countries like the UK, traditionally a nation of seafarers, took to the waves, while sailors could work out their latitude - how far north or south they were - from the positions of stars or the sun, knowing how far they’d gone around the world - their longitude - was impossible. Because rough seas meant that a traditional pendulum couldn’t keep a clock ticking. This was called the Longitude Problem. Josh Nall from the Department of History and Philosophy of Science at the University of Cambridge joined Chris Smith and Adam Murphy to explain how it was ultimately solved...

Josh - Well, particularly in the British context, Britain is an expanding Imperial nation, it's active in the Atlantic slave trade, it has colonial holdings in places like India and that means long range seafaring; and knowing your position in East and West becomes extremely important when you begin to approach land so that you don't, for example, run aground and lose ships. And this was becoming by the turn of the 18th century a very serious problem for the British, in terms of losing ships going out to India and coming back.

Chris - And it just comes down to the simple fact that a clock would not tick and keep time reasonably when you're rocking all over the place on rough seas.

Josh - Absolutely. I mean at that point, not only could a clock not work, but when people like Isaac Newton were asked about the potential to solve this problem, he stated very clearly that it was effectively impossible to make a clock that would work at sea.

Chris - Why are we solely married to a clock as the solution? Indeed, is that the only way to solve this problem?

Josh - Well, many possible solutions were offered, but a clock seemed the best. For the simple reason that very intuitively we understand that as we move East or West, there's a time difference. So if you have a one hour time difference between two places on earth, we know that that's a 15 degree change in longitude. So if you know your local time, which you can find from the altitude of the sun, and you know the time at a reference location, which the British have always taken to be Greenwich observatory, then the difference in time gives you a very easy and quick read of your difference in longitude. So of all of the possible schemes proposed, it was always seen that timekeeping at sea would be the best solution.

Chris - And what, did someone throw down the gauntlet then? And say, "This is a major problem. It's costing us ships. It's costing us lives. It's costing us money. We need to solve it?"

Josh - Absolutely. So following quite a serious Naval disaster in 1707, where the fleet of the wonderfully named Sir Cloudesley Shovell ran aground on the Scilly Isles, and over 1600 British sailors were drowned. Parliament was pushed to act, and in 1714 they passed an Act of Parliament offering very significant financial rewards for anyone who could propose a workable solution to finding longitude at sea.

Chris - The one person who is often hailed as the hero of the day is John Harrison who was a watchmaker. He made timepieces didn't he? Was he the only player? Presumably, if there was a big financial incentive, didn't lots of people enter the race?

Josh - A very large number, to the point that there were a great many satires at the time of the number of absurd proposals that were being put forward! But certainly Harrison has become known, probably better than any other, because he is the person who first begins to develop clocks that can be effectively used at sea. But he's certainly not the only that the board of longitude is supporting and funding through the 18th century. At the same time that Harrison is working, there is an equivalently well funded project to try and develop an astronomical solution, which is effectively to use the moon as a clock because you can actually at any point on the earth if you measure the angle between the moon and certain given stars with the right kinds of astronomical data to hand, you can calculate time at Greenwich. And so that solution which involved using an instrument called a sextant and using astronomical tables that the Royal observatory had issued was also very well funded and was in a certain sense set up as something of a rival solution to Harrison. But in actual fact, the reality is by the end of the century, both techniques, taking working clocks but also taking sextants and astronomical tables, they tended to be used in conjunction.

Adam - Why would you want to use the system of measuring the moon and complex angles and sextants as opposed to just having a really good clock onboard?

Josh - There are two really good reasons. The first is that clocks are always going to be dangerously unreliable. So if your clock breaks at sea, you have no way of recovering the time that it was carrying, because it was carrying Greenwich time. And so you've then lost your one navigational technique. The second reason is cost. Chronometers were exceedingly expensive valuable pieces. Whereas taking astronomical tables, taking a sextant was a much more affordable, and therefore a much more general and repeatable technique.

Chris - So John Harrison invents a clock that solves the problem - A, how did he do that? And B, what did he win for doing it?

Josh - It's really a lifelong journey of clock making and clock improving that takes him to this eventual clock, which is generally now referred to as H4. And that's because it's the fourth major clock that he develops. And he starts working on these clocks in the early 1730s, and it's not until the mid 1760s that these are trialled at sea and demonstrated to be keeping time reliably at sea. And at that stage he has gone through many, many iterations and improvements, improving things like temperature compensation. You would think that motion at sea would be a really big problem, but if you think about it, pocket watches already existed. One of the really big problems alongside motion was temperature change, which really wreaks havoc with a clockwork mechanism because all of your metal parts expand and contract, and that just means your rate of timekeeping varies unreliably.

Chris - And what did, did he, when did he get the full price? Did it just go to him or any of these other solutions sort of co-awarded?

Josh - The answer is yes and no. Harrison got a lot of money from the board of longitude. They kept giving him money over the years to keep funding his work and his development, but at the end of his life, they didn't then decide to give him the full 20,000 pound award. Very controversially. Harrison was extremely upset. They were concerned principally about reproducibility. Their worry was that he had developed a clock, a single clock that worked, but they were extremely worried that they wouldn't then be able to produce more. So they offered him 10,000 pounds of the 20,000 prize if he would reveal the workings of his clock, which he did very reluctantly. And then they said they would give the other 10,000 if then the clock could be proved to be generally useful and usable. And this is the point that Harrison gets very upset and ultimately appeals to George III because he thinks he should just get the 20,000 pounds straight off.

Chris - And did they manage to reproduce it easily and give him the other 10,000 or did he go away an unhappy man?

Josh - They did. Ultimately parliament awarded him nearly all of the rest of the 10,000. They offered him 8,750 pounds. So no one in the end was happy because he got almost 20,000 uh, but not quite

An egg timer showing time running out

The strange physics of time
David Tong, University of Cambridge

We’ve looked at how time ticks along, and how it can change over a day, or across the world. But time can get very strange, very fast, as Adam Murphy found out when he went to speak to University of Cambridge physicist David Tong…

Adam - Measuring longitude lets you travel far. Well, what happens when you travel fast, really fast, speed-of-light fast. Then physics gets a little bit strange and something called time dilation kicks in, put together by Albert Einstein. This theory says that the faster you move, the slower time will run for you compared to someone else. But that opens up a lot of questions like what does the person who is going fast feel? Well, thankfully theoretical physicist, David Tong from the University of Cambridge is on hand to help.

David - I feel exactly the same thing as I did before. I feel exactly the same thing as you do, but you think that I am ageing more slowly than you are. The important speed, and it's a speed limit in the universe, is the speed of light. Light travels at 300 million meters per second. That's fairly fast. And the surprising thing is that it travels at that speed. No matter how fast you're travelling. So you stand still, somebody shines light at you, you think it's travelling towards you at 300 million meters per second, roughly. Now you run towards it as fast as you can. Let's say you run towards it almost at the speed of light. You still see it coming towards you at 300 million meters per second. So, uh, we had things happen with time and in fact with space, when you're travelling at these speeds close to the speed of light.

Adam - And that's all very, very strange indeed. But how commonplace could something like this possibly be?

David - Yeah, it sounds weird, but now we just do experiments on a daily basis where these effects occur. One of the first times we saw this is in something called cosmic rays. So cosmic rays are particles which travel across the universe before they finally hit the earth. When they hit the upper part of the Earth's atmosphere, they typically split into many other particles. It's kind of like having an LHC particle collider, but put at the top of the atmosphere. And one of the things they create as a particle called a muon.

A muon doesn't live for very long. It lives for 1 millionth of a second, roughly speaking. Um, and 1 millionth of a second isn't long enough for the muon to make it down from the top of the atmosphere to the earth where we can detect it. And yet we see many of these muons coming from the top of the atmosphere. And the reason is that although the millionth of a second wasn't long enough, the muon thinks it doesn't take that long. The muon's travelling so fast that it thinks time has slowed down, and from its perspective it's lasted its usual millionth of a second before it disappears, but that was then long enough for it to come down. Now these days we do these experiments routinely. We do them in particle colliders, managing to speed up particles to very close to the speed of light and when they get to those speeds, their lifetime is extended often by up to about 3000 or 4,000 times.

Adam - And it's not just speed that can mess with time. Big, heavy things can as well.

David - Einstein had two theories of relativity. There was the special theory of relativity from 1905: this is the theory that tells us what physics looks like as we approached the speeds of light, that's where the time dilation due to traveling at high speeds comes from. And 10 years later he had what's called the general theory of relativity, which is our best theory of gravity. He replaced Newton's theory of gravity that had been around for a couple of hundred years. General relativity says that what we think of as gravity is actually due to the bending and warping of space and time, and so if you have ever heavy objects in the universe like stars or planets, then a space warps around them but also time warps around them. The net effect is that again, there's a time dilation.

When you're close to a heavy object, time goes slower for you, so you age less quickly if you're close to a heavy object, then if you're far away. Yeah, GPS systems only work because of general relativity; or maybe that's a slight exaggeration. If we didn't include general relativity, GPS would be off by a few meters. There was an experiment done in the 1970s by Hafele and Keating. It was a very simple experiment. They got some atomic clocks. I guess it wasn't simple to build atomic clocks, but they got some very precise atomic clocks, and then they just bought a ticket for them on a plane and they flew around the world commercial. I think business class! There's lovely photos of them actually have them sitting in one seat and his big atomic clock strapped into the seat next to them. The plane did one route around the world. It landed and they tested the atomic clock that had been on the plane versus atomic clock that was just left behind, and it's exactly as was predicted by the theory of relativity.

A close up of a wall calendar

Time in our heads
Luke Jones, University of Manchester

Do you remember, as a child, journeys seeming to take forever on the way there, but then much less time on the way back. Do the years seem to be flying past increasingly quickly? Why? Luke Jones is from the University of Manchester and he joined Chris Smith and Adam Murphy...

Luke - It kind of depends on what type of timing we're talking about. Although we talk about people who are having a sense of time, there's different types of timing judgment that we make. So you have a sense of duration, how long things lasted for. You have a sense of where you are in time, you know, when am I or what time is it now? And you have what we call passage of time judgment. So how quickly time seems to pass for you. And there seems to be different mechanisms that control these different types of timing judgment

Chris - And how good are we on average at working out how fast time is passing?

Luke - How quickly time is passing, we're very variable at it. In fact, it's a very weird question, if you think about it. We know that time passes at the same rate, unless you're close to a black hole or travelling at the speed of light. But if I say to you that time passed more quickly when I was playing on my Nintendo this afternoon, or that it crawled when I was waiting for a taxi to get here, then you understand what I mean. There seems to be this disconnect between our knowledge that time passes at the same rate and the way we feel time passing.

Chris - I remember reading in the book Catch 22, that the main character says he likes spending time during his days off with a certain other character 'cause that person's really boring and makes time go really slowly. So it seems to make the leave last longer. But why is that? Why do things that are very engaging seem to make the time whiz by, whereas things which are tedious seem to take forever?

Luke - So although we think of those two extremes, so the unpleasant situation, and the pleasant situation being kind of polar opposites of each other, they seem to operate in quite different ways. So in the pleasant situation, you're probably not paying attention to time. You're engaged in the event, you're not looking at the clock. And it's only when you receive a phone call, or something alerts you to what time it is, that you kind of retrospectively think, Oh my gosh, so much time's past. When you're in an unpleasant situation, you're aware of it at the time. You're aware of every single second ticking, ticking along and crawling along. So the, the, the pleasant situation of time flying seems to be a kind of retrospective or we look back and infer that it must have passed quicker.

Chris - I read one proposal by a group of experimenters, who were throwing themselves off bungee platforms while watching a watch, and saying their theory was that because they were taking more sort of, mental snapshots provoked by fear, their memory was much richer for the experience, that when the brain worked out, well roughly how long something had took, because it had so many mental images of what had happened in that period of time it assumed it must have taken longer than it did, which is what was creating the sense of time slowing down under that circumstance.

Luke - Yeah. So that's really interesting, so there seems to be, we haven't worked this out yet, but there seems to be an interesting link between the rate at which we process information, and our perception of how quickly or slowly time passes. So in those extreme situations, and a classic example is a car crash. So when people talk about that they say "it seems as if time slowed down, seems as if the van coming towards me was in slow motion." And you can imagine that in that situation you might have a kind of big injection of adrenaline, you know kind of fight or flight response, and this speeds up the rate at which you process information. If we're using that as a kind of feel of how quickly time seems to pass, then you can imagine that there'd be a link between those two things.

Chris - And do you think that that is what is happening with age then? That because we're processing information a bit less because there's less novelty in everything for us, it gives the perception that time is passing quickly because the brain's on autopilot more?

Luke - Possibly. The age thing is a really weird thing, the more you think about it. People have noted this idea that the time passes more quickly as you get older for hundreds of years, and there's an old idea of a year being a smaller and smaller ratio of your age as you get older, or maybe you process less information, but hardly anyone's actually collected any data on this and those that have, have found that it doesn't quite scale up in this way. So in order to feel that time is passing twice as quickly, you might need to be four times as old. And there's some evidence that it actually peaks in middle-age rather than carries on going as you get older. But the real mystery is what do people really mean? Is the question meaningful? If I ask you how quickly time passed now compared to when you were half your age, you'll give me an answer, but do you really carry around in your head a model or a memory of how quickly time passed when you were younger?

Adam - I find myself every autumn starting to say things like, "Oh, Christmas is coming earlier every year." What's going on there?

Luke - Now, isn't that strange? Do you think that you would update your notion of how quickly Christmas comes around? Well, why? Why are you caught out every single year? It's quite an odd one that. Again, it's whether that question has meaning. We've certainly feel it and people talk about this anticipation of Christmas, but it's odd that people don't update their notion of how quickly it takes for a year to pass.

Chris - And Luke, are there any things that can go wrong that will affect our sense of timing? 'Cause we've talked about healthy people all the way through so far. Are there any situations where people's time clock goes wrong and their perception of time is off?

Luke - There's very little evidence. It seems as if there's something so intrinsic about your sense of time, or at least your orientation in time that if you lose that you've kind of, you've already lost a lot of other cognitive strategies. So actually looking at those cases, there's hardly any of them to draw any conclusions from.

A green and yellow dish sponge

QotW: Should I microwave sponges?

We asked Alice Taylor, a friendly biochemist, and we tested this at home. We also reached out to microbiologist Markus Egert, from Furtwangen University in Germany to share the results of his experiments around microwaving sponges...

Mel - Microwaving sponges would save a lot of them from being used and thrown away wouldn’t it? Especially since plastic sponges take at least 500 years to decompose in landfill. Luckily I knew Alice Taylor, a friendly biochemist, and we tested this at home..

Alice - We decided to do a very simple experiment using Agar plates, containing all the nutrients bacteria could ask for. We took the in-use kitchen sponge and very quickly dabbed the sponge onto the agar plate. We then popped the sponge in the microwave for about a minute.

Mel - the sponge started to make some smoke in the microwave, so we quickly took it out as the fat on the sponge might catch fire.

Alice - Now we can dab the very hot microwaved sponge onto another agar plate. We then put these plates in a warm place for around 36 hours.

Mel - So Alice, is there a difference between the two plates?

Alice - Lots of bacteria grew on the agar plate that have been in contact with the non microwaved sponge which is a tad alarming. However, on the plate that has seen the microwaved sponge there is next to no bacterial growth. It seems that microwaving a kitchen sponge is an effective way to kill the bacteria.

Mel - Markus Egert, a microbiologist in Furtwangen University in Germany took our experiment to the next level and found that cleaning sponges can have some unintended consequences.

Markus - Microwaving indeed significantly reduces the number of germs inside a kitchen sponge. Dishwashing might even work better due to the use of dishwashing detergents in addition to elevated temperatures. However, putting them into the washing machine at a temperature of at least 60 degrees centigrade and using a bleach containing heavy duty detergent is probably the best way to sanitise kitchen sponges and cloths

Mel - The problem is, the long-term effects of regular microwaving (or any other cleaning method) on the microbial community of a kitchen sponge or cloth are largely unknown.

Markus - Our research suggests that long term cleaning might select for potentially pathogenic and/or smelly bacteria. We think this is because some bacteria can adapt to the cleaning process, survive the microwave or dishwasher, and can easily grow to higher numbers again. This is a classical selection process, very well known from biological systems.

Alice - Bacteria also proliferates in wet environments, so keeping your sponge dry is a good way of preventing bacteria from growing.  In general we should avoid using the sponges for too long

Mel - Thanks Markus and Alice. Next week we’re answering this question from John

John - Dogs come in all sizes, from tiny Chihuahuas to giant Great Danes. Their head size is hugely different, as must be their brain size. Does this mean that a Great Dane is massively more intelligent than a Chihuahua?


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