Is there time on Mars?

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1:16Hello, welcome to Inside Science from the BBC World Service with me, Tom Whipple. What is time? Asked St Augustine of Hippo in 400 AD. If nobody asks me, I know. But if I were desirous to explain it to one that should ask me, plainly I do not know. Didn't stop others trying. Einstein had a bash. Time, he said, is an illusion. John Wheeler said time is what prevents everything from happening at once. Well, here we've had our own go, and we have a small slice of that time apportioned by the BBC World Service schedulers to talk to you about time and about science.

1:5427 minutes to tell you about a mission to Mars and back. Or 1620 seconds in which we also have to squeeze in an interview from Roland Pease, who takes us to the top of the world to a new finding that climate change stopped the next ice age in its tracks. Or, put another way, we have 1.5 times 10 to the 13 oscillations of a microwave beam when tuned to a cesium atom to also squeeze in our final item on updating the atomic definition of a second. And in between all that, we need to find a few microwave oscillations to chat to Penny Sarchet from New Scientist about all the other news.

2:31Penny, what have you got? Well, the mathematicians are revolting. In every sense, I know from having studied maths and sat in closed spaces with them.

Mission to Phobos

2:41On Tuesday at 4.41am Japanese time, a rocket took off from Tanegashima Space Centre. Its cargo was bound for Mars, just one of the many scientific craft we have sent to explore the red planet. This time, though, there was a crucial difference. That difference, it intends to come back, and to do so carrying 10 grams of material it didn't have when it took off. It intends to bring back a little bag of dust from Phobos, the moon of Mars, and leave behind a lonely, noble rover named after Obelix's dog.

3:21We spoke to Naomi Murdoch, part of the scientific team, who have an anxious five years to wait to see if it succeeds. This mission, the Martian moons exploration mission, it is a Japanese mission that is going to go and take a sample of one of the moons of Mars to understand a little bit more about where the Martian moons come from. It's one of the outstanding questions that we have today about our solar system is the origin of the Martian moons. A lot of listeners will have followed the progress of all sorts of rovers on Mars itself,

3:54and it'll feel like slightly old hat to go onto Mars and explore it. But coming back, this is a real engineering problem, isn't it? Why is it so much harder to come back? Well, what's great about this mission is that we're going to actually the moons of Mars, so we're not going down to the surface of Mars, which has, of course, many challenges linked to landing on the surface of a large planet and then taking off again. We're going to travel towards the Mars system for the next few months, and we'll be arriving in August 2027. And then we're going to have several months where we're going to take a lot of images,

4:27a lot of data with all of the different instruments that are on board MMX. There are several different instruments. And then late 2028, we will deploy the small rover called Idafix down to the surface of the Martian moon Phobos. The rover will survive on the surface, will function on the surface. After that, the main MMX spacecraft will come down, land, take a sample, take off again. And we're relying on the heritage that the Japanese Space Agency have of sample return missions to asteroids.

4:59They've already done two fantastic missions, Hayabusa and Hayabusa 2, that brought back samples from asteroids. And we're using all of that expertise to go and take a sample from the surface of these small Martian moons that are similar in size to asteroids and use that to bring it back to Earth. What's the gravity there? How is it even going to adhere to the surface? Idafix faces many technical challenges. So there is the very low gravity. Gravity is about 1,500, 2,000 times less than the gravity on Earth.

5:31So, first of all, getting down to the surface is challenging because we have to land and we have to rebound. The rover will have to be entirely autonomous to upright itself and open its solar panels when we land, after which time we'll be able to communicate with the MMX spacecraft and with Earth. And the big problem with driving on the surface of Phobos is that when we drive, the traction comes from the gravity because the gravity pulls a car down and it's the traction. It comes from that gravitational force between the road and the car and that's what pushes the car along.

6:06So here we have no gravity or very, very low gravity. So what's going to happen is we lose traction compared to the same driving conditions on Earth. We're going to have to drive extremely slowly to combat that, literally at the speed of a snail. We're actually hoping to cover, in the lifetime of the rover, which is about 100 days on the surface, we're hoping to cover a distance of tens of metres up to maybe 100 metres on the surface. What's it looking for? What's the information it's going to send back so that the mission can be successful?

6:37The main information is information about the physical properties of the surface. Is the surface soft? Is the surface hard? Are we sinking into the surface? Are we able to stay on the top? What are the typical particle sizes that we're seeing? All of this information is going to be so important for MMX as it plans its landing and sampling operations. So all the information they can have before they attempt those operations is very useful for them. And we just don't know. We don't know whether it's a soft, hard surface. We don't know what to expect.

7:07We've never seen Phobos up close before. So we have low resolution images. We have other data which give us some indications and some clues about what to expect. But today we've never seen the surface up close and we've never tried to touch the surface of Phobos before. OK, so then it sends back this information and your main lander comes down and it lands. And what happens there? Does it just take up a scoop and then take off straight away? Yeah, it's going to stay on the surface for some time. It's going to take different samples. There's different sampling mechanisms on board. It will take those samples and then lift off again.

7:41And as it lifts off, it will use thrusters to move away from the surface of Phobos and move up back into quasi-static orbit around Phobos. And what about poor Ida Fix? So we will be on the surface at that time. We're still trying to work out the details of exactly where we will be and how close we will be to the main NMX spacecraft when it comes down. So, of course, our number one concern is to try to protect Ida Fix during the landing. So we have to still to decide whether we are going to be able to observe the landing directly or whether that will be too dangerous for the rover.

8:13And these discussions are still going on at the moment. But will Ida Fix then die a lonely death on Phobos, watching its only link to the home disappear back to Earth? Yeah, so that is another technical challenge for Ida Fix, is we rely on NMX to phone home. So we rely on NMX, the main spacecraft, for all communications with Earth. And so when the NMX spacecraft leaves the Phobos system to move and explore the second moon of Mars called Deimos, we will be saying goodbye to Ida Fix, indeed.

8:43A noble sacrifice for science. Indeed it is. But we will have had so many firsts coming out of this mission. No one's ever driven a wheeled vehicle on a world like this before. So we'll be learning so much about Phobos and low gravity environments in general as we go. Naomi, thank you very much indeed for joining us and good luck over the next five years.

Redefining the Second

9:02Thank you very much. Right, so Penny, after chatting to Naomi, we have now had about 500 seconds of our programme, which means we have roughly 1,100 left. We've been thinking a lot more about what a second actually is recently, haven't we? Yeah, we have. Last week, a meeting of the International Bureau of Weights and Measurements voted to abolish the leap second. Very exciting. Leap seconds were invented to keep our clocks in sync with the Earth's rotation because the Earth's rate of rotation fluctuates.

9:39And without kind of trying to adjust it every now and then, our clocks would otherwise sort of drift out of synchrony with the position of the sun in the sky, which of course is how we used to define time. So since we invented the leap second, we've deployed them 27 times since 1972. But now the idea is that actually we're going to let our clocks drift out of sync with astronomical reality, perhaps for centuries at a time until the difference is about a full hour and then we'll correct them,

10:10which is quite an exciting move. But it's sort of a reminder that this problem only really came about because we've been developing increasingly more accurate ways of defining what a second actually is, which is quite a difficult thing to do. OK, so the leap second exists because we used to measure time by the rotation of the Earth, by looking at where the sun was. And then we divided a day by 24 and by 3600 again. But then we screwed it all up by making an atomic clock, which it turned out is more accurate than that.

10:46And this got us thinking, you know, if that's what time is, what even is a second? What's an atomic second? And this is particularly pertinent because it turns out that there are moves afoot to change time again, despite it causing so much hassle the last time. We went to a lab where they're looking to redefine the second using a different atom tuned in a different way. This is our interview with Rachel Godham on site at the National Physical Laboratory in Teddington.

11:20And it was recorded a couple of weeks ago, so we know how long it'll be. So, Penny, look, I'll see you in 150 quadrillion oscillations of an atterbium clock. So, we're in the UK's National Timescale Laboratory. This is where time is created and disseminated for the whole of the UK. And this is underpinned by lots of very accurate atomic clocks. OK, so at the moment, tell me what a second is. So, at the moment, one second is defined based on a cesium atom. And you rely on the fact that you can use microwave radiation to excite one of these atoms from one level to another.

11:58And by definition, the right frequency is 9,192,631,770 oscillations of the microwaves per second. You know you've had one second. I would guess that means that you can tell a second to within a nine billionth of a second. Actually, you can do even better than that. If you kind of average for even longer, you can measure better than to one oscillation. Is that not enough for you? Yeah, so the optical atomic clocks that we work on are 100 times more accurate.

12:34To give an idea of how accurate these need to be, you've got a screw in your lab, haven't you? Tell me about your screw. OK, so we have to worry about all sorts of things that might disturb the clock frequency. And one of those things is even the gravity potential that the clock experiences. So depending on how high up your clock is in the Earth's field, that can change the frequency output of the clock. This is Einstein's relativity. This is Einstein's theory of general relativity. So this has nothing to do with the specific nature of our clock.

13:05This is just time itself runs at different rates in different gravity potentials. So that means that if we want to compare our clock with a clock somewhere else, we need to take account of those gravity potential differences, or effectively their height differences. You know the altitude of your screw. And so, indeed, we know the altitude of a screw on the floor to the nearest couple of centimetres above a reference level. But even that's not enough, is it? Because the Moon comes into play. Because of the Moon, we're very familiar with the ocean tides, but there are also solid Earth tides.

13:37So the actual, the whole solid Earth is deforming as well, two periods a day, based on the Moon. And the scale of that effect is surprisingly large. So the ground beneath our feet is going up and down by 50 centimetres, peak to peak, every day, because of these distortions that are created by the Moon. Why do we need it? What are the applications of a clock even more accurate than an atomic clock? I mean, there are very few people who are right now saying, gosh, I need to know one second to 18 decimal places.

14:07But here at the National Physical Laboratory, because we are trying to realise the sort of primary standards for the UK and then disseminate those to end users, you want to make sure that kind of at the top of that metrology chain, you've got the very lowest uncertainty, the very best realisation. But there are applications that are getting close to being able to make use of that accuracy that we're now achieving. And we've been using our clock to put some limits on special relativity. We've been using our clock to look for dark matter and how it couples to ordinary matter.

14:40So you can do these incredibly precise measurements that no one's ever done before. And so a normal atomic clock, as you said, it's about exciting those cesium atoms. What's your clock doing? It works on exactly the same principle as a cesium clock in terms of exciting the internal energy levels of an atom. The reason it's called an optical atomic clock is because the frequency of radiation that will excite the atom is an optical frequency. And because that frequency is so much higher, the clock is effectively ticking that much faster.

15:12And so once you've got a clock that's now ticking that much faster, you can kind of subdivide time into smaller and smaller intervals. And it's that that gives you this ability to have a more accurate clock. And having done that, are we then going to change our definition of what a second is? That's very much the plan now. And there's a target date of 2030 to be ready to redefine the second. And that's what the international community is working towards. If anybody notices a difference, we've done our job wrong.

15:42So the redefinition is all about being able to know more accurately and to generate more accurately one second in the laboratory. But you must go home eventually and sort of think, what is this thing? What is an interval of time? What is time? What is marching on? I think it's a very philosophical question, isn't it? I think there is no easy answer to what is time. If you ask me what is the time, then I can give you a very good answer. I can tell you very accurately to many decimal places. But, yeah, the concept of time is a bit more tricky.

16:13That was Rachel Godwin at the National Physical Laboratory. Now, that time, whatever it is, continues to tick on. But we do have enough of a sliver of it to get a quick hit of a story from Penny. Penny, have you got any news for us?

Mathematicians against AI

16:29Yes, I imagine if you're a mathematician, it probably feels like over the last few months, time has accelerated massively. Because as you've been covering, AI has just totally blown open the field. We've seen the solving of the Navier-Stokes Millennium Prize problem. We've also seen the release of hundreds of papers on some of the open problems in mathematics. And so, you know, what we're seeing now is the field is in turmoil. It's not just the fear of mathematicians of being replaced by AI.

16:59There's also this problem that many of the AI solutions that are coming out, often they're not verified as accurate. So then is it the job of a human to then go formalise them? Or even when they are formalised, sometimes they're in sort of an impenetrable AI way of solving a problem, to the extent that humans might struggle to interpret them or understand or really derive value from them. So I think it really seems like the backlash is beginning now. And this week, my colleague Matthew Sparks has reported on a big step in that.

17:32More than a thousand mathematicians have joined what I think is a brilliant name, the Association of Human Mathematics. And so to join this Auguste Association, there are several pledges and you can take various combinations of them. And it sort of splits you into two flavours. There's the hardline vegans, if you will. And these are the mathematicians who are saying they will not be using AI at all. And then there's the vegetarians who are promising that they won't work for AI firms and that they won't use chatbots at least to write their papers and their textbooks and that kind of thing.

18:09There's obviously quite a few motivations for this. Some of the people who have joined, they're citing environmental concerns about the heavily intensive energetic use of AI. There's clearly a degree of self-preservation here. You know, what is the field, what will human mathematicians do if AI keeps coming in and just blowing things up? But I think, you know, most interesting potentially is the philosophical one. People are saying, who are joining this organisation, that maths is a creative, inherently human endeavour.

18:42I did wonder, Tom, with your background, what you make of that. I mean, I have a tremendous sympathy for them. I can't help but feel there's something immensely sad that's happening in that maths is, you know, proving theorems is this amazing, you get this amazing moment. I'm not pretending I've had this in any really important way, but where you realise something is true that's always been true and always will be true. And you as a human has found it. But I can't help but feel like they're like sort of Huguenot weavers saying, I'm not going to use your looms.

19:19I mean, you know, so have they not just signed their own, even more so, signed their own obsolescence? Yeah, it'll be interesting to see. I have some sympathy for that argument of, well, what's the point in solving it if we don't really derive anything from the journey of how you got there or what you found? I'm not enough of a mathematician to really know how much that sort of stands up as an argument. But it's quite compelling, I think. I mean, one of the things I find interesting is we've got the story which is breaking now as we talk about these massive cyber attacks.

19:53Now, when all of that open AI stuff was released, or all of those theorems, Peter Schultz, who's a fields medalist, the equivalent of the maths Nobel, he said something. He sort of lamented some of what they were seeing. But what he also says is what is worrying me the most at the moment is the insecurity of cryptography. And he said finding algorithms breaking standard cryptographic protocols is a number theory problem whose difficulty does not, to my non-expert, you know, he's a fields medalist, but to my non-expert eyes, not significantly exceed what those systems are now capable of.

20:31A few people said it's interesting they hadn't tackled any cryptography. Now, I wonder whether there's some cryptographic problems that it's going to solve, and then we're going to just, you know, quietly break the internet. Yes, all this time we've been worrying about quantum computers doing it, and now along comes AI. You're listening to Inside Science from the BBC World Service. Tell us what science you think we should be investigating. Our email address is insidescience at bbc.co.uk.

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Climate change and the next ice age

22:02Now, time to check in with Roland Pease and an idea that if it weren't for climate change, we could be heading towards another ice age. The United Nations Environment Programme warned earlier this week that we'll have to work really hard if we're to avoid 1.8 degrees of man-made warming. To put that concern in context, if the planet had been left to itself, it would actually be slowly cooling right now. Very slowly. Indeed, a study out this week says that the glacial creep towards a new ice age did start around 2,000 years ago.

22:36The evidence, gathered by Nicholas Young and colleagues, comes from traces they've studied from the edge of a small mass of ice on Baffin Island, between mainland Canada and Greenland, that was once part of something far mightier. So the Barnes Ice Cap sits up on a Baffin Island plateau, and it's the last remnant of what was once the Laurentide Ice Sheet. So about 20,000 years ago, the Laurentide Ice Sheet covered the North American continent and had about 70 to 80 meters of sea level equivalent.

23:09And so starting about 20,000 years ago, that ice sheet started retreating across the landscape. And what's left today is this little ice cap on Baffin Island called the Barnes Ice Cap. You know, most people think that the Laurentide Ice Sheet completely disappeared, but that's actually not true. And how big is it now? Its maximum, the Laurentide, was about 70 to 80 meters of sea level equivalent. And right now, the Barnes Ice Cap is about 5 millimeters of sea level equivalent. So it's very small. It's about 40 kilometers wide.

23:41And we also know that in a few hundred years, the Barnes Ice Cap is going to completely disappear. And so that will truly be the disappearance of the Laurentide Ice Sheet. Now, the important message of your paper is that actually, if we'd gone back to about Roman times, it was not shrinking, but it was actually growing. Yeah, this was a bit of an unexpected finding. So ice sheets always go through periods of expansion during what we call glacial periods, followed by periods of retraction during interglacial periods.

24:17Which is what we're in at the moment. Correct. We're currently in an interglacial. Us geologists call it the Holocene. And so what we figured out was that about 3,000 years ago, the last remnant of the Laurentide hit the smallest point that it was ever going to get during the current interglacial, the current warm period. And then starting about 2,000 years ago, this ice sheet actually started to re-expand. And so this, we think, is the very start of what should have been the next ice age.

24:48That's extraordinary. So I guess this is what the ice sheets have been doing for about at least 2 million years, is a pulse almost of tens of thousands of years of ice sheets growing and then shrinking for, you know, maybe 5,000 or 10,000 years. And then it goes again. Right. So the glaciations of the last about 2.5 million years is one of the most sort of fundamental pacemakers we have across Earth's systems. And so it's been almost predictable that an ice sheet expands and then it contracts and then expands again.

25:24And over the last million or so years, this happened at about 100,000 year cycles. So the ice sheet would slowly grow and grow for about 90,000 years and then retreat for about 10,000 years. And then we start the cycle over again. So we see this in a lot of records. This happens over and over and over over the last two and a half million years. And what's unique here is that this is some of the first evidence where we can actually say that the new Laurentide ice sheet was just starting to expand and sort of start the next ice age.

25:57And it expanded for about 2,000 years until essentially recent times in the middle of the 20th century put that expansion to a halt. And it's now undergoing a fairly quick retreat. So essentially what you're saying is that global warming has just interrupted that sort of natural cycle. Exactly. I mean, give me a sense of the difference between 2,000 years ago, the middle of the 20th century and now. I mean, are you talking sort of meters of growth or kilometers, a percent or doubling?

26:32Yeah, we're actually talking very small changes in the ice sheet. So 2,000 years ago, we think it was a little bit smaller. So maybe like a millimeter of sea level equivalent, really not much. And then it very, very slowly started to re-expand. And so it was expanding quite slowly. We're talking only a few meters per year or even less over the last 2,000 years. If we hadn't intervened with our greenhouse gases and changed the climate very dramatically in basically the past 50 or maybe 100 years, how long would it take for the next ice age to turn around?

27:12I was looking at the literature and it was very unclear at what point we'd start saying, uh-oh, this is another ice age. Yeah. So we're talking about thousands to tens of thousands of years here. This is a very long process. And so we tend to think of things on geologic timescales. So I think in the immediate future, had we not pumped all these greenhouse gases into the atmosphere, you know, I don't think humanity would honestly notice all that much. But if you were to let things go for a few thousands of years, then things would start to matter.

27:45Of course, the ice cap is getting bigger, but positive feedbacks are making climate cooler. And then these are the things that people start to worry about in terms of, like, crop production is, like, a good example. And this was actually a very real concern back in the 1970s when scientists were trying to figure out when the next ice age might actually start. On the current trends, it's been cancelled, I guess. Absolutely. I think we have evidence that the ice age started. It was just the beginning. And had we not interfered, things would have been well underway.

28:18But the amount of greenhouse gases that are in the atmosphere now, coupled with the magnitude of gases that are projected to go into the atmosphere, I think makes it very clear that a new ice age is definitely not on the horizon. It's quite a thought. Nicholas Young is a glaciologist at Columbia University, and the study was just published in Science. Thanks, Roland. And you've been listening to BBC Inside Science with me, Tom Whipple. It is goodbye from me and goodbye from Penny.

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