Hey friend, do you ever find it hard to keep up with pop culture? Well, from the latest Apple TV shows on everyone's mind to difficult conversations about protecting Canadian culture in this moment, that is where commotion comes in. We are tapping to what's going on in the world of art.
and entertainment so you'll find out which movies you need to catch in theaters or the albums that you should be streaming or other stories affecting the culture. You can catch Commotion every weekday on YouTube, Spotify, or wherever you get your podcasts. This is a CBC Podcast. Hi, I'm Bob McDonald. Welcome to Quirks and Quarks. On this week's show, the ears have it.
Biologists discover that our ears might have evolved from fish gills. Evolution's a tinkerer. It's not coming up with completely new things, but kind of reusing programs that have been around for a long time to do things that are very different with them. And... big babies. Scientists investigate infant elephant seals to learn more about the mysterious places they go. We're mostly weighing the one month old weanlings, which are still pretty heavy, still about 160 kilograms at 30 days old.
It's a workout for sure, but it's pretty cool. Plus, caveman cannibalism. Who were they having for dinner? rabbits eat a toothsome diet, and how the universe's time zones could doom dark energy. All this today on Quarks and Quarks. The ocean's twilight zone is a deep, dark, mysterious place. It's the dimly lit layer of water that stretches around the planet from 200 to 1,000 meters below sea level, just out of reach of sunlight.
This Twilight Zone also teems with and is home to an incredible amount of exotic biodiversity, like blobfish, giant squid, and a carpet of plankton so thick that World War II sonar operators mistook it. the sea floor. It's also incredibly difficult to study, as it's inaccessible to most of the tools we use to monitor the oceans. Well now scientists have a little help from a surprising source, elephant seals, living in a colony off the coast of California.
Researchers working on a decades-long project looking into the life and movements of these animals have figured out that they can use the elephant seals as sentinels to help shed light on some of the oceanic conditions in the deep dark sea. Ms. Allison Payne is a Ph.D. candidate in the Beltran Lab at University of California, Santa Cruz. She's part of the research team behind the work. Hello and welcome to Quirks and Quarks. Hi, thanks so much for having me.
Now, I understand you just went out to visit the elephant seals just today. What's it like to be in that colony? Yeah, this is the elephant seal breeding season right now. So it's starting to wind down. But during the breeding season... the entire beach is covered in seals pretty much. So there's these big males weighing about 2000 kilograms, slamming into each other, fighting over control of the beach. There's females all around. They're still.
pretty big about 650 kilograms and they're all giving birth snapping at each other and then all of their pups are just screaming so it's a very wild uh experience to to be out there and to get to see them Certainly sounds like a crazy place. What's it like working with elephant seals?
They keep you on your toes. They're really cool animals, but they're definitely ones to be careful around and to really respect. So I really enjoy working with them. And right now we've got a lot of the weanlings who are out there. just stopped nursing. They're about 30 days old and they're the cutest. It's the cutest part of their life. So it's good out there right now. Well, tell me about your research project. How have you and your colleagues been studying the seals?
yeah so um the research that we do is part of a long-term program that's been going on for over 50 years at uc santa cruz and there are two parts to it one of them is this long-term demographic study. So when seals are born, we tag them with cattle ear tags on their flippers so we can track them over their lives and we can see when they have a pup, when those pups have pups, and so on. So that's one really important aspect of the work that we do.
And the other important thing is we put out satellite tags and other kinds of instruments on the seals as they go off on their long foraging migrations. Because unlike a lot of other seals that spend a lot of time near the coast, our elephant seals... are on land for only about two or three months out of the year, and the rest of the time they're on these extremely long foraging migrations.
out into the open ocean. And we found from tracking them with GPS that the seals will swim thousands of miles offshore and dive to thousands of feet below the surface. Wow. Well, how did you figure out how to use these elephant seals as sentinels to find out what's going on in the mysterious Twilight Zone? Yeah, so elephant seals spend most of their lives down there in the Twilight Zone, but...
Luckily for us, unlike most other Twilight Zone animals, twice a year they're coming back on land and giving us lots of opportunities to track and measure them. So we collect measurements of how much they weigh, how often they...
give birth, how long those pups survive, and how well that they do in the rest of their lives. And we were able to connect that to oceanographic conditions more broadly to show that when ocean conditions are favorable, we have more successful females with bigger pups and those pups are more likely to survive. Okay, now before we go any further, how do you weigh an elephant seal that can weigh up to 2,000 kilograms?
Yeah. So for this data set, we're mostly weighing those weanlings I was talking about, the one month old weanlings, which are still pretty heavy, still about 160 kilograms at 30 days old. But we've got a carbon fiber. tripod and a big bag that we were able to put those in. It's a workout for sure, but it's pretty cool. And to weigh the adult females, we use the same tripod, but no bag for them.
Wow, that's an amazing feat. So what did you find when you examined both the size of the seals when they came back and their birth rates and the size of the pups? What we were able to find was that in years that had favorable oceanographic conditions, the seals did a lot better. They ate about a kilogram more fish per day.
which meant that overall they gained 20% more mass in years with favorable versus unfavorable conditions. And that cascaded throughout their whole lifetime. So a female that was eating a lot of fish. meant that she was four times more likely to give birth and have a nice fat pup. And then if that pup is big, then it's six times more likely to survive the first year of its life. And then that advantage continues to last during their whole lives.
And the seals that are born in those favorable years will ultimately produce more than twice as many pups themselves. So what kind of variations have you seen then in how many fish are in the sea over that time period? Yeah, so we were able to kind of back calculate what we think was happening in the mesopelagic during those times. And in the years with worse conditions, we definitely see a lot skinnier seals and a lot fewer pups in general.
Why is a seal the best way to tell us about this zone in the ocean and how many fish are in it? I think that one of the best reasons is because they do spend so much time down there, but unlike any other animal, they're... actually coming up onto land, not only...
to a place that's accessible, but somewhere that's only 20 minutes from our lab by car. So that's pretty convenient for us considering how inconvenient it is to get to the Twilight Zone. So that's pretty cool. It means that we don't have to send a robot. thousand meters below the surface that just gets that one tiny snapshot of that one time, which is really important work. But instead, this is kind of an opportunity to see what's happening over a broader scale and get a...
an idea of what's happening in the Twilight Zone as a whole. Why is it important to know what's happening in this dark part of the ocean? Yeah, there's really not very much information out there on the Twilight Zone. It's starting to be under more and more pressure, not just because of things like climate change, but also because there's so much biomass there, there is increased fishing pressure.
We need to know what's happening. Can't just let it be out of sight, out of mind. Just one last thing. When you're out on the beach with these animals, now that you know how far they go and how deep they dive, what impresses you about them? I think that one of the things that's impressive is just how athletic they are. They are really huge. And just knowing that they're so out of their element on the beach, I think it makes me wish that I could see them when they were in the...
in the deep dark ocean, because I feel like that's really their home. Ms. Payne, thank you so much for your time. Thank you so much. Ms. Alison Payne is a PhD candidate in the Beltran Lab at University of California, Santa Cruz. At the end of the last ice age, a group of hunter-gatherers called Magdalenians roamed much of Europe. They may be best known for their famous cave paintings in France.
But new research suggests they had a darker side, too. Human bones from that era, found in a cave in Poland, appear to show evidence of systematic and violent cannibalism. Francesc Marginetas led this latest research. He's a PhD candidate at the Catalan Institute of Human Paleoecology and Social Evolution in Tarragona, Spain. Hello and welcome to our program.
Thank you. Thank you very much for having me. Who were the people living 18,000 years ago in Poland? It's a good moment for these populations. It starts like a warmer period after the last glacial maximum. and these warmer conditions means more resources and also means an increasing on the population in europe And also there's a movement of population from the Western Europe to the center and the north. Some parts of Europe that were previously covered by ice because of the ice age.
So these people were moving around. Does that mean they were hunter-gatherers? Exactly. Yes, they were hunter-gatherers. Well, tell me about these particular bones that you studied. Matitska cave human remains. They were found in the 19th century. It's a very beautiful cave, about 20 kilometers from Krakow.
And there's more than human remains. There's also like some bones with very beautiful engravings. There's faunal remains that were also consumed. So these first excavations recovered all these materials. And then new excavations during the 80s recovered more specimens and allowed to have a better picture of what happened with all these remains.
So what did you discover when you studied them more recently? It was quite surprising because we started first studying these same bones that were previously published. And then we started taking a look on some boxes of fauna remains that they had in the same museum. And we discovered that there were some human remains.
mixed with these animal remains that's a very interesting thing because until this moment what we had was just skull fragments and now what we found it's long bone fragments from the arms and from the legs and this actually gives us a lot of information on how the bodies were treated like in a general way and not only the skulls. Well, what do you see on these long bones that suggest cannibalism to you? Basically, what we can see is the same that we can see, I don't know, if we eat at home.
like any any kind of animal it's based on cat marks when we use knives and we have this not only in the human remains but also in the fauna mixed in these in in this site and also we have like what we call anthropogenic breakage, which is very characteristic from all this hunter-gatherer behavior through the whole prehistoric times. Wow, signs of butchering. That sounds pretty grisly. Yes.
Well, what allowed you to detect these signs of cannibalism on the bones that had not been recognized before when they were studied last time? So using more complex microscopes allowed us to characterize better. the whole surface of these bones and to identify gap marks that were not previously identified. So we used a confocal microscope. which is a laser microscope that is very complex in characterizing
all these modifications. Oh, I see. So you can see much more detail in the cut marks of the bones. Exactly, yeah. And it's better to compare it with other modifications that are naturally produced.
Now, you mentioned you saw marks on the long bones, the arms and legs. What about the skull? Actually, skulls are very interesting because if we compare the skulls from this side to other Magdalenian sides, we have like... A major difference, for example, in Ghost Cave in the UK, there's this manipulation of the heads to manufacture an object called skullcap.
so basically it's the removal of the face and the lower part of the of the skull to preserve the upper part as as an object like with a bowl shape The function, we don't know exactly the function, but we know that it's an object manufactured specifically for the cannibalistic event. And in Machicka, we don't have that. So you're saying that in the Polish cave the skulls were not so carefully manipulated? Exactly, no. We think that they were just broken, defleshed, and broken to extract.
all the nutritional parts that we can find in the skull. So what are the reasons historically for societies turning to cannibalism? In general... we can say that there's like two major situations one is more related to to warfare to to the war a way to manipulate your enemies and the other one actually the opposite it's more related to the funerary world
And you consume your own relatives and members of your group and your family because you love them and you don't want them to be decomposed. So what do you think was the reason in this case? We think that Mechitska Cave is a case of warfare cannibalism because not only the marks we can see in the bone surface, but also because of the context, the context of the findings.
There's no sign of like a special treatment or respect, at least the way we understand respect today. And it's something that we can see and we can identify like in other. Cannibalistic sites like Ghost Cave in the UK, they were just like butchered and consumed. Is it surprising to find cannibalism like this in prehistoric humans? during the last one million year we have cannibalism almost in all the human species that lived in europe and the two main
periods in which we have cannibalism is during the Magdalenian and during the Neolithic. Interesting times to be alive, or not. Yes. Mr. Marginaitis, thank you so much for your time. Thank you so much. Francesc Marginedas is a PhD candidate at the Catalan Institute of Human Paleoecology and Social Evolution in Tarragona, Spain.
Despite decades of work trying to understand who we are and where we come from, there are still plenty of mysteries in evolutionary biology. To spot one of these mysteries, you just have to look in the mirror, at your ears. Humans and most mammals have an outer ear, which we like to adorn with jewelry, tug on to give baseball signals, and cover with headphones to listen to our favorite science podcast.
But how we got these strange cartilaginous appendages is an evolutionary puzzle. But new research from the University of Southern California has traced our ears to a very unexpected source. the gills of our ancient fishy ancestors. Dr. Gage Crump is a professor of stem cell biology and regenerative medicine at University of Southern California. He led the research. Hello and welcome to our program.
Thanks for having me. What makes our outer ears so mysterious? Yeah, so only mammals have outer ears. They're not in other vertebrates. And they're used in many ways. One is to funnel sound into the ear. They're also used as thermoregulation to modulate body temperature. And so it's really a mystery how such an amazing structure would...
kind of evolve seemingly out of nowhere from our non-mammalian ancestors. But we have other parts of our body that are made of cartilage, like my nose, for example. How are the ears different? Yeah, so the ears have actually a very unique type of cartilage called elastic cartilage, which is different from most of the rest of the cartilage in the body. And this allows our ears to be very floppy, but yet still have some support.
How this unique type of cartilage rose was quite a bit of a mystery when we started the project. Well, what led you to suspect it might be related to fish gills? We had no intention to work on the outer ear. We actually mainly work on zebrafish because it's a genetic model for a lot of birth defects that affect development of the human face and head. And so... While we're looking at zebrafish, we were profiling all the different cell types in the head.
And what we noticed is that they actually had two very different types of cartilage, one which we knew about, which was the typical cartilage. Then it had this other second mysterious cartilage type. And when we looked more closely at it, we realized that this was actually very similar.
to the elastic cartilage that's in our outer ears. And when we look at fish, this elastic cartilage was only in the gills. And so that really made us to wonder, could there be a deeper connection between gills and outer ears evolutionarily? Well, take me through your research. How did you study this to try to make that connection? The first thing we did is we looked at all the genes that are expressed where they make RNA and protein, because we have...
Every cell in our body has 25,000 or so genes, but each cell only expresses a small number of those genes, which makes our cells very different from one another. So what we did is we essentially, using DNA sequencing... We looked at all the genes expressed just in these special gill cartilage cells. And then we actually did the same thing for the human outer ear. We looked at all the genes that they made. And when we compared them together, we actually found that there are...
very similar in the types of genes that they made. Okay, so once you saw that the genes involved in the zebrafish gills are the same genes that are involved in our ears, how did you proceed from there? Yeah, so this was... I think one of the conceptual leaps of the project. And what we looked at is not only the genes themselves, but the pieces of DNA which control where those genes are made in the developing embryo. And what we found is that these...
pieces of DNA that control expression in the fish gills can also control gene expression in the mammalian outer ear. So if we take this piece of fish DNA and we put it in a mouse to make a marker protein... That piece of DNA that controls gill expression in fish actually controls outer ear expression in mouse. And then if we do the opposite experiment, if we take these DNA control elements...
from the human outer ear and we pop them into the zebrafish genome, they can turn on fluorescent proteins in the gills of zebrafish. And remarkably, some of these DNA sequences are actually conserved. They're the same sequences present in our genomes, even though we don't have gills. And what has happened is that this DNA element, it's still there in our genome because now it has a different purpose to make an outer ear rather than a gill.
That's astounding. So let me see if I got this right. You're saying you take the genes that make the gills and the fish, you put them into the mouse, and it lights up in their... ears and then you take the genes from ears and put them into fish and it lights up their gills. Yeah, essentially. Yeah. Wow. Were you surprised by that? We were. You know, we had this hypothesis that there may be similarities, but I think the most striking moment is when we took one of these pieces of DNA near us.
fish gill gene, and we made a mouse. And when we looked at the mouse, the outer ear just lit up compared to all the rest of the mouse. And so that really kind of convinced us that there was this deep similarity between gills and outer ears. But they're very, very different structures with different purposes. I mean, Gil's...
take oxygen out of water. Ears take sound out of the air. They don't even look alike. Yeah, so I think that's what has made it so difficult to figure out where outer ears came from during evolution. because there really is nothing similar looking in other non-mammalian vertebrates. And also the outer ear and its cartilage is not mineralized like bones, so there's no fossil record of these transitions.
So how do you think the sequence worked from crawling out of the water to mammals? That's a long road. In order to kind of look at that road, we actually did some work on frogs and lizards as well. And what we find is in frogs... The tadpole stage, they also have gills. And so what we did is we took these fish gill DNA sequences or the human outer ear sequences. We also put them in frogs and their tadpole gills lit up as well.
And then the last link is, well, when amphibians became reptiles before they became mammals, what happens there? And so we actually, we weren't able to do, put DNA into lizards. It was too technically challenging, but we did look at their ear canal and it turns out their ear canal. has very similar elastic cartilage to our outer ears. So what we think is that somewhere between amphibians and reptiles, this elastic cartilage moved from gills to the ear canal.
And then when mammals evolved, they essentially just grew out their ear canals to make these very extended outer ears. Wow. So how far back in time do you think these genes go? Yeah, so that was the other very surprising part of the story is we actually looked even before fish. So it turns out that there's a lot of marine invertebrates, such as horseshoe crabs, that have gills.
And in their gills, they have structures that look very similar to cartilage in us. And so we actually also looked at horseshoe crab gills and their cartilage. And what we found is that their DNA control elements from a horseshoe crab... If we put them in a zebrafish, it also lights up in the gills. So what we think actually is that this elastic cartilage may be this remnant even before vertebrates evolved.
very distant to marine invertebrates, something like a horseshoe crab or a trilobite. And this might be the most ancient type of cartilage on that. So one way to think of it is that our ears kind of contain this remnant of invertebrate cartilage, whereas the rest of the cartilage in the bone in our body is really what's new about being a vertebrate. So how far back in time are we talking here?
Probably somewhere at least 400 or 500 million years of evolution. So pretty distant. That's astounding. That's astounding that these genes would be recycled so often and repurposed over such a long period of time. Yeah, I think it just... reinforces this idea that evolution's a tinkerer. It's not coming up with completely new things, but kind of reusing programs that have been around for a long time to do things that are very different with them.
Kind of makes you wonder what it's going to do next. Yeah. Dr. Crump, thank you so much for your time. Yeah, it was a pleasure talking with you. Thanks for having me. Dr. Gage Crump is a professor of stem cell biology and regenerative medicine at University of Southern California.
If the New Year's resolution you made to read more books is not quite panning out, don't sweat it. I've got you covered. I'm Mateo Roach, and my new podcast, Bookends, is all about discovering great books and getting to know the writers behind them. Like Brian Lee O'Malley, whose personal connection to Toronto helped him create the icon, Scott Pilgrim. Bookends with Mateo Roach is available now wherever you get your podcasts.
I'm Bob McDonald and you're listening to Quirks and Quirks on CBC Radio 1 and streaming live on the CBC News app. Just go to the local tab and press play wherever you are. Coming up later in the program... Dark times for dark energy. Some cosmologists suggest new observations mean we should re-evaluate our understanding of how the cosmos works and have a new theory. It's about time.
And it's fundamentally different from the standard model of cosmology because it abandons this assumption that the universe is the same and uniform in every direction. If you own a pet rabbit... you know that, given a chance, they will chew through most things. Enclosures, carpets, furniture, even electrical cords. This is because their teeth are continually growing.
So they need to constantly gnaw on something. But their constantly growing chompers have to be made from something. And that something is the vital, but sometimes scarce mineral, calcium. And that intrigued Dr. Johanna Makitaipala. She's a veterinary orthopedic surgeon who has investigated how rabbits get enough calcium. And what she's discovered is that rabbits are gifted recyclers.
Dr. Maki Taipala is a postdoctoral researcher at the University of Helsinki, Finland. Hello and welcome to our program. Thank you for the invitation. Now, I understand that your study all began with a broken leg. Yes, yes, that is true. When I was newly graduated veterinarian and also a rabbit owner. I heard stories from my orthopedic colleagues that fractures in rapids are really tricky to treat.
Bones are fragile and break easily during surgery or refracture again soon after the surgery. I broke my own leg and I was lying on the couch for a couple of months. been a bit bored and suddenly got an idea. Why do rabbits have such thin bones? I think it's because they are prey animals. So rabbit bones, they are long. light and there is minimal amount of cancellous bone inside the long bones like tibia.
So this makes rabbit bones like hollow glass tubes. So when they break, the fracture is complex and has a lot of fissures. So when... dealing with fractures in rabbits, we need to take these things into consideration. Well, tell me about your study. What did you try to look at in the rabbits' calcium intake? A research group in Zurich had made a study where they showed that the growth rate of rapid... teeth is depending on the diet. So it means that when the rapid eat diet that is very abrasive.
the tooth grade is greater, so they are growing faster compared. to rabbits that have softer food, so non-abrasive diet. And that made me think that if the rabbits need all the calcium... for the dental growth from their diet. So then people should know how abrasive the diet is, how much they should give the calcium for the rabbits. And I thought maybe rabbits are able to reuse.
which is released from their dental tissue and reuse it for the dental growth. Oh, I see. You're saying if the rabbits are eating abrasive food, their teeth are being ground down? And they're ingesting the calcium from their own teeth. Yes, that's true. How did you test that? We made this study where we had eight rabbits divided into two groups. And these rabbits were... fed with two different diets for 15 days.
each. After 15 days, the diets were changed so that both group ate both diets and these two diets were otherwise identical complete pellet diets. But the source of calcium was different. In the first diet, the calcium carbonate and the calcium phosphate were used as a calcium source. And the other diet... contained ground rabbit teeth as calcium source. Wow. Yeah, yeah, that was, you know. So in one diet, it's a calcium supplement and the other one is teeth. Yes, yes.
And what results did you see? Yeah, that was very interesting. The results showed that rabbits can use very well the calcium from the ground teeth. And this means that we don't need to exaggerate the amount of calcium in rabbits' diet because the dental grows. So they can reuse, like recycle the calcium that is released from there. Now, you're saying, though, that that's when they're eating abrasive food, their teeth are going to go down. But what if they're eating soft food?
In case the rabbits are eating more soft food, then the dental growth is slower. So that means they don't need that much calcium for the dental regrowth. So therefore, the need for... calcium is less. So for rabbit owners such as yourself, what's the best diet for them? Well, rabbits should eat hay and grass. That's absolutely the best diet for them and should be... at least 80% of their daily diet. And also during the summertime, some non-toxic wild plants as well. And in the wintertime...
We can get some herbs and salads and kale from grocery stores. Now when you had these two groups, the ones on the calcium supplements and the ones on the ground teeth, was there a difference in the amount of calcium they were absorbing? Yeah, they actually used better ground teeth. It was a better calcium source. How has this changed the way you look at your own rabbits? Well, years and years.
people have been thinking that we need to give a lot of calcium for rabbits in their diet, that calcium deficiency is very common in domestic rabbits. But this study showed that that's not true. Rabbits will reuse the calcium that is released from their dental tissue. So, of course, they need calcium in their diet, similarly as other animals and humans. But we do not exaggerate that because that can cause also some problems if we overfeed calcium for them. For example, urinary stones.
I think the feeding of pet rabbits and domestic rabbits, if you stay on hay and grass diet. and you only give small portion of these commercial rabbit diets, and you give pelleted diets, then I think pet rabbits will do quite okay. And also... The amount of this commercial food should be limited. So when it comes to calcium, rabbits are very good at recycling. Yes, they are really good in that. Dr. Maki Taipala, thank you so much for your time.
Thank you very much. Dr. Johanna Makitaipala is a veterinarian and postdoctoral researcher at the University of Helsinki, Finland. There's a cosmic controversy brewing in the universe. It centers around the theory of dark energy, a theory that emerged as the result of a 1998 discovery that led to the world's greatest prize in science. The Royal Swedish Academy of Sciences has decided to award the 2011 Nobel Prize in Physics.
for the discovery of the accelerating expansion of the universe through observations of distant supernovae. After that discovery, theoreticians immediately began to try to understand how this was happening. They conceived of something that became known as dark energy, that was pushing the universe apart, and thus was responsible for this anomalous expansion of the universe.
But since that discovery, astronomers have been measuring more and more supernovae, as well as other bright objects in the distant universe. And they've started to see a problem. Not all parts of the distant universe seem to behave the same way. This has led some to explore a new theory. dubbed the Timescape Model, that might explain the behavior of the universe on the largest scales a little better.
Dr. Ryan Ridden has been working on this problem. He's a Rutherford Postdoctoral Research Fellow in Astronomy at the University of Canterbury in New Zealand. Hello and welcome to our program. Thank you for having me. It's a pleasure being here. Now, first of all, let's take this a little slowly and start back in 1998. What exactly was observed at that time that reshaped our picture of the universe's development?
Yeah, so we've been using a specific type of exploding star called a type 1a supernova to try and map out the evolution of the universe's expansion throughout its... lifetime and type 1a supernova are a very particular type of exploding star where we've come to understand them very well we understand how they should be exploding and that lets us understand how bright they should be. So if we understand their fundamental brightness and we measure how bright they appear
to our telescopes, we can actually calculate a distance between us and that object as much the same as if you hold a torch up close to your eye, it looks incredibly bright. But if you take that torch far away, it looks dimmer. The torch hasn't changed its brightness, just the distance between us has changed. So that's one of the fundamental measurements. Another one is something we call redshift. So this is just a measure of how much...
that same light coming from the supernova, has been stretched out to redder wavelengths from the expansion of the universe. So by combining this distance we measure from light and the redshift, we can begin to piece together how the universe has expanded over time. Okay, well that's all nice. So where did dark energy come in to explain this?
So if you go forth and observe a whole bunch of Type 1A supernova, as they were starting to do in the late 80s and then into the 90s, you could start to piece together a picture of building up a data set. that lets us test our cosmological models. So these are the things that we use to model how we expect the universe to change and evolve over time. And the really interesting thing that came out of the supernova analysis is that they didn't fit our
explanation where we expected that the universe would have started expanding from the big bang and then gravity should start slowing things down instead it looked like the universe was accelerating in its expansion which is quite bizarre it's like saying well if you jump you would suddenly start accelerating faster and faster upward. Gravity didn't really seem to be playing a major role in these measurements. So this is where this idea of dark energy has come from.
notion that there is something else in the universe that we don't understand, which is pushing against. the universe itself to make it expand faster to fit the data that we observe with supernova. Since then, other sources of data have come up, which also... agree with this interpretation of there being an accelerated expansion, but as we're exploring now it's not the only way that you can produce these results.
Okay, so the dark energy, and I know when scientists say dark, that means we don't know what it is, but it's pushing against gravity. It's pushing the universe out. So here we are 25 years later, more than that. What's proving to be the problem with the idea of dark energy? So the idea of dark energy is kind of built on a very big assumption. So it's an assumption that the universe is a kind of featureless fluid. It's the same in all directions everywhere on a certain scale.
And this fluid, if you go through and do the equations, you need to have this idea of a dark energy-like substance to fit observations with the data. cracks that are starting to emerge with a few different things, like we're starting to see irregularities in the distribution of very distant objects in the universe, which you shouldn't expect if the universe is uniform.
and the same in all directions. We're also starting to see problems with other measurements, so measurements of distributions of... galaxies in the universe, we expect the distribution of galaxies to be kind of controlled by things that happened very early in the beginning of the universe when the universe was small, hot.
and dense, and sound waves could propagate through. So these sound waves in the very early universe kind of set up a fundamental scale for which we begin to find galaxy clusters sitting along. and there was a recent result by the dark energy spectroscopic instrument which showed that this idea of Dark energy doesn't quite explain their measurements either. They were starting to think that perhaps something like a time evolving dark energy would be necessary to explain their observations.
So what our telescopes are seeing and measuring doesn't match the dark energy model. Is that the idea? Yeah, so that's pretty much what it's coming down to. The standard model of cosmology is an incredibly good descriptor of the universe. as with every model, they're only true insofar as they can reproduce the data. And now that we've got all of these enormous and incredible surveys going on in astronomy that are collecting...
enormous amounts of data that dwarf any data set that we've had before, we're starting to see or test the very limits of this model. And we're starting to see, at least from my perspective, that Perhaps the assumptions that we're making to build the standard model of cosmology don't quite match up with what we're seeing in the universe around us.
The universe isn't cooperating with us. Yeah, it's unfortunate when that happens, but it can lead to some really cool discoveries. Okay, well, let's go to the alternative explanation that might fit... the universe a little better. Tell me about your new Timescape model. How does it work? Yeah, so the Timescape model is the creation of Professor David Wutcher, who's a general relativist and cosmologist here at the University of Canterbury. And he's been working on it for a while now.
And it's fundamentally different from the standard model of cosmology because it abandons this assumption that the universe is the same and uniform in every direction. Instead, the basis of the timescape model is that... In fact, we see in the universe around us today that there are giant cosmic structures, so enormous...
filaments and walls filled with galaxies and galaxy clusters. And in between those filaments and walls, we have giant voids of nothing. We don't find galaxies sitting inside these voids. So you can imagine it like blowing air into a...
water filled with soap you get all the bubbles forming on the surface so this is kind of what our universe looks like today we have galaxies forming along the edges of the bubbles and where the bubbles meet and then in the middle there is pretty much nothing going on So the idea with timescape is that these structures will play a significant role in the evolution of our universe. And the way that they work is that in general relativity...
There's this idea that acceleration or deceleration changes the rate at which time passes for you. So the faster you decelerate or the faster you accelerate, the slower your clock will tick. So if we go all the way back to the early universe, where it was very smooth, hot, and dense, there are tiny, tiny differences in that early universe, slightly denser regions and slightly less dense regions.
So what we expect to happen is that gravity will pull more on these more dense regions. So the acceleration that these regions feel is greater than what the less dense regions will feel. Okay, so let me just see if I got this right. The universe started out fairly smooth, but there were little lumps that appeared. And over time, these turned into filaments, your soap bubble model. And it's along where the edges of the bubble are. That's where galaxies are.
masters more gravity and that's going to affect time yeah so um The universe starts expanding from the Big Bang. There's just one kick, and the universe is expanding away. Now, in the timescape model, there is no dark energy, so you just have gravity that's pulling on the universe, trying to slow it down.
And because there are small density fluctuations in the universe, gravity is pulling on some parts of the universe more than others. And as gravity pulls, it slows down the expansion of those denser regions.
and this difference in acceleration between the more dense and less dense regions isn't necessarily a lot but if you fast forward through the history of the universe and measure the cumulative impact they have it has quite a significant change on the time that passes in those regions to the point where for us observers sitting inside dense regions of the universe
We would find that the universe is perhaps around 14.2 billion years old, but for the very middle of these giant voids, you might find that they are in fact 21 billion years old. So time is ticking differently for these different regions. In the empty spaces, time is passing more quickly than in the dense places where we are. Yeah, exactly. So it's to do with the deceleration of...
the universe is giving us this timescape of varying times across the universe. Because quite often when we're thinking about cosmology and the standard model,
We just assume there's one fixed time for the entire universe. In fact, it's quite common for people to say that the entire universe is around 13.7 billion years old. But we know from general relativity that these effects must... have some kind of impact so the timescape model goes to kind of the the fundamental basics of cosmology questions the assumptions that we're there, and then builds this new model which incorporates more aspects of general relativity into it.
So how do these two effects, that time travels more slowly in the dense regions of the universe and more quickly in the voids, add up to what looks like a universe that's accelerating, that's speeding up? Yeah, that's a very good question. So as the universe is... experiencing these different time frames, you also see that these dense regions begin to contract. They're getting smaller.
Whereas the less dense regions are expanding more or less at the same rate they were at the beginning of the universe. So over time, the total volume of the universe will become dominated by... this kind of empty space that's expanding at the same rate. So what this has for observers like us and dense regions, the effect is that when we look out across these great big...
void regions, the cumulative effect is that it begins to appear that the universe is accelerating in its expansion. Wow. So the voids are still expanding at kind of the same rate they were at the Big Bang, perhaps a little bit slower. But from our perspective, we're seeing an apparent acceleration. So it still fits the same supernova data. It's just what we could...
claim to be an acceleration, is just the result of our position in the universe, this kind of mass-biased position that we have. Okay. So the universe is expanding, but it's just not speeding up. That's it. Yeah, pretty much. It's a perceptual thing rather than a physical thing. Well, tell me about what you've been seeing in observations of supernovae more recently.
Yeah, so the most recent study that we've conducted is taking a supernova sample called the Pantheon Plus sample. Now, this is a fantastic achievement by the Pantheon team. They've accumulated... supernova observations since the 1980s to build a fairly unified sample of around 1550 type 1a supernova. And this enormous sample set allows us to make very precise tests of cosmological models. Because while we may say that perhaps the standard model of cosmology
isn't the correct description of the universe, it is still a very good description of the universe. So any model that wants to kind of compete with the standard model needs to make very similar observational predictions. So if you need to distinguish these two models, you need a very big data set that's very precisely calibrated and the errors understood quite well.
So how does this new enormous data set fit the timescape model versus the standard model? So this was kind of the crux of our recent paper where we did a direct comparison between the timescape model and... the standard model of cosmology. And what we found in our analysis by comparing against the entire data set is that the timescape model was strongly preferred over the standard model of cosmology.
However, if we started cutting away the close-by supernova, we saw that preference begin to decrease until it was... Pretty much both models fit the data just as well as each other. But then the interesting thing, for me at least, was when we went past the distance at which even the standard model of cosmology considers the universe to be smooth and the same.
in all directions, the timescape model was slightly preferred over the standard model of cosmology. So the really interesting thing here is that we could... at least produce slightly favorable results with the timescape model without the need for a completely unknown quantity in the universe, this dark energy. We could explain it just from the principles of general relativity.
So your model works back when the universe was younger and smoother. Yeah, so it can go from completely smooth universe up to the modern universe where we have large-scale cosmic structures. Okay, so in your timescape model, invoking the concept of dark energy isn't necessary. No, we don't need it at all. And we don't need it to explain the supernova data.
Alright, so if we don't need dark energy, what does this mean for the ultimate fate of our universe? Yeah, it's a very fascinating question, right? Because a lot of our understanding of the evolution of the universe has been driven by this idea that it's accelerating. But in the timescape model, it's not accelerating. It's just kind of going along more or less at the same rate where the voids are slowly, slowly decelerating over time.
So if we were to run the clock forward an incredible amount, so trillions upon trillions of years, then perhaps you could imagine that gravity slowly wins out and it's... starts to stop the expansion of these voids and brings everything back down. Or it could be that gravity never quite gets over...
the expansion of the universe, and the universe just keeps expanding continuously. The main difference, I guess, between timescape and the standard model of cosmology here is that in the standard model... The universe is always accelerating. So eventually, even nearby galaxies should just be picked up and run away from us. So we'd be left in kind of this isolated universe where...
a small galaxy cluster will be left on its own. In Timescape, you would have galaxy clusters sitting on these kind of soapy edges of the bubbles. all still could see each other, but the centers of these bubbles would grow absolutely enormous, so you'd only be able to look at your nearby companions. So it wouldn't be quite so lonely at the end of the universe. No, no. As David Wutcher likes to say, astronomers would still have a job to do in the late timescape universe.
So what will it take to convince everyone that your timescape model is the one that defines the universe and that we don't need dark energy? Yeah, this is a very good question. And it's one that the creator of the model has been kind of contesting with since around 2007, 2008. And so far, it's been just the lack of precise data, which has limited.
At the moment, the biggest question that we've been getting is, sure, the supernova data can be explained with the timescape model, but the distribution... of galaxies in the universe through measurements known as baryon acoustic oscillations. they can't be explained well by Timescape at the moment. So that's actually a big area of active research we're working on, is trying to extend the Timescape model so that we can do these measurements and see if they do agree with Timescape.
While Timescape seems to kind of go back to the fundamental basics of general relativity, it does make some calculations a little more challenging. So it's a little bit of work for us to extend it to these different areas. So the universe is still ahead of us in understanding. Just one last thing.
Do you feel like you're on the edge of another revolution in our understanding of the universe? Like going back to Hubble, discovering that our Milky Way is not alone, that there are other galaxies out there, it's much bigger than we thought, that the universe is expanding. Now you're on another... sort of perceptual change here? Yeah, it's a very fascinating point to be in in cosmology. I don't know if necessarily timescape will be the thing that causes the change, but I think...
The community is starting to feel it now, where there's enough data starting to mount up to suggest we do need a fundamental change in cosmology. That this idea of dark energy isn't quite cutting it anymore. Dr. Ridden, thank you so much for your time. Thank you. Dr. Ryan Ridden is a Rutherford Postdoctoral Research Fellow in Astronomy at the University of Canterbury in New Zealand.
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