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00:30
This is a CBC Podcast.
00:34
Welcome to the Best of Quirks and Quarks. This program was originally broadcast on June 27, 2026.
00:46
Hi, I'm Bob McDonald. Welcome to Quirks and Quarks, and yet another edition of our always intriguing, always enlightening listener question show. Now, we've been answering your burning science questions for the past 50 years, so surely by now we've answered every question there is to answer, right?
01:05
When I go into a sauna, what exactly am I sweating out?
01:09
Ooh, that's fun. I don't think we've gotten that one before.
01:12
Why are cats' tongues rough and dogs' tongues smooth?
01:16
I never thought of that either. Why is that? Are comets eternal? Wow. Okay, I guess there are always more science questions for us to tackle.
01:26
Did any dinosaurs produce milk?
01:28
All right, all right, you made your point. You probably have another 50 years worth of questions for us to get to, and we love it. So let's get to it. All these answers and more coming up on the Quirks and Quarks Listener Question Show.
01:45
We've been answering your science questions since day one of this program, and we had some real doozies right out of the gate during our first season.
01:54
She sent in a very terse letter, and she wants to know, wart is a quark. Several listeners want to know about death.
02:03
What is a hangover?
02:06
For human beings, what is falling in love? Why the sky at night is as dark as it is. They don't really have smelly urine after they eat asparagus.
02:15
Columnist Richard Lubbock would handle all the answers back then. In that first season, after a particularly riveting interview with cosmologist Carl Sagan, we got a flurry of listener questions about black holes. Here's Richard speaking with David Suzuki on January 14, 1976.
02:36
And that seems to have attracted a lot of interest from people who have written in they want more information about black holes, And in particular, I got a letter here from Michael Martin of Ottawa, who is strongly skeptical about the whole thing. It seems to me, writes Mr. Martin, that astronomers are doing more fantasizing than fact-finding work these days.
02:57
Even though we now know more than ever about black holes, they continue to draw us in and spark questions about what they are and how they work. Like this one.
03:07
Hi, my name is Miguel and I'm eight years old. I live in Burnaby, British Columbia and my question is, I know the moon orbits the earth, the earth orbits the sun, and the sun orbits a black hole, but what does a black hole orbit?
03:24
For a cosmic perspective, we've turned to Dr. Jeremy Heil, an astronomer at the University of British Columbia in Vancouver. Hello and welcome to our question show.
03:34
Hello, Bob. Thanks for having me.
03:36
So does the sun actually go around a black hole?
03:39
Coincidentally, it does. The sun orbits the center of our galaxy.
03:45
And in the center of the galaxy, right at the center, is a supermassive black hole. And Supermassive means much more massive than the sun. And in fact, it's about 2 million times the mass of the sun. And our sun does go around it. However, it's not really orbiting the black hole because between our sun and the center of the galaxy, There's about 100 billion solar masses of material. So our sun is really pulled in by the gravity of all that material.
04:19
And the black hole just happens to sit in the very middle of it. So it's hard to say, you know, the sun doesn't really orbit the black hole. We don't really feel that much gravity from that black hole.
04:32
I see. So it's really the whole galaxy, our whole Milky Way galaxy is going around the black hole and our sun's part of that.
04:39
Exactly. And we're really feeling the gravity of the whole galaxy that pulls us around in this orbit.
04:47
How far away is our black hole?
04:49
Well, it's about 25,000 light years.
04:55
And what that is in kilometers is a lot of kilometers.
05:00
It certainly is. And how long does it take us for our galaxy to turn for us to go around that black hole once?
05:07
It takes about 230 million years for our sun to go around the center of the galaxy. So if you think about it, our sun has only taken about 20 circuits. And we call those loops galactic years because it's sort of like the earth going around the sun is one year. The sun going around this galaxy, we call a galactic year. So, you know, our son is a baby. It's only 20 years old, 20 galactic years, that is.
05:39
Okay. So that's us going around the black hole. So our question, Miguel wants to know, what does the black hole orbit?
05:47
Well, it turns out that the black hole in the center of our galaxy has a whole bunch of stars orbiting it. It's the most massive object down there. And people have measured the motions of those stars to measure the mass of the black hole. And also people have even taken images of the black hole with radio telescopes as well.
06:13
And in general, there are sort of two types of black holes, these supermassive black holes that are in the centers of galaxies. And then there's black holes that form from the death of stars. And until recently, all of the black holes that we have seen that form from the death of stars have another star orbiting and they're accreting from that second star. But over the past 10 years, we've discovered black holes that are orbiting other black holes because they emit gravitational radiation that we can detect.
06:49
And we've also found black holes that are orbiting stars that are far away from them. So we just see the, not that any matter is falling into the black hole, but we just see the motion of the other star Because it's orbiting a black hole, we can tell from its motion across the sky that there's a black hole there. So our pictures of black holes or knowledge of black holes has expanded dramatically even over the last 10 years.
07:20
Okay, so black holes could orbit other black holes or other stars. But if we look at the whole Milky Way galaxy that we live in, does it, along with the black hole, orbit anything else?
07:35
Well, our galaxy and the Andromeda galaxy, which you can even see with your naked eye here in Canada, if you're in a dark place, those two large galaxies are orbiting each other. And eventually the orbit isn't very circular. So the Andromeda galaxy will run into our galaxy in a few billion years. So our galaxy is part of a little group of galaxies that we call the local group. And they're all orbiting each other.
08:07
Dr. Heil, thank you so much for your time.
08:09
Thank you very much for having me on.
08:12
Dr. Jeremy Heil is a professor of physics and astronomy at the University of British Columbia in Vancouver.
08:23
Our next question is all about sweating the small stuff.
08:26
Hello, Bob. My name is K.J. Cooper and I'm in Victoria, B.C. My question is, When I go into a sauna, what exactly am I sweating out?
08:36
Dr. Pascal Imbo, an exercise physiologist at the University of Ottawa, is here with the answer. Hello and welcome to our show.
08:44
Thank you, Mr. McDonald. Thank you for inviting me. So when we go into a sauna, what exactly are we sweating out? Basically, it's water. 99% of the sweat is composed of water and we sweat a bit of electrolyte. And that's why when we taste sweat, it's a bit salty.
09:01
And some people may think that we also sweat some toxicants that we accumulate in our body, but this is very, very negligible. So I would say that mostly you're sweating sweat or water. Oh, so it's not detoxifying, as we're often told? That's correct. This is a claim that a lot of people think of or that we hear about. But, you know, I would say that, you know, when you were releasing this sweat, you do eliminate a small amount of, you know, toxicant. But this is very, very negligible.
09:33
So there's no evidence on there supporting that sauna is a primary detox method.
09:39
Okay.
09:40
So what kind of health benefits does going into a sauna actually provide then?
09:44
Oh, there are some great benefits of, you know, having a sauna on a regular basis or just one shot sauna is actually very good. So there are some physical and also mental health benefits. So physically speaking, one thing that you're going to encounter when you're going to get into the sauna is to feel the heat. And this heat will basically... increase the blood vessel of your body and this will favor the dilation of your blood vessel and then increase the blood flow in your system. So basically that makes your heart pumping a little bit, even if you're in a passive mode while you're in the sauna.
10:17
So this is the physical kind of benefit of it. Mentally speaking, there are some studies out there that shows, and we feel it also when we are out of the sauna, it creates deep relaxation. So it favors the release of these feel-good hormones that we call endorphins. And these are the benefits of taking a sauna on a regular basis or just a one-shot deal sauna.
10:41
Now, I noticed that a lot of saunas have several different benches in them. Is there a difference if you sit low down or higher up?
10:49
There is, yeah. It's a bit like when you're, you know, in a hot day in a house where you've got air conditioning. If you go in the basement, you'll feel a bit cooler. And if you go in your second floor, then you're going to feel a bit hotter. So it's the same in a sauna. So higher you are on a bench in the sauna, hotter it's going to be. So it's going to probably trigger a bit more sweating response. There's no benefit or, you know, better spot. It's basically depending on your comfort zone. So if you want to be hot right away, go on the top.
11:20
If not, you just go progressively start at the bottom and you can move up, you know, up to your sauna session. Yeah.
11:26
Now, most saunas have a sign on them, a warning sign, no more than 15 minutes or so in here. Why is it important to limit your time in there?
11:34
Yeah, the major reason why we suggest people, especially when you're not experienced with sauna, to stay not too long. In fact, 15 minutes is definitely a good time. guideline for that is just to avoid some dehydration because when you're in a sauna you basically lose water you know not substantially but you know to some extent so I'm just going to give you an example so if you stay for example for 15 minutes in a sauna you're going to lose probably around 300 to 500 milliliters of sweat so this is basically to avoid dehydration and
12:10
Dr. Imbo, thank you so much for your time. Oh, I appreciate. Thank you. Dr. Pascal Imbo is an exercise physiologist at the University of Ottawa.
12:24
Our next question is so bright, you might want to wear shades.
12:29
Hi, my name is Jim Tiro from the Okanagan Valley in British Columbia. My question is, how do animals and birds such as polar bears and living on ice and snow, and the albatross living with a lot of ocean glare, protect their eyes from damage from continual bright, high UV light.
12:46
And here with the answer is Dr. Amber LaBelle, a veterinary ophthalmologist at Bright Light Veterinary Eye Care in Ottawa. Hello and welcome to our listener question show.
12:56
Hi Bob, thanks for having me.
12:58
So first of all, what is it about UV light that's so damaging to tissue?
13:03
Lots of types of energy come from the sun. Everything from the visible light spectrum that we see to infrared rays that warm us up to UV light. And so UV light or UV radiation is absorbed into the body and that UV radiation can actually damage the insides of the cells that make up our bodies. So one thing that can get damaged inside is the DNA. Remember, DNA is like the blueprint or the roadmap for how a cell functions.
13:36
Or the actual organelles, which are the working machinery and parts inside of the cell.
13:43
So what's the difference then between, say, skin cells and eyeball cells and how they respond to UV light?
13:50
Skin cells and cells on the surface of the cornea, the cornea is the clear windshield at the front of the eye, theoretically are very similar. They're all epithelial cells, cells that belong on the outside of your body. But the reason that your skin isn't see-through, which we all agree would be kind of weird and gross. is because your skin epithelial cells have pigment in them, and they're also keratinized, which means as they go through their life cycle, they actually develop a thick layer of keratin in them before they slough off.
14:23
On the other hand, the cells of the cornea, that clear windshield at the front of the eye, They have no pigment and they're not keratinized. And that's what enables them to be transparent. So what that means for UV light is that skin cells are going to be a little bit more resistant to the impacts of UV light because they've got that pigment to protect them. Whereas the cells of the cornea are going to be more susceptible to UV damage.
14:48
Oh, that's because the UV light can go through the transparent cornea deeper into the eye.
14:53
That's right.
14:54
So what's the result? What kind of damage does UV do to the eyes?
14:58
So you may have heard of something before called snow blindness. Snow blindness from a medical perspective is a form of photokeratitis. Photo meaning from the light and keratitis meaning inflammation of the cornea or the surface of the eye. So when you've been out skiing on a bright, sunny spring day where you've got bluebird skies and lots of sunlight bouncing off of the snow, that reflected uv light damages the surface of the eye and those epithelial cells that can cause wounds on the surface of the eye conjunctivitis and really really severe eye pain wow okay well let's get to jim's question then what about the animals like polar bears that live in the arctic environment and albatross that live over the ocean Let's talk about the albatross first.
15:48
So albatross, by virtue of their huge wingspan, can spend incredible amounts of time like days on end soaring around over the ocean with very, very little muscular effort expended. So you would think that they'd be exposed to a lot of UV light reflected from the ocean. However, because they're so high up in the air, the minimal amount of UV light that is reflected from the surface of the ocean is not really going to be impacting albatross eyes.
16:19
So we don't have to worry about our albatross friends. On the other hand, our polar bear friends who are living on snow and ice, there are very good reasons to be concerned for them. So snow and ice have a very, very high albedo. And albedo is a measurement of the amount of reflectivity of the surface of something on Earth. Fresh snow covered ground has an albedo of about 0.85, which means 85% of the light reflects back off the surface of the snow.
16:53
That means you're getting very high UV light exposure when you're standing on a fresh snowy surface.
16:58
Wow. So if snow is 85% reflective, how does that compare to the ocean?
17:05
The ocean actually has the lowest albedo of any surface on Earth at 0.1. So the majority of the rays that come from the sun are actually being absorbed by the ocean.
17:19
So how then do animals that live in these snowy conditions protect their eyes?
17:24
They've got a couple of features that help them out. One is that they're going to have bushy, thick eyelashes. They're going to have dark eyelids and they're going to often have dark irises. And so the eyelashes and dark eyelids kind of act like natural sunglasses, whereas the dark iris prevents the light from going in the eye and then getting reflected back and hitting the backside of the cornea.
17:50
Dr. LaBelle, thank you so much for your time.
17:52
Thank you, Bob, for having me.
17:53
That was Dr. Amber Labelle, a board-certified veterinary ophthalmologist in Ottawa.
18:04
Next up, an egg-cellent question about conspicuously colored bird eggs.
18:10
Hi, my name is Tina Hopkins from Delta, British Columbia. My question is, why are a robin's eggs such a beautiful blue?
18:20
Here with the answer is a biologist who actually studied the evolutionary side of this question. Dr. Felina English is a biologist with Fisheries and Oceans Canada in Nanaimo, BC. Hello and welcome to our question show. Hi, thanks for having me. Now, blue is not a very common color in nature, so where does this robin egg blue color come from?
18:43
It actually comes from common pigments in our bodies. It's derived from our hemoglobin. The hemoglobin ring breaks down into what's called biliverdin, which has a blue-green color, and they deposit that into the shells while they're developing in the oviduct.
19:00
So at what point through the egg-making process does the pigment get added to the shell?
19:06
So it varies a bit. With the blue pigment, it has to happen a little bit earlier in the process because the blue shows up on the inside of the shell as well as the outside. So it's being deposited early enough in the shell development to soak in all the way through the shell.
19:24
Whereas brown pigments are much more...
19:27
either patchy in the shell, so put on kind of like an inkjet printer or a paint gun in small spurts, more so on the surface of the shell.
19:38
Okay, so it's blue all the way through. But if this biliverdin is a blue-green pigment, why are the robin's eggs powdery sky blue?
19:48
Well, the reality is they aren't when they're fresh and in the nest. They vary. They're not all the same richness, but some of them are really deep, rich blue-green. But once the egg is broken and the shell dries out, all you have then is the white crystals that make up most of the shell scatter light in a pretty much pure white. And then I guess that fades out the green component and mostly you're left with the blue.
20:16
Now, you would think that blue eggs that the robins lay would make them easy to spot for predators. I mean, what's the evolutionary advantage for robins to produce such a conspicuous egg color?
20:28
And that's one of the wonderful mysteries of biology still. We don't really know. To some extent, they may be a little bit less conspicuous than a pure white egg.
20:40
But then why wouldn't you just make it a brown egg that was totally inconspicuous?
20:45
And there's a number of theories out there.
20:48
For one thing, once you have a big cup nest, like the kind of nest a robin makes, the nest itself is already conspicuous. So how camouflaged your eggs are may not matter so much.
21:03
It may be like a sunscreen, UV protection for the embryo.
21:09
And the brown pigment would work in a similar way, but it absorbs more heat faster. So blue may be a way of protecting from solar radiation without getting too hot.
21:22
Now, what about things like sexual selection?
21:24
Yes. So that's the other theory that because the bilivaridin pigment itself acts as a powerful antioxidant in the body, only the healthier females may be able to make their eggs very, very blue.
21:39
And there's some evidence in some species of a correlation between health and the blueness of the eggs.
21:45
I see. So the males will select that female because their eggs are so blue.
21:49
Well, it can't really work that way because once the egg is laid, the male's already made his choice.
21:56
So it may elicit additional effort on the part of the male to help care for those eggs. In some species, the male actually helps incubate, and so it could be an indicator of pull your weight, do more of the incubation, because these are really valuable chicks we're going to hatch here. And my study was to use fake eggs and put either pale eggs or richly blue-green eggs into a nest, and then put the chicks back in afterwards and see how much the male fed.
22:30
And he fed almost twice as often when he had really bright, richly blue-green eggs in the nest rather than the more pale ones. Wow.
22:38
That's interesting. Dr. English, thank you so much for your time. Thank you. Dr. Felina English is a biologist with Fisheries and Oceans Canada in Nanaimo, B.C.
22:50
I'm Bob McDonald, and you're listening to the Quirks and Quarks Question Show on CBC. Find and follow us wherever you get your podcasts so you don't miss out. Coming up next, got milk?
23:02
It's certainly possible to imagine that among the vast diversity of dinosaurs, there were some species that actually generate milk in the way that pigeons, flamingos, and penguins do.
23:15
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23:28
Every other Thursday, the Sounds Good newsletter will bring you one must-hear show from CBC Podcasts. And because we're true audio nerds, we'll also tell you about shows that we love that we didn't make. Go to cbc.ca slash soundsgood to subscribe.
23:48
The recent success of the Artemis II mission that launched Canadian astronaut Jeremy Hansen around the moon landed many questions into our inbox. Like this one from Anna in Ottawa who asks, What would happen to our Earth if we no longer had a moon? For the answer, we're joined by Dr. Laurie Russo-Nepton, an astronomer at the University of Toronto. Hi, welcome back to our question show. Hi everyone, thank you. So what do we know about how the moon affects the Earth?
24:18
moon is there for the tides it also kind of stabilized the earth quite a bit if it wasn't there the moon it's kind of slowing us down so the earth would suddenly rotate on itself much faster so basically the day would be shorter they're short enough as they are yeah yeah but much much shorter like uh six or eight hours for one day
24:41
Well, let's look at what the moon is doing for us now. I mean, what effect is it having on us besides the spin of the Earth?
24:49
By generating very strong tides along with the sun, it helps the ocean to mix, and especially around the coasts. And so it's really the motor or the engine behind lots of life that lives in very shallow water near the coasts.
25:06
Wow. So you're saying that the moon is actually partially responsible for life on Earth?
25:12
Oh, absolutely. And actually, it's been told that in the early ages when the earth was still, you know, in like rough changes and there was no life yet, because the moon was there, and apparently back then the moon was much closer to the earth, the tides were even stronger. So we can imagine that this continuous change and mixing of water and nutrients along the coast really, really help for the first form of life to emerge.
25:39
Okay, so now let's suppose that the Earth never had a moon right from the beginning. You mentioned that one effect is that our days would be shorter. What else would be happening?
25:49
Suddenly, the winds... the air around the Earth would move much faster. And so you could think of having a major storm just starting from the get-go. And so the wind would be 200 kilometers per hour almost everywhere on Earth, especially close to the equator. And not only that, but the way it's rotating with respect to the stars would not be as stable. So over time, it would start to tilt and wobble very significantly. And you can imagine that the pole, like the North Pole or the South Pole, could at some point be literally pointing towards the sun, melting all of the glacier very, very fast.
26:27
And so if it wasn't there and hadn't been there, the planets would be completely transformed. And most likely, the weather systems that we know of, the stability that we thrived in, would have never been there.
26:42
Sounds like a lot of extreme weather, really bad days on planet Earth.
26:47
Yeah, yeah. The moon is there to protect us in many ways.
26:50
Okay, so let's hypothetically imagine that for some reason the moon was to just instantly disappear tomorrow.
26:59
What would happen on Earth?
27:01
you would see a very rapid decline in the biodiversity. So many plants, insects and animals have life cycles that are driven by the moon cycle. And especially at the very base of the food chain, when we think about coral and bacteria in the ocean, they are driven by the cycle of the moon and some of them spawn and reproduce during the full moon cycle and so on. And so very quickly, the base of the food chain would be drastically changed And very quickly, lots of species would disappear.
27:33
And it would be much darker at night. Maybe good for us astronomers who are looking for dark nights to observe the infinite of our universe. But I think we would have much more problems than that.
27:46
Well, just one last thing. Is there any chance we could lose our moon?
27:50
Oh, well, no. The moon is there to stay, fortunately for us. It's one of the largest moon of the solar system. So even if there was a massive asteroid hitting it, it would just happen. And it would still rotate around the Earth and be there for the rest of time. And so we're fortunate to have it, and it's going to stick with us.
28:12
Well, it's good to know that our protector will always be there.
28:15
Absolutely.
28:17
Dr. Rousseau-Neptin, thank you so much for your time.
28:19
I very appreciate. Thank you.
28:21
Dr. Laurie Russo-Nepton is an assistant professor of astronomy and astrophysics at the University of Toronto.
28:33
We think you're going to lap up this next question.
28:36
Hello. My name is Jennifer Smith from Toronto, Ontario. My question is, why are cats' tongues rough and dogs' tongues smooth? Don't they serve the same purpose?
28:48
For the answer, we're joined by Dr. Kate Shoveler, who is a pet nutrition researcher with the University of Guelph. Hello and welcome to our question show.
28:56
Thank you for having me, Bob.
28:58
First of all, tell me the difference between a cat's tongue and a dog's tongue.
29:03
Well, they serve two very different purposes for different functions. And so cats do a lot more grooming with their tongues. And so that almost brush-like surface of a cat's tongue is really meant for helping to groom their coat. But then also, because they're primarily carnivores by nature, it also helps to remove tissue from solid surfaces.
29:33
So if you think about this, when they predate, they can then rip the tissue off of bone, partially with the help of that rough tongue.
29:44
Well, take me down to microscopic level. If I could stand on the surface of a cat's tongue, what would it look like?
29:50
So it does kind of look like a brush, but they have these projections like a brush tooth, but that projection is a thicker on the bottom and then it comes to a point near the top. So it's more like a cone. And so when a cat cleans its coat, what happens with each one of those cones is that they get hair in between those cones and those cones wrap around that hair.
30:23
And they also help to deposit saliva as they're going through that hair and grooming.
30:30
So they've they pose a really good purpose for grooming, but they can also adhere certain liquids to them as well. And so there is a role for each one of those little cones to also adhere water and help them lift water into their mouths as well. Whereas dogs, they have a smooth tongue and And they get water in their mouth by making an upside down ladle. And then in essence, tossing the water into their mouth where cats lower their tongue into water, make a little tiny scoop at the bottom.
31:08
But then if there's water adhering to those rough surfaces on their tongue, it adheres to their tongue and then they lift it into their mouth.
31:17
Okay. So the dog's tongue you say is smooth. So what purpose does it serve?
31:22
Primarily, they'll use it similar ways that we use it. So dogs and cats do have taste receptors. They are also really important for drinking. So that upside down ladle that I already talked about. But then dogs don't sweat.
31:38
And so when they need to thermoregulate or get rid of heat from their body, that's why they put their tongues out and they start to pant. Now, part of that heat dissipation from panting is coming from the respiratory system. So that exhale, you know, if we exhale on a window pane, you'll see that humidity. Well, along with that humidity is, of course, heat. So that's a way to dissipate heat. But they will also dissipate heat. And so tongues are really important for thermal regulation in dogs.
32:11
So how do you think these different tongue strategies between dogs and cats came about?
32:19
Ah, well, I think it's their very distinctive evolutionary path. And so dogs that we live with today are absolutely domesticated. We largely control their breeding. So we've selected them and they're quite a bit different than their originator, which is the wolf. Whereas cats, we generally do not control their breeding. So they actually don't One of our domestication profiles.
32:51
So they have continued to select themselves. But cats by nature have gotten all of their food and for that matter, their water intake. from the prey that they consume. And so the prey items for cats and that need to get all the meat off of any bones that they might collect or a whole prey ingested probably led to the preservation of that tongue as well for the purposes of feeding.
33:27
Dr. Schopler, thank you so much for your time.
33:30
Thank you very much. It's been a pleasure.
33:32
Dr. Kate Shoveler is a Professor and Champion Pet Foods Chair in Canine and Feline Nutrition, Physiology and Metabolism, and University of Guelph Research Leadership Chair.
33:49
Now for a question that takes us to some cool new heights.
33:54
Hello. My name's Sierra. I'm 11 years old, and I live in Burnaby, British Columbia, Canada. This is my question.
34:01
They say hot air rises. So then why, when you're outside, for example, when you're on a mountain, is there usually snow at the top, but there's nothing farther down?
34:14
Standing by at ground level with the answer is Dr. Morgan O'Neill. She's an atmospheric physicist at the University of Toronto. Dr. O'Neill, welcome to our question show.
34:25
Thanks so much. I think this is a great question. I'm excited to talk about it.
34:29
Well, let's start with the beginning. First of all, why does hot air rise?
34:34
Yeah, hot air rises because, most simply said, it's less dense than the air around it. It is less heavy per unit volume than the stuff around it. And so the displaced heavy stuff around it pushes it upward. And so you can think of it as completely analogous to heavy things falling down.
34:54
And light things rising up.
34:56
Yeah, exactly.
34:57
Okay, so the hot air is rising up, then why is it cool on top of mountains?
35:04
This is a very subtle problem. And it's so easy for us to think about hot water rising and cool water sinking in something like a water glass. But with a gas, it's really special because gas can be squished in a way that liquids can't. You can think about a person, maybe a diver, who's going to go on some deep dive in the ocean. They can bring oxygen along with them. And that oxygen is compressed to very high densities. We can squish air in a way that we can't squish water.
35:36
And in fact, the gas that comprises the atmosphere, let's say the atmosphere is, you know, approximately maybe 100 kilometers tall. You know, instead of a water glass now, we have a glass in our minds of 100 kilometers in height. And the air that's at the bottom of that column is really dense compared to the air at the top. It's really squished.
35:58
And you don't get something from nothing. And another thing that we like to say in physics is energy is conserved.
36:05
And if some air near the bottom of our atmospheric column, let's say near the ground where we live, is warmed up a little bit and becomes less dense than its neighboring air, it's going to rise. But the special thing about gas is when it rises, it's going to expand because now its neighbors are as it goes up a little bit, are less squished. And so the gas itself is going to perceive less pressure around it and it's going to expand. But what is expansion? It's the gas pushing on its neighbors.
36:36
And this is an energetically expensive process.
36:40
Because we don't get energy from nothing, if the air is pushing on its neighbors to expand, to colloquially breathe a little bit, then that energy comes at a price of a different reservoir of energy. It cools down. And so even though hot air is constantly rising from the surface of the Earth because the surface is heated by the sun, it's cooling every time it goes up another kilometer.
37:06
Why does a gas get cooler as it expands?
37:09
As gas expands, it's doing work. It has to do this energetically expensive job of pushing on its neighbors. And it turns out with gases, it's able to do that expensive thing by dropping its temperature. That's the trade-off. The parcel can't remain the same temperature if it has to expand. I will say we don't teach this to our undergraduates in physics at the University of Toronto until the fourth year. LAUGHTER
37:36
Okay. So as the gas pushes outward, the higher up you go, it needs energy to expand and it gets that from heat energy.
37:45
That's exactly right. Energy is lost in the temperature form so that the parcel can push air out of the way.
37:52
Okay. So will it keep getting colder as it goes higher up, say all the way out into space?
37:58
So interestingly, the temperature profile of the atmosphere zigzags. It's like three Zs stacked on top of each other, just back and forth and back and forth. And this is due to the dynamics and the chemical makeup of the atmosphere. For example, we all know that we have to wear sunscreen because of the ultraviolet light pouring down on us from the sun. Well, fortunately, that ultraviolet light isn't as bad as it could be because of the ozone layer. And the ozone layer is a little bit higher than where commercial airplanes fly.
38:29
And it absorbs a lot of that ultraviolet light. Well, what happens when a gas absorbs a lot of light? It warms up. So now all of a sudden, it's cold on your mountaintop. But once you get to that ozone layer and you keep going up, it's getting warm again.
38:43
And that's because of really complicated chemical transformations between different molecules.
38:49
Wow.
38:49
Yeah. So the ozone layer actually changes everything.
38:52
And that's why there's snow on top of mountains, even in the summertime.
38:55
That's right.
38:57
Great question.
38:58
Dr. O'Neill, thank you so much for your time.
39:00
Thank you. What a pleasure.
39:01
Dr. Morgan O'Neill is an assistant professor of atmospheric physics at the University of Toronto.
39:12
For our next nourishing question, Nicole Corrado from Beaconsfield, Quebec asks, Flamingos and pigeons produce milk and all birds are dinosaurs. But did any dinosaurs who are not birds produce milk?
39:32
To properly milk this answer, we're turning to Dr. Corwin Sullivan. He's a vertebrate paleontologist at the University of Alberta and adjunct curator at the Philip J. Curry Dinosaur Museum. Hello and welcome to our question show. Thank you very much, Bob. So let's get right to it. Did any dinosaurs make milk?
39:52
Well, they certainly wouldn't have made milk in the mammalian sense. And it's important to distinguish between the crop milk that some birds produce and the true milk that humans and other mammals make in their mammary glands and normally deliver milk. through a teat or a nipple to the offspring what birds do is actually generate a milk-like substance in the digestive tract and then the birds will spit it up essentially so that their chicks can consume it and pigeons do this both male and female pigeons and also flamingos and at least one species of penguin So crop milk is something that pops up in birds here and there.
40:34
A few birds have independently evolved it to help with their parental care. We don't have any particular evidence that dinosaurs, which were the ancestors of birds, did the same thing. But it's certainly possible to imagine that among the vast diversity of dinosaurs, there were some species that generated crop milk in the way that pigeons, flamingos, and penguins do.
40:59
So the bird milk, I mean, we see photographs of birds regurgitating food to their chicks, but there's actually a milk in there. Is it like mammal milk?
41:10
It's similar in composition to the milk of mammals. It's rich in fats. It's rich in proteins. It's very nourishing, but it's actually extruded from the digestive tract. So a lot of birds will take food into the crop, which is an expansion of the esophagus. So an expansion of the digestive tract. and store the food there and spit it back up for the chicks to consume.
41:35
But pigeons, flamingos, and penguins will actually generate milk in the digestive tract. Pigeons do it in the crop. Penguins don't really have a well-developed crop. They just do it in the upper digestive tract. Flamingos, I believe, do it in both the crop and the esophagus. But they'll generate milk within the digestive tract and regurgitate it for the chicks to consume.
42:00
So what evidence do you have in the fossil record that shows how dinosaurs cared for the young, whether they produce milk or not?
42:08
Yes. Well, when we're talking about dinosaur parental care, it's a good idea to start with what modern species do. Birds are essentially modified dinosaurs. Paleontologists think of birds as living dinosaurs with some odd modifications. And then crocodilians, crocodiles and alligators, are dinosaur cousins. And a lot of birds and crocodilians do have some level of parental care. In birds, it can be quite extensive. In crocodilians, it's a bit more rudimentary. But that suggests that parental care was probably widespread in dinosaurs.
42:42
And there are actually fossils of some dinosaurs sitting on nests, right? There will be a parental skeleton sitting on a nest of eggs, which indicates that some dinosaurs at least brooded their eggs the way birds do. And there's other circumstantial evidence that at least some dinosaurs had extensive parental care.
43:00
So by parental care, what do you mean by that?
43:04
Well, parental care can take different forms, right? Before hatching, it can mean sitting on the nest and incubating it to keep the eggs viable. But after hatching, it can mean providing food to the hatchlings. It can mean protecting them. It can mean leading them to places where they can forage. And we see all these behaviors in different kinds of birds. And it's not easy to infer behavior from the fossil record, but we do see some evidence that different forms of parental care were present in some dinosaur lineages.
43:37
Now, do you think some of them just abandoned their nests and let the young take care of themselves like, say, turtles do?
43:45
It's quite possible that some dinosaurs laid their eggs and abandoned them. We actually see that not only in turtles, but in one group of modern birds. They're called the megapodids or the brush turkeys, and they live in Australasia. And those birds will bury their eggs in a mound of vegetation. essentially, and the vegetation decomposes. As it decomposes, it produces enough heat to keep the eggs viable. And then the young will hatch in the absence of their parents and just start foraging for themselves.
44:15
So that's one extreme, right? It's an example of a bird that requires zero parental care. There are also birds that require very extensive parental care. and birds that are somewhere in the middle. And if I had to guess, I would guess that dinosaurs probably had that very same spectrum, with some requiring no parental care, some requiring a lot, and many in between.
44:38
Dr. Sullivan, thank you so much for your time. Thank you very much, Bob.
44:42
Dr. Corwin Sullivan is an associate professor at the University of Alberta in Edmonton and adjunct curator at the Philip J. Curry Dinosaur Museum in Wembley, Alberta.
44:58
We've got a mega-size question coming up next.
45:02
Miklos Orovitz asks, Some dinosaurs were reptilian giants. Even some mammals, like the beaver, the cave bear, and the saber-toothed tiger, were giant during the last ice age. Why do some animals get big and some don't? And were there ever any giant humans?
45:21
For the answer, we've reached out to someone who studied some pretty big creatures throughout history. Dr. Danielle Fraser is the head of paleobiology at the Canadian Museum of Nature in Ottawa. Hello and welcome back to our question show.
45:35
Hi, thanks for having me.
45:37
So first of all, have there ever been bigger humans or human relatives throughout history?
45:42
There certainly were some species in the same genus Homo that were a bit larger than modern Homo sapiens, but they certainly did not get giant. They didn't get giant like mammoths or giant ground sloths, for example. But definitely since around the industrial revolution within Homo sapiens, there has been an increase in body size. And this really has to do with enhanced access to nutrients. So we've got sort of industrial farming and things like this. that allowed us to have access to nutrients for growth.
46:13
More food and we have healthcare.
46:15
Yep.
46:17
Okay. So what selective factors lead to an animal getting bigger?
46:22
So there are a bunch of reasons that animals get bigger. One, for example, is cooler climates. Another is a change in the availability of nutrition.
46:32
There can be factors like competition and predation. So for example, in cooler climates, we expect animals to get larger. And that's because as you get larger, the relationship between your surface area, so that skin that you can lose heat over, changes relative to your body mass. So as you get bigger, you have less surface area to lose heat over.
46:53
Lower nutritional availability. If you get bigger, you have what we call a lower metabolic rate relative to your size. And so you're able to survive on sort of lower value food. And when there's competition or predation, you might change your size to avoid competing with an animal of similar size or to avoid predation pressure.
47:15
Well, that's interesting that you're saying that the big animals in the cold climates can eat lower quality food because you think if you're big, you'd have to eat a huge amount of food, even more.
47:25
Yeah, so you do have to eat more food, but you can eat lower quality food. So I think about something like a mammoth.
47:33
So mammoths are generally thought to be grazers. but they lived in cold climates. They lived in a lot of places with food with lower nutritional value, like grasses. But what they're able to do is eat a lot of food, pump it through really fast as well.
47:46
Now, you're talking about animals in cold environments, but what about like the dinosaurs, which lived on an earth that was warmer than it is today?
47:54
Yeah, and of course, the largest land animals that ever existed belong to dinosaurs. We think about some of the giant sauropods. And I think, to me at least, that's somewhat of a mystery, because we think about those animals, in sort of the opposite way that we think about mammals. It's often proposed that dinosaurs like sauropods got really large because there was a high oxygen environment and that there was really high nutritional value food for them to eat. We think about it in the opposite way when we think about things like mammoths, for example.
48:24
So it's a mystery to me.
48:27
So is this tendency to grow large universal? Because some animals don't. I mean, some animals stay small.
48:34
Yeah, it certainly isn't universal. And it really depends on the relatives that the animal descends from, the environments in which the animals live. There's genetic and evolutionary limitations. There's limitations on the structure of your bones. And then there's just whether they're experiencing any kind of actual selection, right?
48:56
So what do you think would have to happen for humans to go through our own megafauna phase for us to turn giant?
49:03
Yeah, well, humans, we certainly would have to go through massive changes to our skeletal system. Bones need to kind of resist both bending and compression, and they do that in a variety of ways. And that includes, you know, collagen, microstructures and things like this. But for humans with their fully upright stance, we would have to entirely change the architecture of our bones. And the second thing is we've got this fully upright stance and we've already got sort of knee and lower back issues. So I can't imagine how those would respond to getting larger.
49:37
Dr. Fraser, thank you so much for your time.
49:40
Thank you.
49:41
Dr. Danielle Fraser is the head of paleobiology at the Canadian Museum of Nature in Ottawa.
49:54
Our next question is out of this world, and the solar system for that matter.
49:59
Shirlene Smith in Ryandale, British Columbia, wants to know about the interstellar interloper that was first spotted in our solar system back in July 2025.
50:09
The 3I Atlas comet comes from outside our solar system and is extremely old, which made me wonder, are comets eternal?
50:21
How is it possible they can zip around for billions of years? Shouldn't they reduce in size gradually and become mere nubbins?
50:30
Thanks very much.
50:30
Love your show.
50:32
Here to answer Shirlene's question is Dr. Elena Hyde. She's an astrophysicist at York University. Hello and welcome back to our question show.
50:41
Oh, it's wonderful to be here. I love these kinds of questions.
50:44
So let's get to this 3I Atlas Comet. If it's been around for billions of years, why hasn't it been reduced to nubbins?
50:52
Well, the cold actually does help quite a lot out there in interstellar space. You have to imagine that it is substantially colder than what we normally get here in Canada. We're looking at not too far above the coldest possible temperature, which is absolute zero in some places. And, you know, we're thinking, oh, you know, maybe minus 40 Celsius in Ontario would be really cold.
51:20
Minus 263 Celsius would be what you're looking at out there in some of these places. And at that kind of temperature, as you know, the ice turns to a very solid, solid rock. And This comet out there in interstellar space is really, really cold. So it's really not losing anything as it travels through that cold, icy outer space. Unless, of course, it gets too close to a very hot thing like our star.
51:50
And that's why we're watching all of these comets with a lot of interest. Because they're coming into our solar system, coming closer to our star. And we want to know what's going to happen to them.
52:03
Okay, so when they do encounter a star, like Three-Eye Atlas did as it went by our sun last fall, it developed a tail, so it was losing material. So how much does it lose every time it does that?
52:16
Well, that's going to depend entirely on how close it gets.
52:20
We've had Comet Swan and we actually had Comet K1 Atlas, which is not to be confused with Comet 3I Atlas. They're from the same Atlas program, but very different comets. K1 Atlas did get too close to our star and actually was photographed breaking into fragments. But...
52:42
3i atlas we expect this one to keep going back out into icy icy outer solar system you know into between the stars where it's going to get really really really properly cold again and who knows how many millions or even billions of years it will take before it gets close enough to another star to lose a little bit more material so it could last for a very very long time
53:07
Okay. So it does lose a little bit, but it has to encounter a lot of stars before it gets reduced down. So, I mean, will that happen or do you think comet 3I Atlas could be eternal or can comets become eternal?
53:20
Well, I always say we have to watch out with the word eternal because you never know what's going to happen out there in space. We never really know what the full orbit of these things are, because once you start trying to trace an orbit, it's really, really hard to predict exactly where it's going to go next. So if its next star that it comes by is a closer approach, that might be it for this comet in a few millions or billions of years. But if that one's also a far away approach, like this one that we're seeing now as it flies through our solar system, maybe it keeps going for even farther.
53:57
So it becomes a great kind of little thought experiment to wonder how long will they survive these comets.
54:05
Dr. Hyde, thank you so much for your time. Absolutely. Dr. Elena Hyde is the director of the Allen I. Carswell Observatory and an associate professor at the Department of Physics and Astronomy at York University.
54:20
And that's it for this edition of our listener question show. Next week, we're back with a brand new season of Quirks and Quarks, kicking off with our summer science special.
54:31
To get in touch with us, you can email us at quirks at cbc.ca. Our webpage is cbc.ca slash quirks, where you can check out our past episodes and find more information on the research we cover in the show.
54:46
The Quirks and Quarks listener question show was produced by Amanda Buckowitz, Sonia Biting, Rosie Fernandez, Sarah Hamilton, and Livia Diring. Our senior producer is Hannah Hogue. I'm Bob McDonald. Thanks for listening.
55:04
For more CBC podcasts, go to cbc.ca slash podcasts.
