Instant Genius - Unlocking the invisible rainbows of the Universe

Episode Date: May 21, 2026

Our world may look vibrant and full of color. But in reality, our human eyes are only picking up the tiniest slice of all the light shining in the Universe. To astronomers this hidden light is just as important as the red greens and blues we can see. We talk to Alfredo Carpineti about what secrets are lying in the Universe beyond human vision, while celebrating another aspect that the rainbow has come to represent - the LGBT+ community. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Every Monday and Friday, you'll hear world-leading experts and scientists talking about the most fascinating ideas in science and technology today. I'm Ezi Pearson, commissioning editor at BBC Science Focus. In today's episode, I'm talking to science journalist and astrophysicist Dr Alfredo Carpenetti. Our world may look vibrant and full of colour, but in reality, our human eyes are only picking up the tiniest slice of all the light shining in the universe. When astronomers are trying to understand the cosmos around us, this hidden light is just as important as the red, greens and blues we can see. In his latest book, Invisible Rainbows, The Unseen Universe Beyond Our Senses, Alfredo explores what secrets are lying in the universe beyond the realms of human vision, while celebrating another aspect that the rainbow has come to represent, the LGBT Plus community. Hello Alfredo and welcome to Instapy.

genius. Loisi, thank you very much for having me. Thank you very much for being here. Now, my first question for you today is going to be one of those questions that I think is a bit deceptively simple. What actually is light and how much of it are we actually seeing? You are absolutely right. That is deceptively simple. So when you start thinking about it in our day-to-day experience is something that most of us can experience is something that we see through our eyes. But even people that cannot see still experience some form of light because their thermal receptor during their skin can feel heat, which is also another form of light. And we're going to start seeing like, oh, things already started getting complicated. In general, light is electromagnetic vibration going to

through space and it move through vacuum, something that we actually didn't know for most of our history. And actually, when you think, when going through the history of light, there are so much complications and so many different ideas. We didn't know if light was a particle or was a wave because certain aspects of light behave like a wave. A certain aspect of it behave like a particle. thousands of years of philosophers and scientists have been arguing one way or another. And then we encounter quantum mechanics, which allowed us to say it is actually both. Always when quantum mechanics gets involved. It's just that's when everything starts getting way too complicated. But I think it was way too complicated from the get-go. There are some very, very weird idea in

philosophy like that light didn't come from objects into our eyes, but actually came out from our eyes, like the, I don't know, like Superman laser vision. You were all shooting laser beams like Superman. And there are so many weird ideas, but they were all trying to explain a phenomenon that is bought, as you say, simple, is something that we experience all of us, one way or another, but it's full of mysteries. And then in the 1800, we realized that what we can see is just a small portion

of what's actually out there, which added to the complication. So we weren't even sure that if it was a wave or particle back then and suddenly like, oh, and there is light that is invisible to us. That is a problem, isn't it? It is unfortunately, it's the only way that we can really look out at the universe is with life. Actually, yes, but also no, because we are... Now that's not true. Yeah, we are clever, little clever apes that came up with technology to help us understand

what's beyond our senses. But you're absolutely right, the way we approach reality is through our senses. This is why, I don't know, talking about quantum mechanics, it is so complicated, so mysterious, so beyond us, it always makes you feel like, oh, there's something wrong with all of this, because it's not something that we can experience with our senses. It doesn't make sense that, I don't know, electrons have just a probability of being somewhere, that they're not in a position, or if you know very well the position,

their motion is very uncertain. That doesn't make sense. Like, I don't know, if you have a marble somewhere, you know, and even if you flick it, you know that where it is and where and how fast is moving. So the idea that fundamentally we are bound by our senses, but as I said, we're pretty clever, so we come up with maths and technology that has helped us help us. see beyond, understand what else is out there, understand what we cannot experience, and I think it is something that I was so happy to explore in the book, there is so much that we know thanks to what we cannot experience, and if we weren't able to do that, we would have missed so much of the universe, and we still miss so much of the universe.

because there are a lot of things that we have not got to yet. And there is so much of this light that we can't see, but we have developed ways of detecting. Why, when we're trying to understand the universe, is it so important to look beyond just what our human eyes can perceive? The reason why it's so important is because a lot of the celestial bodies, a lot of the cosmic phenomena, don't just emit. invisible light. They emit

across a broad range of wavelengths. Some will favorite one range more than others, but there are so many objects and events that we study across the wavelengths, and each

wavelengths tell us something different. One thing that I am pretty sure it's in every chapter of the book, so I divided the each chapter along the line of the six broad categories of light beyond the visible. Radio waves, microwaves, infrared, ultraviolet, x-rays and gamma rays. And one protagonist that appears in every chapter is black holes. The reason why they appear in every chapter is because we use the different wavelengths

to study different properties. There are things that we learn in radio waves about black holes that we wouldn't be able to understand if we were just using x-rays. And x-rays are very important when we study black holes because black holes can produce really energetic events around them. So this balance, this in a way, holistic approach to study the universe with a lot of wavelengths, is giving us a lot of incentives. is giving us a lot of insight. If we were just stuck into no, astronomy is just visible light, which is what a lot of astronomers felt back in the 60s, that the only way to do astronomy was to actually pointing a telescope

and look through it, and in a way that you would be able to perceive, we wouldn't miss stuff like pulsars, we wouldn't miss black holes, we would have missed the formation of planets, the formation of stars. We would have missed what's going on around the sun and predicting solar storms. There is so many things that we would have missed if we were just stuck in that, no, astronomy is what we can experience. Everything else is a different discipline. So you've got these different wavelengths.

You've got radios and all the way up to gamma rays. Why are they so different? and what's happening differently to create them? So they're different because they have different wavelengths or different frequency, depending on how you would like to divide them and define them. In general, if we consider light in terms of its particle, which is the photon, the particle of light,

it means that a gamma-ray photon is a lot more energetic than a radio wave photon. so they are usually probing a different energy regime. Let's put radio waves aside for one second. From microwaves to gamma rays, you are considering things of different temperature. It's very easy to see that that is the general picture. Things that are in visible light needs to be very, very, very hot. very, very hot. The middle visible light, yellow, is what the sun is pretty much like,

and that it is at around between 5,000, 6,000 degrees Celsius. So, very hot. Things that are cooler, gets into the infrared, and things that are very cold, you get to the microwave regime. To get to radio wave emission like that with a temperature, you need to have something, that is colder than the universe. So far, we can only do that in the lab. On the other end, you have something that are very hot. So, for example, we studied the sun in ultraviolet and x-rays because there are a portion of the sun above its surface.

They are much hotter than those 5,000, 6,000 degrees. The corona, which is the atmosphere of the sun, gets into the million of degrees. So we study in x-rays. and layers in between are getting hotter and hotter, so we study in ultraviolet. And then gamma rays, you produce when you have supernovae and massive explosions in the universe, something extremely energetic. But as I said to the answer of the first question, light is an electromagnetic interaction. So you can produce light event even with magnetism or with magnetism,

or with other the so-called non-thermal processes. So not a temperature of something emitting this light, but some other weird process. And this is where usually radio waves come in because there's so massive black holes produce massive jets that become larger

than entire galaxies. There are some jets that are 32 times the size of our own galaxy. And that is produced by a single black hole. And it's incredible. You can have something that stretches for million of light years produced by a single object. And a way for us to study them is radio waves. And it's not because they are very cold.

Actually, some of them can be very hot. But it's because the processes are in them with a particle moving being thrown at almost the speed of light, produce a radio emission. So it's part of it. We divide them in these seven little blocks, mostly out of historical reason. Some in the way we started studying them when we discovered them. And some two just make them a little bit special. Like I feel that there's not much difference between a certain end of the microwaves

and radio on one side and infrared on the other, but microwaves are very important. because the evidence that there was a Big Bang, a beginning of the universe, is the cosmic microwave background. So we really need to give a microwave a little special place. And in each group of wavelengths, so we find something that is very special. So I feel that it's obviously completely arbitrary division, but it's useful for how we approach things. Because we can't see these with our eyes, we have had to develop these incredible technologies to be able to observe them. How difficult actually is it to see some of these wavelengths? From the ground, we have only two windows in the atmosphere where the atmosphere is transparent

and is visible light and a little bit of near infrared and radio waves. Radio waves is great. This is why we can build so many lovely radio observatory, but we have challenges even there, because to make them extremely precise, you need to have a lot of radio dishes, and you need to connect them in a way, then you can build a sort of virtual radio observatory much larger

than what you actually have. This is why, for example, when we took the first photos of the Surmassive Black calls M87 Star and the one of the center of our galaxy Sagittarius A-Star. We had to connect the radio observatory from Greenland to the South Pole, from Europe to South America, and make them work together to the millisecond to create a virtual telescope the size of our planet. That was the only way to see something that is relatively quite small. the Sagittarius A star

are neighborhood friendly neighborhood it would fit in the orbit of Mercury and it's 26,000 light years away in terms of precision that this telescope needed to have it would be like you with your naked eye being able to

see a donut or a bagel on the surface of the moon can imagine that is quite the precision and this is why you need to connect all this telescope and make this connection but at least you can do it on the ground. Infrared becomes complicated because of water vapor in the atmosphere. So that absorb some of the infrared and sometimes emit some of the infrared, making the observation more complicated, and that stretches a little bit into the microwaves. And I always point out that is

astronomers always complain about all these things that are in these. atmosphere that we say that very important for life on Earth. For example, water in the atmosphere, very, very important for life on Earth. We do kind of need that. We kind of need that. And the other thing is, there is a reason why we cannot do ultraviolet astronomy from the ground. The Halsome layer, another pretty important thing to life on Earth. As much as I'd love to do more into ultraviolet astronomy, I am kind of glad the ozone layer is there. Yes, it's, I agree with you, but you start to think, there are a lot of things that make astronomy very complicated. So we put a lot of telescope in space

because that's where we can actually do that kind of astronomy. And when you go to the higher energy, x-rays and gamma rays, what gets complicated is that the single photons, so each particle is so energetic that you cannot just have a little camera system like a normal camera. No, you need to come up with a way to slow down the photon so that you can then capture it. And sometimes for x-phrase and memories, what you talk about, who have seen this thing,

you're literally talking about, oh, I have seen 20 photons from this object. Wow. This episode is brought to you by Activia. You might already be eating yogurt, but not all yogurts are created equal. Activia contains over 1 billion probiotics per serving to survive and reach the gut alive. When it comes to gut health, Activia is the number one family doctor-recommended probiotic yogurt brand. Choose Activia, feel good from the inside out. Visitactivia.ca for more details.

When you think about it, x-rays, those are the ones that we use to look inside of things because they go through so much stuff. So it must be quite hard to make a detector. Pretty much you try to make the photon have a little bounce, so it's not going directly into the detector, but is bouncing at angles to slow down. And one approach for gamma rays, that doesn't involve having anything in space, is actually looking at the atmosphere.

And when a gamma ray photon hits the atmosphere, it produces particles. And those particles tend to decay very quickly, and they've rained down on Earth. And there are a few detectors. They're just looking for those particles. And from those particles, they work out, oh, okay, there was this gamma-ray photon

that has done something to the atmosphere. And the brightest of all time called Boat event, it was a gamma-ray burst, a supernova explosion over two billion light years away. It was so powerful that affected the atmosphere of the earth for, I think, about 12 hours. From something two billion light years away. I know, and it's amazing. And before anyone get worried, there is nothing in our vicinity that could create something like that and destroy us.

It is very fortunate we live in a very boring corner of the universe. Oh, absolutely. it's like it's, I think, what is, the Douglas Adam quote of the unfashionable arm of the Milky Way. Yes, it's good. Seriously, our closest star that could go supernova is Beetlejuice and is around 600 light years away. So even if that went, it would not create something quite as dramatic as this. It is incredible, like, how far away that we can see with all of these various wavelengths. I know that particularly at the moment, the JWST, which is an infrared telescope, keeps, like, every week there seems to be a, it's seen an even more distant galaxy. What is it about infrared that makes it so good at seeing things that are very far away? The answer is not just about infrared, it's about something very profound in the universe. and it's the fact that the universe is expanding

and it's expanding with an acceleration. As the universe expand, the light from distant galaxies is stretched. It's a process called redshift, and it is similar to the Doppler effect that we might experience with sound where, for example, an ambulance is coming towards you on the street. As the ambulance approaches you,

the pitch of the ambulance gets higher and higher. Why? Because the sound waves are traveling towards you, but at the same time, the ambulance is moving towards you. And then the ambulance passes you, and suddenly the sound waves are still reaching you, but the ambulance is going away, so they are stretched a little bit. So as the ambulance was approaching you, you get compressed, higher pitch, as moves away, gets stretched out. Similarly, you can do that with light. If you have something moving really fast towards you, its light would become bluer,

because the wavelength will be a little bit more compressed. If it moves away from you, the light will become stretch and will become a little redder. It is not a real doppler effect, this redshift, because it's the universe that is expanding and stretching the light. It's not the galaxies, they're just moving away for some reason. It's not that everyone in the universe hates us, and everyone is running away from the Milky Way.

It's actually a physical property of the universe. So those wavelengths are getting redder and redder. And that's where infrared comes in. Because suddenly by looking at the universe in infrared, you are looking at a lot more galaxy. and you are looking at the most distant galaxies that we can possibly find. On the addition is that Jet Odyssey is the biggest mirror we ever put in space. It's an incredible work of engineering,

and it is absolutely fantastic that we have such an instrument. And that allows to not only see the most distant galaxy, but seeing so much better, so many more details about those galaxies, even the one that are a little bit closer. And you're absolutely right. Every week there is a new story, and there are so many mysteries that are just like, what are these things that we're finding?

Like the little red dots. And I love it because it's just like, oh, what are they? Early galaxies, super massive black holes as they were forming. the first generation of stars that we have never seen, but somehow covering a big cloud of hydrogen. And we do not have an answer. I love to cover so many different study about them because everyone seemed pretty confident

because obviously they've written a paper and are like, yeah, we are absolutely right. And then they need to put the caveat. But this could be explained with other things because it's just been so brilliant that they do not have any clear hallmark of like, oh, this is the thing. Oh, it's so obvious that it's that thing. They're just like this big puzzle. And I think it's fantastic. I think it's a wonderful time to be

a galaxy astronomer because we are just getting a treasure trove of findings from JWA. People don't necessarily realize that one of the best things that a scientist can say is, hmm, that's weird, because that means that there's something new and interesting that you need to investigate. Yeah, whoever says that the most important phrase in science is Eureka, no, they're wrong. It's always, and what is that? You want to be surprised. I feel that the moment you are too confident about knowing something about the universe is the moment that the universe is I'm, No, no, no, no, no.

No, hubris will be punished. So I think we've established that light is incredible and all of the different flavors that it comes in is a fantastic way to look at the universe. But another aspect that you explore in the book is something a bit more personal and closer to Earth, which is the LGBT Plus community. And there's a lot of voices from LGBT plus astronomers

throughout the book. why were you so keen to bring their voices specifically to this topic? I actually started thinking about this book after done an event at Norris Science Festival and it was a LGBTQ event where I was making some space-themed cocktails and mocktails. And it was really fun and it turned out to be. extremely oversubscribed. So I had to change my plan because I had promised cocktails

and they told me, oh, it's the last event of the festival, is after hours, it's probably going to be like 15 people. I can make 15 cocktails while I speak about astronomy. And then suddenly there were 50 people. That's a bit more of an ask. More of an ask, but we raised to the occasion.

And afterwards, somebody asked, oh, what would you have done differently? I was like, oh, I would have teamed to the LGBTQ aspect and do a rainbow cocktail or a layer cocktail. You can talk about the density of liquids, et cetera. And they asked, oh, are there rainbows in space? And I'm like, I don't know, let's look it up. And at the time, there was just this article

about potentially having rainbows on Titan, because Titan is this moon of Saturn that has rivers and lakes and seas, but they're made of methane because it's so cold there. And it's the only other place in the solar system that has river, lakes, and seas on its surface. We suspect that there is rain, actually, now we know, but at the time it was strongly suspected, made of methane, and methane is transparent to the last. light in the good range, so like, oh, it should be possible.

What's interesting about Titan, though, is that has this orange hazy atmosphere. So if you look at it with visible light, it's quite boring. It's literally just a boring orange ball. But if you look at it in infrared, suddenly you see these dunes, these rivers, these massive lakes. and the idea that I suggest is that if there are rainbows, they're invisible to our eyes, but they are in infrared. And I remember walking back to the hotel, and the only thing in my head was invisible rainbows, invisible rainbows, invisible rainbows,

there is something there, there is something there. And then I started looking at different aspect of the... electromagnetic spectrum of light beyond the visible, and this idea of rainbows of different colors when we study things continue to came up over and over. And I will start putting together this, and I'm like, I don't know, this might be my only chance to write a book. And if I need to do something that is meaningful, I want to raise the profile of people that might not get the chance. And it's called invisible rainbows. And there is another invisible community in astronomy.

And it is LGBTQ astronomers. So what if I go and look for astronomers that are doing something cool, doing something cutting edge, doing something different in astronomy? And once I started doing that, suddenly I had people that have discovered certain type of galaxies that I had never been seen before. People that are trying to find aliens. People that are using radio waves to protect us from dangerous asteroids. People that are studying the most powerful explosions in the universe. People that are studying extreme aurorae on the giant planets of the Earth.

the solar system. And it was just like it all made perfect sense to have this group of people talking about all this light and all these events and phenomena that we can not

directly experience, but somehow we have brought into our knowledge, thanks to technology. And actually quite late, I started looking at the history of non-visible astronomy and I found that

in the 1960, a lot of astronomers were against it. So they found it there was something that it was brand new, something that it was unnecessary and it made me laugh so much because the parallel at the same time with the

civil rights movements that was happening at the same time, it was just like oh my God, so it was truly a shift across civil society and scientifically society, there were new ideas coming in, there were new discoveries, and what was, in a way, really pushing that was that the discovery of things like radio signals from the center of the Milky Way was from the 30s. There have been studies of the moon in infrared in the 1800s. None of it

was newfangled astronomy, but it's the fact that some of the world. the technology was easy and affordable enough to bring all of this to every astronomer. And at the same time, when it comes to the civil rights movement, there were discussion about how society needed to be for everyone, the importance of rights for everyone. And I found the parallel between the two just like, oh, this is too good. It's interesting there, but you're talking about the sort of like the civil rights. movement and stuff. Do you think that having a more diverse range of astronomers changes how we look at the universe? Absolutely. And this is why I feel that I try my best to have diversity, not just

in terms of, yes, they are all in the LGBTQ plus community, but I try my best to have them from all over the world, have a good mixture of genderability, seniority in their careers. And I think, and I hope they comes across, that all of that is needed. You cannot just rely on the people that have had the biggest grant they are the most senior to just understand everything. because there are plenty of example of senior people not believing in certain new theories. Albert Einstein didn't accept most of quantum mechanics, just as an example. And I think it's very important that there is this diversity.

Diversity of identities leads to diversity of thought. and if we can create a society in which that is not just allowed but actually encourage, we create a better society just because we have different ideas. And it's not about the fact that we need to agree with all the ideas. I don't go into it much in the book, but for example, the end of the universe. There are multiple ideas about the end of the universe, and I have my preference, the one that I think would be the coolest, and I think I have the one that I think is most likely.

And I could argue, like, well, I have six-year experience as a researcher, 10-year experience as a science communicator. I think I have a pretty solid idea of why that is the most likely. But at the same time, I cannot swear that, oh, I am right and you're wrong. Obviously, when you are a researcher and you need to defend your research, you need to be a little bit more aggressive. I think I am going to have to ask which one's the one that you like and which is the one that you think is most likely. Okay. The theory that I like the most is called the false vacuum decay. and is this idea that the universe is in a pretty stable energy state,

what is called quantum mechanics, the ground state. And in general, the ground state is a place where you are in equilibrium that you cannot change much. You can imagine you are a little bowl in a little valley. So you could give a little kick here and there, but it will go back to the bottom of the valley. The false vacuum decay suggests that we are in a little valley, but there's actually a more, a deeper valley just over a little hill. And if somehow, somewhere in the universe, something gets a little bit more energy, somebody gets a kick and send it over that hill, suddenly the whole universe will change.

They will create a bubble that will expand and destroy everything because this new, true, true, ground state, lowest possible energy level, will have different properties of particles, different properties of interaction. So things will be weirder. And I like that because it's extremely dramatic. It certainly is dramatic. And there's nothing you can do about it. And I feel that the, I don't know what it says about me, but I feel that it's the fact that is completely without rhyme or reason, really appeals to me. I can see that. Yeah.

The one I think it's most likely is the heat death of the universe. The universe will continue to expand, will continue to cool down, and at some point we'll, in a number of years that we cannot even comprehend, will reach a point that

maximum entropy, nothing happens. It is unfortunately also the most boring ending. Yeah, boring, boring. You see, I got really excited because there was, there's actually a couple of papers that came out last year that were trying to argue that the big crunch, the idea that the universe will collapse again on itself,

might be a little bit more likely. I was excited about them. I think they were very good papers, but I didn't completely bought the whole thing. But I was like, ooh, I want to keep looking. at this, I want to see what you do as follow-ups, because they were very interesting. And also, I feel that that would be a lot more interesting that are like, oh, the universe will continue to exist with such a long time for human brain that it might as well be infinite,

but for most of it, nothing will happen. Boring, boring. Let's have a false vacuum decay. As you said, with all of these different ideas, that's why it's so important to have so many different voices. And thank you so much for bringing so many of them to light in this book. And thank you so much for talking to us today. Thank you for having me. It was such a pleasure.

Thank you for listening to this episode of Instant Genius, brought to you by the team behind BBC Science Focus. That was Dr. Alfredo Carpinetti. To discover more about the topics we've discussed, check out their latest book, Invisible Rainbows, available from the 21st of May. If you like what you just heard, then please consider subscribing to the Instant Genius podcast

on your preferred platform of choice. If you'd like to see our guests and hosts in person, then why not check out our YouTube channel at ScienceFocus. The current issue of BBC ScienceFocus is out now. Pick up a copy wherever you buy your favourite magazine or download us on your app store of choice. You can also find us on Apple News or online at sciencefocus.com.