Alison Stewart: This is All Of It on WNYC. I'm Alison Stewart. To close out today's show, we're talking about outer space. February is a big month for space happenings. This year marks the 100th anniversary of the discovery by Edwin Hubble that there's more to our universe and there are other galaxies out there besides our own.

February also marks two anniversaries of space missions to study the sun, which we're seeing more and more of since the solstice and December. Later this month will be a stargazing opportunity that we won't have again until the year 2161. It's called the Great Planetary Alignment, or less formally, a planetary parade. With all that, we thought it was time for a space roundup.

Joining me now to share his expertise, please welcome physicist Brian Cox, who studies particle physics at the particle accelerator at CERN in Switzerland. He'll be touring his live show for the first time in the US in the spring. It's called Horizons: A 21st Century Space Odyssey. We'll hear about that as well. Brian, thank you so much for being with us.

Brian Cox: Oh, pleasure.

Alison Stewart: Let's start with, I'm calling this Sun 101 [chuckles]. We'll talk about the axial tilt. Am I saying that right?

Brian Cox: Yes, that will do.

Alison Stewart: It'll do. All right. Can you explain the Earth's axis is tilted and how that creates the seasonal climates that we expect?

Brian Cox: Well, yes, the seasons, I always think they're a wonderful thing because they're evocative and we all know what they are. Obviously, we're in the winter now, and it snows, and then summer, it's hot, but this manifestation of the geometry, the arrangement of the solar system-- Of course, the Earth goes around the sun once every year, but the Earth's axis is tilted about 23 degrees or so.

That means that at some points of the year, if we're in the northern hemisphere, the northern hemisphere is pointing towards the sun and at other times is pointing away from the sun. Now, why is the axis tilted? Well, it's tilted, we think, because the Earth got hit by something very early on in the history of the solar system, so four and a half billion years ago, which knocked the Earth over. You realize that this gentle passing of the seasons is telling you that you're on a tilted spinning ball of rock tearing around a star.

[laughter]

Brian Cox: The radius of the Earth's orbit is about 93 million miles away or so from the sun. It's going very fast around the sun and obviously once a year. I like the fact that it reminds-- Every time you see that snowfall or the leaves fall off the trees in the fall, you can imagine why that is. It's a history going back four and a half billion years. It's a story of big lumps of rock orbiting around a nuclear fusion reactor.

Alison Stewart: That's a beautiful way to put it.

Brian Cox: Yes. It connects us with the wider universe that we don't always-- It's not natural to think you're on a ball of rock tearing through space because we don't feel it.

Alison Stewart: Sometimes it's natural. Sometimes you just think, "I'm a dot."

Brian Cox: Yes.

[laughter]

Alison Stewart: I do sometimes, I guess.

Brian Cox: "I'm a very tiny dot." The sun, you can fit a million Earths, roughly speaking, inside it. Although it's a kind of small thing in the sky because it's over 90 million miles away, a million Earths inside it is a big thing, actually.

Alison Stewart: I'm a smaller dot. Let's talk about the two launch anniversaries that are related to the study of the sun. On February 5th, 2002, NASA launched HESSI to study solar flares. Then on February 10, 2020, I believe it was, NASA launched the SolO, Solar Orbiter. Could you walk us through both of these anniversaries, how they've helped us understand the sun?

Brian Cox: Well, yes. Your question is a really a good one. The deeper point, you might think that we understand how the star works. We sort of do in broad terms, but even that, it's only in the last hundred years or so when you go back a century and there were people calculating how long- what the lifetime of the sun would be if it was burning coal [chuckles] because we didn't know about the atomic nucleus.

If you don't know about nuclear physics, which is a 20th-century discovery, you can't understand how something could emit so much energy and yet we knew how far away it was. That was measured in the 1700s. It was one of the great conundrums, actually. Solar research itself is only about 100 years old.

Now we're interested in questions about how stars work in detail. Again, you might say, well, does it really matter? Does it concern us? Well, it does, because solar flares, for example, that you mentioned, they're eruptions from the sun. They're to do with its magnetic field, which we don't fully understand by any means, but they reach the Earth and we see them as aurora, so again experiencing. When you see the aurora borealis, the northern lights, or the southern lights, you're seeing eruptions from the sun, charged particles from the sun interacting with the Earth's magnetic field.

They're important. They're not only pretty and a beautiful thing to see in the sky, but they can affect communication satellites. At the largest level, the biggest solar flares, there was one called the Carrington flare, which was sometime in the 1800s, I can't remember the exact date, which is a huge solar flare. We saw aurora in Hawaii.

If such an eruption happened today, now we have modern technology and communication satellites and solars, it would be tremendously disruptive. We want to understand better those solar storms, those eruptions from the sun because they have a direct impact on us. Potentially, it can be quite a very serious impact, actually.

Alison Stewart: Those are the ones, it's an 11-year cycle?

Brian Cox: Yes. The sun has an 11-year cycle. We don't really fully understand that. Sometimes it's not as active, sometimes it's more active. Its magnetic field flips around. The Earth's magnetic field flips around, but on hundreds of thousands of years' timescale, the sun does it on a few- it's decades. Again, it's interesting to me that we don't fully understand by any means how our neighboring star works. That's what these missions are doing. As I said, some of it's just pure curiosity. We want to understand how stars work, but some of it's space weather, and space weather is actually important.

Alison Stewart: When you think about the Solar Orbiter mission, it's scheduled to go through 2026. It can be extended to 2030. If you could have a say in it, what questions would you want answered?

Brian Cox: Well, it's those fundamental questions about stars, about the way that they're big spinning magnets in a sense. Why are they big spinning magnets? How does that all interact? How is it that these huge eruptions of energy form and sometimes affect the Earth and sometimes don't? There are practical questions. I think it's interesting as we go further out into space and become more reliant on space, and we're already-- We all use satellite navigation and communications and weather forecasting and earth observation, all those things.

As we get more and more involved in the space economy, we're going to become more reliant on it. The study of stars, it's a beautiful example of the wider question of why we do science. Ultimately, we do it because we're interested. We're interested in how stars work, curiosity.

Also, it tends to turn out that the study of nature, finding out more about the way that nature works is useful to us. It's worth reminding ourselves sometimes that what might seem like rather esoteric questions, often lead to tremendous advances and, in this case, just understanding the way that the environment up there in space works.

Alison Stewart: I remember I interviewed a scientist in her lab and she says, "I just ask questions." [laughs]

Brian Cox: It's the way that it precedes one of my great heroes, Richard Feynman, very famous Nobel Prize-winning scientist. He used to say that you ask very simple questions. Those are the only questions we can answer, actually. We can't answer grand philosophical questions about the meaning of it all and the origin of the universe and those things. We're not at that level yet.

By asking very simple questions, it could be why is the sky blue, or what is the aurora, or why is there oxygen in our atmosphere, those kind of questions, you're led to a deeper understanding of nature that can then sometimes lead to quite profound ideas.

You mentioned Hubble, the anniversary of Edwin Hubble showing that these so-called nebulae in the sky, the misty patches that we'd seen in the sky for a long time since the invention of the telescope. Actually the Andromeda Galaxy, our nearest neighboring large galaxy, you can see with the naked eye in the right conditions. It was known this little patch was there. What is it?

It's a remarkable discovery that he made building on work that had been done for many years by a great astronomer called Henrietta Levitt, did a lot of work on these particular kinds of stars called Cepheid variable stars. He used that work to measure the distance to this misty patch and found that it was outside our galaxy. We now know it's two and a half million light years away, which is the modern number for that measurement, but what a remarkable thing.

How do you measure the distance to a star, never mind the distance to a galaxy? Ultimately, by the way, it begins by measuring the distance of the Earth from the sun. Without that, you can't measure the distance to the stars. That was the big [crosstalk]--

Alison Stewart: It all comes back to the sun.

Brian Cox: It does, and so you need to know the distance of the Earth from the sun. That was in the 1700s as well. It's quite relatively recent, actually, that we've understood that these things are far outside our own galaxy.

Alison Stewart: My guest is physicist Brian Cox. He's joining us to talk about the latest space news as well as about his show, Horizons: A 21st Century Space Odyssey, which will be coming to the US this spring. Check online for shows and tickets. By the way, I'll turn over my microphone to our listeners. If you have questions about space or the nature of the universe or anything else you want to ask Brian Cox, give us a call now. 212-433-WNYC, 212-433-9692. We'll be right back.

[music]

Alison Stewart: You are listening to All Of It on WNYC. I'm Alison Stewart. My guest in studio is physicist Brian Cox. He's joining us to talk about the latest space news and about his live Show Horizons: A 21st Century Space Odyssey. I want to know about the show. What do you cover in the show?

Brian Cox: Well, I mentioned before the break that science, you start with simple questions and then sometimes it led to rather grand questions. In that, I ask the question at the start, actually, once you consider the size and scale of the universe, and we mentioned the Andromeda galaxy, in fact, 2.5 million light years away. We now think there is something like 2 trillion galaxies, each with hundreds of billions of stars in the universe that we can see.

Questions arise, and I say at the start, "When you consider cosmology, you think what does it mean to live a finite, fragile life in an infinite, eternal universe?" which is a very good question. I point out I don't know the answer, so don't buy a ticket. If I knew the answer, I'd charge a lot more for tickets.

[laughter]

It's remarkable how much progress we've made in trying to understand why is the universe the way that it is. Why does the universe allow life to exist? I talk about life in the show. It's easy to dismiss, again, as we said before, the fact that we are we take for granted that we exist, but we're just collections of atoms. The great Carl Sagan once said that a physicist is a hydrogen atom's way of learning about hydrogen atoms.

You say, "Well, how can it be that the universe 13.8 billion years ago is just full of hydrogen and helium, the simplest chemical elements?" 13.8 billion years later, there are collections of atoms like us, you and me and everyone that's listening, that can think and learn about the universe and consider these great existential questions. What properties of the universe allowed that to happen? What do we know about those properties?

Quite immediately after we've done a tour of the universe-- I should say there are huge LED screens, as much as we can fit in the town hall here in New York. I was down there yesterday, actually, you can fit a lot of LED in there, so it's going to be great, but you see these pictures. Then quite quickly, because I'm interested in these questions, we start to talk about the origin of life, the evolution of life. Questions like, well, how many civilizations might there be in a galaxy like the Milky Way? My guess is there might be very few.

In fact, my guess is, and it's a guess based on the history of life on Earth, there might be one, which would be us. Then you get an interesting question about, well, how, notwithstanding our physical insignificance, they say we're little dots on one planet around one star amongst 400 billion stars in one galaxy amongst 2 trillion galaxies in the observable universe. Notwithstanding that, imagine that this is the only place where a civilization currently exists. Then suddenly this little rock is tremendously valuable, and so we talk about that. Soon, we're off into rather more profound terrain.

Alison Stewart: We actually have a question about that. Let's talk to Tierney from Putnam Valley. Hi, Tierney, you're on the air.

Tierney: Hi, how's it going?

Alison Stewart: Okay. What are your thoughts?

Tierney: I wanted to ask if you think that there's a chance that we are living in a simulation.

Brian Cox: [chuckles] It's a great question. The answer is that I have no idea. The scientific question becomes, "How would you know?" What I would say is that I can see nothing in the laws of physics that would rule that out, but I also see nothing that would rule it in. At the moment, in scientific terms, it would become- the question would be, could you make an observation, or do an experiment, or learn something that would tell you that you live in some kind of simulation?

The last thing I'll say very quickly is there is interesting evidence from-- We're trying to understand at the moment what space and time are in physics. It turns out that one of our pictures of space and time is that they emerge from a deeper structure which looks a bit like a quantum computer. That would not be evidence that we live in a simulation. It just might say there's a description of the universe that looks a bit like a quantum computer. That's what I would say to you.

The answer is nobody knows. The really interesting thing, the challenge to you and everybody else that's thinking about it is what kind of an observation would convince you that we are.

Alison Stewart: Let's talk to Ed, who's calling in from Clifton. Hi, Ed. You are on the air with Brian Cox.

Ed: Thank you so much. My question is 50 years ago, exactly, I was a freshman in college. Due to the inquisitiveness that you spoke about, I took an astronomy class. In that class, the most interesting thing that I recall is they talked about quasars. They didn't understand how a quasar could exist because they were too bright to be at the distance that the redshift indicated they should be at. It was a puzzle. Since then, I've never really heard an answer. It seems you don't hear about quasars anymore. I'd like to understand that better.

Brian Cox: Yes, it's a great question because you say they weren't discovered so long ago. For everybody listening, they're very, very, very bright sources of radiation energy in the centers of galaxies very far away. We're pretty sure-- I'd say they are associated with supermassive black holes. Now, supermassive black holes, 50 years ago, we didn't know that-- we had very little evidence that these things existed beyond theory. They were kind of predicted from Einstein's theory back in 1915, but we didn't have good evidence for them.

Now we do. Nobel Prizes have been awarded for the discovery of these things. We have a photograph of one which is in the center of a galaxy called M87, which is 55 million light years away, which is 6 billion times the mass of our sun. We talked about the sun earlier, and I said, you can fit a million Earths inside this thing. There's a black hole in the center of that galaxy that's 6 billion times more massive than our sun. These are tremendous sources of energy.

The exact mechanism, you're right about it, to do with the way these things interact with the wider galaxy, I think it's-- This is not exactly my area, but I think it's fair to say the exact mechanism is still a source of research. I also think it's fair to say that it's certainly associated with these incredible supermassive black holes.

Alison Stewart: I want to get back to one more thing that's going to happen this month, February 28th. They're calling it the planetary parade. It's Saturn, Mercury, Neptune, Venus, Uranus, Jupiter and Mars will be in the same region in the sky. Explain to us the significance of this event.

Brian Cox: It's significant aesthetically. It's very beautiful. It's just to do with the fact that from our vantage point on the Earth, when we look out, the planets are at the right place in their orbits around the sun such that they line up in our sky. There's no significance. It doesn't do anything to us. It's just that we're just looking out into the solar system and it's moved into this arrangement, but it is tremendously beautiful.

You can see the brighter planets. Uranus and Neptune, you can't see unless you have a telescope, but you'll see Saturn and Jupiter and Mars, and it's worth looking at them. Mars is obviously red. The moment you know what you're looking at-- You could get one of those apps on the phone that are free to get, and just identify them because then your mind can be transported.

If you have a small telescope, you can see the rings of Saturn and the clouds on Jupiter. Even if you don't, just with your eyes, you can see these worlds. You can see their different colors. Then you can start to think that Mars is this planet with polar caps on the-- It probably, almost certainly once had oceans and rivers in orbit around Jupiter. You look at Jupiter, these point of light. If you have binoculars, you'll see it's moons, it's brighter moons.

We have two missions on the way to those moons, in particular, a moon called Europa. You can let your mind wander. Europa is an ocean world with a frozen surface with a saltwater ocean. There's more water in the ocean than in all the oceans of the Earth combined. We think it's a possible habitat for life. We have two spacecraft in flight going there.

I think that one of the beautiful things about astronomy is that you don't need anything other than your eyes. You can familiarize yourself with the sky. Then the more you know about the points of light that you're looking at, the more magical it is.

Alison Stewart: This text says what was here before the Big Bang according to its theory and what did it look like?

Brian Cox: We have a theory that the Big Bang was something that happened in a preexisting universe. It's a theory called Inflation. The idea is that before, the universe was very hot and very dense, which is what we call the Big Bang. That's the thing we have a measurement back to. We know that 13.8 billion years ago, then, the universe was very hot and dense. The question is, is the caller said what happened before that?

There’s a theory called Inflation, that the universe was still around. Space was stretching very fast and that period in the universe's life came to an end. In coming to an end, that's what kind of nucleated the Big Bang, if you like. You might say, what a ridiculous thing to say, but that theory, it was in 1980s that theory was explored, and it made some predictions in particular, a beautiful prediction about how galaxies are distributed on the sky.

When you look, we see thousands of galaxies and you might think they're random like a snowstorm, but they're in fact patterns in them. This theory predicted the pattern before it was-

Alison Stewart: Patterns?

Brian Cox: Pattern, yes, before it was observed. It's almost like there's a message written in galaxies across the sky which is telling us something about this early universe. It is the textbook theory, the thing I've just described, called Inflation. The aim now is to test it as far as we can. We have some tests, and it's past the tests.

Alison Stewart: Let's try to get Mark in. Mark, real quick, what's your question?

Mark: My question is about Planck length and the subatomic world and the universe. What's going to be the smallest object, or can it be infinitely small?

Alison Stewart: Answer this in one second. One minute left.

Brian Cox: Way back, actually turn of the 20th century, Max Planck noticed that you can measure the strength of gravity, and you can measure the speed of light, and you can measure something called Planck's constant, which is associated with quantum mechanics and the way that light is emitted from things and so on. If you get those three things which are really fundamental, you can construct the length. You can make them into something that you can measure in meters. It's 10 to the -35 meters, which in English is 0.000 with 35 noughts, one of the meters, tiny length.

It seems to be really fundamental, a fundamental property of the universe. I'll give you one example of how it's fundamental, which is if you look at a black hole and you look at this thing which has a-- You can say, well, what's the event horizon which defines where this black hole is, where if you go inside, that you can't get out? The amount of information contained in the black hole is equal to the surface area of the event horizon of the black hole in square Planck lengths.

It's telling us something fundamental about space, and time, and information. I would say, yes, the Planck length is the smallest thing we can conceive of and it has any meaning in physics, 10 to the -35 meters.

Alison Stewart: My guest has been Brian Cox. Thank you for your time, Brian.

Brian Cox: My pleasure.

Alison Stewart: His show is called Horizons: A 21st Century Space Odyssey. It'll be coming to the US in spring. Check online for shows and tickets. I will meet you back here tomorrow.