a professor of astronomy at UC Santa Cruz and he's an expert on galaxy formation and

Andromeda. And he's going to give us a talk about our place in the cosmos today. He's

also started a innovated program for high school students to do research at UC Santa

Cruz this summer and he's going to talk a little bit about that towards the end of the

talk. So I'm trilled to introduce Raja. >> GUHATHAKURTA: Thank a lot Jeff and thanks

Boris. Can you hear me okay at the back there? Okay, great. And thank you both for setting

this up. In fact, the high school program that Jeff mentioned is the exact reason for

my connection to Jeff. His daughter is in this program. So, I'm going to talk about

that at the very end. And I see a bunch of high school student, I see a bunch of middle

school students here, right? Middle or elementary? >> Elementary.

>> GUHATHAKURTA: Elementary. Even better. Good to start early. So, I'm going to talk

about galaxies today but I want to explain why it's important to talk about galaxies.

I'm going to explain why I study galaxies. And, so the title of today's talk is, "Our

Place in the Cosmos." And what I want to do is explain why, you know, why galaxies have

any connection at all to you and me. By way of, you know, giving credit where it's due,

these--many of the slides you'll see today, most of the narrative you'll see today, was

put together with the help of one of my colleagues at the UC Santa Cruz Astronomy Department.

Her name is Sandra Faber. Sandy has been studying galaxies for 30 years, she's one of the world's

experts in study of galaxy formation and evolutions. I've had the privilege of working with her.

We've worked together to keep this narrative current. As the years have gone by, we've

adapted our story to new findings. We've adapted the images and animations to new findings.

So, I hope to give you a little bit of a tiny flavor of the kind of galaxy research that

goes on at Santa Cruz and around the world. So, I wanted to put in a little bit of a disclaimer

also, that astronomy and cosmology are often confused with astrology, gastronomy, and cosmetology.

And I just want to set those three topics aside. They actually rear their ugly head

more often than I care in my studies especially when people find out I'm from India and I

study astronomy, I always get asked about palmistry and telling the future. I know absolutely

nothing about astrology. I know a little bit about gastronomy, it keeps me alive. And I

know very, as you can tell looking at me, I know nothing about cosmetology at all. So,

but I'll--where they do rear their ugly head, I'll mention them but I, you know, this is

a good example of cosmetology rearing its ugly head, no pun intended. So, let me--let

me actually give you a little bit of a road map of where we're going to go with this--with

this narrative today. So, I'll start with our place in the universe, in the cosmos.

And, it turns out our place in the cosmos is directly linked to a concept that's best

thought of as recycling. Recycling of chemicals, recycling of the elements in the periodic

table but done by the cosmos. Not done by West Valley Recycling, it's done by--on a

much larger scale in the cosmos. And it's done inside galaxies. Galaxies are the cosmos'

recycling plants. Now, galaxies do a whole bunch of thing in addition to cosmic recycling.

They are also cannibals, they like to eat their own. They like to eat their children

in particular. So, nothing to be scared about, you kids. Your parents are not at all like

that. But galaxies, in fact, do this all the time. And I'll talk about how cannibalism

plays an important role in galaxies. So you can see, gastronomy is already rearing its

ugly head here. The formation of galaxies involves cannibalism but only in the late

stages of galaxy evolution. Today, there's a lot of cannibalism going on in the Milky

Way, in Andromeda. But in the early stages, you don't have cannibalism because there's

nothing to cannibalize. You need to have galaxies in place for them to cannibalize one another.

So, the early stages of galaxy formation actually involve other processes, and I'll talk a little

bit about that. The early formation of galaxies involves ripples in the fabric of the cosmos.

I'll talk a little bit about the processes that give rise to those ripple. It has to

do with quantum mechanics. It has to do with a phenomenon called inflation, not the economic

kind but the kind the universe does. And it has to do with gravity. So, I'll talk about

those things. And at the--at, you know, the end of the science part of the presentation,

what I want to emphasize is that astronomy is a physical science. So like everything

in the--in the sciences, it's evidence-based. So if I tell you a story, I have to also tell

you the basis behind the story. Why, you know, why do we believe the story, why do we believe

what we believe, not just what we believe. So I'll tell you a little bit about this evidence

and that really has to do with using telescopes as time machines to test theoretical predictions.

Okay, so I'll start with Our Place in the Cosmos. And if I could have the lights down

a little bit in the front of the room if possible because many of my slides have a dark background.

I don't know--if that's easy to do. If not, it's--things are pretty visible on this--on

this screen anyway. I just realized that many of my--you know, the night sky is dark. So

when I take pictures of the night sky, the background is dark. It's not my fault. It

really is that way. But Jeff, this is already helping a lot.

>> [INDISTINCT] >> GUHATHAKURTA: Yes. This is--this is good.

So, oh, this is even better. >> [INDISTINCT]

>> GUHATHAKURTA: Yes. Thank you. Thank you. So when I think of our place in the cosmos,

I think of my, you know, my favorite people up there, you might think of your favorite

people up there. So I am going to put up an example of who I think of when I think of

our place in the cosmos. You know, on the right is my--is my daughter, she was seven

years old at that time. And on the left is my newly adopted son at that time. Okay. He

was--he hadn't been groomed in a while, so I apologize for his appearance there. But

what is common to those two entities, you know, it's a form of K9 life and human life,

is our protein molecules. So my biochemist friends tell me that protein molecule are

the basic building blocks of life. Now if I were being absolutely precise with my language,

I should say protein molecules are the basic building blocks of life as we know it. Now,

we know of many forms of life here on earth, from the simplest viruses, they're made of

RNA, to the most complex mammals. DNA and RNA are examples of protein molecules. Enzymes,

hormones, these are all neurotransmitters. These are all important aspects of life and

it's fair to say protein molecules are the basic building blocks of life as we know it.

Protein molecules are very complex as this picture shows, but if we would extend our

definition of life a little bit, another way to write that phrase would be to say complex

molecules are almost certainly the basic building blocks of any kind of interesting life. So

if there is life outside the solar system, and you know there might be, we haven't discovered

it, we can only speculate about it at this point. But if there's life beyond the solar

system, the kinds of life we'd be most interested in better be rich, better be diverse, like

the kinds of life we see here on earth. Those are the kinds we'd be interested in. And to

have any kind of rich and diverse life, you can bet they would have to have at its--at

its basis some kind of complex molecule. Because complex molecules have lots of chemical bonds,

they are capable of--they have many degrees of freedom, they are capable of taking on

many forms. Those are the kinds of life forms that we'd be interested in. Now, so to form

protein molecules or to form complex molecules of any kind, you need atoms with lots of electrons

and protons in them. You need things that are not right at the beginning of the periodic

table but somewhat into the periodic table. In the case of protein molecule, those atoms--I

am highlighting carbon, nitrogen and oxygen, I'm leaving out hydrogen deliberately. Hydrogen

is actually formed in copious quantities early in the universe's history. Electrons and protons

are initially moving around too rapidly for them to be bound by each others electrostatic

forces. Because the universe is very hot in its earthly phases. Hot means high temperature,

high temperature means rapid motion. When electron and protons have too high an energy,

they can't bind stably because, you know, their collisions are too energetic for them

to be--to remain bound. So when the universe cools down to a certain point, about 300,000

years after the Big Bang, the first hydrogen atoms formed, and hydrogen protons and electrons

mate for life. They stay together for 14,000,000,000 years. Now, it's a little more difficult to

produce more complex elements like carbon, nitrogen, oxygen. Actually hydrogen, helium,

traces of lithium and beryllium, form early in the universe's history just through this

natural collisions of particles. But carbon, nitrogen and oxygen don't form that easily.

They are actually cooked inside stars. They are cooked, when I say cooked I mean through

nuclear fusion reactions, they are produced inside stars. So, you might look at this and

say, "Okay, all is well." You know, we know where the carbon and nitrogen and oxygen came

from because we live around such a star. We live around the star that's undergoing fusion

reactions [INDISTINCT] that's what you see on the right there. It turns out the sun's

atmosphere contains carbon, nitrogen and oxygen. You know very well that the earth certainly

contains C, N and O. You know, if you've been to a barbeque recently or if you're wearing

a diamond ring or if you are breathing, which you certainly are, you are taking in nitrogen

and oxygen. So these elements are present in abundance on the earth, in the oceans,

on the earth's crust. These elements are present in abundance. But there is a little bit of

a mystery here. The sun, even though it contains carbon, nitrogen and oxygen actually has no

business to contain them because the sun has not yet produce these elements through nuclear

fusion reactions. The sun is merely converting hydrogen to helium in its core. That what

gives the sun, you know, the--that's what gives helium its name. Helium comes from the

Greek word for Helios. The sun is merely converting hydrogen to helium, near the end of its life,

about 5,000,000 years from now, 5,000,000,000 years from now, the sun is going to cook helium

into lithium, beryllium, boron, it will get up to carbon, nitrogen and oxygen and then

die. Die in the sense it will stop nuclear fusion reactions. So about 5,000,000,000 years

from now, the sun will have some legitimate claim to some carbon, nitrogen and oxygen

because it would have cooked it within its interior. So what business does it have containing,

you know, having some of these elements today? Well, its business is, it is descendant of

other stars. And what I mean by that is there are other stars--this is a picture of a star

field--there are other stars that lived and died before the sun came into being. And I--what

I mean by died is these stars rapidly cooked these elements, nuclear--they went through

nuclear fusion reactions. They cooked all the elements up to iron in fact within their

interiors, through nuclear fusion reactions. It turns out iron has the--is the most stable

of the elements in terms of binding energy per nucleon. So fusion is favorable energetically

as long as you go up to iron. Beyond that, you don't produce elements through fusion.

You actually produce them in stellar explosions through neutron bombardment in supernova explosions.

So, but the point is the sun is not a first generation star. The sun was born well after

some of its ancestors rapidly cooked these elements in their interiors, carbon, nitrogen

and oxygen, and indeed, many other elements. And these ancestral stars, their ancestors

in the same way we have ancestors, these stars died before the sun was born. They were very

efficient cooks. They cooked all these elements within their interior, but they were also

very generous cooks. They die in a spectacular way. These stars explode when they died. And

you--what you are seeing here is a real picture of an exploded star as it looks a thousand

years after the explosions, so about a thousand year old explosion that you see over there.

So the stuff that was once inside the star, was once cooked inside the star, gets generously

dispersed into surrounding space. So the sun was born out of the dust, the stardust, the

exploded ashes of many, many, many stars. So, in the words of Crosby, Stills, Nash & Young,

"We are stardust." You know, and for the young ones among you, you don't know who Crosby,

Stills, Nash & Young are, they are not a law firm. They are a rock group. And they must

have known some astronomy because they knew exactly what they were talking about when

they said, "We are stardust." So indeed, if you look around you, your neighbor, the chair

you are sitting on, the stuff that makes up this beautiful building, all of these was

once cooked inside a star. Not the sun but some other star, that enriched the cloud of

gas and dust from which the sun and earth, and the other planets formed. So that's a

remarkable--that is actually a remarkable thing to think that our origins are spatially

quite large. That is our--the elements that make up our bodies come from a large region

within our collection of stars. Now, a collection of stars is what we had to be part of. And

a collection of stars is what we call a galaxy. Because if we weren't part of a collection

of stars, if the sun were alone, the nebula from which the sun formed were alone with

no other stars around it, there's a pretty good bet that we would be made of hydrogen

and helium today. Not any of these other elements. And believe me, a speaker who is made of only

hydrogen and helium is far less interesting than, you know, than I hope to be. Okay, and

indeed, an audience made of hydrogen and helium is far less interesting than you are. So this

particular picture is a picture of a galaxy. But some of you have already guessed that

this is not a picture of the Milky Way Galaxy because we live inside the Milky Way Galaxy.

We can't take pictures like this of the Milky Way Galaxy. What we do instead is we take

pictures of our siblings. This is our sister galaxy, she's our older sister. Well, at least,

a biggest sister, I don't know about older. But this is the Andromeda Galaxy. This is

my favorite galaxy in the whole world, as Jeff mentioned, and I'll talk about it in

some more detail. Now, it's worth pausing here for a little bit to reflect on what we

are doing here. We live in a world without mirrors. We can't see ourselves. You know,

we can't see our Milky Way Galaxy. Imagine if you lived in a--imagine, you kids, living

in a world without mirrors. It will take you much less time in the morning to get ready

and go to school. That would be a benefit. But the downside is you wouldn't know what

you looked like. You would have no idea. You would have to look at your siblings, you would

have to look at your neighbors to figure out what you look like form the outside. That's

what we do here. Another analogy might be living in a house that you can never leave.

You wouldn't know what buildings look like until you looked out your window and looked

at your neighbor's buildings. And that's what we're doing here. This is our neighbor, the

Andromeda Galaxy. And to give you a sense of scale, light would take a hundred thousand