The family tree of the universe | Debbie Bard | TEDxStanford


Transcriber: Zsuzsa Viola
Reviewer: Tanya Cushman Before I get going, there’s one thing
that I think I need to clear up and that’s not associated with
how we think particle physicists look. I’m not from around here. This is typically the first thing
people notice when they meet me, so I thought I should address
this right now. I’m from the UK originally. I’ve been living in the Bay Area now
for about eight years, more or less, but I’ve managed to retain
my British accent, which I’m very proud of. So this is normally a first thing
people notice when they meet me. And very often the first thing
that people will want to tell me is that they have
some family connection to the UK. (Laughter) And you probably would do this as well
if we meet later on – let me know that you have
maybe grandparents from England or maybe a great-grandparent
that came from Scotland. And this is a very natural way
of establishing a connection with people. I do the same thing. I have grandparents
from Ireland and from Poland, so if I meet people from those countries,
I like to kind of compare notes with them, like see if we have any overlap
in our family history. This is because family
is very important to us; whether we’re aware
of the influence or not, our family history has
a real influence on who we are, where we come from informs who we are. And so I like to extend this metaphor
beyond our family tree to the entire Universe. So the Universe, as well, can be thought of as having
a family history, a kind of a family tree. There are generations of stars
that are born and die, and they all influence everything
that comes after them, including us. And I mean this in a very real way,
in a very direct way. All the atoms in my body,
all the atoms in your bodies, all the atoms in the Earth
were forged in the heart of dying stars. So we really are made from the ashes of the previous generations
of the Universe. Where the Universe comes from
impacts who we are. And where the Universe
is going in the future is going to impact where we’re going. This is one of the reasons
why I study cosmology. Cosmology is the study
of the history of the Universe. And I think there’s something that’s really important
to our identity as people, to understand something about
the history of the Universe as a whole and also our place in that Universe. So when we want to get an idea
about the origin of our species, origin of Homo sapiens, we go to archaeology, which looks back maybe tens
or hundreds of thousands of years. And in cosmology, we’re looking back
to the history of the Universe, and the Universe
is 13.8 billion years old. So you can think of cosmology as being
a real extreme form of archaeology. But that doesn’t mean that it’s something
that’s an abstract science. It doesn’t mean that it’s, you know,
it’s just hand waving. It’s something that we
really do have a connection to. In archaeology, when we see cave paintings like these, made by our ancestors
thousands of years ago, we have a real visceral reaction
to something like this. We imagine what it might have been like
to put our hands up on that cave wall and make an imprint. And so we start to imagine what the life was like for the people
who made those cave paintings. And in a similar way, when we see a galaxy
that’s millions of years old or maybe even billions of years old, we make that same connection
to our own galaxy, to our Milky Way. And we might imagine, well, perhaps this is a adolescent version
of our own galaxy, or maybe it’s the completely
different branch of the family tree from our own galaxy. But we still have a connection
to what we see out there. And the reason that we can see this, the reason that we can see galaxies
from millions or billions of years ago, is because light travels very fast
through the Universe – it’s the fastest thing there is – but the size of the Universe
is unimaginably vast. The distances that light has to travel
to reach us are huge. I mean, even light from the Sun –
that she’s our closest star – it takes eight minutes to reach us. So something crazy
can be going on with the Sun, it can wink out like this, and it’ll take eight minutes
for us to even notice that’s happening. But if we can catch a glimpse of light
from very distant galaxies, then that light will have traveled
through the universe for billions upon billions
of years to reach us. And so this allows us to take
a glimpse back in time, to see what the Universe was like
when it was very young. This is kind of like finding
a fossilized tooth or a bone shard or something like that in archaeology. You might only have
a fragment of information, a little shard of information, but that can still tell us
an enormous amount about what the environment
was like back then. So we see galaxies
because they emit light. We use telescopes, which look at the sky through various
different wavelengths of light. And so we see the stars in the galaxies. We also see the dust
in the gas in the galaxies. We see these with different
types of telescope because they emit
different wavelengths of light. But we know – we found out
in the last 40 years or so – that everything we’ve ever seen
through our telescopes only makes up 20%
of the matter in the Universe. The other 80% is made up
of what we call “dark matter.” And this is something
that’s pretty exciting for scientists. So dark matter is surprisingly,
I guess, well named. In astronomy, we often assign things
somewhat obscure names like cluster Abell 1689. It’s not obvious to people
what this means. But dark matter’s got
a very sensible name, very logical name: it’s dark, which because it doesn’t glow,
doesn’t interact with light, it is literally dark. But that doesn’t mean
that it’s intangible. It’s matter, so that means
that it has mass, it has heft. And because of that we see the influence
of dark matter through its gravity. If something has mass and it has gravity and we see the effect
of the gravitational pull of dark matter wherever we look in the Universe – not just in galaxies – in fact, if we sort of take a step back and sort of take the wider
picture of the Universe, we might want to do something
like taking a census of the Universe, maybe making a survey
of where all the galaxies are. I mean, when we look at our data
from a survey like this, we see that the galaxies
aren’t distributed around randomly and they’re not evenly distributed
throughout space. There’s a definite pattern
to where the galaxies are; it kind of looks like a bit of a web. We call this the “cosmic web.” The pattern of galaxies
is not sort of smoothly distributed; it’s all clustered together. And this is simply
because of the force of gravity. It’s a force of the gravitational pull
of the galaxies themselves and also of the dark matter. So we can run computer simulations of a universe that contains
regular matter and dark matter, and we’re able to reproduce
this kind of pattern, this kind of cosmic web, pretty well. So we don’t know what dark matter is. That’s the big caveat to all this. We’ve never sort of been able
to catch a bit of dark matter and, you know, look at it,
and try to measure it itself, but we’ve got a really good idea
about what dark matter does, and we knew this because
of its gravitational pull. So we think that we’re got
a fairly good idea of what the Universe is made of, we think we understand something
about what’s in the Universe, but of course, that’s
only one part of the puzzle. If we want to learn something about
and understand something about the history of the Universe, we need to include the dimension of time, and we need to see how the Universe
is changing over time. In these figures here
are the vertical axis, is the distance of
the galaxies away from us. So as you look up the wedge,
you’re basically looking back in time. And if you look at the very top
of the wedge there, we’re looking back in time
about two and a half billion years. And you’ll notice there that the galaxies are not sort of located
in this same web-like structure and they’re much more evenly distributed. They sort of look
more randomly distributed. And this is simply because
nothing stays static over time; the Universe certainly
doesn’t stay static over time. It takes time for gravity to pull everything together
in these structures. So the Universe is not a static place. Of course, the generations of stars
are being born and dying, galaxies are colliding
and merging all the time, but underneath that, space itself
is expanding underneath us. You can kind of think of this as species on Earth
evolving quite happily, completely oblivious to the movements
of the tectonic plates under us; it’s not something that we can feel. But space itself is expanding. And about 15 years ago, we discovered
that not only is space expanding, but that expansion is accelerating, the expansion of space is speeding up. And this is really exciting for scientists because we don’t have a good explanation
about why this might be happening. And we called this “dark energy.” Whatever’s driving this accelerated
expansion of the Universe, we call it dark energy. And here it’s called “dark”
mostly because we’re in the dark about it. We don’t have a good explanation for it, but we do love a good mystery
to get our teeth into as scientists, so it’s one of the, probably the – I think personally
because this is something I work on – I think it’s probably
a most important mystery in science today, the most important thing that we need to understand
in science today, because without it, we simply are not going to be able
to understand the history of the Universe. We won’t be able to get a coherent picture
of the history of the Universe without understanding
what dark energy is and what it’s doing. So the tools that we use to gather together
all these diverse bits of information are telescopes. And probably the most famous telescope
of all is the Hubble Space Telescope. I think it’s everybody’s
favorite telescope; even astronomers. We get fantastic astronomical
scientific data from the Hubble Telescope as well as beautiful images of the cosmos
and really spectacular pictures. So Hubble is a telescope
which is in space, it’s in orbit around the Earth, and this means
that it has a real advantage because it doesn’t have to worry
about day or night, it doesn’t have to worry about
whether it’s cloudy or it’s raining. It can stare at the same tiny patch of sky
for days or even weeks, which means that it’s the ideal tool for catching a glimpse of light
from these very distant galaxies and allowing us to catch
a glimpse back in time to when the Universe
was in its adolescence or even in its childhood. But if we wanted to take
a census of the Universe and try to make a survey of space, then the Hubble’s just not
the right tool for the job. It’d be kind of like trying to light up
a room with a laser pointer, maybe. It’s just not going to work. So I wanted to tell you about a revolutionary
new telescope that I work on that’s going to really allow us to make a comprehensive survey
of the Universe. So whereas Hubble
is kind of a precision instrument, kind of like a scalpel, you can think of this telescope
as being a cosmic excavator. It’s going to unearth information
about tens of billions of galaxies. It’ll be taking this survey
for about 10 years, and at the end of that 10 years, this telescope will have seen
more of the Universe than all previous telescopes put together. It’s going to be fantastic. It’s called the Large Synoptic
Survey Telescope. And as you can imagine, for something that’s going to be taking
such a big survey of the Universe, this is not your average
back-garden telescope. You’re not going to be using this
to go stargazing in your backyard. This isn’t probably going to fit
in your backyard. It’s a huge telescope. It’s as big as a house. The main mirror alone is about
eight and a half meters in diameter, which is, you know, a significant proportion
of the size of this stage. It’s a very big instrument. And as was mentioned in the introduction, I work at the SLAC National
Accelerator Laboratory. And up there, we’re responsible for delivering
the camera for the telescope and fitting me for something that’s going to give us
the big picture of the Universe. This is going to be the biggest
digital camera the world’s ever seen. This is also enormous: it’s about the size of a car. And the focal plane alone
is this kind of size, about like 50 or 60 centimeters across, and it contains more
than three billion pixels. That’s more than 500 times as many pixels
as you get in your average iPhone. So this is we’re really pushing
the limits of camera technology by developing this camera. And who knows, maybe some time in the future, some of the delicate instrumentation
we’re developing for this camera will find its way into your iPhone – I certainly hope so. So there are hundreds
of scientists and engineers working on this project in the US
and all around the world, and we’re busy at the moment preparing for the flood of data
we’re going to get from this telescope. It’s going to be coming pretty soon. This is what’s really exciting
about this project, is that we’re going to start construction
in just a few weeks from now. The Large Synoptic Survey Telescope is going to be built
on a mountaintop in Chile, where the air is clear
and the weather is very predictable. And so we start construction
in a few weeks, and then, around eight
or nine years after that, we’re going to start what is effectively
the most extreme archaeological dig the world’s ever seen. LSST is going to give us the first really comprehensive
survey of the Universe, and it’s going to allow us
to understand the history of the Universe in a way we’ve never
been able to do before and to understand
our place in that history. So 15 years ago, when I was in college –
it was only 15 years ago – we didn’t know about dark energy; I never learned about this in college. This wasn’t something
that we knew existed. And you can imagine,
15 years from now what other surprises the Universe
might have to throw at us. So I think for me this is a tremendously exciting time
to be a cosmologist, to be on the brink of all this data,
all this information, all this potential discovery. And I really think it’s an exciting time
to be a human being. So I really hope that you will all be excited
and inspired by what we discover. Thank you. (Applause)

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