The Universe Is, Like, Seriously Huge (33c3)

33C3 preroll music

Herald Angel: Okay, our next speaker is
Michael Büker. He is a science

communicator and an astrophysicist. He is
also a science journalist and a writer.

So, he's currently living in Dresden and
he wrapped his mind around this very

question so how do you measure these great
distances and how do you get an idea of

how huge the cosmos really is, since the
universe is like seriously huge.

Michael, your stage.

applause

Michael: Okay, thank you very much. Thank
you everyone for being here.

While after the kind of year that we've had it's
natural to be thinking about where and how

fast you might be able to get away from
earth. So let's all be a little bit like

Maddie was a couple of months ago, when
she thought that actually the Voyager

probe is winning, because it's quite far
away and we're gonna be talking about even

larger distances. But, to think about
distances in the universe and how we can

measure them and how we can determine how
far away stuff is from each other, it all

starts when we look at the sky, because
when we look up at the sky all we see is

basically moving dots. This is a nice
picture that shows the very large

telescope and above it there is the moon,
Venus, and the planet Jupiter shining.

And these will be moving across the sky in a
way that we are familiar with, but if they

are just moving at the sky and every night
the pattern repeats, how can we find out

about the distances, how far these are
away from us, from anywhere else and we

are gonna be looking at, actually, how
that works. Even in antiquity, this sketch

is from 200 years before the common era,
so it's more then 2200 years old now, the

answer was clever geometry. If you measure
exactly at what point on our sky stuff

appears at certain times instead of just
saying, well, it's somewhere up there and

later it's gonna be like over there. If
you do this precisely, you can get a grasp

at where stuff is and how far away it is
from us and relative to each other.

There was a small break in progress in this, because

laughter

for a time people chose to believe
that actually the earth was at the center

of the solar system and then none of your
measurement make any sense So, okay, we

kind of wasted 1000 years on that
question. But then in the 1600s there came

a very important breakthrough, actually 2
of them, first was Johannes Kepler, who

found out that the way that planets move
around the sun, including the earth,

follows a very specific mathematical
pattern and then this was comprehensively

explained by Isaac Newton when he formulated
the general laws of gravitation and how they

work. So it was found out that these all
follow a certain law and from this you can

determine the distances relative to each
other. So they were able to tell how much

exactly further away from the sun is the
average orbit of Mars than earth. So, we

had a relative idea of how far away stuff
is from the sun, but we didn't know what

the exact value was. So, if during the
17th century you were to ask an

astronomer, how far away is Jupiter from
the sun, he would say, about five times as

much as the earth, but then if you ask him
but how much is that in miles or whatever,

they wouldn't be able to tell you. So with
this one measurement, if we measured this

AU, which stands for astronomical unit,
which we just conveniently define to say

well, the average orbit the earth has
around the sun is 1 astronomical unit, if

we found out that one value, we would be
able to determine all the distances of all

the planets in the solar system from the
sun. And again, the answer was clever

geometry. In a way that I'm not going to
go into in much detail, when the planet

Venus transits the star, we saw transits
in an earlier talk, is when a planet moves

in front of a star and kind of blocks the
light from it a little bit. If you time

this exactly and measure exactly the way
that it moves from different points on the

earth, this gives you a clue. But, there
is a big problem, is that transits of

Venus as seen from the earth come in pairs
8 years apart - which is okay - but that only

happens every 120 years So, the very first
one that was really observed was in 1639,

but that was basically just one guy in
England in his backyard and he didn't

really have colleagues, he didn't have
good equipment and anything. So the number

that he found was not very precise. Then
astronomers spent, after Kepler and Newton

had made their discoveries, astronomers
spent decades preparing, they set up

telescopes in different places in the
earth, they coordinated, they wrote

letters to each other. But they were
trolled by how they didn't really

understand how their telescopes worked
very well. So then astronomers said, okay

that didn't really work out. We're gonna
doing it real well in 120 years.

laughter

So again they coordinated extremely well
the telescopes have gotten much better

they distributed around the earth, which
was easier due to railways, well you

couldn't fly, but there was, you know,
there was the railways and everything, so

communication and transportation was a
little easier and they distributed all

around the earth and they did this again
in the 1870s and 1880s and they were

trolled by how their clocks were not
precise enough. So, because the

comparative measurements were off by as
much as a minute in time they didn't get a

value as exact as they were hoping for. I
mean, here we see 149 million km and then

there is an uncertainty of 160.000 it's
not so bad. Actually in astronomy that's

pretty amazing for accuracy, but it's not
enough if you're trying to send stuff to

Venus. So they were probably hoping for
the early 2000s to really finally find the

true distance, the true value of the
astronomical unit, but then before that

something else happened. So, in the 1960s
big radio transmitters, radio antennas,

became good enough to actually beam a
radio signal at the planet Venus and then

wait and measure how long it takes to
bounce back. So we did a radar ranging

experiment to the planet Venus and that
gave a value for this astronomical unit

that was good enough to actually build
probes that would fly to Venus. And then

if you have something there which is not
just a wave bouncing off of the planet,

but you actually have a spacecraft there
you can pretty much exactly time all the

transmissions from the antenna on the
spacecraft and everything and that's how

we found that value. So from this, we
know, and this is actually the defined

value, so it doesn't change anymore, we
just said that this is the astronomical

unit, and we know that very well, and this
helps us to establish all the distances in

the solar system. Still, the transit of
Venus that happened in 2004 and 2012, it

just gave us amazing pictures like these,
taken in Greece in 2004 or this one taken

from a Japanese space probe in 2012. Now,
if you weren't around to witness those,

well, next one is up in 2120 or something.
So, just wait around.

laughter

Now, as we moved towards the stars, so we
basically covered the solar system, but we

also wanna know how far away are the
stars, which is the next logical step, if

we are looking outwards in the universe we
have to talk about the concept of

parallax. And it's a bit complicated, it
involves geometry, but we can cover it

sort of in a way of the layout of this
Saal. So if there was somewhere, someone

up there on the Rang of Saal 1 and they
were looking straight at the stage and see

me here and walking from one side of the
Saal to the other, then first I would be

appearing like a little to the left of
their field of vision, if they were

looking straight ahead, with their nose
pointed at the screen. And then as they

move to the other side of the Saal I would
appear in the other direction and there

would be an angle which corresponds to how
far they moved. And if they precisely

measured this angle and how far they moved
they can calculate the distance towards

me. Now, in this Saal that would mean
about 40 meters and it would be a parallax

angle of about 10 to 20 degrees and that
would then give you the information that

from up there I'm probably about 50 meters
away. We can do that with the stars. Now,

on earth we can move from one place on
the earth to the other, but that's

actually a small baseline that doesn't
give us an angle that's a lot of fun to

work with. But luckily, since earth moves
around the sun all time for free, we can

just use that and measure the position of
a star, wait 6 months, and measure it

again. And we will be at a totally
different place, well basically 300

million km away and we can use that as a
baseline for this measurement. So we look

at a star, we wait half a year, we look at
the same star, and precisely measure how

much the star wobbles. Unfortunately, this
leads us to the definition of the distance

unit of the parsec, and the parsec is a
unit of distance. Please do not confuse it

with other stuff as some might do. So how
is the parsec defined? Well, if we have

this angle, I told you that from Saal 1,
from there to there it might be something

like 10 to 20 degrees. If a star is a
parsec away then over the course of a

year over our geometrical baseline of the
earth moving around the sun, 300 million

km apart in the 2 points, it will have to
be the angle of an arcsecond. Now what is

an arcsecond? It's just an extremely
small angle. You have a full circle

divided into 360 degrees, then each of
these degrees is divided into 60 minutes,

and then each of these minutes is divided
into 60 arcseconds. An we're looking at

an angle of 1 arc second that these stars
would over the course of 1 year be

wobbling in the sky from our movement
around the sun. Let's take an example of

looking at the international space station
from down on the ground. You might have

seen this, it's actually quite fun to see,
you can look it up on websites at what

point in time the international space
station will be above you. And the angle

of one arc second would be the size of an
astronaut floating next to the

international space station as you're
looking at it from the ground. Obviously,

you can't see an astronaut from the ground
that's because our eyes can't pick out

the angle that is one arcsecond. Another
example might be, again for someone way up

there at the end of Saal 1, looking at me at
a distance of about 50 meters, the angle of one

arcsecond would be the width of one the
hairs of my beard. And if you could see

that you would have a detector that is
capable of distinguishing one arcsecond.

Now, if we do that, and if we manage to do
that, the telescopes are actually good

enough to do this, one parsec is the
distance to a star that wobbles by

1 arcsecond. But, actually, our closest
neighbor is even further away. So, we

don't have any star that does that. 1.3
parsecs is the distance to Proxima

Centauri, and the Alpha and Beta Centauri
system, so these are even smaller. And

270.000 astronomical units is the distance
to that one, so that means it's way

further away. I mean, in the solar system
we can move 2, 3, 5, maybe 10, 20, 30

astronomical units if we are doing well
with our rockets and it takes a bunch of

years, but to cover 1000s or even 100s of
1000s of astronomical units tells us that

the propulsion systems and the rockets that
we have today are not capable of getting us

to the stars in the way we do it right
now, which we also heard, of course, in

the talks before. Telescopes on the ground
are nice, but actually telescopes in space

can give us an even better resolution. And
the Hipparcos satellite, which was active

in the last couple of decades, measured up
to 2 milliarcseconds. Now think of it. The

arcsecond with the astronaut in the sky
and my beard and stuff. A 1/1000 of that

as an angular resolution is what the
Hipparcos satellite was able to measure

and this gave us the distances to
basically all the stars in our field of

view that were up to 100 parsecs away. And
we know exactly how far these are away.

The Gaia satellite, which is now just
coming into operation, commissioned by the

European space agency, this is about to
have an even better performance, it will

look at a billion stars, that's what it's
called, the Billion Stars Surveyor, it

will be good for distances of up to 5000
parsecs and it's gonna tell us the

distances to all these stars, it's gonna
be an amazing step in looking at how far

away the stars are and forming a map of
all the stars around us. And, there is

something missing? No. Let's talk about
standard candles now, because that's

another important tool apart from the
geometry that we saw before. A standard

candle is just something where you know
exactly how bright it is. And then you can

calculate how far away. A standard candle
would be, well, like any, let's image a

set of candles and all of them burn at the
same brightness. So if you measured the

brightness of one of these candles, you
could tell how far apart it was. Actually,

maybe a better picture is streetlights in
the night. If you see a car coming towards

you, you can kind of estimate by how
brightly you see the light if the car is

still far away, or if it is close to you,
because you have an intuitive

understanding of how bright the lights of
a car should be if it is right next to you

or a couple of 100 meters away or many
kilometers away, if it's a clear night.

And so we want standard candles in space.
We want stuff in space, where we have a

good idea of how bright it should be. And
then from how bright we see it, how much

of the light actually reaches us, we can
calculate the distance. And this we can do

with the help of these, one of the most
important diagrams and all of

astrophysics, which is the
Hertzsprung-Russel diagram. It basically

sorts stars by their colors and by how bright
they are. And because of the way that stars

work, the color and the brightness are
also intermittently connected to their

mass and what's happening inside the stars
and then if we see a bunch of stars, we

can do this very well with clusters, which
are groups of 10s or 100s up to 1000s of

stars in one place, at basically the same
distance, and they have sort of a standard

population, then we can estimate how far
away they're. Let's think of it like this,

we jut had the picture of the car and the
night, which was light, but let's think of

it as sound. Think of groups of children
in maybe preschool and let's imagine that

every preschool group of children always
had 20 children in it, just because. And

now, you can estimate how loud 20
preschool children just playing around actually

are and from the sound of when you hear
the children you can tell how far away

that group is from you. If we have a group
of stars and we know the light, the

different colors that they have, we can
actually match it to this graph and see

how far away this group is by estimating
the properties that they have in this way.

And so this then gives us an overview of
basically our galactic neighborhood, so

the other stars in our galaxy. The number
of stars in our galaxy is about 200 billion,

but before I bombard you with
more numbers, we have a chance to get a

great overview of what that's like from
the artists of Monty Python.

Song: Just remember that you standing
on a planet that's evolving,

revolving at 900
miles an hour.

Michael: Sorry.

applause

Thank you Monty Python. Now, the numbers
that they present have changed over time.

Now scientists speak of 200 billion stars
in the galaxy instead of 100 billion, but

still it gives you an amazingly good overall
idea. And whenever I try to think of the

parameters of the milky way galaxy, like
100.000 light-years side to side, I just

have the song in my head. And it works
amazingly well. Except also for the one

part where it says that the universe is
expanding at the speed of light, like we

heard in the talk before, that's not
actually true. The expansion of the

universe actually exceeds the speed of
light, but common, they are comedians, so.

laughing

Cut them a little slack on that one. Other
galaxies, the milky way galaxy that we

have just gotten this nice overview over
is by far not the only one, there are

other galaxies and we are part of groups
of galaxies, actually the one that's

called the local group, which has 3 very
large galaxies, which is ours, the milky

way, the Andromeda galaxy, which is
actually larger, and another one which is

a bit smaller. And then there's a bunch of
dwarf galaxies also moving around there

and we gonna be looking at how we find
about distances in that regard. Now again,

we have a sort of standard candle here,
and these are stars called Cepheids, and

what you see here is the brightness of the
star pulsating. So you look at the star

and you say, okay it's this bright, oh no
wait, it's dimmer again, oh wait, it's

getting brighter again, over the course of
a couple days. And if you measure this

brightness very precisely, you just have
to wait a few days, it's not a difficult

measurement in that regard, you can find
out that the duration of these variations

is actually closely linked to how bright
they are. So, calculating or measuring the

period of these oscillations gives you the
brightness and then these stars, called

Cepheids, can work for you as a standard
candle and this works out into other

galaxies. So, we look at like the
Andromeda galaxy, which is a couple of

million light-years away, and we see a
Cepheids star in there somewhere, we

measure the period of it's oscillations
and then we can tell how far apart it is

and this gives us a good idea of how away
that galaxy actually is. That doesn't work

for galaxies where they appear so small in
our field of view that we can't point out

a single Cepheid star. So these groups of
galaxies also form together into something

called Superclusters. And the Virgo
Supercluster is an idea of what our group

is actually in. So I mentioned the local
group of a couple of maybe 100 dwarf

galaxies and three large ones. And this is
actually orbiting something called the

Virgo cluster. So we are a bit out, but I
mean this is an abstract graphic. What

does it look like to look at the Virgo
cluster? Well, We can look at that. And

you see that we look at the sky and
there's just a bunch of large galaxies

there. You're looking at something that's
probably pretty similar to what our own

galaxy is like, and it's just hanging
there in the sky. And by, for example,

this Cepheid measurement method, we can
get an idea of how far away it is. But these

local galaxies are not the only ones we
see. There is an example that's called the

Hubble Extreme Deep Field, where the
Hubble space telescope, that's orbiting the

earth, took pictures of a very small patch
of the sky. Here, the moon is shown to

scale. So, if you look at the moon, the
photograph that I'm about to show you

right now, shows this small part that's
marked by the XDF. And if you look at it

long enough and collect a lot of light,
that's why it's called a Deep Field, it

actually looks like this. And there's a
huge amount of galaxies and they all look

different. Some are spiral galaxies, some
are elliptical galaxies, and they even

have different colors. Some appear red,
some appear blue, and this all has to do

with the way that they evolve and we not
even done quite in understanding how they

come to look like that. You can actually
help with this. There are so many galaxies

just recorded in pictures that we don't
have good catalogs of them all. So you can

visit galaxyzoo.org and they will show you
a picture of a galaxy somewhat like this

and you have to click, is it a spiral
galaxy, is it an elliptical galaxy. Does

it look like blue color, does it look like
red color. It's crowdsourced citizen

science and you can help classify a whole
bunch of galaxies, and it's a lot of fun,

just click through while
you should be working.

laughterapplause

Now, also when we look at these galaxies,
similar to the way we can look at stars

with the Cepheids and their variation,
there is a bunch of methods I'm not going

to get into a lot of detail, but if you
look at galaxies and the way they move and

the way that the light emanates from
them, and someway you can correlate that

to the distance, and so examining these
galaxies very closely can give us an idea

of how far away they are from us. But
actually everyone's favorite standard

candle, the one thing that astronomers and
astrophysicists really love to use, is

supernovae of the 1a type. Now in the talk
before we saw that sometimes little white

dwarf stars can gain mass from their
companion stars, so stuff is falling onto

them, until the mass of the white dwarf
star that's gaining weight becomes so

large that it explodes in a thermal
nuclear explosion and this then is a

supernova of type A. And what's amazing
about these explosions is that basically

they are almost the same brightness. Or
you can determine the brightness very well

if you look at how quickly the light fades
out. So, whenever we see, like you see

here on the top-left picture, whenever we
see a galaxy and there is a supernova 1a

happening right at that moment, and they
only are visible for a couple of days

mostly, hours to days. So if we look at
that closely and we measure how the light

fades away, then we can get a very good
idea of how far away that galaxy is. And

even larger structures emerge then, and we
think about the Virgo Supercluster that I

just showed you, which was groups of
galaxies around groups of other galaxies

and the latest idea of the sort of the
large scale structure that the earth and

our milky way is part of, is the Laniakea
Supercluster that was proposed just 2 or 3

years ago. And here you don't even see
individual galaxies. It's more like the

density of stuff in the universe that's
grouped together. And you see these lines,

they represent sort of the way that
gravity is pulling everything. And yeah,

that's a pretty amazing idea. And like
we've heard in the talk before, the

universe is expanding and this also
affects the light, the light gets

redshifted. If there is a lightwave
traveling through the universe, and while

it's traveling space expands, that also
means that the light changes it's

wavelength. It just becomes a different
color. And it shifts towards the red,

which is why this thing is called
redshift. And so galaxies that are very

far away, because between us and where
that galaxy is space is expanding and has

been expanding for a while, these galaxies
appear to look red. And we can actually see

that in the pictures, like this one. Yeah,
you can see it on the screen, it's this

very faint red dot, and that actually
tells us that this is a galaxy which

should actually have blue light, like most
of the other galaxies, but because it's so

far away and space has stretched while the
lightwaves were traveling in our direction

it now appears red. And 4 gigaparsecs, so
we're looking at 4 billion parsecs of

distance towards this, which we can kind
of extrapolate of how far it's redshifted,

so how far the light has been reddened, is
how we can get an idea of this. And it's

not just the one, this, at least a couple
of years ago, was the furthest away galaxy

that had ever been observed, but actually
there's a whole bunch of those and they

are everywhere, and like we saw there is a
very large number of galaxies to be seen

everywhere. And to give us a final idea of
how matter is really distributed in the

universe, I have another video which is a
simulation of how these super galaxy

clusters are actually distributed. So let
me pull that up. Now we're looking at some

generic super galaxy cluster and we're
kind of circling it. And as the camera is

moving out and the picture is getting
larger, we see that this one super galaxy

cluster is actually sort of connected to
other regions where there is a high

density of galaxies. Remember, this is not
stars, we're looking at galaxies. And they

are sort of strung together in something
that's called filaments. And these

filaments stretch along the lines of
regions where there is almost no galaxies

which are called voids, and these voids
are between 10 and 50 million light-years

in diameter, more or less. And this is
just the way that everything stretches

out. So, super galaxy clusters are
gathered in filaments around voids and it

looks like a sort of a soap bubble or
maybe a bee hive structure. And okay, this

is a simulation, it looks nice, and this is
gathered from data that we have about how

far away these galaxies are, how we think the
universe evolved, but how about real data.

Can we look out there and actually measure
galaxies, and actually measure how stuff

looks, and see the structure in the
universe? Turns out, we can. And it looks

like this. And it just blows my mind.
Because you see this whole bee hive

structure, you see the voids, you see the
filaments of super galaxy cluster

structures sort of strung together. And
that's just real data. That is the largest

scale structure of all the galaxies, of
the observable universe, that have ever

been recorded. And this relies on the
measurements of type 1a supernovae, and of

the galaxies which relies on measurements
of, for example, the Cepheids stars, which

rely on measurements of the parallax, of
the geometrical parallax, like we

discussed here in this room. So, the way
of looking at the universe like this, of

all the super galaxy clusters, actually
begins when we string together these to

form what's called the cosmological
distance ladder of all these different

methods building upon each other. And it
starts right here, when we look up at the

sky. So, I hope you enjoy that,
thanks for your attention.

applause

Herald: Thank you very much, Michael. So,
we still have time for questions. Line up

at the microphones if you want to ask any
here and now. And we get a little

preference on the Internet, are there any
questions, Signal Angel?

That doesn't seem to be the case,
and we start with microphone 3, please.

Mic 3: Regarding the redshift of the
further away galaxy, red light has less

energy than blue light, where
does the energy go?

M: It's lost. In the process of the
universe expanding, energy is not

conserved. And that's a big
headache for physics.

laughter
Herald: Microphone 4.

Mic 4: So, I was thinking that in the case
that you try to measure the distance to a

far away galaxy, where we are talking in
the scale that there is not sufficent

accuracy via parallax, so you rely on
supernovas. So, you point the telescope in

a patch of the sky and you pick up a
supernova. But you cannot really know, I

suppose, that the supernova belongs to the
galaxy where all the other stars around

that are, or perhaps it's very far away on
the z-axis in a different galaxy that's

just behind. Is that possible?
How do you go around that?

M: Yes, you're right. You may find
pictures, and I may find a picture of this

where galaxies are actually overlapping.
So in this thing that I showed you from

the galaxy zoo, yeah, I think you see some
galaxies overlapping now. This might mean

that they are close together and actually
colliding, but it might also mean that

they just happen to be in the same
direction. But then the type 1a supernova,

if you measure it, gives you an idea of
how far away it is and then hopefully you

can estimate if it was the front galaxy or
the back galaxy. But you can't be exactly

sure, you're right.

Herald: Okay, microphone 1, please.

Mic 1: Okay. Thanks, this is really
fascinating. This might be a stupid

question. If the outer edges of our
observable universe are expanding at

faster than the speed of light and we
detect very far away galaxies with light,

how is the light ever reaching us?

M: We see only as far as the expansion of
the universe will allow us. And, like we

heard in the talk before, stuff is falling
behind the horizon. There are regions in

the universe now, where at a later point,
because space is expanding, the light from

these regions will not be able to reach
us. So if we look way out into the

universe to the very edge of what we can
see, there is stuff disappearing there and

there is just no getting around there,
if it's gone, it's gone.

Herald: Okay, this concludes the Q & A. A
warm round of applause for Michael Büker.

applause

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