The search for dark matter -- and what we've found so far | Risa Wechsler

Prevoditelj: Nina Bassi Recezent: Sanda L

Do you ever think about what would happen

Razmišljate li ikada što bi se dogodilo

if the world were a little bit different?

kada bi svijet bio malo drugačiji?

How your life would be different

Kako bi vaš život bio drugačiji

if you were born 5,000 years from now

da ste rođeni 5 000 godina od sada

instead of today?

umjesto danas?

How history would be different

Kako bi povijest bila drugačija

if the continents were at different latitudes

kada bi kontinenti bili na različitim paralelama

or how life in the Solar system would have developed

ili kako bi se razvio život u Sunčevom sustavu

if the Sun were 10 percent larger.

da je Sunce 10 posto veće.

Well, playing with these kinds of possibilities

Pa, igranje ovim mogućnostima

is what I get to do for a living

je ono što ja radim za život,

but with the entire universe.

samo uključujući cijeli svemir.

I make model universes in a computer.

Pravim modele svemira na računalu.

Digital universes that have different starting points

Digitalni svemiri koji imaju različite polazne točke

and are made of different amounts of different kinds of material.

i koji su napravljeni od različitih količina različitog materijala.

And then I compare these universes to our own

I onda usporedim ove svemire s našim

to see what it is made of and how it evolved.

kako bih vidjela od čega je napravljen i kako se razvijao.

This process of testing models with measurements of the sky

Ovaj proces testiranja modela s mjerenjima neba

has taught us a huge amount about our universe so far.

nas je naučio mnogo o svemiru do sada.

One of the strangest things we have learned

Jedna od najčudnijih stvari koju smo naučili

is that most of the material in the universe

je kako je većina materijala u svemiru

is made of something entirely different than you and me.

napravljena od nečeg potpuno drugačijeg nego mi sami.

But without it,

Ali bez toga

the universe as we know it wouldn't exist.

svemir kakvog poznajemo ne bi postojao.

Everything we can see with telescopes

Sve što vidimo teleskopima

makes up just about 15 percent of the total mass in the universe.

zauzima jedva oko 15 posto cjelokupne mase u svemiru.

Everything else, 85 percent of it,

Sve ostalo, 85 posto toga,

doesn't emit or absorb light.

ne emitira ili ne apsorbira svjetlost.

We can't see it with our eyes,

Ne možemo je vidjeti očima,

we can't detect it with radio waves

ne možemo je detektirati radio valovima,

or microwaves or any other kind of light.

mikrovalovima ili bilo kojom svjetlošću.

But we know it is there

Ali znamo da je tamo

because of its influence on what we can see.

zbog utjecaja koji ima na ono što možemo vidjeti.

It's a little bit like,

Otprilike je kao

if you wanted to map the surface of our planet

kada biste htjeli zabilježiti površinu našeg planeta

and everything on it

i sve na njemu

using this picture of the Earth from space at night.

koristeći ovu sliku Zemlje iz svemira po noći.

You get some clues from where the light is,

Dobijete neke tragove tamo gdje se svjetlost nalazi,

but there's a lot that you can't see,

ali mnogo toga ne možete vidjeti,

everything from people to mountain ranges.

od ljudi pa sve do planinskih lanaca.

And you have to infer what is there from these limited clues.

I morate zaključiti što se tamo nalazi uz pomoć ovih ograničenih tragova.

We call this unseen stuff "dark matter."

Ovu nevidljivu stvar nazivamo "tamna tvar".

Now, a lot of people have heard of dark matter,

E sada, puno ljudi je čulo za tamnu tvar,

but even if you have heard of it,

ali čak i ako ste čuli za nju,

it probably seems abstract,

vjerojatno vam se čini apstraktnom,

far away, probably even irrelevant.

dalekom, čak i nevažnom.

Well, the interesting thing is,

Pa, zanimljiva stvar je

dark matter is all around us

da je tamna stvar svuda oko nas,

and probably right here.

vjerojatno i baš ovdje.

In fact, dark matter particles

Zapravo, čestice tamne tvari

are probably going through your body right now

vjerojatno upravo prolaze kroz vaše tijelo

as you sit in this room.

dok sjedite u ovoj prostoriji.

Because we are on Earth

Zato što smo na Zemlji

and Earth is spinning around the Sun,

a Zemlja se okreće oko Sunca,

and the Sun is hurtling through our galaxy

a Sunce juri kroz našu galaksiju

at about half a million miles per hour.

brzinom od oko 800 000 kilometara na sat.

But dark matter doesn't bump into us,

Ali tamna tvar se ne sudara s nama,

it just goes right through us.

samo prođe direktno kroz nas.

So how do we figure out more about this?

Stoga, kako da otkrijemo više o ovome?

What is it,

Što je ona

i kakve veze ima s našim postojanjem?

and what does it have to do with our existence?

Well, in order to figure out how we came to be,

Pa, kako bismo shvatili kako smo nastali,

we first need to understand how our galaxy came to be.

prvo trebamo razumjeti kako je nastala naša galaksija.

This is a picture of our galaxy, the Milky Way, today.

Ovo je slika naše galaksije, Mliječnog puta, danas.

What did it look like 10 billion years in the past

Kako je izgledala prije 10 milijardi

or what would it look like 10 billion years in the future?

ili kako će izgledati za 10 milijardi godina?

What about the stories

Što je s pričama

of the hundreds of millions of other galaxies

o stotinama milijuna ostalih galaksija

that we've already mapped out with large surveys of the sky?

koje smo već zabilježili uz pomoć brojnih promatranja neba?

How would their histories be different

Koliko bi njihove povijesti bile drugačije

if the universe was made of something else

da je svemir napravljen od nečeg drugog

or if there was more or less matter in it?

ili da je u njemu manje ili više tvari?

So the interesting thing about these model universes

Zanimljivost u vezi s ovim modelima svemira je ta

is that they allow us to test these possibilities.

da nam omogućuju testirati ove mogućnosti.

Let's go back to the first moment of the universe --

Vratimo se unazad do prvog trenutka u svemiru --

just a fraction of a second after the big bang.

samo jedan djelić sekunde poslije Velikog praska.

In this first moment,

U ovom prvom trenutku

there was no matter at all.

tvar uopće nije postojala.

The universe was expanding very fast.

Svemir se ubrzano širio.

And quantum mechanics tells us

A kvantna mehanika nam govori

that matter is being created and destroyed

kako se tvar stvara i uništava

all the time, in every moment.

cijelo vrijeme i u svakom trenutku.

At this time, the universe was expanding so fast

U to vrijeme svemir se toliko ubrzano širio

that the matter that got created couldn't get destroyed.

da se tvar koja je nastajala nije mogla uništiti.

And thus we think that all of the matter was created during this time.

I zato mislimo kako je sva tvar nastala u tom vremenu.

Both the dark matter

Oboje, i tamna tvar

and the regular matter that makes up you and me.

i normalna tvar od koje smo napravljeni i vi i ja.

Now, let's go a little bit further

A sada, krenimo malo dalje

to a time after the matter was created,

u vrijeme nakon nastanka tvari,

after protons and neutrons formed,

nakon što su se formirali protoni i neutroni,

after hydrogen formed,

nakon nastanka vodika,

about 400,000 years after the big bang.

otprilike 400 000 godina poslije Velikog praska.

The universe was hot and dense and really smooth

Svemir je bio vruć i gust i veoma gladak

but not perfectly smooth.

ali ne potpuno gladak.

This image, taken with a space telescope called the Planck satellite,

Ova slika, napravljena svemirskim teleskopom nazvanim satelit Planck,

shows us the temperature of the universe

nam pokazuje temperaturu svemira

in all directions.

u svim smjerovima.

And what we see

I ono što vidimo

is that there were places that were a little bit hotter

je da su postojala mjesta koja su bila vruća

and denser than others.

i gušća od ostalih.

The spots in this image

Točke na ovoj slici

represent places where there was more or less mass in the early universe.

predstavljaju mjesta gdje je bilo više ili manje mase u ranom svemiru.

Those spots got big because of gravity.

Te točke su se povećale zbog gravitacije.

The universe was expanding and getting less dense overall

Svemir se širio i postajao sveukupno rjeđi

over the last 13.8 billion years.

tijekom posljednjih 13,8 milijardi godina.

But gravity worked hard in those spots

Ali je gravitacija bila jaka u onim točkama

where there was a little bit more mass

gdje je bilo malo više mase

and pulled more and more mass into those regions.

i uvlačila je sve više i više mase u te dijelove.

Now, all of this is a little hard to imagine,

E sada, sve ovo je malo teško za zamisliti,

so let me just show you what I am talking about.

zato ću vam jednostavno pokazati o čemu govorim.

Those computer models I mentioned allow us to test these ideas,

Kompjutorski modeli koje sam spomenula nam omogućuju testirati ove ideje

so let's take a look at one of them.

pa pogledajmo jednu od njih.

This movie, made by my research group,

Ovaj film, koji je napravila moja istraživačka grupa

shows us what happened to the universe after its earliest moments.

nam pokazuje što se dogodilo sa svemirom nakon njegovih prvih trenutaka.

You see the universe started out pretty smooth,

Vidite kako je svemir krenuo kao prilično miran,

but there were some regions

ali su postojali neki dijelovi

where there was a little bit more material.

gdje je bilo nešto više materijala.

Gravity turned on and brought more and more mass

Gravitacija se aktivirala i privukla sve više i više mase

into those spots that started out with a little bit extra.

u te točke koje su imale malo više mase u samom početku.

Over time,

Tijekom vremena,

you get enough stuff in one place

dobijete dovoljno stvari na jednom mjestu

that the hydrogen gas,

da se vodik

which was initially well mixed with the dark matter,

koji je u početku bio pomiješan s tamnom tvari,

starts to separate from it,

počne odvajati od nje,

cool down, form stars,

hladiti, stvarati zvijezde,

and you get a small galaxy.

i dobijete malu galaksiju.

Over time, over billions and billions of years,

Tijekom vremena, tijekom milijardi i milijardi godina,

those small galaxies crash into each other

te male galaksije se sudaraju

and merge and grow to become larger galaxies,

i stapaju i rastu te postaju veće galaksije,

like our own galaxy, the Milky Way.

kao naša galaksija, Mliječni put.

Now, what happens if you don't have dark matter?

E sada, što se događa ako nemate tamnu tvar?

If you don't have dark matter,

Ako nema tamne tvari,

those spots never get clumpy enough.

te točke nikada ne postanu dovoljno velike.

It turns out, you need at least a million times the mass of the Sun

Ispada kako treba barem milijun puta mase Sunca

in one dense region,

na jednom gustom dijelu

before you can start forming stars.

prije nego se počnu formirati zvijezde.

And without dark matter,

A bez tamne tvari

you never get enough stuff in one place.

nikada ne dobijete dovoljno tvari na jednom mjestu.

So here, we're looking at two universes, side by side.

Ovdje gledamo dva svemira jedan pokraj drugoga.

In one of them you can see

U jednom vidite

that things get clumpy quickly.

kako se stvari brzo grupiraju.

In that universe,

U takvom svemiru

it's really easy to form galaxies.

se galaksije lako formiraju.

In the other universe,

U drugom svemiru

the things that start out like small clumps,

stvari koje počnu kao male grude,

they just stay really small.

jednostavno ostanu jako male.

Not very much happens.

Ne dogodi se puno toga.

In that universe, you wouldn't get our galaxy.

U tom svemiru ne biste dobili našu galaksiju.

Or any other galaxy.

Ili bilo koju drugu galaksiju.

You wouldn't get the Milky Way,

Ne biste dobili Mliječni put,

you wouldn't get the Sun,

ne biste dobili Sunce,

you wouldn't get us.

ne biste dobili nas.

We just couldn't exist in that universe.

Jednostavno ne bismo mogli postojati u tom svemiru.

OK, so this crazy stuff, dark matter,

Dakle, ova luda stvar, tamna tvar,

it's most of the mass in the universe,

je većina mase u svemiru,

it's going through us right now, we wouldn't be here without it.

prolazi kroz nas upravo sada; ne bismo bili tu bez nje.

What is it?

Što je ona?

Well, we have no idea.

Zapravo, nemamo pojma.

(Laughter)

(Smijeh)

But we have a lot of educated guesses,

Ali imamo puno hipoteza

and a lot of ideas for how to find out more.

i puno ideja kako saznati više.

So, most physicists think that dark matter is a particle,

Većina fizičara misli kako je tamna tvar čestica,

similar in many ways to the subatomic particles that we know of,

u mnogočemu slična subatomskim česticama koje poznajemo,

like protons and neutrons and electrons.

kao što su protoni, neutroni i elektroni.

Whatever it is,

Što god da je,

it behaves very similarly with respect to gravity.

ponaša se veoma slično u odnosu s gravitacijom.

But it doesn't emit or absorb light,

Ali ne emitira i ne apsorbira svjetlost

and it goes right through normal matter,

i prolazi direktno kroz normalnu tvar

as if it wasn't even there.

kao da ni ne postoji.

We'd like to know what particle it is.

Htjeli bismo saznati koja je to čestica.

For example, how heavy is it?

Na primjer, koliko je teška?

Or, does anything at all happen if it interacts with normal matter?

Ili, događa li se išta ako dođe u interakciju s normalnom tvari?

Physicists have lots of great ideas for what it could be,

Fizičari imaju mnogo odličnih ideja što bi ona mogla biti;

they're very creative.

sve su veoma kreativne.

But it's really hard,

Ali je jako teško

because those ideas span a huge range.

zato što te ideje imaju veliki raspon.

It could be as small as the smallest subatomic particles,

Mogla bi biti mala kao najmanja subatomska čestica,

or it could be as large as the mass of 100 Suns.

ili bi mogla biti velika kao masa od 100 Sunaca.

So, how do we figure out what it is?

Dakle, kako zaključiti što je?

Well, physicists and astronomers

Pa, fizičari i astronomi

have a lot of ways to look for dark matter.

imaju mnogo načina za traženje tamne tvari.

One of the things we're doing is building sensitive detectors

Jedna od stvari koju radimo je da gradimo osjetljive detektore

in deep underground mines,

u dubokim podzemnim rudnicima

waiting for the possibility

čekajući mogućnost

that a dark matter particle, which goes through us and the Earth,

da se čestica tamne tvari, koja prolazi kroz nas i Zemlju,

would hit a denser material

sudari s gušćim materijalom

and leave behind some trace of its passage.

i ostavi za sobom nekakav trag prolaska.

We're looking for dark matter in the sky,

Tražimo tamnu tvar na nebu,

for the possibility that dark matter particles

mogućnost da bi se čestice tamne tvari

would crash into each other

mogle sudariti jedna s drugom

and create high-energy light that we could see

i stvoriti visokoenergetsku svjetlost koju bismo mogli vidjeti

with special gamma-ray telescopes.

uz pomoć specijalnih teleskopa s gama zrakama.

We're even trying to make dark matter here on Earth,

Čak nastojimo i napraviti tamnu tvar ovdje na Zemlji

by smashing particles together and looking for what happens,

tako da sudaramo čestice i promatramo što se događa,

using the Large Hadron Collider in Switzerland.

upotrebljavajući Veliki hadronski sudarivač u Švicarskoj.

Now, so far,

Do sada

all of these experiments have taught us a lot

su nas ovi eksperimenti naučili mnogo

about what dark matter isn't

o onome što tamna tvar nije

(Laughter)

(Smijeh)

but not yet what it is.

ali još ne o onome što ona jest.

There were really good ideas that dark matter could have been,

Bilo je mnogo dobrih ideja gdje bi se tamna tvar mogla vidjeti

that these experiments would have seen.

koju bi ovi eksperimenti mogli pronaći.

And they didn't see them yet,

Ali je još nisu pronašli,

so we have to keep looking and thinking harder.

tako da trebamo dalje tražiti i više razmišljati.

Now, another way to get a clue to what dark matter is

A sada, drugi način kako saznati što je tamna tvar

is to study galaxies.

je proučavati galaksije.

We already talked about

Već smo pričali o tome

how our galaxy and many other galaxies wouldn't even be here

kako naša galaksija i mnogo ostalih ne bi uopće bile ovdje

without dark matter.

da nema tamne tvari.

Those models also make predictions

Ti modeli također predviđaju

for many other things about galaxies:

mnoge druge stvari o galaksijama:

How they're distributed in the universe,

Kako su raspodijeljene po svemiru,

how they move,

kako se kreću,

how they evolve over time.

kako se razvijaju tijekom vremena.

And we can test those predictions with observations of the sky.

A mi možemo testirati ta predviđanja uz pomoć promatranja neba.

So let me just give you two examples

Dat ću vam dva primjera

of these kinds of measurements we can make with galaxies.

ovakvog tipa mjerenja koja možemo napraviti na galaksijama.

The first is that we can make maps of the universe with galaxies.

Prvi je da možemo napraviti karte svemira s galaksijama.

I am part of a survey called the Dark Energy Survey,

Dio sam istraživanja koje se zove Istraživanje tamne energije

which has made the largest map of the universe so far.

koje je napravilo najveću kartu svemira do sada.

We measured the positions and shapes of 100 million galaxies

Izmjerili smo položaje i oblike 100 milijuna galaksija

over one-eighth of the sky.

unutar jedne osmine neba.

And this map is showing us all the matter in this region of the sky,

Ova karta nam pokazuje svu tvar u ovom dijelu neba,

which is inferred by the light distorted from these 100 million galaxies.

što je zaključeno na temelju svjetla iskrivljenog tim 100 milijuna galaksija.

The light distorted from all of the matter

Svjetlošću iskrivljenom svom tvari

that was between those galaxies and us.

koja je bila između tih galaksija i nas.

The gravity of the matter is strong enough to bend the path of light.

Gravitacija tvari je dovoljno jaka da savije putanju svjetlosti.

And it gives us this image.

I to nam daje ovu sliku.

So these kinds of maps

Tako da ove vrste karata

can tell us about how much dark matter there is,

nam mogu reći koliko tamne tvari postoji,

they also tell us where it is

također nam pokazuju gdje se nalazi

and how it changes over time.

i kako se mijenja tijekom vremena.

So we're trying to learn about what the universe is made of

Tako da nastojimo naučiti od čega je sastavljen svemir

on the very largest scales.

veoma opsežno.

It turns out that the tiniest galaxies in the universe

Ispada kako najmanje galaksije u svemiru

provide some of the best clues.

daju najbolje tragove.

So why is that?

Zašto je to tako?

Here are two example simulated universes

Evo dva primjera simuliranih svemira

with two different kinds of dark matter.

s dvije različite vrste tamne tvari.

Both of these pictures are showing you a region

Obje ove slike pokazuju dio

around a galaxy like the Milky Way.

oko galaksije kao što je Mliječni put.

And you can see that there's a lot of other material around it,

I možete vidjeti kako je mnogo materijala oko nje,

little small clumps.

kao male grude.

Now, in the image on the right,

A sada, na slici desno

dark matter particles are moving slower than they are in the one on the left.

čestice tamne tvari se kreću sporije nego na onoj s lijeve strane.

If those dark matter particles are moving really fast,

Ako se te čestice tamne tvari kreću jako brzo,

then the gravity in small clumps is not strong enough

onda gravitacija u malim grudama nije dovoljno jaka

to slow those fast particles down.

da uspori te čestice.

And they keep going.

I one se i dalje kreću.

They never collapse into these small clumps.

Nikada se ne sudaraju s tim malim grudama.

So you end up with fewer of them than in the universe on the right.

Tako da završite s manje njih nego u svemiru s desne strane.

If you don't have those small clumps,

Ako nema tih malih gruda,

then you get fewer small galaxies.

onda dobijete manje malih galaksija.

If you look up at the southern sky,

Ako pogledate prema južnom nebu,

you can actually see two of these small galaxies,

zapravo možete vidjeti dvije od ovih malih galaksija,

the largest of the small galaxies that are orbiting our Milky Way,

najveće od malih galaksija koje kruže oko naše Mliječne staze,

the Large Magellanic Cloud and the Small Magellanic Cloud.

Veliki Magellanov oblak i Mali Magellanov oblak.

In the last several years,

U zadnjih nekoliko godina

we have detected a whole bunch more even smaller galaxies.

otkrili smo mnogo još manjih galaksija.

This is an example of one of them

Ovo je primjer jedne

that we detected with the same dark energy survey

koju smo otkrili istim istraživanjem tamne energije

that we used to make maps of the universe.

koje smo koristili kako bismo napravili karte svemira.

These really small galaxies,

Ove zaista male galaksije,

some of them are extremely small.

neke od njih su stvarno jako male.

Some of them have as few as a few hundred stars,

Neke od njih imaju svega nekoliko stotina zvijezda,

compared to the few hundred billion stars in our Milky Way.

u usporedbi s nekoliko stotina milijardi koje ima Mlliječni put.

So that makes them really hard to find.

Zbog toga ih je teško pronaći.

But in the last decade,

Ali u posljednjih deset godina

we've actually found a whole bunch more of these.

smo pronašli mnogo više takvih.

We now know of 60 of these tiny galaxies

Sada znamo za 60 ovih minijaturnih galaksija

that are orbiting our own Milky Way.

koje kruže oko našeg Mliječnog puta.

And these little guys are a big clue to dark matter.

I ovi malci su veliki korak prema tamnoj tvari.

Because just the existence of these galaxies tells us

Zato što nam samo postojanje ovih galaksija govori

that dark matter can't be moving very fast,

da se tamna tvar ne može brzo kretati

and not much can be happening when it runs into normal matter.

i ne može se mnogo toga dogoditi kada se sudari s normalnom tvari.

In the next several years,

U sljedećih nekoliko godina

we're going to make much more precise maps of the sky.

napravit ćemo puno preciznije karte svemira.

And those will help refine our movies

I one će nam pomoći da usavršimo naše filmove

of the whole universe and the entire galaxy.

cijelog svemira i cijele galaksije.

Physicists are also making new, more sensitive experiments

Fizičari također prave nove, osjetljivije eksperimente

to try to catch some sign of dark matter in their laboratories.

kako bi uhvatili neki znak tamne tvari u svojim laboratorijima.

Dark matter is still a huge mystery.

Tamna tvar je i dalje velika zagonetka.

But it's a really exciting time to be working on it.

Ali je jako uzbudljivo vrijeme za raditi na tome.

We have really clear evidence it exists.

Imamo jasne dokaze da ona postoji.

From the scale of the smallest galaxies

Od veličine najmanjih galaksije

to the scale of the whole universe.

do veličine cijelog svemira.

Will we actually find it and figure out what it is?

Hoćemo li je zaista pronaći i shvatiti što je?

I have no idea.

Ne znam.

But it's going to be a lot of fun to find out.

Ali će biti jako zabavno saznati.

We have a lot of possibilities for discovery,

Imamo mnogo mogućnosti kako bismo je otkrili

and we definitely will learn more about what it is doing

i sigurno ćemo naučiti više o tome što radi

and about what it isn't.

i o tome što ne radi.

Regardless of whether we find that particle anytime soon,

Bez obzira na to nađemo li česticu uskoro,

I hope I have convinced you

nadam se da sam vas uvjerila

that this mystery is actually really close to home.

kako je ova zagonetka blizu otkrivanja.

The search for dark matter

Potraga za tamnom tvari

may just be the key to a whole new understanding of physics

bi mogla biti ključ novog shvaćanja fizike

and our place in the universe.

i našeg mjesta u svemiru.

Thank you.

Hvala.

(Applause)

(Pljesak)