Why our universe might exist on a knife-edge | Gian Giudice

Prevodilac: Aleksandra Kovačević Lektor: Mile Živković

So last year, on the Fourth of July,

Prošle godine, četvrtog jula,

experiments at the Large Hadron Collider

eksperimenti na Velikom hadronskom sudaraču

discovered the Higgs boson.

otkrili su Higsov bozon.

It was a historical day.

Bio je to istorijski dan.

There's no doubt that from now on,

Nema sumnje da će se od sada pa nadalje,

the Fourth of July will be remembered

četvrti juli pamtiti

not as the day of the Declaration of Independence,

ne kao dan proglašenja nezavisnosti,

but as the day of the discovery of the Higgs boson.

već kao dan otkrića Higsovog bozona.

Well, at least, here at CERN.

Pa, makar ovde u CERNu.

But for me, the biggest surprise of that day

Ali za mene, najveće iznenađenje tog dana,

was that there was no big surprise.

bilo je to da nije bilo velikog iznenađenja.

In the eye of a theoretical physicist,

U očima teoretskih fizičara,

the Higgs boson is a clever explanation

Higsov bozon je domišljato objašnjenje

of how some elementary particles gain mass,

toga kako neke elementarne čestice dobijaju masu,

but it seems a fairly unsatisfactory

ali deluje kao prilično nezadovoljavajuće

and incomplete solution.

i nepotpuno rešenje.

Too many questions are left unanswered.

Previše pitanja ostavljeno je bez odgovora.

The Higgs boson does not share the beauty,

Higsov bozon ne poseduje tu lepotu,

the symmetry, the elegance,

tu simetriju, eleganciju,

of the rest of the elementary particle world.

koju imaju ostale elementarne čestice.

For this reason, the majority of theoretical physicists

Iz ovog razloga, većina teoretskih fizičara,

believe that the Higgs boson could not

smatra da Higsov bozon ne može

be the full story.

biti cela priča.

We were expecting new particles and new phenomena

Očekivali smo nove čestice i nove pojave

accompanying the Higgs boson.

pored Higsovog bozona.

Instead, so far, the measurements

Umesto toga, za sad, merenja

coming from the LHC show no signs of new particles

koja dolaze iz VHS ne pokazuju znake postojanja novih čestica

or unexpected phenomena.

niti neočekivanih pojava.

Of course, the verdict is not definitive.

Naravno, presuda nije konačna.

In 2015, the LHC will almost double

2015. VHS će skoro udvostručiti

the energy of the colliding protons,

energiju protona koji se sudaraju,

and these more powerful collisions

i ovi snažniji sudari

will allow us to explore further the particle world,

omogućiće nam da dalje istražujemo svet čestica

and we will certainly learn much more.

i sigurno da ćemo saznati mnogo više.

But for the moment, since we have found

Ali za sada, pošto nismo pronašli

no evidence for new phenomena, let us suppose

nikakav dokaz novih pojava, recimo da su

that the particles that we know today,

nove čestice koje danas poznajemo,

including the Higgs boson,

uključujući i Higsov bozon,

are the only elementary particles in nature,

samo elementarne čestice u prirodi,

even at energies much larger

čak i kada su u pitanju mnogo veće količine energije

than what we have explored so far.

od onih koje smo do sada ispitali.

Let's see where this hypothesis is going to lead us.

Hajde da vidimo kuda će nas ova pretpostavka odvesti.

We will find a surprising and intriguing result

Naići ćemo na iznenađujuć i zanimljiv rezultat

about our universe, and to explain my point,

o našem svemiru, i kako bih objasnio šta hoću da kažem,

let me first tell you what the Higgs is about,

dozvolite mi prvo da vam objasnim o čemu je Higs u stvari,

and to do so, we have to go back

a da bih to uradio, moramo se vratiti unazad

to one tenth of a billionth of a second

do jedne desetine milijarditog dela sekunde

after the Big Bang.

nakon Velikog praska.

And according to the Higgs theory,

I prema Higsovoj teoriji,

at that instant, a dramatic event took place

u tom trenutku, dramatičan događaj

se odvio u univerzumu.

in the universe.

Space-time underwent a phase transition.

Prostor-vreme pretrpelo je faznu promenu.

It was something very similar to the phase transition

Nešto vrlo slično faznoj promeni

that occurs when water turns into ice

koja se dešava kada se voda pretvara u led

below zero degrees.

na temperaturi ispod nule.

But in our case, the phase transition

Ali u našem slučaju, ova fazna promena

is not a change in the way the molecules

nije promena u načinu na koji su molekuli

are arranged inside the material,

poređani unutar materijala,

but is about a change

već se radi o promeni

of the very fabric of space-time.

same strukture prostor-vremena.

During this phase transition, empty space

Tokom ove fazne promene, prazan prostor

became filled with a substance

ispunio se supstancom

that we now call Higgs field.

koju danas nazivamo Higsovim poljem.

And this substance may seem invisible to us,

Ova supstanca može nam delovati nevidljivo,

but it has a physical reality.

ali postoji u fizičkoj stvarnosti.

It surrounds us all the time,

Okružuje nas sve vreme,

just like the air we breathe in this room.

baš kao vazduh koji udišemo u ovoj prostoriji.

And some elementary particles interact

I neke elementarne čestice su u interakciji

with this substance, gaining energy in the process.

sa ovom supstancom, dobijajući pri tom na energiji.

And this intrinsic energy is what we call

I ova unutarnja energija je ono što nazivamo

the mass of a particle,

masom čestica,

and by discovering the Higgs boson, the LHC

i nakon otkrivanja Higsovog bozona, VHS

has conclusively proved that this substance is real,

je ubedljivo dokazao da je ova supstanca stvarna,

because it is the stuff the Higgs bosons are made of.

jer je to ono od čega je Higsov bozon sagrađen.

And this, in a nutshell, is the essence of the Higgs story.

I to je, ukratko, suština priče o Higsu.

But this story is far more interesting than that.

Ali ova priča je daleko zanimljivija od toga.

By studying the Higgs theory,

Proučavajući Higsovu teoriju,

theoretical physicists discovered,

teoretski fizičari su otkrili,

not through an experiment

ne kroz eksperiment,

but with the power of mathematics,

već uz pomoć matematike,

that the Higgs field does not necessarily exist

da nije obavezno da Higsovo polje postoji

only in the form that we observe today.

samo u obliku u kom ga mi danas posmatramo.

Just like matter can exist as liquid or solid,

Baš kao što materija postoji u tečnom ili čvrstom stanju,

so the Higgs field, the substance that fills all space-time,

tako i Higsovo polje, supstanca koja ispunjava čitavo prostor-vreme,

could exist in two states.

postoji u dva stanja.

Besides the known Higgs state,

Pored već poznatog Higsovog stanja,

there could be a second state in which the Higgs field

moguće je da postoji i drugo stanje u kom je Higsovo polje

is billions and billions times denser

milijardu i milijardu puta gustije

than what we observe today,

od onog kako ga mi danas posmatramo,

and the mere existence of another state

i samo postojanje drugog stanja

of the Higgs field poses a potential problem.

Higsovog polja predstavlja mogući problem.

This is because, according to the laws

Iz razloga što, prema zakonima

of quantum mechanics, it is possible

kvantne mehanike, moguće je

to have transitions between two states,

imati prelaz između dva stanja

even in the presence of an energy barrier

čak i u prisustvu energetske barijere

separating the two states,

koja razdvaja dva stanja,

and the phenomenon is called,

i ta pojava naziva se

quite appropriately, quantum tunneling.

sasvim prikladno, kvantno tuneliranje.

Because of quantum tunneling,

Zbog kvantnog tuneliranja,

I could disappear from this room

mogao bih da nestanem iz ove prostorije

and reappear in the next room,

i pojavim se u susednoj prostoriji,

practically penetrating the wall.

bukvalno probijajući se kroz zid.

But don't expect me to actually perform the trick

Ali nemojte od mene očekivati da izvedem trik

in front of your eyes, because the probability

na vaše oči, jer je verovatnoća

for me to penetrate the wall is ridiculously small.

da probijem zid smešno mala.

You would have to wait a really long time

Trebate da čekate zaista dugo

before it happens, but believe me,

pre nego šro se to dogodi, ali verujte mi,

quantum tunneling is a real phenomenon,

kvantno tuneliranje je stvarna pojava,

and it has been observed in many systems.

i uočena je u mnogim sistemima.

For instance, the tunnel diode,

Na primer, tunelska dioda,

a component used in electronics,

komponenta koja se koristi u elektronici,

works thanks to the wonders

radi uz pomoć čuda

of quantum tunneling.

kvantnog tuneliranja.

But let's go back to the Higgs field.

Ali, hajde da se vratimo Higsovom polju.

If the ultra-dense Higgs state existed,

Ako ultra-gusto Higsovo stanje postoji,

then, because of quantum tunneling,

onda, zbog kvantnog tuneliranja,

a bubble of this state could suddenly appear

mehur ovog stanja bi mogao iznenada da se pojavi

in a certain place of the universe at a certain time,

na određenom mestu univerzuma u određeno vreme,

and it is analogous to what happens when you boil water.

i slično je onome što se desi kada prokuvate vodu.

Bubbles of vapor form inside the water,

Mehuri od isparenja se stvore unutar vode,

then they expand, turning liquid into gas.

zatim se šire, pretvarajući tečnost u gas.

In the same way, a bubble of the ultra-dense Higgs state

Na isti način, mehur ultra-gustog Higsovog stanja

could come into existence because of quantum tunneling.

se može pojaviti zbog kvantnog tuneliranja.

The bubble would then expand at the speed of light,

Mehur bi se zatim raširio brzinom svetlosti,

invading all space, and turning the Higgs field

zauzeo sav prostor i promenio Higsovo polje

from the familiar state into a new state.

iz poznatog stanja u novo stanje.

Is this a problem? Yes, it's a big a problem.

Da li je ovo problem? Da, veliki problem.

We may not realize it in ordinary life,

Možda ne možemo to da shvatimo u svakodnevnom životu,

but the intensity of the Higgs field is critical

ali jačina Higsovog polja je od suštinske važnosti

for the structure of matter.

za strukturu materije.

If the Higgs field were only a few times more intense,

Kada bi Higsovo polje bilo samo nekoliko puta jače,

we would see atoms shrinking, neutrons decaying

videli bismo atome kako se smanjuju, neutrone koji slabe

inside atomic nuclei, nuclei disintegrating,

unutar atomskih jezgara, jezgra koja se raspadaju,

and hydrogen would be

a vodonik bi bio

the only possible chemical element in the universe.

jedini mogući hemijski element u univerzumu.

And the Higgs field, in the ultra-dense Higgs state,

I Higsovo polje, u ultra-gustom Higsovom stanju,

is not just a few times more intense than today,

nije samo nekoliko puta jače nego danas,

but billions of times,

nego milijarde puta,

and if space-time were filled by this Higgs state,

i kada bi vreme-prostor bilo ispunjeno tim Higsovim stanjem,

all atomic matter would collapse.

sva atomska materija bi se srušila.

No molecular structures would be possible, no life.

Ne bi bilo molekularnih struktura, niti života.

So, I wonder, is it possible

Stoga se pitam, da li je moguće

that in the future, the Higgs field

da će u budućnosti, Higsovo polje

will undergo a phase transition and,

podleći fazi promene

through quantum tunneling, will be transformed

i da će se kroz kvantno tuneliranje transformisati

into this nasty, ultra-dense state?

u to opako, ultra-gusto stanje?

In other words, I ask myself, what is the fate

Drugim rečima, pitam se, koja je sudbina

of the Higgs field in our universe?

Higsovog polja u našem univerzumu?

And the crucial ingredient necessary

A suštinski element koji je neophodan

to answer this question is the Higgs boson mass.

da bismo dali odgovor na to pitanje je masa Higsovog bozona.

And experiments at the LHC found that the mass

Eksperimenti na VHS otkrili su da masa

of the Higgs boson is about 126 GeV.

Higsovog bozona iznosi oko 126 gigaelektronvolta.

This is tiny when expressed in familiar units,

Ovo je sićušno kada ga izrazimo u poznatim jedinicama,

because it's equal to something like

jer je jednako otpilike

10 to the minus 22 grams,

10 na minus 22 grama,

but it is large in particle physics units,

ali je veliko u jedinicama fizike čestica,

because it is equal to the weight

jer je jednako težini

of an entire molecule

čitavog jednog molekula,

of a DNA constituent.

konstituenta DNK.

So armed with this information from the LHC,

Naoružani ovim podacima iz VHSa,

together with some colleagues here at CERN,

zajedno sa još nekim kolegama ovde u CERNu,

we computed the probability

izračunali smo verovatnoću

that our universe could quantum tunnel

da bi naš univerzum mogao da prođe kroz kvantno tuneliranje

into the ultra-dense Higgs state,

i pređe u ultra-gusto Higsovo stanje,

and we found a very intriguing result.

i dobili veoma zanimljiv rezultat.

Our calculations showed

Naši proračuni pokazali su

that the measured value of the Higgs boson mass

da je izmerena masa Higsovog bozona

is very special.

veoma posebna.

It has just the right value

Ima tačno one vrednosti koje bi omogućile

to keep the universe hanging

da univerzum lebdi

in an unstable situation.

u nestabilnom stanju.

The Higgs field is in a wobbly configuration

Higsovo polje ima klimavu konfiguraciju

that has lasted so far

koja je trajala do sad

but that will eventually collapse.

ali koja će se na kraju srušiti.

So according to these calculations,

Sudeći po ovim proračunima,

we are like campers

mi smo kao kamperi

who accidentally set their tent

koji su slučajno postavili svoj šator

at the edge of a cliff.

na ivicu stene.

And eventually, the Higgs field

I na kraju, Higsovo polje

will undergo a phase transition

će podleći fazi promene

and matter will collapse into itself.

i materija će se urušiti sama u sebe.

So is this how humanity is going to disappear?

Je li to način na koji će čovečanstvo iščeznuti?

I don't think so.

Ne bih rekao.

Our calculation shows that quantum tunneling

Naši proračuni ukazuju na to da se kvantno tuneliranje

of the Higgs field is not likely to occur

Higsovog polja najverovatnije neće dogoditi

in the next 10 to the 100 years,

u narednih 10 do 100 godina,

and this is a very long time.

a to je veoma dug period.

It's even longer than

To je čak duže nego

the time it takes for Italy to form a stable government.

period koji je potreban Italiji da formira stabilnu vladu.

(Laughter)

(Smeh)

Even so, we will be long gone by then.

Čak i da je tako, do tad nas već odavno neće biti.

In about five billion years,

Za oko 5 miljardi godina,

our sun will become a red giant,

naše sunce postaće crveni džin,

as large as the Earth's orbit,

veliki koliko i Zemljina orbita,

and our Earth will be kaput,

i naša Zemlja će nestati,

and in a thousand billion years,

a za hiljadu milijardi godina,

if dark energy keeps on fueling

ako tamna energija nastavi da ubrzava

space expansion at the present rate,

širenje svemira današnjim tempom,

you will not even be able to see as far as your toes,

nećete biti u stanju da vidite dalje od svojih nogu,

because everything around you

jer se sve oko vas

expands at a rate faster than the speed of light.

širi tempom koji je brži od brzine svetlosti.

So it is really unlikely

Tako da je veoma mala verovatnoća

that we will be around to see the Higgs field collapse.

da ćemo postojati tada da vidimo urušavanje Higsovog polja.

But the reason why I am interested

Međutim, razlog zbog kog sam ja zainteresovan

in the transition of the Higgs field

za promenu Higsovog polja

is because I want to address the question,

je taj jer želim da se pozabavim pitanjem,

why is the Higgs boson mass so special?

zašto je masa Higsovog bozona tako posebna?

Why is it just right to keep the universe

Zašto ima vrednosti taman tolike da održava univerzum

at the edge of a phase transition?

na ivici fazne promene?

Theoretical physicists always ask "why" questions.

Teoretski fizičari uvek postavljaju pitanja sa "zašto".

More than how a phenomenon works,

Pre nego kako se neka pojava dešava,

theoretical physicists are always interested in

teoretske fizičare zanima

why a phenomenon works in the way it works.

zašto se neka pojava dešava na način na koji se dešava.

We think that this these "why" questions

Smatramo da nam ova pitanja sa "zašto"

can give us clues

mogu dati ključ

about the fundamental principles of nature.

o fundamentalnim principima prirode

And indeed, a possible answer to my question

I zaista, mogući odgovor na moje pitanje

opens up new universes, literally.

otvara nove univerzume, bukvalno.

It has been speculated that our universe

Nagađa se da je naš univerzum

is only a bubble in a soapy multiverse

samo jedan mehurić u sapunjavom multiverzumu

made out of a multitude of bubbles,

sačinjenom od mnogobrojnih mehurova,

and each bubble is a different universe

i svaki mehur je univerzum za sebe

with different fundamental constants

sa različitim fundamentalnim konstantama

and different physical laws.

i različitim zakonima fizike.

And in this context, you can only talk about

I u ovom kontekstu, možemo samo razgovarati

the probability of finding a certain value of the Higgs mass.

o mogućnosti nalaženja određene vrednosti Higsove mase.

Then the key to the mystery

U tom slučaju, ključ za rešavanje misterije

could lie in the statistical properties

se možda nalazi u statističkim odlikama

of the multiverse.

multiverzuma.

It would be something like what happens

To bi ličilo na ono što se dešava

with sand dunes on a beach.

sa peščanim dinama na plaži.

In principle, you could imagine to find sand dunes

U suštini, mogli biste zamisliti da nađete peščane dine

of any slope angle in a beach,

bilo kog ugla nagiba na nekoj plaži,

and yet, the slope angles of sand dunes

a ipak, uglovi nagiba peščanih dina

are typically around 30, 35 degrees.

se tipično kreću oko 30, 35 stepeni.

And the reason is simple:

A razlog za to je jednostavan:

because wind builds up the sand, gravity makes it fall.

zato što vetar nanese pesak, gravitacija ga vuče dole.

As a result, the vast majority of sand dunes

Kao rezultat toga, većina peščanih dina

have slope angles around the critical value,

ima ugao nagiba koji se kreće oko kritične vrednosti,

near to collapse.

blizu kolapsa.

And something similar could happen

I nešto slično tome može da se dogodi

for the Higgs boson mass in the multiverse.

masi Higsovog bozona u multiverzumu.

In the majority of bubble universes,

Kod većine mehur-univerzuma

the Higgs mass could be around the critical value,

Higsova masa može biti negde oko kritične vrednosti,

near to a cosmic collapse of the Higgs field,

blizu kosmičkog kolapsa Higsovog polja

because of two competing effects,

zbog dva međusobno suprotstavljena efekta,

just as in the case of sand.

kao u slučaju peska.

My story does not have an end,

Moja priča nema neki kraj,

because we still don't know the end of the story.

jer još uvek ne znamo kraj te priče.

This is science in progress,

Ovo je nauka je u razvitku,

and to solve the mystery, we need more data,

i da bismo razrešili misteriju, potrebno nam je još podataka,

and hopefully, the LHC will soon add new clues

i VHS će, nadajmo se, uskoro otkriti nove detalje

to this story.

ove priče.

Just one number, the Higgs boson mass,

Samo jedna brojka, masa Higsovog bozona,

and yet, out of this number we learn so much.

a ipak, iz ovog broja možemo toliko toga da naučimo.

I started from a hypothesis, that the known particles

Počeo sam od pretpostavke, da se sve do sad poznate čestice

are all there is in the universe,

nalaze u univerzumu,

even beyond the domain explored so far.

čak i van područja koje je do sad istraženo.

From this, we discovered that the Higgs field

Iz ovog smo otkrili da se Higsovo polje

that permeates space-time may be standing

koje se prožima kroz prostor-vreme, verovatno nalazi

on a knife edge, ready for cosmic collapse,

na prelomnoj tački, spremno za kosmički kolaps,

and we discovered that this may be a hint

i otkrili smo da je ovo možda samo naznaka

that our universe is only a grain of sand

da je naš univerzum samo zrno peska

in a giant beach, the multiverse.

na ogromnoj plaži, multiverzumu.

But I don't know if my hypothesis is right.

Ali ne znam da li je moja pretpostavka tačna.

That's how physics works: A single measurement

Tako je to sa fizikom: jedno merenje

can put us on the road to a new understanding

nas može odvesti na put novog shvatanja

of the universe

uiverzuma

or it can send us down a blind alley.

ili nas može odvesti u ćorsokak.

But whichever it turns out to be,

Ali kako god bilo,

there is one thing I'm sure of:

jedna stvar u koju sam siguran je:

The journey will be full of surprises.

put će biti pun iznenađenja.

Thank you.

Hvala vam.

(Applause)

(Aplauz)