We know about our universe’s past: the Big Bang theory predicts that all matter, time, and space began in an incredibly tiny, compact state about 14 billion years ago. And we know about the present: scientists’ observations of the movement of galaxies tell us that the universe is expanding at an accelerated rate. But what about the future? Do we know how our universe is going to end?
Znamo za prošlost svemira: po teoriji „velikog praska”, sva materija, vreme i prostor nastali su u neverovatno malom, kompaktnom stanju pre oko 14 milijardi godina. Znamo i za sadašnjost: naučna posmatranja kretanja galaksija govore nam da se svemir ubrzano širi. Ali šta je sa budućnošću? Znamo li kako će naš svemir završiti?
Cosmologists have three possible answers for this question, called the Big Freeze, the Big Rip and the Big Crunch.
Kosmolozi imaju tri moguća odgovora na ovo pitanje: zvana „veliko hlađenje”, „veliko kidanje” i „veliko sažimanje”.
To understand these three scenarios, imagine two objects representing galaxies. A short, tight rubber band is holding them together— that’s the attractive force of gravity. Meanwhile, two hooks are pulling them apart— that’s the repulsive force expanding the universe. Copy this system over and over again, and you have something approximating the real universe. The outcome of the battle between these two opposing forces determines how the end of the universe will play out.
Kako bismo razumeli ova tri scenarija, zamislite dva objekta koji predstavljaju galaksije. Kratka zategnuta gumica ih drži zajedno - to je sila gravitacije. U međuvremenu, dve kuke ih vuku jedan od drugog - to je sila odbijanja koja širi svemir. Ovo umnožite iznova i iznova, i imaćete nešto slično stvarnom svemiru. Ishod bitke između ove dve suprotne sile odlučuje kako će se odvijati kraj svemira.
The Big Freeze scenario is what happens if the force pulling the objects apart is just strong enough to stretch the rubber band until it loses its elasticity. The expansion wouldn’t be able to accelerate anymore, but the universe would keep getting bigger. Clusters of galaxies would separate. The objects within the galaxies– suns, planets, and solar systems would move away from each other, until galaxies dissolved into lonely objects floating separately in the vast space. The light they emit would be redshifted to long wavelengths with very low, faint energies, and the gas emanating from them would be too thin to create new stars. The universe would become darker and colder, approaching a frozen state also known as the Big Chill, or the Heat Death of the Universe.
Scenario „velikog hlađenja” će se desiti ako je sila koje odvlači objekte dovoljno jaka da rasteže gumenu traku dok ona ne izgubi elastičnost. Širenje ne bi moglo da se više ubrzava, ali svemir bi i dalje postajao sve veći. Grupisane galaksije bi se razdvojile. Objekti unutar galaksija - sunca, planete i solarni sistemi bi se međusobno razdvojili dok se galaksije ne rasplinu u usamljene objekte koji odvojeno plutaju u ogromnom prostoru. Svetlost koju emituju bi bila pod uticajem crvenog pomaka, sa dugačkim talasnim dužinama sa veoma malom i slabom energijom, a gas koji emituju bi bio suviše redak da bi se stvorile nove zvezde. Svemir bi postao mračniji i hladniji, približavajući se stanju smrzavanja, poznatom kao „veliko hlađenje”. ili „nestanak toplote svemira”.
But what if the repulsive force is so strong that it stretches the rubber band past its elastic limit, and actually tears it? If the expansion of the universe continues to accelerate, it will eventually overcome not only the gravitational force – tearing apart galaxies and solar systems– but also the electromagnetic, weak, and strong nuclear forces which hold atoms and nuclei together. As a result, the matter that makes up stars breaks into tiny pieces. Even atoms and subatomic particles will be destroyed. That’s the Big Rip.
Ali šta se dešava ako je sila odbijanja toliko jaka da istegne gumenu traku preko njene granice elastičnosti, te je u stvari pocepa? Ako širenje svemira nastavi da se ubrzava, to će na kraju prevazići ne samo gravitacionu silu - razarajući galaksije i solarne sisteme - nego i elektromagnetnu, slabu i jaku nuklearnu silu koje drže atome i jezgra zajedno. Kao rezultat, materija od koje su stvorene zvezde će se razbiti u najsitnije komade. Čak će biti uništeni i atomi i njihovi delovi. To je „veliko kidanje”.
What about the third scenario, where the rubber band wins out? That corresponds to a possible future in which the force of gravity brings the universe’s expansion to a halt— and then reverses it. Galaxies would start rushing towards each other, and as they clumped together their gravitational pull would get even stronger. Stars too would hurtle together and collide. Temperatures would rise as space would get tighter and tighter. The size of the universe would plummet until everything compressed into such a small space that even atoms and subatomic particles would have to crunch together. The result would be an incredibly dense, hot, compact universe — a lot like the state that preceded the Big Bang. This is the Big Crunch.
Šta je sa trećim scenarijom, gde gumena traka pobeđuje? Ovo odgovara mogućoj budućnosti u kojoj sila gravitacije zaustavlja širenje svemira i zatim ga preokreće. Galaksije bi počele da jure jedna prema drugoj, i dok se približavaju, njihova gravitaciona sila bi postajala još jača. Zvezde bi se takođe vrtele i sudarale. Temperatura bi rasla, a prostor bi bio sve manji i manji. Veličina svemira bi se smanjivala dok na kraju ne bi sve bilo stisnuto u mali prostor u kome bi se čak i atomi i njihovi delovi sudarali. Rezultat bi bio jedan neverovatno gust, vruć i kompaktan svemir - slično onome što je prethodilo „velikom prasku”. Ovo je „veliko sažimanje”.
Could this tiny point of matter explode in another Big Bang? Could the universe expand and contract over and over again, repeating its entire history? The theory describing such a universe is known as the Big Bounce. In fact, there’s no way to tell how many bounces could’ve already happened— or how many might happen in the future. Each bounce would wipe away any record of the universe’s previous history.
Da li ova mala tačka materije može da eksplodira u drugi „veliki prasak”? Može li svemir da se širi i skuplja iznova i iznova, ponavljajući celu istoriju? Teorija koja opisuje ovakav svemir poznata je kao „veliki skok”. U stvari, ne postoji način da se ustanovi koliko je skokova već bilo, niti koliko će ih biti u budućnosti. Svaki skok bi izbrisao bilo koji trag istorije svemira.
Which one of those scenarios will be the real one? The answer depends on the exact shape of the universe, the amount of dark energy it holds, and changes in its expansion rate. As of now, our observations suggest that we’re heading for a Big Freeze. But the good news is that we’ve probably got about 10 to the 100th power years before the chill sets in — so don’t start stocking up on mittens just yet.
Koji će od ovih scenarija biti onaj pravi? Odgovor zavisi od tačnog oblika svemira, količine mračne energije koju sadrži i promena u brzini njegovog širenja. Do sada, posmatranja sugerišu da idemo ka „velikom hlađenju”. Dobra vest je da imamo verovatno još oko 10 do 100 galaktičkih godina, pre nego što nastupi zahlađenje - tako da još uvek nema potrebe za pravljenjem zaliha rukavica.