Black holes are among the most destructive objects in the universe. Anything that gets too close to the central singularity of a black hole, be it an asteroid, planet, or star, risks being torn apart by its extreme gravitational field. And if the approaching object happens to cross the black hole’s event horizon, it’ll disappear and never re-emerge, adding to the black hole’s mass and expanding its radius in the process. There is nothing we could throw at a black hole that would do the least bit of damage to it. Even another black hole won’t destroy it– the two will simply merge into a larger black hole, releasing a bit of energy as gravitational waves in the process. By some accounts, it’s possible that the universe may eventually consist entirely of black holes in a very distant future. And yet, there may be a way to destroy, or “evaporate,” these objects after all. If the theory is true, all we need to do is to wait.
Crne rupe se svrstavaju u najdestruktivnije objekte u svemiru. Sve što se suviše približi središnjem delu crne rupe, bilo da je reč o asteroidu, planeti ili zvezdi, rizikuje da bude razoreno njenim ekstremnim gravitacionim poljem. Ako pak objekat koji se približava pređe horizont događaja crne rupe, on nestane i nikada se više ne pojavi, dodavajući masu crnoj rupi, pri tom šireći njen poluprečnik. Ne postoji ništa što bismo mogli da bacimo u crnu rupu, a što bi moglo bar malo da je ošteti. Čak je ni druga crna rupa neće uništiti - njih dve će se jednostavno spojiti u veću crnu rupu, pri tom oslabađajući malo energije u obliku gravitacionih talasa. Po nekim proračunima, moguće je da će se ceo svemir sastojati samo od crnih rupa u dalekoj budućnosti. Pa ipak, možda postoji način da se unište ili „ispare” ovi objekti. Ako je teorija tačna, jedino što nam treba jeste da čekamo.
In 1974, Stephen Hawking theorized a process that could lead a black hole to gradually lose mass. Hawking radiation, as it came to be known, is based on a well-established phenomenon called quantum fluctuations of the vacuum. According to quantum mechanics, a given point in spacetime fluctuates between multiple possible energy states. These fluctuations are driven by the continuous creation and destruction of virtual particle pairs, which consist of a particle and its oppositely charged antiparticle.
Godine 1974, Stiven Hoking je teorijski razvio proces koji bi mogao da dovede do toga da crna rupa postepeno izgubi masu. Hokingova radijacija, kako je postala poznata, je bazirana na dobro znanom fenomenu zvanom kvantna fluktuacija vakuuma. Prema kvantnoj mehanici, određena tačka u prostor-vremenu fluktuira između više mogućih stanja energije. Ove fluktuacije su izazvane neprekidnim stvaranjem i razaranjem parova virtualnih čestica,
Normally, the two collide and annihilate each other shortly after appearing, preserving the total energy. But what happens when they appear just at the edge of a black hole’s event horizon? If they’re positioned just right, one of the particles could escape the black hole’s pull while its counterpart falls in. It would then annihilate another oppositely charged particle within the event horizon of the black hole, reducing the black hole’s mass. Meanwhile, to an outside observer, it would look like the black hole had emitted the escaped particle.
koji se sastoje od čestica i njihovih suprotno naelektrisanih antičestica. Ove dve se sudaraju i uništavaju jedna drugu, ubrzo nakon pojavljivanja, čuvajući ukupnu količinu energije. Ali šta se dešava kada se pojave na samoj ivici horizonta događaja crne rupe? Ako su pravilno postavljene, jedna od čestica bi mogla da umakne sili crne rupe, dok njena suprotnost upada. To bi onda uništilo drugu česticu sa suprotnim naelektrisanjem na samom horizontu događaja crne rupe, smanjujući njenu masu. U međuvremenu, posmatraču sa strane
Thus, unless a black hole continues to absorb additional matter and energy, it’ll evaporate particle by particle, at an excruciatingly slow rate. How slow? A branch of physics, called black hole thermodynamics, gives us an answer.
bi izgledalo kao da crna rupa ispušta pobegle čestice. Tako da, ukoliko crna rupa ne nastavi da uvlači dodatnu materiju i energiju, to će uništiti česticu po česticu, bolno sporim tempom. Koliko sporim? Deo fizike poznat kao termodinamika crne rupe daje nam odgovor.
When everyday objects or celestial bodies release energy to their environment, we perceive that as heat, and can use their energy emission to measure their temperature. Black hole thermodynamics suggests that we can similarly define the “temperature” of a black hole. It theorizes that the more massive the black hole, the lower its temperature. The universe’s largest black holes would give off temperatures of the order of 10 to the -17th power Kelvin, very close to absolute zero. Meanwhile, one with the mass of the asteroid Vesta would have a temperature close to 200 degrees Celsius, thus releasing a lot of energy in the form of Hawking Radiation to the cold outside environment. The smaller the black hole, the hotter it seems to be burning– and the sooner it’ll burn out completely.
Kada svakodnevni objekti ili nebeska tela ispuste energiju u svoju okolinu, mi to primećujemo kao toplotu, i možemo koristiti ispuštanje energije da izmerimo njihovu temperaturu. Termodinamika crne rupe navodi da na sličan način možemo izmeriti temperaturu crne rupe. Po toj teoriji, što je veća masa crne rupe, temperatura je sve manja. Najveće crne rupe svemira bi imale temperaturu razmera od 10 na -17 snage Kelvina, veoma blizu apsolutnoj nuli. Sa druge strane, crna rupa koja ima masu asteroida Vesta bi imala temperaturu blizu 200 stepeni Celzijusa, tako da bi oslobađala mnogo energije u obliku Hokingove radijacije u hladnu okolinu. Što je manja crna rupa, izgleda da sve toplije gori - i brže će sagoreti do kraja.
Just how soon? Well, don’t hold your breath. First of all, most black holes accrete, or absorb matter and energy, more quickly than they emit Hawking radiation. But even if a black hole with the mass of our Sun stopped accreting, it would take 10 to the 67th power years– many many magnitudes longer than the current age of the Universe— to fully evaporate. When a black hole reaches about 230 metric tons, it’ll have only one more second to live. In that final second, its event horizon becomes increasingly tiny, until finally releasing all of its energy back into the universe. And while Hawking radiation has never been directly observed, some scientists believe that certain gamma ray flashes detected in the sky are actually traces of the last moments of small, primordial black holes formed at the dawn of time.
Koliko brzo? Pa, načekaćete se. Pre svega, većina crnih rupa nagomilava ili upija materiju i energiju mnogo brže nego što emituju Hokingovu radijaciju. Ali čak i kada bi crna rupa mase našeg sunca prestala da nagomilava, trebalo bi 10 na 67. stepen energetskih godina - što je po opsegu mnogo više od trenutne starosti univerzuma - da u potpunosti ispari. Kada crna rupa dostigne oko 230 metričkih tona, živeće samo još jedan sekund. U toj poslednjoj sekundi, njen horizont događaja postaje sve manji, sve dok konačno ne oslobodi celokupnu energiju nazad u svemir. Dok Hokingova radijacija nikada nije direktno posmatrana, neki naučnici veruju da su određeni bljeskovi gama zraka uočeni na nebu u stvari tragovi poslednjih momenata malih, praiskonskih crnih rupa formiranih na početku vremena.
Eventually, in an almost inconceivably distant future, the universe may be left as a cold and dark place. But if Stephen Hawking was right, before that happens, the normally terrifying and otherwise impervious black holes will end their existence in a final blaze of glory.
Na kraju, u skoro nedokučivo dalekoj budućnosti, svemir bi mogao postati hladno i mračno mesto. Ali ako je Stiven Hoking bio u pravu, pre nego što se to desi, obično zastrašujuće i neprobojne crne rupe će završiti svoje postojanje u konačnom bljesku slave.