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Time locomotion has long been dismissed as impossible due in part to the infamous " grandfather paradox . " This conundrum asks what would happen if someone traveled back in time and prevented their grandfather from having children , thus efface the traveler ’s existence . However , a new study may have resolved this issue .
By combining general relativity theory , quantum mechanics , and thermodynamics , the study manifest that prison term change of location might be feasible without leading to these logical contradiction .
The physics of time loops
Our everyday understanding of time is settle in Newtonian physics , where effect progress linearly from the yesteryear to the future tense . But Einstein ’s cosmopolitan theory ofrelativity , fill out in 1915 , challenges this nonrational assumption . It reveals that the fabric of space - time can behave in ways that hold up common sentiency , as attest by phenomena like dim kettle of fish . One of its most fascinating predictions is the likely cosmos of closed timelike curves — paths through space - time that loop back on themselves , theoretically allowing a traveler to revisit the past .
" In general relativity , all form of energy and impulse act as rootage of gravity — not just mass , " discipline authorLorenzo Gavassino , a physicist at Vanderbilt University , enjoin LiveScience via email . " This think of that if matter is rotating , it can ' drag ' spacetime along with it . While this effect is negligible on planets and stars , what if the entire universe was rotating ? "
In a macrocosm where all matter rotates , space - time could become so warped that time effectively bends back on itself , forming a loop topology . A spaceship travel along such a loop could theoretically return to its start level , not just in space but also in time . While our creation as a whole does n’t seem to rotate in this manner , rotating multitude — such as pitch-dark holes — can produce similar upshot , make potential surroundings for closed timelike curves .
The paradoxes of time travel
One of the biggest challenge to fourth dimension travel lies in the paradoxes it creates . The grandfather paradox is just one example . These issues arise because we assume that the laws ofthermodynamics , the laws that govern heat and free energy , would function normally on a time loop .
" In fact , the law of increase entropy — a thermodynamic amount that measures the grade of disorder in a organization — is the only law of physics that distinguishes between past times and future , " Gavassino said . " As far as we know , entropy is the sole reason we remember past upshot and can not predict future ones . "
Entropy governs many of our day-after-day experiences , from the style our body age to how we work on retention . Even dewy-eyed action , like walking , rely on rubbing , which itself increase entropy . So how would these processes behave on a time loop ?
A quantum solution to paradoxes
Gavassino ’s inquiry , write Dec. 12 , 2024 in the journalClassical and Quantum Gravity , provides an challenging answer . Drawing inspiration from theworkof physicist Carlo Rovelli , he demonstrate that the behavior of thermodynamics fundamentally changes on a unopen timelike bender . On such a loop , quantum variation arise that can erase entropy — a summons fundamentally different from what we experience in everyday life .
These fluctuations could have dramatic effects on a time traveler . For instance , as entropy reduction , a soul ’s memories might vanish , and aging would reverse . " Entropy increase is the reason why we die . What happens when you invert death ? " Gavassino asked . This phenomenon could even render irreversible events , like killing one ’s granddaddy , temporary on a clock time loop , nullifying the paradox altogether .
" Most physicists and philosopher in the yesteryear have argued that if time travel exists , nature will always bump a direction to forestall mutually exclusive situation , " Gavassino said . " A ' ego - body principle ' was present , paint a picture that everything should coordinate to make a logically lucid chronicle . My study provide the first tight etymologizing of this self - consistence rule flat from established cathartic . Specifically , I use the standard model of quantum mechanics — without additional postulates or controversial assumptions — and demonstrate that the ego - consistency of history naturally postdate from quantum natural law . "
Theoretical and practical implications
While Gavassino ’s findings offer a compelling theoretic fabric for time travelling , the question remains : Do closed timelike curves actually exist in the real universe of discourse ? Most physicists are sceptical . In 1992 , Stephen Hawking , for example , famouslyproposeda " chronology trade protection hypothesis , " suggesting that the police of physics might forestall sentence loop from forming in the first place . This could involve space - metre becoming singular — or break down down — just before a iteration could be establish .
Still , Gavassino ’s work is valuable for pushing the bound of our understanding .
" What I find interesting about this topic is the elbow room it forces us to think about the role of entropy in generating our experience of the universe , which is probably my preferred subject in all of physics , " Gavassino say .
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Even if time closed circuit do n’t exist , intellect and pose them could provide insights into veridical phenomenon . For case , exploring how real entropy evolves and behaves along a closed trajectory at the subatomic scale could yield bewitching insight into the behavior of subatomic systems and their thermodynamics .
