The science behind time-travel:-
Time travel remains as a concept largely explored in theoretical physics and science fiction. There is no scientific idea behind the practicality of time-travel. Several theoretical frameworks within physics, such as general relativity, allow the possibility of the time dilution. The idea of time travel also raises various paradoxes, such as the “grandfather paradox”.
Grandfather paradox:-
The grandfather paradox is a concept that is often related with the physics behind time-travel. The paradox is named after the hypothetical situation which involves a person travelling back in time and accidentally preventing their grandfather meeting their grandmother, and hereby, preventing their own existence. The scenario follows like this:-
Time traveller’s journey
A person travels back in time, say, a period before their parents were born.
Grandfather’s meeting
The person meets their grandfather. They also prevent the meeting between their grandmother and grandfather.
Nonexistent parent
Due to this interference, their parents would have never been born.
Time traveller's existence
Since their parents wouldn’t have been born, nor would the person, which creates a logical inconsistency. If the time traveller was never born, how could they have travelled back in time to prevent their own existence?
This paradox highlights one of the conceptual challenges for the science behind time travel. In the case of the grandfather paradox, it questions whether time travel to the past could result in events that could bring an end to time travel in the first place. The resolution of such paradoxes remains an open question to scientists and philosophers.
Special relativity and CTC:-
Albert Einstein’s theory of special relativity and time dilation introduces a concept where time can pass differently for observers moving at different velocities. It demonstrates that time is relative and that it can be influenced by factors such as motion. It also allows the theory of gravity, which allows the existence of wormholes, which are hypothetical tunnels in space. If transferable wormholes exist, they might offer a shortcut between different points in time and space.
In Einstein’s equations, closed timelike curves (CTC) are theoretical paths that loop back on themselves in spacetime. These curves could allow for time loops and closed causal loops.
Parallel Universes:-
The parallel universe, also known as the multiverse or alternate verse, is a hypothetical self-contained plane of existence that coexists with our universe. The idea of a parallel universe arose from various branches of astronomy and theoretical physics, including quantum mechanics, cosmology, and string theory, making the parallel universe a trend for decades. Some theories propose that time travel could result in branching timelines, where changes in the past create new parallel universes rather than altering the original timeline.
Novikov’s self-consistency principle:-
The physicist Igor Novikov proposed that laws of physics prevent the occurrence of events that could create a paradox. This means that any actions taken by a time traveller in the past would be consistent with the events that lead to their journey.
Chronology Protection Conjecture of Hawking:-
Stephen Hawking's chronology protection conjecture suggests that the laws of physics prevent the creation of closed timelike curves to avoid the occurrence of time travel and potential paradoxes.
Time travel in thermodynamics:-
Thermodynamics is a branch of physics that deals with the principles governing the interactions and transformations of energy.
Zeroth law of thermodynamics:- If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
First law of thermodynamics:- The total energy of an isolated system is constant. Energy can be transferred between the system and its surroundings in various forms, such as heat, and work.
Second law of thermodynamics:- The total entropy of an isolated system can never decrease over time.
Third law of thermodynamics:- As the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum value.
Time travel defies the second law of thermodynamics, which states that the entropy of an isolated system can never decrease over time.
Time travel in science fiction:-
The works of the popular author H.G Wells consists of the concept of time travel which has been portrayed in various works of his. In his book ‘The Time Machine’, Wells suggested that time travelling machines could be done mechanically.
Conclusion:-
Time travel is a topic that has been researched by various scientists and authors. Even though time travel is a concept that has not been scientifically proved by the various scientists and researchers, it still remains as an open question and an intriguing topic to research on, for centuries altogether.
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