The concept of time travel is a topic of great interest and speculation, both in science and popular culture. However, the question of whether time travel is possible remains open and is still a subject of ongoing scientific inquiry and debate.
According to our current understanding of physics, particularly within the framework of Einstein's theory of relativity, there are some theoretical possibilities for time travel. One of the well-known concepts is "time dilation," which occurs due to the relative motion of objects or gravity. Time dilation predicts that time can pass at different rates for objects in different conditions. For example, a person traveling at high speeds or near a massive object would experience time passing more slowly compared to a stationary observer.
However, these effects of time dilation do not necessarily enable the kind of time travel commonly depicted in science fiction, where one can travel backward or forward in time at will. Theoretical models, such as traversable wormholes and certain solutions of general relativity, have been proposed as possible mechanisms for time travel. Still, they involve speculative and hypothetical constructs that require exotic matter or energy conditions that have not been observed or confirmed.
As for the question of knowing if time had been changed, it becomes a complex matter. In most scientific models, time is considered as a linear progression, and events occur in a specific order. If time travel were possible, it could potentially disrupt this linear progression and create paradoxes or inconsistencies. The consequences of time travel and the ability to detect changes would depend on the specific model or theory of time travel being considered.
In the realm of speculative physics, various ideas have been proposed to address the detection of time travel, such as the "butterfly effect" or the notion that small changes in the past could have significant impacts on the future, potentially leading to observable differences. However, these ideas remain largely theoretical and have not been experimentally confirmed.
In conclusion, while time travel remains a fascinating subject, its feasibility and the methods for detecting changes in time are still areas of scientific exploration, and there is currently no definitive evidence or consensus on whether time travel is possible or how we would recognize alterations in the timeline.