time travel, as commonly depicted in science fiction, is not considered scientifically possible. The prevailing understanding among physicists is that time travel to the past, particularly to events that have already occurred, is highly unlikely.
The main reason is that it would require bending the laws of physics in ways that are not currently supported by scientific evidence. Time travel to the past raises several paradoxes, such as the famous grandfather paradox, where someone travels back in time and inadvertently prevents their own existence.
However, it is worth noting that there are some speculative theories in physics, such as certain solutions within general relativity, that propose the existence of "wormholes" or "time loops" that could potentially allow for some form of time travel. These ideas are still purely theoretical and have not been demonstrated or confirmed by empirical evidence.
Regarding your question about deceased individuals being alive if time travel were possible, it would depend on the specific theoretical framework of time travel being considered. In most scenarios, if time travel were possible, it would involve traveling to a different point in time, but the individuals in that time would remain unchanged. In other words, you would encounter them as they were at that specific moment in the past, but they would not be aware of any future events or changes that might occur after your departure.
However, it's important to emphasize that time travel to the past remains speculative and hypothetical at this stage, and further scientific advancements and understanding would be required to determine its feasibility.