How do we process the concept of time?, that it travels from the past present to the future. It’s linear and forever moving forwards and never backwards, this is how most people perceive time to flow. If we were to break time down from a year to a month, month to a week, week to a day, day to an hour, hour to a minute, minute to a second, then we kept splitting each millisecond down until we reached the smallest portion of time recordable in this day and age, which is .12 of a nanosecond. This is how accurately the atomic clocks keep time, with over 22 billion dollars invested into it’s creation, for the purposes of evaluating time differences with differences in speed and in space.
What if we were to continue splitting each nanosecond in half indefinitely, where would it end?. It can only inevitably end at an instant moment, the smallest fragment of time possible. If you were to picture a film real with each frame being an instant moment followed by another instant moment flowing from the present to the future continuously, eventually the instant moments will accumulate into something recordable.
Is the past a solid place?, typically in adulthood it takes 7 years for every single cell in our bodies to burn out and die then become replaced with a new cell. This process for children is more rapid. Are you the same human you were 10 years ago?, the short answer is no, there will not be a single cell in your body that is the same, you physically are a different person. You have faded in from the past and into the present, from a person who physically doesn’t exist any more. None of the physical past held in buildings or trees or anything else, will be the exact same as it was before, only an impression of the past with the impression of the present. Ruined castle walls, will not be the same stone it was 500 years ago, not the exact same composition at a molecular level. Though stone does have the highest rates for retaining carbon atoms, which in a mountain is around 250,000 years, though surface erosion will inevitably happen. The physical past fades into the present with the impression of times gone around us, while we fade into the present at the same rate leaving our non existent selves behind.