Many people like to ask whether the future is determined. This has relevance to issues like free will, for example.
I would like to address the reverse question: Is the *past* determined?
In other words, is the past fixed once we pass it?
Another interpretation of the problem, possible a different spin: Given the state of the universe *now* (and I am flexible about what this means), is the entirety of the past determined? Can every event of the past be *theoretically* deduced from the information of the present?
When framed in this way, I have to say that it seems unlikely. For example, it seems quite unlikely that the weight of Casar's last drink is fixed from anything available in the universe today. It seems unlikely that the question 'was there a T-Rex standing in this spot 68 million years ago exactly' actually has an answer that is determined by the state of the universe now.
So, to what extent is the past determined? If it is NOT determined, how does that affect your views of the past? if it *is* determined, in what sense is it so?
Are you familiar with E8? I'm not but trying to grasp the idea.
An 8 dimensional universe which exists that we perceive 3/4 dimensionally. Like if you take a cube and hold it up to the light and project the image onto a flat surface. All we would observe would be the shadow of the cube, not the entire cube. Depending on the rotation of the cube the shadow could appear as many different 2D dimensional shapes.
Some have the idea that the past, present and future exist simultaneously. Time being one of these dimensions. So what we perceive as the passage of time is like the rotation of the cube. We see the universe changing but what we are perceiving is a "shadow" of the universe. Nothing is actually changing except the rotation of how we perceive the universe.
So the universe is determined, actually unchanging. It is our perception of it that is changing.
If we could exactly reverse our sequence of perceptions of the universe, I suppose we could perceive the exact universe/shadow that we perceive x number of perceptions before. Or perhaps there exists an infinite numbers of pasts that could be perceived.
The exact "shadow" of the universe that we perceive before still exists, exists now, but there is no way to say with any certainty that we would ever be able to perceive that exact same "shadow" of the universe that we did before.