(a2a) The magic words you are looking for are “Akashic Records” – google this phrase to research more info. The basic principle is that every thought that has ever existed has left its imprint on the Akasha, which is like Universal Mind-Substance (also known in old books of occultism as “Ether” or just “Spirit.”) Hence it ought to be possible to psychically attune yourself to the Akashic Records and examine the past through a kind of clairvoyance.
The important point to remember is that although you would see and observe the past, you would not be able to interact and interfere with it. Still, great for historical research or for doing things like recovering past-life memories.
In ceremonial magic, the Archangel Tzaphqiel (whose name means “Knowledge of God”) is thought to be the keeper of the Akashic Records, so if you were to go down this route you should think of trying to invoke this being.