How can I know of something that happened billions of years ago if I cannot even recall what happened just a day before I was born? Just wondering.
closed as unclear what you're asking by Conifold, christo183, Mark Andrews, Eliran, Swami Vishwananda Mar 7 at 6:47
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You technically can't surely know what happens to you. Humans are taught things, and since you were taught about prehistoric things, you know what happened. But it is still possible you don't know, if we were all wrong. We only know what happened based on clues.
The sources of knowledge are basically always some combination of sensory perception, testimony and reasoning. When it comes to knowledge of the past, the primary difference is that direct sensory perception of past events themselves is not possible; we can only observe their effects.
Testimony obviously plays a very important role in our knowledge of the past. For example, it is primarily through testimony that I know that the United States declared its independence on the 4th of July in 1776.
To some extent we can also verify knowledge about the past through reasoning based on perception of evidence. For example, I've seen fossils of extinct dinosaurs with my own eyes, which supplements the knowledge I have from the testimony of science books.
There is also the possibility of a priori knowledge of the past. For example, even if nobody ever told me that my mother was born before I was, I could have figured it out simply by understanding the fact that she was my mother. Here reasoning is the primary source of my knowledge.