Sort of, but that cat actually counts as an observer. If that sounds facetious, remember that two bodies exerting a gravitational force on one another are observing one another. Very little goes unobserved. At any rate, I can’t see how any individual observer would exert much influence.
Without time travel we can’t access information about the past, only information about the present that has been affected by the past, so I would say that the past only exists as information in the present. But as for the past being knowable, assuming we don’t mean something too strong by the word “knowing” I would say we can know it. Still, if the past exists in the present as a model built from evidence of what led to now, then that model has a tension between incorporating more recent evidence or not. Evidence of what existed in a certain era would lead us to say Phlogiston theory expresses quite well what we mean when we say “heat” but we also have evidence that says that Phlogiston theory gets heat wrong.
I think I brought up the Phlogiston example to try to present the idea that concepts come before words and definitions. I see more similarity between my idea of heat and that of an ancient person than I do between the scientific ideas of heat from the present and the past. The similarity of the concept allows us to say that they were speaking of heat and we are speaking of heat, rather than saying they were speaking of Phlogiston and we are speaking of some combination of molecular kinetic energy and radiant heat (I will admit I probably don’t understand heat well).
So when Aristotle famously proposed that a human is a featherless biped, we could all say that he was wrong because a kangaroo is not a human (or, the plucked chicken from the ancient example). We know that kangaroos should not be included in the definition of “human” because we have a concept that the definition tries to express.
At the same time, it seems obvious to me that concepts must change over time. As individuals I would think we will nearly always make mistakes about the past because we view it through the lens of today.
I believe my one month should expire on February 10? Please bring my attention to any instances of non-prime English.
