My assertion is that science does not know the state of the past on earth.
It depends on your epistemological stance, I suppose.
Using the epistemological stance that science takes, scientists do indeed know things about the past on earth.
One could hypothesise some kind of Omphalism (a past where some abrupt change in the nature of reality results in a world that appears old, but actually its not as old as we think), but there is no reason to suppose that is true - there is no causal mechanism that can be identified that would result in a Omphalistic universe. It would require either a tremendously improbable coincidence of events or a stupendously deceptive and powerful agent that conspired to generate patterns that appear to be consistent with a certain past. Neither is evidenced. Any related hyperskepticism, quickly falls into madness. Where do you draw the line between the known and the unknown? How can you draw a line? How can you say you know anything once you start down this path?
quote:
Although the grasses were only a moment old at their creation, they appeared as if they were months old. Likewise, the trees, although only a day old when they sprouted forth, were nevertheless like ... years old as they were fully grown and fruits were already budding on their branches
St. Ephrem the Syrian
What we can say is that if we suppose that the fundamental units of the universe work today as they did yesterday, and the day before etc., a consistent, coherent, useful understanding of the world and the universe forms. We can make reasoned inferences on the location of resources, the prevalence of certain elements, the future of our sun and other stars. They all tie together into a coherent understanding of the world and our existence. Omphalistic objections simply become...ahem...naval gazing exercises with no illumination, understanding or utility to be gained.
In science you say 'if this is true, it implies this other thing....let's check that other thing, hrm that other thing is so. This lends credibility to the hypothetical that started this. If that other thing is true AND if this addition idea is true, then that would suggest....' - this reasoning leads us to explanations. The reason y is the case, is because s,t,u,v,w and x result in y. s,t,u,v,w and x appear to be so due to observations a,b,c,d,e and f. It is always possible that some alternative hypothesis is actually the truth, but there comes a point when that possibility requires sufficiently unreasonable propositions that run counter to our observations and this, in the epistemologies that scientists use, means we can say 'we know'. We might be wrong. And one can always think of a variety of hypothetical possibilities which would result in us being wrong, but until observations suggest those hypothetical possibilities have any correspondence to reality - we can stick to using verb 'to know' for the sake of communication.
As with solipsistic objections, Omphalistic type objections are an obviously foolish way to proceed. As you also say:
We know lots of details from the last few hundred years
Since you opened the door to Omphalism I could just reductio ad absurdum you and say that we don't know any details from the last few hundred years due to Last Thursdayism.
quote:
There is no logical impossibility in the hypothesis that the world sprang into being five minutes ago, exactly as it then was, with a population that "remembered" a wholly unreal past. There is no logically necessary connection between events at different times; therefore nothing that is happening now or will happen in the future can disprove the hypothesis that the world began five minutes ago.
Bertrand Russell
Either the verb 'to know' has some meaning and we can use it, or it does not. Your perspective, whether you realize it or not - renders the verb meaningless or at least useless. Science's perspective gives us a reasonable use for the verb.
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