I am sorry, I didn't build a long enough sentence and my idea was, perhaps unclear. However, I didn't use the word "prove". I used the word "do".
While you could not prove such theories, you could rebuild them, do the work that was done ages ago. Granted enough time and patience of course.
In the Earth case, it is basically an experiment, I presume that's the source of confusion, here. Since the work we are talking about has been done before, there is, technically, no counter-example.
Yes, and it's actually rare, but some people need to prove things before accepting them as a fact. But I don't know if it's bad. As a community, we base our work on trust at some point. And mark my words, I didn't said blind faith, I said trust.
It makes things smooth. For example, when you write here, you assume that there is actually someone talking to you, but even if you knew all the mathematics behind it, you didn't prove it.
Because it's wasted time. That's the same idea here. We don't have to rebuild everything. We have to make sure it has been done right, we trust it, and we have to build on top of it. And considering the ammount of time it takes to prove everything, it is probably better that way, don't you think ?