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When great scientific ideas do fall, on rare occasions, they do so of many grievous wounds followed by the rethinking of the total picture.
The idea, literally worshiped in creationist circles, that you can disprove a theory by whipping out some cute, isolated "proof" that settles everything at once and for all, is not scientific.
Since careful inspection shows no signs of such a flood, the earth can't be older than a few weeks! We do need to know something about the system under study. No one familiar with tides would assume that the rate of water going out is constant over weeks of time!
Just as obvious, at least to the experts, our sun could not have been continuously shrinking over millions of years as described by some creationists.
(The better the model, the more farfetched the loopholes are.) If you crave the certainty of a real "proof," the final word as it were, then you had better stick to mathematics or logic!
Those are the only arenas where absolute proof plays any serious role.
To sum up our first point, the shrinking-sun argument rests squarely on a naive extension of a rate measured over a relatively short period of time.
One can always dream up possible scenarios that will contradict even the best scientific models.The one thread running through "scientific" creationism is a fixation on particular arguments or "proofs" to the exclusion of all else.