As an economist today, I feel a great kinship with the oracles and soothsayers of ancient times who advised leaders and kings. While today, people in our profession establish their credibility by throwing around equations with varying levels of meaning, I'm interested in how it was done in the past.
While I assume a great deal of it had to do with cultural traditions, religion, and the like, did oracles and the like ever gain credibility on the basis of predicting natural events? In particular, by predicting those events using a method that genuinely outperformed random chance or would otherwise be considered scientifically sound today? (I don't mean to imply a scientific method were used to obtain their method; simply that modern scrutiny would assert it had some basis in fact.)
For example, I imagine a modern astronomer might be able to establish their credibility in the past by precisely predicting astronomical events. I suppose a clever and observant person could get a lot of mileage forecasting weather and other events just by observing astronomical, meteorological, and animal phenomena.
Also, while I'm also certain the answer to this question will be no, I have to ask. Is there even the shred of an excuse to allow me to believe that someone might have used dogs and this principle to ascertain solar flares were occurring and then predict impending aurora borealis occurrences? I know, I know, but it would be a delightful to hear if there were even a tiny possibility that something similar ever occurred in history.
Additionally, I beg your forgiveness in advance for using the phrase oracles and soothsayers -- I'm not sure what the proper words for each time period and culture would be.
Thank you!
So I'll address the area I've studied.
The Ancient Greeks did know how to predict eclipses, and according to tradition Thales of Miletus, a natural philosopher of the 6th century BC, was the first to predict an eclipse. Cf. Herodotus 1.74.2:
They were still warring with equal success, when it happened, at an encounter which occurred in the sixth year, that during the battle the day was suddenly turned to night. Thales of Miletus had foretold this loss of daylight to the Ionians, fixing it within the year in which the change did indeed happen.
I don't know if any oracles predicted eclipses or other such things; to my knowledge, this is not mentioned in ancient sources.
However, the main way oracles established credibility in Greece was through their status as religiously dedicated individuals--at Delphi, the Pythia was likely chosen from a class of priestesses.
With most of the Greek oracles, it was rare that they would be inaccurate. If you look at prophecies that are recorded which described an event that would happen (most of the oracles were suggestions, such as telling settlers where they should found cities), they are all heavily ambiguous, and could be spun to be accurate regardless of what occurred. This is sort of similar to the way modern fortune tellers operate--they make ambiguous statements that can be spun to fit various circumstances. Here are some examples:
On Croesus attacking the Persians:
if he should send an army against the Persians he would destroy a great empire (Herodotus 1.53.3)
Agesipolis, King of Sparta, asking about whether he should accept the offer of a truce
Now when Agesipolis learned that he was to lead the ban, and when the sacrifices which he offered at the frontier proved favourable, he went to Olympia and consulted the oracle of the god, asking whether it would be consistent with piety if he did not acknowledge the holy truce claimed by the Argives; for, he urged, it was not when the appointed time came, but when the Lacedaemonians were about to invade their territory, that they pleaded the sacred months.2 And the god signified to him that it was consistent with piety for him not to acknowledge a holy truce which was pleaded unjustly. Then Agesipolis proceeded straight from there to Delphi and asked Apollo in his turn whether he also held the same opinion as his father Zeus in regard to the truce. And Apollo answered that he did hold quite the same opinion. (Xenophon, Hellenica, 4.7.1-2)
These are just a few examples of oracular statements. As you can see, they could go several ways, and had intentional ambiguity.