Conditionals

I'd pick the first one. It's not a question of something that might have been long ago; if it had been long ago, it would still be. The latter version implies that the problem deals with something in the past.

Grammatically, the first version is the correct one. Sorry, Parenna, it is not about the "content" of the sentences being the issue per se, rather, JillWu must decide if the statement may or may not be realized. Consider this: If I were god, I would've made the world know no evil. In this case, I would never be god, ever. So, the pair of words: WERE and WOULD'VE must be used (notice that it is irrespective as to the subject, all must use the Were). Compare it with this: If I were to be artistic, I would write my comment in color.
So, "street talking"ly speaking, the second version is much said all over the nation. I've been around a lot. This usage is not restricted to a particular area(s).

Unggit, I think rather that your explanation emphasizes the content of the sentences.

Or, we are speaking of the same idea, actually. Something that can't be realised can't be realised, which state of things applies now as well as it did in the past. So I think your explanation too deals with time, or, tenses.

What makes it difficult is the latter part of the sentence, which casts an overview in the past ("long ago") although the first part deals with the present time.

The following examples with small realisable contents show what I mean:

1) If there had been apple juice, I would’ve drunk it.
2) If there were apple juice, I’d drink it.
3) If there were apple juice, I would’ve drunk it long ago.

Now I must admit that I’m not completely sure whether the third sentence is correct or not. In Finnish we could say exactly like that.

I realise :) I'm asking the same question as Jill Wu in his/her opening post.

Parenna, I've neglected to include one piece of info. on my last comment. It was (and is) the American English [grammar] that I was referring to. Again, grammatically, your 2nd and 3rd sententences are correct. The 1st one, just like JillWu's, is not. Which English [grammar] do you use in your duscussion? I wander about JillWu's?

Unggit, I don't consciously think about which grammar I use in my English. Perhaps I should. At school and in the university I learnt British grammar, but movies and particularly computer and the Internet have, no doubt, influenced my usage of English since.

Back to business: I think my 1st sentence is correct too, conditional in the past:
http://english.nazory.cz/grammar/conditional.php
http://www.geocities.jp/cosmos_akino/english/grammar4.html
http://grammar.englishclub.com/verbs-conditional_4.htm

Perhaps not. Seems to me, you use mostly British English, not only spoken (in this case discussion) but also your written (most of your spelling were and are of British, e.g.: learnt, realised). And that's OK. I "grew up" in America and learned the American English. I know so little about other English [grammars], like that of the British or Australian, etc.
An interesting finding of the three links in supporting your arguments. And so, you are and have been correct, good job friend! Thanks Parenna.

I would go with the first one, but in either case I'd be confused by the second clause. I mean, the finding of scientific evidence is independent of whether or not tides cause earthquakes. Adding something thing "to support this hypothesis" after the word 'evidence' would make the whole thing sound better.

I'd definitely go with the first option.

Grammatically, both sound fine to me (having learned BE at school and been mostly around people speaking BE), but the second one sort of implies that the subject of discussion (causal relation between quakes and floods) is something that could change with time, which it isn't.

The reason why Parenna's third example may sound strange is because the meaning of were can be slightly different:

3a) "If there were [any] apple juice [here], I would've drunk it long ago."

3b) "If there were [such a thing as] apple juice, I would've drunk it long ago."

The first one is a little strange, because it seems to imply some sort of reverse causality: "If A were the case now, I'd have done B long ago."

The second one is more like the original example, it discusses a mostly immutable state of affairs: Either people have or haven't invented apple juice, either there is or there isn't a causal connection between quakes and floods.

Ignoring the grammar, it's logical fallacy. The sentence suggests that, since evidence has not been found, then it must be impossible for tides to cause earthquakes. Since negative proof is impossible, it'd be better to phrase it as:

"Since no scientific evidence has yet been found, it is unlikely that tides cause earthquakes."