Learn Turkish: Atmosfer çok hızlı değişir miydi? - Would the atmosphere change very fast?

In Turkish, combining the aorist tense (the general present, -ir) with the past tense (-di) creates a meaning similar to 'used to' or the hypothetical 'would' in English. Here, değişir (it changes) + mi (question) + ydi (past) becomes 'Would it change?'.

Why is the past tense suffix -di attached to the question particle mi instead of the verb?

When asking a question using a combined tense like this, the first tense marker (-ir) stays on the verb, but the second one (the past tense -di) attaches to the question particle. That is why it is değişir miydi? instead of değişirdi mi?. The y is just a buffer letter between the vowels.

Hızlı is an adjective meaning 'fast'. Why doesn't it need an adverb ending to mean 'fast' or 'quickly' here?

Just like in English, some Turkish words act as both adjectives and adverbs without changing their form. While you can say hızlıca or hızlı bir şekilde for 'quickly', using the plain adjective hızlı directly before the verb is very common and perfectly natural.