The mass really isn’t changing. The translation of the mass is changing. It will go fully into effect on Sunday, November 27, the First Sunday of Advent.
The “master copy” of the mass, so to speak, is written in the Latin language. It is the standard (typical) edition of the mass, and it was released in 1970 by Pope Paul VI. From this Latin version comes the masses in the other languages, like English, German, Russian, etc. Groups of people assigned to a specific language get a copy of the Latin version and translate it into their language.
In the early 1970s, the first vernacular translations came out. There is a group, called the International Commission on English in the Liturgy (ICEL), that is responsible for translating the Latin original into English. So they did. But translation methods differ.
There are two main translation theories: formal equivalence and dynamic equivalence.
The formal equivalence theory tries to preserve as much of the original content as possible. Think of it as being a word-for-word translation method. The formal equivalence theory is a direct translation method. It tries to present in the new language, with as little correction/addition/removal as possible, exactly what is said in the original language, even if it sounds a tad bit odd. Translations following this method usually are somewhat complex, at least compared to dynamic equivalence translations.
The dynamic equivalence theory tries to present the idea of what the translator thinks is being conveyed in the original language. Think of it as being an idea-for-idea translation method. The dynamic equivalence theory is a more indirect translation method. It tries to present in the new language, with usually many corrections/additions/removals, the “gist” of what is being said in the original language, usually overlooking exactness. Translations following this method usually are somewhat simple, at least compared to formal equivalence translations.
Back in the day (time frame noted above), the powers-that-be in the Vatican issued an instruction that translations from the Latin original to the various languages follow the dynamic equivalence theory of translation. The Vatican favored this method, because bishops of the world expressed their wish that the translations be somewhat simple. So, ICEL translated the Missale Romanum into English. It was in the year 1973 that the final product came out.
There were many criticisms of this and other translations of the Roman Missal, but most notably the English edition. Most of them centered around the fact that many people found the wording too simple. They noticed that if you compared the Latin prayers to the English prayers, the English often did a very poor job at expressing what the Latin expressed. They found that the poetic nature of the Latin original was not captured or was captured very poorly in the English translation.
Two things, then, were blamed for this: the method of translation itself (dynamic equivalence theory, which does not stress exactness) and the very short amount of time the translation took (1970-1973).
Therefore, in the year 2001, a document was released by Pope John Paul II called Liturgiam authenticam, which means “authentic liturgy.” In it, the Pope ordered that the translations be as exact as possible, and that they preserve as much of what the Latin says as possible. Naturally, a new translation of the English version of the Roman Missal was needed. It was originally translated using the dynamic equivalence theory, and it was to be re-translated, because of Liturgiam authenticam, using the formal equivalence theory.
So, ICEL met up again, and they began to retranslate the missal. I’m not going to explain the whole process of how they did it, because I don’t think it’s important here. Anyways, they finished this translation in 2008; it took them seven years. The Vatican approved the translation. The Bishops’ Conferences of the English-speaking countries decided (with a few exceptions) that the new translation was to be implemented on November 27, 2011, and that date is now rapidly coming upon us. You will find that, starting that Sunday, the language of the mass, both yours and the priest’s, will be very much elevated in formality and eloquence over what we have been using for the past forty years.