[Note that the bold text is a translation of the actual Talmud text, while the regular font is additional wording from the translators to help make sense of the cryptic text.]
As is appropriate the Talmud begins with a question, which, of course, has three answers. The differences in the answers primarily focus on how long one has to recite the Shema in the evening. The Sages seem to agree that the time begins at night fall (when the stars appear). However, there is disagreement about until when: one says, “until the end of the first watch” (the hours of night, which varied during seasons where divided into three watches); another says “until midnight”; and another says until “the light of dawn rises.”
One of the things that I find interesting and characteristic of this Mishnah is the line regarding distancing a person from sin. Throughout the Talmud there are discussions about what is Biblically commanded and what is Rabbinically commanded. It seems to me that many, if not most of the Rabbincally commanded actions have this goal in mind – distancing a person from sin. Therefore, they will extend or add to commandments in order to help ensure that there is not even the presumption of sin.
In the Gemara there is a discussion about why they started with the evening Shema and not the morning Shema – one answer given relates to the Jewish view of a day, which starts in the evening and comes from the order “from the Creation of the world, where it is written: And there was evening and there was morning, one day.”
Also in the Gemara there is a discussion of why the time for when one can begin “the time the stars appear” is given in such a roundabout way and not a precise time. The answer, the Sages wanted to teach something else as well—then they go into a discussion of when the Kohanim are permitted to eat terumah (one of the offerings).
This discussion of when can begin goes on for the rest of the daf (sides A and B of the page). In the Artscroll addition in the notes, which are translations of the various commentaries from the page and additional ones, there is a summary of this discussion. I think you will find it interesting.
They summarize the various opinions on the earliest time to recite the evening Shema:
- R’ Eliezer – from the time the Sabbath is sanctified, i.e. sunset
- R’ Meir – from the time Kohamin who are tamei (ritually impure) immerse themselves, just a few moments prior to the appearance of the stars
- R’ Yehoshua – from the time Kohamin who are tamei are permitted to begin eating terumah again, i.e. at the appearance of the stars
- R’ Chanina – from the time a poor person enters to eat his daily evening meal of bread and salt, which is sometime after the appearance of the stars
- R’ Meir of the second Baraisa – from the time people enter to eat their meal on the Sabbath eve
- R’ Achai, and some say R’ Acha – from the time people enter to eat their evening meal during the week, which is even later than the time of a poor person, and the latest time of all.
Perhaps this offers a glimpse into the lively world of the Talmudic Sages and their discussions.
What is also interesting is that Maimonides or Rambam decided to create a compilation of all the Halakhah from the Talmud and various other Rabbinic texts. In the Rambam’s Code, he summarizes this whole discussion this way:
“9. At what time does one recite the Shema in the evening? The obligation obtains from the time the stars come out till midnight. If one transgressed and did not recite before midnight but recited before dawn, he nonetheless fulfilled his obligation, since they only said “until midnight” in order to distance one from transgression.”