Dear Rabbi Mordecai Kornfeld
At http://dafyomi.shemayisrael.co.il/berachos/br-ch-01.htm it says: "Berachos Chart #1
Berachos Daf 2b "FROM WHAT TIME MAY ONE READ THE SHEMA AT NIGHT?
(A) TANA'IM
(B) TIMES, FROM EARLIEST TO LATEST
1) REBBI MEIR OF THE FIRST BERAISA AND REBBI ACHA OF THE LAST
(according to RI) When people eat their meal Friday night (according to RI)(1)
2) REBBI ELIEZER OF THE BERAISA When Shabbos begins(2)"
What is the rational of the Rabbi Eliezer of the Beraisa?
Sincerely
Yisrael Asper
Dear Yisrael,
The Torah requires Shema at the time of "be'Shachbecha", the time of lying down.
Some learn that the lying-down process begins when the evening meal is eaten. Rabbi Eliezer learns that when Bein Hashemashos starts (Rashi 2b DH miSha'ah Shekidesh), which is when Shabbos begins, the time of lying down has started.
All the best,
Reuven Weiner