CREATE TABLE table_30277 ("Series no." FLOAT, "Season no." FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT, "U.S. viewers  ( millions ) " TEXT)

When was originally aired the episode with an audience of 1.57 million us viewers?
SELECT "Original air date" FROM table_30277 WHERE "U.S. viewers (millions)" = '1.57'
SELECT "Original air date" FROM "table_30277" WHERE "U.S. viewers (millions)" = '1.57'