Yevamot 92: The Court's Error

The Gemara addresses what it means for the court to have an opinion - for example, if the court stipulates that the woman who has one witness testifying that her husband has died can remarry. A comparable example is brought with regard to the time that Shabbat ends, based on the darkness of the day - which might be the fault of clouds. In both cases, as it turns out, the court's ruling is in error, but are they the same? Also, a new mishnah: a case where a woman's husband and son travel overseas, and the husband died and then the son dies. Or the reverse. When does yibum kick in? What if it turns out that the testimony is backwards? What about a betrothal to a new man, and then the husband turns up alive? She goes back to the first husband, and the get from the man who betrothed her isn't a full divorce.