To pick up from yesterday, I think that Yaakov was aware that the galut, the diaspora, was beginning now with his going down to Egypt. Ironically, this observation does not seem to have been noticed by Yosef who thought he was controlling everything. Yosef's goal of giving the brothers the opportunity to not repeat what they did to him worked out well. Additionally, Yosef saw himself as saving the family due to his position as viceroy of Egypt. He seems to be unaware of the onset of the diaspora, though. It is not entirely clear why Yosef does not encourage the brothers to go back to Canaan after the end of the famine, but perhaps we'll speak more about that later.
The Ramban calls the book of Exodus the Book of Redemption. There is an implication that Genesis is the book of Diaspora. One way of looking at the long series of events, at least from the time of the b'rit bein hab'tarim where Avraham is given the prediction about his progeny, is that they all lead inexorably to diaspora.
The diasporas which followed the destructions of the first and second Temples are clearly linked to sin on the part of those exiled. Here, however, we don't see a clear sin which brings about the diaspora to Egypt. Furthermore, the family of Yaakov goes quite willingly to Egypt under the circumstances.
Why in fact did the diaspora here come about? That is, what was God's plan in bringing it about? Was it actually God's plan? Did it have to happen?
In that it did take place, though, it has informed the Jewish psyche for millennia. It is only by leaving the land that the children of Israel became a great nation. How does that sound to us living here today?