I recently watched Interstellar with some friends and we didn't come to the same conclusion. In my opinion, the portal they use to go to the other galaxy (to visit the three planets) is not a black hole. My friends tell me it is.
(warning, contains spoiler!!)
To me, it's not because of these points:
- When they are in front of the portal, they can see the other galaxy, which is not the case when Coop goes to the black hole at the end
- When they go to that portal, they "flow" in a tube like channel. Again, that's not the case when Coop goes to the black hole at the end.
- When Coop goes to that black hole, he goes through some sort of light dust that hits his ship, which is not the case when they go to the portal.
- When the robot (I forgot his name) goes in the black hole, his purpose is to collect some quantic data. If the initial portal was also a black hole, he would have made that collection at that time.
- When they goes to the portal, they seems "confident", but when Coop goes to that black hole, it's for killing himself. If the portal was a black hole, they would behave more identical.
So I believe it's not a black-hole, but what is it exactly (maybe not in scientific terms, but in Interstellar's terms)? A Wormhole?