Interstellar movie: What is the "portal" to the other galaxy? 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?
Yes, it is a wormhole indeed. This has been indicated quite clearly in the movie as well, when Dr. Romily explains with a pen and paper to Dr. Cooper. The explanation goes like this :

Imagine a sheet of paper to be 2-D space, then a line joining two points on the sheet of paper is the shortest distance possible to reach that point, but if due to some disturbance, the space is bent ( achieved by folding the sheet of paper), you can pierce a hole in the sheet after aligning the two points together. That is a 2-D wormhole (which is a circle indeed). So what happens when you consider a 3-D wormhole? It becomes a sphere.

Now, you can see the other end of a 2-D wormhole (which is effectively the other hole in the sheet visible from the first hole, and one can see beyond the hole in the other direction as well). Same happens with the 3-D spherical wormhole where you can see to the other side of the wormhole as well.

Now, the means to bend spacetime : Space time can be bent by having a very big mass placed inside the space time (read Einstien's General Relativity ). So, it is safe to assume that the wormhole is a space time disturbance created due to a massive object, but it is not a blackhole.