"<a href=""http://www.youtube.com/watch?v=zJt8yzR2aoY&amp;t=2m56s"">2:56</a><br>would the infinite dynamo really work? There would be nothing to pull it down as the wormhole is between it and the Earth so it would just be still?",(reply>), @Lord Pen<br>Actually, I think I'm wrong in that comment after exploring the idea a bit more while writing this one. Bear with me.<br><br>Assume that the portals are actually 2D but separated by 3D space. The Earth's distortion of space-time is interrupted by the portals, since they are "closed" from the back and space-time has no way to propagate through it from that direction - too much information is lost in the process.<br><br>Because the portals are positioned above Earth, with Portal1 facing "down" and Portal2 facing "up", the local curvature is distorted weirdly around them.<br><br>One could not "fall" into the bottom portal, because the distortion that would cause falling (the Earth) is blocked by the back of Portal2. The closer you got to the entrance, the more you'd be unaffected by distortions parallel to the backs of the portals.<br>In a way, Portal2 acts as a force of anti-gravity.<br><br>It's like you took a piece of cloth, ripped it twice in the middle, and then tied the ripped cloth together, forming a loop between two points on the tapestry, but introducing two tears which are "cut off" on one side, and lead into each other on the other side. You couldn't "walk" across the torn sides to the middle of the cloth, but you could enter from the middle to exit from the middle.,(reply>), Why the opposite direction?,(reply>), Yeah, thinking about it leads me to believe that even if it DID work, it would travel in the opposite direction,(reply>), that is actually a very interesting thought. I guess it would depend on how the portals affect gravity waves and spacetime...,(reply>), If the portals behave like the ones in the video game Portal, then yeah, it would work. Never dropped a box in a portal that leads back to the ceiling, in the game? It keeps accelerating until it hits terminal velocity, and just keeps falling forever.<br>In the video game, even if the portal is underneath you, you're still affected by the gravity of where you are right now, only after you go through the portal that gravity changes. <br>Cheers!