That also implies a couple of other ideas.<br /><br />That means that if you could travel extremely fast (a LOT faster than light) in any direction, you would eventually come back to Earth without having to change direction - by circumnavigating the Universe itself). But it would have to be fast, to avoid that the the "balloon" is expanding so fast that the distance to Earth around the sphere increases faster than you travel - in which case you'd never get back to Earth.<br /><br />It also implies that the universe is, in fact very finite. As the surface of the balloon is finite, the 3-dimensional volume of the universe is finite (although very large and growing every day).<br /><br />Maybe there are other universes/balloons out there, but these would be completely undetectable for us, since we can only see what's on the surface of our balloon, and not anywhere else - unless another balloon intersects our balloon. But if matter or light or information can't cross over to an intersecting balloon, we would never observe it.<br /><br />Using a 4th dimension for fast space travel may be impossible if we're constricted to the 3D "surface" of our sphere. If possible, it may still be impractical, as moving through the center of the balloon to get to the opposite side would still be an extremely long journey. And for short journeys (nearby galaxies - which are still quite a challenge) you would still have to travel practically the same distance (the distance from London to Paris won't get much shorter by going in a straight line cutting through the Earth).<br /><br /><br />Will the expansion of the balloon slow down or stop in the future? Will it collapse back towards itself? A retreating universe would be interesting to experience as all the light from all the stars in the universe would have a decreasing volume of space to be in. When the universe expands, the light produced by stars is spread out quite thin - while in a retreating universe the sky would get quite bright as all that <div class="Discussion_UserSignature"> <p><font color="#ff9900">----------------------------------</font></p><p><font color="#ff9900">My minds have many opinions</font></p> </div>