Wow, I didn't expect so many replies so fast. Let me explain to you guys what I have thought of, explored, and found throughout my class and the internet.
The fourth dimension is both time and space, but it is when they both connect. We here in the third dimension have three dimensional directions, Up/down, North/south, East/west. The fourth dimension has 8, Up/down, North/south, East/west, Ana/kata. The two new directions, as can be defined by 3rd dimensional creatures, is the "stretching" of the third dimension (Up/down) through time. It is confusing, but we have all seen this before-in star trek and star wars when they go into hyperspeed, this is ana. The stars in hyperspeed appear stretched, although everyone who didn't know about the Ana direction stretching always thought it was for the speed effect. Remember, Ana and Kata.
Now, on to the issue of 4th dimension in our world. As was said earlier by someone in the thread, we cannot see the fourth dimension, because we are creatures of the third dimension, and can only see dimensions lower than us. Therefore, in order to understand a fourth dimensional object in the third dimension, we need to use an example of a third dimensional object in the third dimension. Imagine a 2D world, there is length and width, but not height-no up or down. The creatures living in this world are flat, and only have width and length. Now, imagine that for some reason, a Sphere enters this world, and wish to interact with a 2D creature. Because the 3D creature can move up/down, the Sphere can float above flatland, and look down on the creatures. The Sphere then finds a 2D creature, and, from above it, says "Hello". The 2D creature looks around in its 2D world of only length and width and sees nothing. The 2D creature thinks it is crazy, it heard a voice, but no one was there. The Sphere doesn't like that the 2D creature thinks the Sphere is a thought of craziness, so he prepares to enter the 2D world at the 2D creature's level. As he slowly descends, he slowly appears in the 2D world, and the 2D creature slowly sees him. But, the 2D creature can't see up/down, so the Sphere appears instantly and looks like a slowly increasing circle to the 2D creature. The 2D creature is amazed at this strange circle. The Sphere speaks to the 2D creature again, and explains "I am a creature of the 3rd dimension. I was the one who said hello, and you thought i was a thinking of craziness. You are a creature of the third dimension, that being length and width, but i live in the 3rd dimension, where there is also up and down." Now, as you can imagine, the 2D creature is thinking he is crazy. This is how we'd see a 4th dimensional object in our world, it would look 3D, not 4D, but something would be strange with the object.
And on to one theory that i agree with on the universe. The 3rd dimensional universe exists in the 4th dimension. As was said earlier in the thread, the universe is expanding towards a common point. This is true. This point exists ana to us. The best way to explain this is to not imagine the universe expanding in 2nd dimension, as is always taught, but to explain it that the universe is expanding in a spherical path. Imagine, that the "Big Bang" occurred at the bottom of a sphere. The universe then started expanding out along the surface of the sphere. The universe is expanding toward a common point, the top of the sphere. At this point, the universe will collide with itself and implode.
I'm tired from explaining the fourth dimension, time for bed.
