# 4th dimension?

Well, reading all that stuff about the universe got me thinking. If the universe is expanding into the 4th dimension,and not space as we know it… what is the forth dimension? I’m sure i’ve heard about it before… and now that i think of it i can’t recall exactly what the first three are listed as…space time and something else i should remember. Has anyone read ‘A wrinkle in Time’ ? Essentially it’s a kids book with crazy science words and ideas that only someone whos made it to highschool would really know anything about.

The first three dimensions are the spatial dimensions that you can see and measure things in. Length, width, height. (Or, more abstractly, x, y, and z.)

Time isn’t really a dimension as such; relativity stipulates that space and time are part of the same phenomenon, spacetime.

Have you read /Flatland/ by Edwin A. Abbott? It discusses the idea of different dimensions, and mentions the 4th dimension in the 2nd half. Fiction, but based on factual ideas.

Current speculation posits the existence of something like nine or eleven dimensions in total. Most of them do not extend over a few tens of microns (1µ=10[sup]-6[/sup] meter).

I’ll admit I have no idea what I’m talking about, but it seems to me that these alledged dimensions are just made up by people who are trying to explain things they don’t understand. I took an astronomy class once and apparently early astronomers came up with a working model of planet and sun movement with earth as the center, it was extreamely complex, consisting of circles around circles, If I remember correctly there were something like 80 orbits to account for retrograde motion, the point is: these new “unimaginable” dimensions seem like just another overly complex explanation for the unknown

The current understanding is that there are 4 dimensions to the universe…3 of space and 1 of time (i.e., the universe is made of “spacetime”). The expansion of 3D space is not thought to be going into a ‘higher’ 4th dimension of space (although to visualize it otherwise can be difficult and I don’t think I can adequately explain it otherwise except to say Space expands with Time.).

String Theory talks about lots more dimensions of space which are tiny and curled up within the regular 3 dimensions of space. However, these tiny dimensions have yet to be proven to actually exist.

Examples of the “first” three dimensions, assuming you’re sitting in a room right now, are the height of the room, its length, and its width. Each of these dimensions is at right angles to the other two. So, we can say the room is 8ft x 16ft by 20ft. 3 dimensions, see?

We call these three dimensions “spacelike” dimensions. We use them to judge how near two things are to each other, or more exactly whether A is nearer to B than C is.

Unfortunately, 100 years ago, Einstein showed that a lot of those things we take for granted are actually “relative”, meaning they depend on the motion of the observer. For example, a straight line for me may be a wiggly line for someone else. Worse, even time is relative, so that for me event A may appear to happen before event B, whereas for someone else B may appear to happen first, and for a third person they may appear to happen simultaneously.

He realised therefore that 3 dimensions were no longer enough to say whether things were near each other or not, and that things could only be “ordered” continuously if a fourth dimension is taken into account. This fourth dimension is called “timelike”, because it corresponds to our perception of “time”, and together with the other three, it forms the “space-time continuum”.

That really is as clear as I can make it.

There are 4 dimensions comprising space-time. Most of our normal experience is that 3 of these are purely spacial, and one is pure time.

The universe is also expanding along yet another spacial dimensino that is perpendicular to the other 3.

Please see the dozens of other threads regarding relativity, the Big Bang, dimensions, etc.

Actually more dimensions makes things easier ala the String Theory Phobos mentioned. Scientists are looking for the GUT (Grand Unified Theory) or TOE (Theory of Everything) which will unite all forces of nature under one umbrella. You have the Strong Nuclear Force, the Weak Nuclear Force, the Electromagnetic Force and the Gravitational Force. At extremely high energy states (such as existed at the very early moments after the Big Bang) all of these forces should unite into one single force. So far so good but unfortunately Gravity refuses to be easily fit into its place. A Quantum Theory of Gravity is needed but nothing works to the satisfaction of scientists.

Enter the 4[sup]th[/sup] and higher dimensions. It turns out when you do the math for all of these forces in higher dimensions there is enough ‘room’ (for lack of a better word) to fit gravity into the equation. Sort of a higher order language if you will. All of a sudden some of this stuff starts linking together nicely. I guess saying that this is ‘easier’ is a bit misleading since this kind of math is WAY out there and generally only performed by people with lots of degrees under them. I’ve heard that String Theory came before the mathematical tools existed to explore it fully (usually the discoveries are the other way around). Last I heard they expected 10-30 years for math to catch up enough to sufficiently explore the theory.

Does this mean that higher dimensions exist? I don’t know. Perhaps this is all a convenient mathematical trick and has no other basis in reality. If you want to prove higher dimensions exist as Phobos suggested you will need a particle accelerator with the circumference of the earth’s orbit around the sun and the entire mass of Jupiter converted to energy to power it. Basically it’s not something that will happen soon.

Finally, I don’t know if this is meaningful but time as a 4[sup]th[/sup] dimension does work in a coordinate system. You have X, Y and Z axis. With those three coordinates and an agreed upon reference frame I can pinpoint (say) the Skydeck of the World Trade Center. Add in time and I can specify when in time I will meet you there. If you want to get picky and look at things from a galactic scale the Skydeck on the World Trade Center is never in the same place from one moment to the next (earth’s rotation, earth’s orbit, the suns orbit, and the galaxy is moving) so specifying a location with X, Y, Z AND a time coordinate can be very useful. Again I don’t know if this argues for a 4[sup]th[/sup] timelike dimension or not but it looks good to me!

For a brain bender not only are the higher dimensions extremely small but they touch every point in our universe! I.E. There’s not a teeny little high-dimension ball floating somewhere in space. If you built an insanely big atom smasher with the end in your living room you could probe for the higher dimensions there as well as anywhere else (on the moon for instance or another galaxy). Sort of everywhere and almost nowhere. How’s that for counterintuitive!