What if the universe is a four-dimensional ball?

[ZZ9]

I think what he means, is that anything that happened before the Big Bang (maybe another world and life) would not change the future of the universe. Once the universe condenses, all past events are forgotten.

No, he literally meant that spacetime didn't exist before the Big Bang.

[Fraxtil]

Okay, apparently a few of you misunderstood the point I was trying to convey. I well understand that time is generally interpreted as the fourth dimension. However, for the sake of discussing spacial dimensions, consider time to be a different number. southpaw's reference to a hypercube is actually fairly accurate, although the idea I have in mind is the same object in spherical form.

If you have trouble imagining a fourth spacial dimension, think of it this way: If you walk in a line across the Earth, you'll eventually end up where you started. This is because the Earth is three-dimensional. However, due to the immense size of the Earth, it seems like you're walking across a flat surface. Now think of the universe- to us it seems to have three spacial dimensions and no more. But perhaps it only seems this way because the universe is an enormous sphere? In other words, you could travel in any direction across the universe and, much like the Earth, end up where you started.

Another way of picturing this is through a globe. Initially people thought a flat map of the Earth was the only way to represent it, before the discovery of a round Earth. Of course, we know today that a globe is better for accurately scaling the Earth down to a size that humans can manage. In a similar fashion, the most sophisticated way of displaying the observable universe on a human scale is to make a three-dimensional projection of it. Perhaps a three-dimensional projection of the universe is like a two-dimensional map of the earth, and the universe wraps around like a sphere?

I hope this clarifies what I was initially trying to say.

[t̷s͢uk̕a͡t͜ư]

If you have trouble imagining a fourth spacial dimension, think of it this way: If you walk in a line across the Earth, you'll eventually end up where you started. This is because the Earth is three-dimensional. However, due to the immense size of the Earth, it seems like you're walking across a flat surface. Now think of the universe- to us it seems to have three spacial dimensions and no more. But perhaps it only seems this way because the universe is an enormous sphere? In other words, you could travel in any direction across the universe and, much like the Earth, end up where you started.

That is nowhere close to the difference between three spatial dimensions and four spatial dimensions.
You'd end up where you started on a globe eventually because you're restricting yourself to a sphere. You also appear to believe that if a surface looks flat that we perceive it as two dimensional. Every time I've walked around on Earth, I've managed to keep in mind that the ground has depth, that the sky exists, and that I and things around me have mass and volume (which require a third dimension).
You're not going to get another dimension just by curving things; if you curve a line in 2-dimensional space, all you get is a 2-dimensional circle. The shift along an extra spatial dimension is something far more dramatic. It's a transcendence of the previous space entirely, and it offers infinitely more possibilities for range of motion. Curvature or wrapping of any kind is a popular buzzword (buzz-concept?) used by people who don't know what they're talking about; it's not going to help in considering a fourth spatial dimension.

Another way of picturing this is through a globe. Initially people thought a flat map of the Earth was the only way to represent it, before the discovery of a round Earth.

Your middle school teacher was wrong -- Greek mathematicians figured out that the Earth was round, its approximate radius, and approximate distance from the Sun long before explorers started navigating the globe millennia later.

In a similar fashion, the most sophisticated way of displaying the observable universe on a human scale is to make a three-dimensional projection of it.

As I said in either another thread or possibly this one, theoretical physicists frequently use something called phase space, which is 8-dimensional. I'd say that's closer to "the most sophisticated way of displaying the observable universe on a human scale."

Perhaps a three-dimensional projection of the universe is like a two-dimensional map of the earth, and the universe wraps around like a sphere?

I think we're all getting what you're saying -- you're simply failing to put any thought into the idea after you've made it. Start thinking about what that would mean.
If humans could only perceive two spatial dimensions (whereas the universe has three), we'd have our reality influenced constantly by things completely out of nowhere. Imagine if it rained: suddenly, blobs of water would explode out of the air and spontaneously disappear, appearing even inside people and annihilating every 2-dimensional thing and person they hit. The 3-d landscape of the universe varies as well; imagine walking next to someone and talking when all of a sudden they implode and drop out of reality forever. Hell, we wouldn't even be able to influence anything in the universe because we don't have any mass or volume, or resistance to anything in that dimension. From our perspective, energy and mass would be created and destroyed, randomly, chaotically, and constantly. Living and surviving the way we do in our universe requires that we perceive and be able to influence all of the spatial dimensions that the universe has.

[blue_tetris]

*dips his balls into flatworld, confusing the locals*

[Yoshimo]

I went through that phase a year ago, but I did expand my horizons a lot! It would make sense, though, as you could just square a cube.

To put 4-d in my terms of view:
(with 1-d starting as length 2)
1-d=length2
2-d=area4
3-d=volume8
4-d=hypervolume16
5-d=hyper2volume32

If you can understand that.

[Condog]

I went through that phase a year ago, but I did expand my horizons a lot! It would make sense, though, as you could just square a cube.

To put 4-d in my terms of view:
(with 1-d starting as length 2)
1-d=length2
2-d=area4
3-d=volume8
4-d=hypervolume16
5-d=hyper2volume32

If you can understand that.

No, i don't. Please explain the concept of 'hyper volume'.

Also, that list would result in five dimensions. Not four.

[Yoshimo]

It simply continues on...

6-d=hyper3volume64
7-d=hyper4volume128

...For example. Just square 2 by the number of dimensions indicated to get the measure of how much matter can fit in that dimensional space if each line is length2. I put it to five bacause it is possible to go up that high. Oh, and before I forget, hyperspace is 4-d space, so hypervolume. Scientist only add more 'hyper's. Like with 5-d^, hyperhypervolume, or hyper2volume. Note however, that even though it may exist, it can never be proven, because even if we were in a place with 4-dimensions, we won't be able to see into that direction, none the less turn towards it.

By the way, if the universe does loop like that, it must be bound to the 5th dimension to exist in theoretical reality. It keeps looping, so there there is a 5-d side to this theory.

Just a little quiz, how many platonic hypersolids exist?

[Maligus]

okay...having only four dimensions is very unlikely at this point...string theory states that there are in fact not four...but eleven dimensions (pictured below)...and string theory brings both Quantum Mechanics and the laws of Gravity into a single theory of everything...therefore the universe cannot be a four-dimensional ball

[lord_day]

Could you please explain that picture? I only see two dimensions in it.

[Maligus]

Could you please explain that picture? I only see two dimensions in it.

were you being sarcastic or serious?

[unoriginal name]

I posit that the picture Maligus posted, supposedly of eleven dimensions, is in fact made up of only two.

Discuss.

[lord_day]

Could you please explain that picture? I only see two dimensions in it.

were you being sarcastic or serious?

Dead serious. How can that image show me the 11 dimensions?

[Maligus]

Could you please explain that picture? I only see two dimensions in it.

were you being sarcastic or serious?

Dead serious. How can that image show me the 11 dimensions?

obviously it cant because it is a two dimensional image...i have some pictures that might help explain it though

circles in the fabric of gravity represent an additional spatial dimension that is curled up within every point of our familiar three-dimensional space.

Six-dimensional Calabi-Yau shapes can account for the additional dimensions required by superstring theory.

Edit: this means that there are 10+ dimensions in our universe

Edit: @gloomp: yes i think i posted the wrong picture

[Condog]

[Maligus]

lol...thank you for your input Condog...

[Nexx]

Holy shit is that hilarious, Condog.

I should read more xkcd.

[t̷s͢uk̕a͡t͜ư]

Holy shit is that hilarious, Condog.

I should read more xkcd.

Just be sure to regularly check http://www.isxkcdshittytoday.com

[SkyPanda]

http://www.isxkcdshittytoday.com

edit: I just realised it always says yes. Lame.

[Condog]

Holy shit is that hilarious, Condog.

I should read more xkcd.

Just be sure to regularly check http://www.isxkcdshittytoday.com

Haha, wow. The person who made that totally doesn;t hate xkcd. Totally.

[GmN819]

I didn't know everyone in the N community was a quantam physicist :D

[blue_tetris]

I didn't know everyone in the N community was a quantam physicist :D

We have our quantitative moments. Our moments are extremely quantitative.

[Maligus]

I didn't know everyone in the N community was a quantam physicist :D

We have our quantitative moments. Our moments are extremely quantitative.

agreed lol

[rambo5252]

just a thought i had in math the other day....

if x and y are points on a 2D grid and x y and z are points on a 3d grid where would we go for a 4d grid?

[DemonzLunchBreak]

W?

I'm confused about what you think your question means.

[yungerkid]

...erm....we go to the next dimension of course...back on topic...