Is 2-dimensional world exist and can we see it?

[fiwi]

Hi, before I can understand the 4-dimensional world, I just have another question: Does anything other than 3D can exist in real world?
Many people say because we are in 3D world, so we cannot feel or get into 4D world. However, I it seems like we didn't ever seen anything that is 1D or 2D either, or do they even exist?
To be clear, what I mean is REAL 2D. Things like a painting or showing on screen are not, because the ink and the display material still have thickness.

[Rerouter]

2D or "flat landers" only exists as a concept to try and explain higher spacial dimensions, the smallest distance we have is the planck length, so the most perfect square you can ever hope to make will still be at least that high. meaning its a cubic shape

4D, or more the manipulation and translation of 4 or more spacial dimensions is where we come unstuck, as we lack any good reference point for it, so trying to approach it from a lower dimension, where the thought of being able to see all the 2D slices of an object as a 3D shape is easier to grasp than thinking that you represent a 4D shape with 3D slices,

Its not impossible to learn, but its very hard to visualize, kind of like how black holes are technically points with no dimensions, the have no width, height or length, only a location in space, its not easy to wrap our heads around, e.g. you have 100 millions suns mass stored in a point with 0 volume,

Then higher and higher counts of spacial dimensions, and even the concept of a second independent time dimension are thrown in the mix to try and explain things that may be results of us struggling to visualize it, (String theory and its friends)

There are even fun things like the weak force, where how it reacts does depend on its "spin" or orientation, and even which way time is flowing, so you even have physics that depends on how many dimensions there are.

[hamster_nz]

Sidetrack #1... At enough distance 3D looks 2D (e.g. Slime on a petri dish, or people on a large flat area.

Who's to say that iwe are not in a 5D universe but can't perceive it?

Sidetrack #2... Black holes are not be infinitely small. They have a surface area that is related to how massive they are. Also the rate at which the surface area changes with the mass of the back hole hints that the universe had LESS dimensions that we expect.

[Rerouter]

Black hole volume/surface area is usually defining the bounds of the event horizon, not the black hole itself.

[windsmurf]

Sidetrack #1... At enough distance 3D looks 2D (e.g. Slime on a petri dish, or people on a large flat area.

Who's to say that iwe are not in a 5D universe but can't perceive it?

Sidetrack #2... Black holes are not be infinitely small. They have a surface area that is related to how massive they are. Also the rate at which the surface area changes with the mass of the back hole hints that the universe had LESS dimensions that we expect.

According to string theory, we're in a 10 dimensional (superstring theory), 11 dimensional (M-theory), or 26 dimensional (bosonic string theory) universe. Our senses only allow us to observe 4 of them.   

[Bicurico]

There is a great book called Flatlands by E. Abbott.
It can be downloaded for free as the copyright expired.

For example here:

ned.ipac.caltech.edu/level5/Abbott/paper.pdf

Regards
Vitor

[bd139]

Good book. Read it. 

[coppercone2]

you can have a naked singularity

i think the dimensions would be pretty flat, I think it would look like a pringle chip gasket?

[Ian.M]

Its vanishingly unlikely that any 2D (+time) space is observable from our 3D (+time) space unless such spaces are very rare and localised in 3D space.   If there was one anywhere nearby, interaction between observable particles in it, and between them and particles in 3D space would be spatially assymetric from the 3D space viewpoint, in a manner not related to particle spin or spin of nearby masses.  Over 130 years of particle and radiation physics experiments,starting with the Michelson–Morley experiment and at scales ranging from near-atomic to the radius of this solar system, have found no such asymmetry. 

[German_EE]

I once heard an interesting explanation of the dimensions thing that includes 'Flatland' and its variants.

Take a toroid of any dimension and deposit on it a citizen of Flatland. The Flatlander will immediately assume that the universe is a) very large  b) finite and c) curved because no matter what direction they set off in a straight line they will eventually arrive back at their start point. However, being a Flatlander they will have no concept of the mysterious third dimension.

Now add one to the number of dimensions.

Here we are living in a three dimensional world and our understanding of other dimensions is limited at best, we certainly cannot travel in the 4th dimension and any attempt to represent it in three dimensions results in a tesseract and a certain amount of confusion.

[Bicurico]

@German_EE: Look at my post, a little bit upwards and do read the book "Flatlands". It is exactly about what your heard and totally worth reading.

Regards,
Vitor

[BrianHG]

Unfortunately, complex life as we understand it cannot exist in a 2 dimensional world.  Here is a simplistic explanation why: