Our Universe, as we can perceive, has three spatial dimensions and one temporal dimension. Humans are three dimensional beings. Objects in 3D space have different lengths, different heights and different widths. Certain theories in physics suggest that our universe may have additional higher dimensions. Humans, being three dimensional organisms, cannot sense or perceive these dimensions.
To get a rough idea about dimensions, let us start with a point. A point has zero dimensions i.e. it does not have any length, height or width. To enter the first dimension, extrude the point in any direction you want- you get a line. A line has only one dimension i.e. length. Now, to enter the second dimension, extrude the line in a direction perpendicular to the original direction- you get a plane. To enter the third dimension, extrude the plane in a direction perpendicular to the original two directions- you get a cube.
A cube is a 3D object because it has a length, height and a width. Now, to enter the fourth dimension, extrude the cube in a direction perpendicular to the original three directions. When you do this, you get a TESSERACT. A tesseract is four dimensional object but we cannot see it because we’re entrapped in a three dimensional world. However, we can imagine what the projection of a tesseract in a three dimensional space would look like. Check below:
To know more about the fourth dimension, watch this short video:
Now, lets get back to the main question: What would our Universe look like from the fourth dimension?
To understand this, let us first imagine a two dimensional universe with two dimensional beings living in it. These beings would have their senses limited to two dimensions only i.e. they would have no idea that humans exist. They would find it difficult to imagine the third dimension for the same reason why we find it difficult to imagine the fourth dimension.
Since you belong to the higher dimension, you can easily interfere with their world. Consider a paper sheet with a circle drawn on it (circle is a 2D object). Next, draw many dots inside this circle. You can easily see what lies inside the circle. In fact, you can even erase these dots or play with them in any way you want. If the dots were movable, you could even take them out from the sheet and the two dimensional beings would have no idea how this was possible.
4D beings would be able to do exactly the same things with our universe. These beings would have the ability to see what lies inside objects in our 3D universe. They can easily see each and every organ inside your body. In fact, they can even pull these organs out without having to penetrate your skin (for the same reason why you were able to play with the dots inside the circle without having to penetrate it).
Seeing our universe from the fourth dimension would be interesting. Not only will you be able to see organs inside the human body but also you would see Earth’s molten core or possibly even the inside of a black hole.
In a four dimensional universe (with four spatial dimensions), the planet orbits would become unstable because they will have to obey the inverse cube law instead of the inverse square law for stable orbits. Also, a chair would need more number of legs to stand by itself in a 4D universe.
Would you like to see our Universe from the fourth dimension?
Cover Image Credit: NASA/CXC/M. Weiss