# 4th Dimension Explained - Fourth Dimension Explained - Tesseract and Time Dimension - Dimension

### In this video 4th dimension has been explained in detail. This video answers many questions like- What are dimensions, what we mean by the 4th dimension, how many dimensions are there according to different theories, Why we can not perceive higher dimensions, how we can visualize and represent a fourth dimension geometrically using the example of a four dimensional cube known as the tesseract. We will also discuss, can time be considered as the fourth dimension? Here I have used different methods of dimensional analogy like cross section, projection and bounding volume to help you in visualizing and understanding the concept of the 4th dimension. The video also covers how a four dimensional being would see the world and what amazing powers would be possessed by the 4th Dimensional beings. Friends I have also included some very interesting examples to make this complex topic easy to grasp. Before understanding the 4th dimension, it's necessary to know, what actually we mean by dimension? Dimension of a point is defined as the minimum number of coordinates that are needed to specify that point in it. four dimensional objects need 4 coordinates for their representation. 4th coordinate should be perpendicular to the other three coordinates. Actually a four dimensional space is a mathematical extension of the concept of three dimensional space. We can visualize the fourth dimension (4th dimension) by using different methods. Here I will use various techniques like geometry, projection, cross section and bounding volume to explain you the concept of the 4th dimension. But before discussing all these techniques of visualization, let's first know, how many dimensions are there according to different theories. Superstring theory requires 10 spacetime dimensions while according to M theory there are total 11 dimensions. In Bosonic string theory spacetime is 26 dimensional. But why we are not able to perceive higher dimensions? Actually according to some studies extra dimensions may be "curled up" at extremely small scales. The scale is too small to be visible to current experiments. Therefore it is really very hard to imagine higher dimensions for our brains. This 4 dimensional structure is called as the Tesseract. Actually tesseract is the four dimensional analogue of the cube. The simplest way to represent a tesseract is by drawing two 3D cubes one encompassing the other on a 2D plane. These two cubes are separated by an unseen distance. Actually these 8 lines that connect the vertices of both the cubes represent a "single direction" in the 4th dimension, that we can not see. Now I will Discuss is time a dimension? In order to accurately describe the position of an object we need not just the spatial dimensions to tell it's location but also time dimension to know how that position changes with time. Because nothing can move instantaneously in space without moving in time. For moving in space we need to move in time too. Therefore time is a dimension. Dimensional analogy is an important tool to understand higher dimensions. It is used to study how (n - 1) dimensions relate to n dimensions and then inferring how n dimensions would relate to (n + 1) dimensions. Suppose a 3D object passes through a 2D plane then what would the 2D beings see? Actually two dimensional beings can not see anything that is above or below their 2D plane. So when a three dimensional object passes through a 2D plane then the 2D beings would only observe the cross section of the 3D object cut by that plane. As we live in a 3D world and have 2 dimensional retina. So actually we see only 2 dimensional projection of 3 dimensional objects. It is our brain that can create a 3D model of the object using 2D input from our eyes. In the same way 4 dimensional beings would have 3 dimensional retina so they would not be able to see the 4 dimensional object in its entirety. 3 dimensional projection of the 4 dimensional object will be formed on their 3D retina. We can visualize the fourth dimension also by using bounding volumes. As we know that two dimensional objects are bounded by one-dimensional boundaries, In the same way three dimensional objects are bounded by two dimensional surfaces. So We may infer by applying the dimensional analogy that a four dimensional object is bounded by three-dimensional volumes. Now I will discuss what superpowers a 4 dimensional being would have. It would be possible for a person living in four dimensions to go back in time and change the decisions made by him in the past and start a new timeline. it would be able to see inside the solid objects because that being would have 3D retina that can see the whole solid 3D object in its entirety including its internal structure. It would not be possible for 3D beings like us to bound him. As he would escape from the extra physical dimension- the fourth dimension.

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