It is not inherently impossible to imagine or conceptualize three spatial dimensions. In fact, as humans, we live in and navigate a three-dimensional world on a daily basis. We perceive and interact with objects in three-dimensional space, which is why we can envision and understand concepts such as length, width, and height.
However, it can be challenging for us to visualize or imagine more than three spatial dimensions because our everyday experiences and sensory perceptions are limited to three dimensions. Our brains have evolved to process information in three-dimensional space, and our visual system is particularly adept at perceiving and interpreting three-dimensional objects and scenes.
When it comes to visualizing higher-dimensional spaces, such as four or more dimensions, our brains face difficulty because we lack direct sensory input or experiences to draw upon. Our visual imagination is often constrained by our perceptual limitations, making it challenging to visualize dimensions beyond what we experience in our everyday lives.
That being said, mathematicians and physicists have developed mathematical models and tools, such as geometry, algebra, and abstract concepts like vector spaces, to describe and work with higher-dimensional spaces. While we may not be able to intuitively imagine these spaces, mathematical frameworks allow us to reason about them and explore their properties.