According to the theory of general relativity, spacetime is a four-dimensional fabric that is curved and distorted by the presence of mass and energy. However, the concept of thickness is not typically used to describe spacetime.
In general relativity, the curvature of spacetime is determined by the distribution of matter and energy within it. Regions with a higher concentration of mass or energy will cause spacetime to be more curved in those areas. This curvature affects the motion of objects and the behavior of light.
It's important to note that the curvature of spacetime is not uniform throughout the universe. It varies depending on the distribution of matter and energy. For example, near a massive object like a black hole, spacetime is highly curved, while in regions with less matter, the curvature is much weaker.
However, it is not accurate to think of spacetime as having a physical thickness or varying thickness in the way we think of physical materials. Spacetime is a mathematical framework that describes the fabric of the universe, and its properties are described by the equations of general relativity.