Yes, humans live in a four-dimensional spacetime. The concept of four-dimensional spacetime combines three dimensions of space (length, width, and height) with one dimension of time. This idea was first introduced by Albert Einstein in his theory of general relativity.
In our everyday experience, we are aware of three spatial dimensions. We can move forward and backward, left and right, and up and down. These three dimensions define the physical space we inhabit. However, time is also an essential dimension that is intricately linked with space.
While we cannot directly perceive time as we do with spatial dimensions, we experience the passage of time through various means. We have a sense of the present moment, and we can remember past events and anticipate future ones. Our perception of time is subjective and influenced by factors such as our biological rhythms, personal experiences, and the environment we are in.
In terms of experiencing the four-dimensional spacetime, our experience is primarily limited to a three-dimensional "slice" of the entire spacetime. We move through time as it unfolds, perceiving the world around us at each moment. However, we are not able to freely move back and forth in time as we do in space.
According to the theory of relativity, the passage of time is not absolute but can be influenced by factors such as velocity and gravitational fields. This means that time can pass differently for different observers depending on their relative motion or proximity to massive objects. These effects, known as time dilation, have been experimentally verified and are critical in various scientific applications, such as the functioning of GPS systems.
So, while we cannot directly perceive the full four-dimensional spacetime, we live within it and experience it through our movement through time and our interactions with the three spatial dimensions.