mieral said:I read somewhere here (but couldn't find the exact message)
Spacetime is a concept that combines the three dimensions of space (length, width, and height) with the dimension of time. It is a mathematical model that describes the physical universe as a four-dimensional continuum.
The Big Bang theory states that the universe began as a singularity, a point of infinite density and temperature. As the universe expanded, the four dimensions of spacetime came into existence, including time itself.
According to the theory of general relativity, spacetime is a dynamic entity that can be affected by the presence of matter and energy. During the Big Bang, the universe expanded at an incredibly rapid rate, causing spacetime to also expand. However, the expansion of the universe has slowed down over time, leading to a relatively constant size of spacetime in the present day.
One of the strongest pieces of evidence is the cosmic microwave background radiation, which is the leftover energy from the early universe. This radiation is uniform in all directions, indicating that the universe was once much smaller and has since expanded to its current size. This supports the idea of spacetime being the same size during the Big Bang and now.
According to current theories, the expansion of the universe is expected to continue. This means that the size of spacetime will also continue to increase. However, there are also theories that suggest a potential contraction of the universe in the distant future. If this were to happen, spacetime would also change in size once again. Currently, there is no consensus on what will happen in the future, but research and observations continue to shed light on this question.