Space refers to the vast, almost infinite, three-dimensional expanse that contains all matter, energy, and radiation. It is the fundamental nature of the universe, encompassing the entirety of existence, from the smallest subatomic particles to the vast expanses of galaxies and galaxy clusters. The study of space is a multidisciplinary field, drawing on astronomy, astrophysics, cosmology, and other sciences to understand its properties and phenomena.

The observable universe, which is the part of space that can be seen and studied, is estimated to have a diameter of around 93 billion light-years. Space is characterized by the presence of various forms of matter and energy, including stars, planets, galaxies, black holes, dark matter, and dark energy. The properties of space are governed by the laws of physics, particularly Einstein's theory of general relativity, which describes the curvature of spacetime caused by massive objects.

Space plays a crucial role in the formation and evolution of the universe, with galaxies and galaxy clusters forming through the gravitational collapse of matter and energy. The study of space has also led to a greater understanding of the origins of the universe, with the Big Bang theory being the most widely accepted explanation for the universe's beginnings. Space exploration has been a significant area of research, with spacecraft and satellites being used to study the properties of space and the objects within it.

The exploration and study of space continue to be an active area of research, with ongoing and future missions aiming to explore the properties of space, search for life beyond Earth, and better understand the universe. Space agencies and organizations around the world are working to advance our knowledge of space and to develop new technologies that will enable further exploration and utilization of space.