What is space? How does Space expand? Why is it expanding?

Space is the vast, seemingly infinite expanse that exists beyond Earth's atmosphere and between celestial bodies. It is a three-dimensional framework in which all matter and energy exist.

The expansion of space refers to the phenomenon where the distances between galaxies and other cosmic structures increase over time. This expansion is described by the theory of general relativity, proposed by Albert Einstein. According to this theory, space itself can stretch or expand, carrying galaxies along with it.

The reason behind the expansion of space is still not fully understood and remains an active area of research in cosmology. However, scientists have proposed a concept called dark energy to explain this phenomenon. Dark energy is a hypothetical form of energy that permeates all of space and exerts a repulsive gravitational force. It is believed to be responsible for the accelerated expansion of the universe.

Observations of distant galaxies and the cosmic microwave background radiation have provided evidence for the expansion of space. The expansion is thought to have started with the Big Bang, the event that marked the beginning of the universe around 13.8 billion years ago. Since then, space has been continuously expanding, causing galaxies to move away from each other.