Space is a three-dimensional environment in which all matter and energy exists. The word “space” refers to the areas between, around, and within physical objects. It is often considered to be infinite and limitless. In actuality, space is finite. The universe has a defined edge, beyond which there is nothing.
The concept of space is of fundamental importance in physics. It provides a framework within which we can understand and measure distance, time, and other quantities. Without space, the laws of physics would break down.
Euclidean space is the simplest kind of space. It is the kind of space we experience in everyday life. Euclidean space has three dimensions: length, width, and height (or depth). Objects in Euclidean space can be moved around without changing their shape or size.
Riemannian geometry generalizes Euclidean geometry to spaces with any number of dimensions. In physics, Riemannian geometry is used to describe curved spacetime – the kind of spacetime that exists in the presence of gravity.
The most familiar example of curved spacetime is the surface of a sphere (such as the Earth). If you travel in a straight line on the surface of a sphere, you will eventually end up where you started (at your starting point), but if you were to keep going in that same direction you would eventually come back to your starting point (after traveling around the circumference of the sphere). This happens because the surface of a sphere is curved; it curves back on itself so that there are no straight lines on its surface (except for great circles). Similarly, spacetime curvature causes straight lines (worldlines) to curve; this explains why particles follow curved trajectories in gravitational fields such as those near massive objects like stars or black holes.”