Lyskjeglen

Lyskjeglen, meaning "light cone" in Norwegian, refers to a fundamental concept in physics, particularly in the realm of special relativity and general relativity. It is a visualization used to represent the past and future paths of objects through spacetime, illustrating the causal structure of the universe.

The light cone is a geometric representation of all possible events that can be reached from a particular event in spacetime, or all events that could have influenced that particular event. The boundaries of the light cone are defined by the paths of light rays originating from or arriving at a specific point in spacetime. Since nothing can travel faster than the speed of light, these light paths set the limits of what is causally connected.

An event's future light cone encompasses all events that the event can influence, meaning that a signal or object could travel from the event to those future events. Conversely, the past light cone includes all events that could have influenced the event in question. Events outside of an event's light cone are causally disconnected; they cannot influence or be influenced by the event. The region outside of both the past and future light cones is often referred to as the "elsewhere" and represents events that are neither in the past nor the future, and thus cannot be causally linked. The shape of the light cone is determined by the geometry of spacetime, which can be curved by gravity in general relativity.