Light Cone

The light cone is the path a flash of light would take through spacetime. It exists in two-dimensional space where there is an extra dimension of time. So, everything in the universe has its own light cone, except the spacetime fabric, because the light cone is made out of it.This cone consists of a two-dimensional plane, with a cone below it, and an inverted cone above it.

lightcone

The plane is known as the Hypersurface of the Present. The meeting point of the two cones is where present events occur. The past and future light cones are the past and the future. All past events/already happened are in the past light cone, and all future events/ will happen are in the future light cone.

If our sun dies, we will only experience it after 8 minutes, as sunlight takes 8 minutes to reach the earth. This event in the future light cone of the earth. Refer to the Diagram below.

LightConeExample.png

(This diagram is from A Brief History of Time by Stephen Hawking)

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