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Originally Posted by JinnKai
I don't understand why it's conical and not linear? Wouldn't the advancement of time cause the light at the current time to always be in a linear translation from the previous time? In that case, the light cone is only useful for talking about DURING motion, not at actual finite states..?
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Imagine a two dimentional universe. When an event occurs, there will be a circular area within which that event can be the cause of another event. That circle is the maximum distance light could have travelled in any direction in a given amount of time. As time passes, that circular area will grow. Now imagine that the temporal dimention in this 2D universe is mapped onto our third spacial dimention. Instead of an expanding circle, you now have a cone.
Now take the same concept with our 3D universe and an expanding sphere instead of an expanding circle. You get a 4D "cone".