We can understand this concept by gazing upward and knowing that there are countless stars we cannot see because not enough time has passed since the birth of the universe for their light to shine our way ; they are beyond our light cone 要了解这个概念，可以抬头仰望星空，我们知道有数不清的星星是看不见的，因为宇宙形成至今的时间，还不足以让这些星星的光到达地球；也就是说，这些星星位于我们的光锥之外。
