世界上最遥不可及的是天空
[shì jiè shàng zuì yáo bù kĕ jí de shì tiān kōng]
Expressed in a poetic manner as 'the most unreachable thing in the world is the sky'. Using this phrase signifies a profound longing for something that can never be grasped - it could describe unattainable aspirations or the sense that certain things in life will always be beyond reach.