时间旅行的难题在于，你无法前往自己不存在的地方。

The consequences of this problem make themselves felt in bookshops. When you go to a large bookshop and look at the self-help sections, as I sometimes do -- if you analyze self-help book sproduced in the world today, there are basically two kinds. The first kind tells you, "You can do it! You can make it! Anything's possible!" The other kind tells you how to cope with what we politely call "low self-esteem," or impolitely call, "feeling very bad about yourself."

声音可以像任何物理结构一样塑造空间。

Sustainability is not just about planting trees; it's about planting the right trees in the right places and ensuring they thrive for generations.