"It's a very, very beautiful calculation, but it's the best example I know of the relationship between these rather abstract quantities perhaps and something that you can look at in a telescope." 

What happens when you try to look too closely at the fabric of the universe? When we gaze at a Planck length, a scale so small that even light becomes useless for observation, physics pushes back.

The Planck length is not just a tiny number, it’s a boundary where gravity, quantum mechanics, and relativity collide.

Physicist Brian Cox explains why the measurement is a portal to the deep structure of reality, and why going beyond it may break the boundaries of our understanding.

0:00 Introduction
0:45 The importance of measurements
2:40 What are the fundamental quantities?
7:20 How important is the Planck length?
9:20 Why you can’t approach the Planck length
10:30 A theory with more dimensions
13:00 What keeps a star from collapsing?
14:42 The uncertainty principle
17:36 The Planck mass