Prof. dr. Wubbo J. Ockels is a Dutch physicist, and also the Netherlands’ original astronaut. He is a Professor of Aerospace Sustainable Engineering and Technology at the University of Delft.

TEDxAmsterdam: Wubbo Ockels from TEDxAmsterdam on Vimeo.

Ockels explains how ‘time’ is created by human beings, as a way our brains can make sense of gravity. The speed of light is constant, because it is made by us: it’s the clock by which we have calibrated our existence.