How quantum superposition could unravel the ‘grandfather paradox’

The ‘grandfather paradox’ has long been one of the most popular thought experiments in physics: you travel back in time and murder your grandfather before he’s ever born. If you’ve killed your grandfather, you’ve prevented your own existence, but if you never existed, how could you have committed the murder in the first place? Some physicists have avoided the question by arguing that backwards time travel simply isn’t consistent with the laws of physics, or by asserting a ‘many worlds’ interpretation of the Universe. But could the concept of quantum superposition remove what seems so paradoxical from this tale of time travel and murder once and for all?

Video by MinutePhysics

Idea/Knowledge

The tree of knowledge is not an apple or an oak but a banyan

Jonardon Ganeri

Essay/Cognition & Intelligence

Had a good think lately?

Not busy-work, ticking off to-do lists or keeping-up-with-stuff. Just sitting. And thinking. Is it so hard?

André Spicer

Video/Meaning & the Good Life

Late in life, Fred finds joy – and a ‘rhythm in all things’ – through tap dance

6 minutes

Idea/Ethics

Is it moral to respect the wishes of the dead, above the living?

Barry Lam

Essay/Bioethics

Which lives matter most?

Thinking about children who are not yet born confronts us with the question of our ethical obligations to future people

Dominic Wilkinson Keyur Doolabh

Video/Values & Beliefs

An urban cowboy rides through gang-ridden streets, preaching a gospel of redemption

7 minutes