Imagine you’re stood on a train track and look along the tracks as the they disappear off into the distance. The two mutually parallel tracks seem to meet just as they venture over the crest of the horizon. A strange illusion. You know that the two tracks can never meet, because a train has to be able to move over them with a fixed distance between its wheels. Perhaps it is just an illusion, created by the optical receptors in your eye…or perhaps it isn’t.

In Euclidean mathematics two parallel lines will exist alongside each other at a fixed length…

Simon Williams

Particle Physicist interested in science outreach.

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