ELi5: Physicists say space is ‚flat‘, but how can 3D space be flat?

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My assumption is that the short answer is that light travels in a 45 degree angle in a space-time diagram?

In: Physics

6 Answers

Anonymous 0 Comments

Flat refers to the geometry of the universe. A flat universe is the one you always thought you lived in: Angles of a triangle sum to 180 degrees, parallel lines do not intersect, etc.

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