No Center to the Expansion in 1

# No Center to the Expansion in 1 - No Center to the...

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No Center to the Expansion in 3-D Space General Relativity describes gravity as a warping or distortion of space and time near a massive object. In General Relativity, four-dimensional spacetime is curved. You may want to refresh your memory of these concepts by reading the Relativity chapter . To help you understand what curved spacetime means, let's use the analogy of a two-dimensional world curving into the third dimension. Pretend you are confined to the surface of a balloon and you only know about ``front'', ``back'', ``left'', and ``right'', but not ``up'' and ``down''. In your 2D universe you cannot see the third dimension. Your universe appears flat. Yet you know that your 2D universe must be curved because if you walk in a straight line, you eventually arrive back at where you started! The balloon universe has a finite size but no edge. You also know that the angles of large triangles add up to a number larger than 180°! For example, on the balloon the lines of longitude running north-south intercept the equator at a 90° angle and converge at the

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No Center to the Expansion in 1 - No Center to the...

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