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The origins of the universe as we know it, according to Edwin Hubble and Vesto Slipher, began with the discovery of retreating galaxies, suggesting that our universe is in a state of continuous expansion. Coupled with Einstein's relatively new theory of general relativity, this insight propelled scientists towards the conclusion that all energy, mass, and space were once contained within a singularity. The singularity is often described as an infinitely small point where all matter was compacted, leading to the explosive event known as the Big Bang.