In your kitchen cabinet, you've probably got a spray bottle with an adjustable nozzle. If you twist the nozzle one way, it sprays a fine mist into the air. You twist the nozzle the other way, it squirts a jet of water in a straight line. You turn that nozzle to the exact position you want so you can wash a mirror, clean up a spill, or whatever. If the universe had expanded a little faster, the matter would have sprayed out into space like fine mist from a water bottle - so fast that a gazillion particles of dust would speed into infinity and never even form a single star. If the universe had expanded just a little slower, the material would have dribbled out like big drops of water, then collapsed back where it came from by the force of gravity. A little too fast, and you get a meaningless spray of fine dust. A little too slow, and the...
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