I’m trying to come up with an analogy of dark energy, the best I can do is a bath tub full of water representing the dark energy. I drop a solution of permanganate of potash (that purple crystal – dye) into the bath (this represents matter and the big bang).
Diffusion of the purple colour represents the expansion of the universe.

Unfortunately unlike diffusion where the rate of expansion slows with time, the universe’s rate of expansion increases with time. If the analogy were accurate the purple dye would diffuse slowly at first then get faster the more diffuse it became.

Are there any real world analogies that better describe dark energy?

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