According to the models of the universe we discussed in this course, why do the galaxies move apart (why do we have Hubble's law)?

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According to the models of the universe discussed in this course, the galaxies move apart because of the expansion of space itself that started with the Big Bang. This expansion is accelerating, as confirmed by observations of distant supernovae, and is described by Hubble's law. The galaxies are not moving through space like objects on a conveyor belt, but are instead carried along with the expanding space. The expansion stretches the light from distant galaxies, making them appear redder than expected, and the rate of expansion can be measured from this redshift. The cause of this accelerating expansion is currently unknown and is one of the biggest mysteries in physics, leading to the need for concepts like dark matter and dark energy to explain it.

According to the Models of the Universe We Discussed in This