# On what scale does the universe expand?

According to the theory (or my understanding of it), the universe is not only expanding, but speeding up.

If the galaxies are moving apart, are the solar systems within them also moving apart from one another (& the planets within them), if they are, won't the Sun be moving away from the Earth?

Does the expansion of the universe occur at all scales or just large (inter-galactic) scales?

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A longer answer: The current standard model ($\Lambda$CDM model) says that everything started with the big bang. It released a lot of energy that pushed the Universe and is since then expanding. While it's expanding, gravitational attraction has been working to create the structures that we see today (planets, stars, galaxies, cluster of galaxies).