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What Is the Electric Constant and Why Should You Care?
The force between electrical charges is kind of a big deal—without it, the universe would be a primordial soup and you would not exist. That force is determined by the electric constant.
It’s not something you notice, because all objects contain both positive and negative charges at the molecular level, so they have a roughly equal number of attractive and repulsive forces that mostly cancel. The gravitational interaction that keeps you pinned to the Earth is more obvious because it involves only an attractive force (you can’t have negative mass), and because we are puny specks on a giant rock. It had a thin horizontal rod hanging from a fiber so it could rotate freely—all contained in a glass cylinder to shield it from errant breezes.
Or read this on Wired