Where can we find a fifth force of nature?

Hubble image of Messier 54, a globular cluster located in the Sagittarius Dwarf Galaxy. Credit: ESA/Hubble & NASA

We know of four fundamental forces of nature, with no signs of a fifth. But dark matter and dark energy make up over 90% of all the contents of the universe. So the question remains: could there be a fifth force hiding in the “dark sector” of our universe?

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