Clumps of dark matter reveal their presence by distorting the shapes of more distant galaxies, just like waves on the surface of a swimming pool distort the pattern of tiles on the bottom.

Euclid telescope: A scientist tells us of his quest to understand the nature of dark matter and dark energy

Source: space
Source Link: https://www.space.com/the-universe/euclid-telescope-a-scientist-tells-us-of-his-quest-to-understand-the-nature-of-dark-matter-and-dark-energy