Astronomy
Gravitational Lensing and Its Uses
Quick fact
Gravitational lensing can create multiple images of the same distant galaxy, sometimes forming a perfect ring of light called an Einstein ring. The first such ring was discovered in 1987.
Why this is interesting
Imagine a cosmic magnifying glass so powerful it can reveal galaxies billions of light-years away, while also revealing the invisible skeleton of the universe. How can empty space act like a lens?