Gravitational Lens

space · physics · light · gravity

Gravity bends light. When light from a distant star or galaxy travels toward Earth, it can pass near something incredibly massive like a galaxy cluster. The gravity is so strong that it curves the light's path, bending it noticeably, kind of like how a glass lens bends light.

Einstein explained it. Albert Einstein's theory of general relativity predicted exactly how much light would bend around massive objects. It turns out Einstein's prediction is twice as strong as what older physics theories said would happen.

Nature's telescope. Gravitational lensing helps astronomers see really distant galaxies they might not be able to see otherwise. The gravity of closer massive objects acts like a natural magnifying glass, making far-away light appear brighter and bigger.

Multiple images appear. Sometimes a gravitational lens is so powerful that it creates multiple copies of the same distant object in the sky. Light from one galaxy takes different paths around the massive object, arriving at Earth from slightly different angles.