Gravitational redshift
In physics and general relativity, we have something called gravitational redshift. It's like this: Imagine you have light (photons), moving away from a place with very strong gravity, like a star or a black hole. As these photons move away, they look like they are losing energy. This makes them look like they have a lower frequency and longer wavelength, which we call a redshift because this moves light to the red part of the spectrum.