Gravitatiopunasiirtymänä

Gravitatiopunasiirtymänä, often translated as gravitational redshift, is a phenomenon in physics where electromagnetic radiation, such as light, loses energy as it travels away from a gravitational source. This loss of energy manifests as an increase in the wavelength of the radiation, shifting it towards the red end of the electromagnetic spectrum.

The concept arises from Albert Einstein's theory of general relativity. According to this theory, gravity is not a force in the traditional sense but rather a curvature of spacetime caused by mass and energy. When a photon, a particle of light, moves out of a gravitational potential well, it must expend energy to do so. This energy is converted into a decrease in its frequency and thus an increase in its wavelength. Conversely, radiation falling into a gravitational well experiences a blueshift, gaining energy and shortening its wavelength.

Gravitational redshift has been experimentally verified. One of the earliest confirmations came from observations of the Sun's spectrum, which showed a slight redshift compared to terrestrial sources, though solar activity can complicate precise measurements. More definitive evidence has been gathered from observations of light from white dwarf stars, which possess very strong gravitational fields.

The Pound-Rebka experiment in 1959 provided a terrestrial measurement of gravitational redshift using gamma rays, demonstrating that photons moving upward in a gravitational field lose energy. This phenomenon has implications for understanding the evolution of stars, the behavior of matter in strong gravitational fields like those near black holes, and has even been considered in the context of cosmology.