Gravitationsrödskifte

Gravitationsrödskifte, also known as gravitational redshift, is a phenomenon predicted by Albert Einstein's theory of general relativity. It describes the decrease in frequency, or increase in wavelength, of light as it travels out of a gravitational field. Conversely, light falling into a gravitational field experiences a blueshift, increasing its frequency. This effect is a direct consequence of the curvature of spacetime caused by mass and energy.

The gravitational redshift arises because time runs slower in stronger gravitational fields. For an observer far away from a massive object, light emitted from a source closer to that object will appear to have a lower frequency. This is because the frequency of light is essentially a clock, and the clock at the source is running slower relative to the distant observer's clock. The energy of a photon is directly proportional to its frequency, so a lower frequency means lower energy.

This phenomenon has been experimentally verified. Observations of spectral lines from stars, particularly white dwarfs which have very strong surface gravity, show a measurable redshift compared to similar spectral lines from stars with lower gravity. The Pound-Rebka experiment in 1959 provided a terrestrial confirmation by measuring the change in frequency of gamma rays as they traveled vertically through a gravitational field within a tower. Gravitational redshift is also a factor that must be accounted for in precise astronomical measurements and in the functioning of the Global Positioning System (GPS).