There is compelling evidence for time dilation caused by extreme gravitational forces, which is known as gravitational time dilation. This phenomenon arises due to the warping of spacetime by massive objects, such as stars, black holes, or other massive gravitational sources. Here are some of the key evidences supporting the existence of gravitational time dilation:
Gravitational Redshift: When light travels through a gravitational field, its frequency decreases, causing a shift towards the red end of the electromagnetic spectrum. This phenomenon is known as gravitational redshift. The effect was first observed in 1959 by Pound and Rebka in an experiment where they measured the frequency shift of gamma rays emitted at different heights in a gravitational field. The observed redshift confirmed that time runs slower in stronger gravitational fields.
Gravitational Time Dilation near Earth: Precise measurements using atomic clocks have shown that time runs slightly slower closer to Earth's surface compared to clocks at higher altitudes. For example, the experiments conducted as part of the Hafele-Keating experiment in 1971 involved atomic clocks flown on planes traveling in opposite directions around the Earth. The clocks that were closer to the surface experienced a slightly slower passage of time compared to clocks at higher altitudes, confirming the effects of gravitational time dilation.
Gravitational Time Dilation around Black Holes: Black holes are objects with extremely strong gravitational fields, and they provide an extreme environment to study gravitational time dilation. Observations of light emitted by objects in the vicinity of black holes have confirmed that time runs slower as the gravitational field strength increases. For example, the phenomenon of gravitational time dilation has been observed in the form of gravitational redshift in the light emitted by stars orbiting around supermassive black holes at the centers of galaxies.
Gravitational Waves: The detection of gravitational waves, ripples in spacetime caused by the acceleration of massive objects, indirectly confirms the existence of gravitational time dilation. The precise measurement of gravitational waves and their effects on space and time support the predictions of general relativity, which includes gravitational time dilation as a fundamental aspect of the theory.
These pieces of evidence collectively support the existence of gravitational time dilation and demonstrate that the flow of time is influenced by the presence of massive objects and their gravitational fields.