Hello friends,
Welcome back.
Good evening friends. Today I am going to tell you the effect of gravity on time, a newest discovery by scientists.
Physicists in the US and Germany have used two fundamental tenets of quantum mechanics to perform a high-precision test of Einstein's general theory of relativity. The researchers exploited wave-particle duality and superposition within an atom interferometer to prove that an effect known as gravitational redshift – the slowing down of time near a massive body – holds true to a precision of seven parts in a billion. The result is important in the search for a theory of quantum gravity and could have significant practical implications, such as improving the accuracy of global positioning systems.
Gravitational redshift follows on from the equivalence principle that underlies general relativity. The equivalence principle states that the local effects of gravity are the same as those of being in an accelerated frame of reference. So the downward force felt by someone in a lift could be equally due to an upward acceleration of the lift or to gravity. Pulses of light sent upwards from a clock on the lift floor will be Doppler shifted, or red shifted, when the lift is accelerating upwards, meaning that this clock will appear to tick more slowly when its flashes are compared at the ceiling of the lift to another clock. Because there is no way to tell gravity and acceleration apart, the same will hold true in a gravitational field; in other words the greater the gravitational pull experienced by a clock, or the closer it is to a massive body, the more slowly it will tick.
Confirmation of this effect supports the idea that gravity is a manifestation of space–time curvature because the flow of time is no longer constant throughout the universe but varies according to the distribution of massive bodies. Reinforcing the idea of space–time curvature is important when distinguishing between different theories of quantum gravity because there are some versions of string theory in which matter can respond to something other than the geometry of space–time.
Good bye friends, take care, good night. See you in next post.
Welcome back.
Good evening friends. Today I am going to tell you the effect of gravity on time, a newest discovery by scientists.
Physicists in the US and Germany have used two fundamental tenets of quantum mechanics to perform a high-precision test of Einstein's general theory of relativity. The researchers exploited wave-particle duality and superposition within an atom interferometer to prove that an effect known as gravitational redshift – the slowing down of time near a massive body – holds true to a precision of seven parts in a billion. The result is important in the search for a theory of quantum gravity and could have significant practical implications, such as improving the accuracy of global positioning systems.
Gravitational redshift follows on from the equivalence principle that underlies general relativity. The equivalence principle states that the local effects of gravity are the same as those of being in an accelerated frame of reference. So the downward force felt by someone in a lift could be equally due to an upward acceleration of the lift or to gravity. Pulses of light sent upwards from a clock on the lift floor will be Doppler shifted, or red shifted, when the lift is accelerating upwards, meaning that this clock will appear to tick more slowly when its flashes are compared at the ceiling of the lift to another clock. Because there is no way to tell gravity and acceleration apart, the same will hold true in a gravitational field; in other words the greater the gravitational pull experienced by a clock, or the closer it is to a massive body, the more slowly it will tick.
Confirmation of this effect supports the idea that gravity is a manifestation of space–time curvature because the flow of time is no longer constant throughout the universe but varies according to the distribution of massive bodies. Reinforcing the idea of space–time curvature is important when distinguishing between different theories of quantum gravity because there are some versions of string theory in which matter can respond to something other than the geometry of space–time.
Good bye friends, take care, good night. See you in next post.
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