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Solar Spectrum and Fraunhofer lines

 

( photo credit: http://it.wikipedia.org/wiki/Sole )

Let’s assume a massive body able to emit light … its gravitational field interacts with the photons exchanging actions which become energy exchanges … but if a photon changes its energy, its frequency also changes (“redshift”) …

The obvious place to look for the “gravitational redshift” is in spectral lines of the stars. It can be detected in the Sun.
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Fraunhofer lines in the spectrum of the Sun ... are due to atom resonances with definite frequencies ... the “ gravitational redshift ” causes a displacement that can be accurately measured ...
 
 
 
 
 
 
 
 
 
 

Earth also causes a displacement in the spectral lines ...

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Attempts to measure the spectral lines of the Sun have been carried out, but the most accurate measures outcome from the redshift caused by Earth. 

Earth is less massive than the Sun. However, as we live on it, it is possible to arrange highly sophisticated schemes of measurement. 

In particular it will be possible to measure the displacement of the spectral lines between a source on the ground and a source in the open space, very much high up. 

This measurement is possible today, as it implies a consolidated technology concerning artificial satellites.. 

The experiment described involves an element on the ground and one in orbit at an altitude: 10,000 m. 

Following is the: scheme of measurement: 
 
 
 
 
 
 
 
 
 

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Measuring the “Gravitational redshift ” with the use of “hydrogen maser” sources

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“Gravitational redshift”: method of calculation

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The signal is emitted by a stable and consistent hydrogen maser source. 

From space the source transmits with fo. Signal is received by Earth with two components of displacement: 

one due to the doppler effect, caused by the diverse velocities (V1 on ground and V2 in space), 
the other connected with the difference of gravitational potential between Earth and 10,000 m. …

and this is our main interest. 

The ground source emits with fo and is sent back from space towards Earth … 

the two doppler effects sum up together, 
the two gravitational effects nullify each other.

Therefore, only the double doppler effect is left: divide by two and deduct from the other. A function is left: it only contains the gravitational variable ... 

This method allows to measure the gravitational component with a reliability of two parts on 10,000. 
 
 
 
 
 
 
 
 
 

“Gravitational redshift”: detailed calculation, “mks” system

 

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z ( formula:  James B. Hartle – “Gravity” - Addison Wesley 2003) 

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