16   ray in the gravitational field

Gravitational redshift:
   In a gravitational field, if the position of the light source is lower than that for observing, the frequency of the observed spectrum would be relatively low. This is called gravitational redshift. Formerly, people thought that photons overcome gravitation to do work cause gravitational redshift, which is called as "photon potential energy theory". This theory requires that the photons has mass. And this is inconsistent with modern theories. So, people have to give up this theory. Nowadays, people use generally the general theory of relativity to explain gravitational redshift. According to the general theory of relativity, the germ of redshift is from the light sources itself.

1 Use the relations of mass in the gravitational field explain the gravitational redshift
   The mass of object decrease with it fal iIn the gravitational field. Suppose the mass is m0 , so the difference of energy between tow position which all the mass change into light energy.
    
    
   h - Planck's constant.
    ............................Equ.16.1
   the light sources in different heights radiates photons of different energy, which is also the requirement of the covariance in the gravitational field. The mass of atom decrease with it fal iIn the gravitational field. The electric field intensity in atom should become weaker in order to maintain the covariance. However, the electric field of atom is the source of photons.
   Measuring gravitational redshift with Mossbauer Effect is helpful for us to understand the essence of gravitational redshift. When the light sources is placed on the top of the tower and the receptor on the ground, photons can be absorbed, this indicates that the atomic energy level on the ground is smaller.

2 Use the relations of clock in the gravitational field explain the gravitational redshift
   We observed a lower frequency from the high position because the clock in low position is relatively slower. It is easy for us to get the value of gravitational redshift according to the relation of clock about the gravitational field.

3 scale relations in the gravitational field can explain the gravitational redshift very well
    We observed a longer wavelengh from the high position because the ruler in low position is longer. According to the ruler relation.
    ............................Equ.16.2
   We can find that three explanations above about gravitational redshift are consistent. But we would not get the consistent conclusion if according to the current thoery, the mass constant, ruler shorten, time slow in the gravitational field.

Radar echo delaying£º
   To the gravitational field, although the ruler becomes longer, likewise, the clock becomes slower. These change obey relativistic covariance, so the light velocity which measured in the gravitational field is still the c.
   However, to the observers far from the gravitational field, the case is just different, He uses his own ruler and clock to measure the light velocity in the gravitational field. In fact, he regards the distance as shorter and the time as shorter. So he gets the light velocity as:

   
    ....................................Equ.16.3
   We divide the distance that the radar wave has gone through into two parts, one of which is the distance from the earth to the sun, the other is from the sun to the opposite planet. Tthe actual time that the radar wave has gone through is:
   
   
    - distance from the earth to the surface of the sun, - distance from the surface of the sun to the opposite planet, - diameter of the sun, M - the mass of the sun.
    The the theoretical expected values is:
   
   The delay of the radar wave is:
   
   When the opposite planet is the Venus:
   
   
   When the opposite is the Mercury:
  
   These are consistent with the fact.

    About the deflexion of ray in the gravitational field is actually a expression of the difference of light velocity . This is like that ray goes through uneven atmosphere. We can solve the value according to the expression of light velocity in the gravitational field. It is not complex.

Zhan, Li Kui 6/18/2007

Home     previous     Next