Changes

Now we have a problem of which, ''[[invariant mass]]'' or '''relativistic mass''' is responsible for gravitation? It turns out that it is '''relativistic mass''' and therefore it is the energy content of mass. And that's why for light the gravitational effects are the same as for other "masses". Photons (particles of light) don't have ''[[invariant mass]]'' (their [[invariant mass]] is equal zero, that's why they are called "massless" particles). Yet they have '''relativistic mass''' (called energy in physics) and therefore they may take part in gravitational phenomena (as they do).  

Now we have a problem of which, ''[[invariant mass]]'' or '''relativistic mass''' is responsible for gravitation? It turns out that it is '''relativistic mass''' and therefore it is the energy content of mass. And that's why for light the gravitational effects are the same as for other "masses". Photons (particles of light) don't have ''[[invariant mass]]'' (their [[invariant mass]] is equal zero, that's why they are called "massless" particles). Yet they have '''relativistic mass''' (called energy in physics) and therefore they may take part in gravitational phenomena (as they do).  

Energy of each photon <math>E=h \nu=hc/\lambda</math>, where <math>h</math> is Planck constant, <math>\nu</math> if frequency of light, <math>c</math> is speed of light in vacuum, and <math>\lambda</math> is the wavelength of light,  carried by this photon, to which our eyes react with seeing each photon frequency (or wavelengh) as a separate color. We see only light wavelengths between about 400 (violet end of spectrum) to 800 (red end of spectrum) nanometers (one nanometer being equal <math>10^{-9}m</math>), while other animals may have different eye sensitivities. Knowing the wave length (or color of the photon) we may calculate the '''relativistic mass''' of this photon. And if the light is very dimm and we were cats (humans don't have eyes sensitive enough and they need hundreds of photons to see anything) we could even see single photons as flashes of light on the retina of our eyes.  

Energy of each photon <math>E=h \nu=hc/\lambda</math>, where <math>h</math> is Planck constant, <math>\nu</math> is frequency of light, <math>c</math> is speed of light in vacuum, and <math>\lambda</math> is the wavelength of light,  carried by this photon, to which our eyes react with seeing each photon frequency (or wavelengh) as a separate color. We see only light wavelengths between about 400 (violet end of spectrum) to 800 (red end of spectrum) nanometers (one nanometer being equal <math>10^{-9}m</math>), while other animals may have different eye sensitivities. Knowing the wave length (or color of the photon) we may calculate the '''relativistic mass''' of this photon. And if the light is very dimm and we were cats (humans don't have eyes sensitive enough and they need hundreds of photons to see anything) we could even see single photons as flashes of light on the retina of our eyes.  

==See also==

==See also==