Earth Mass Increasing? Photons and Photosynthesis making more matter on earth?

[davenn]

thanks for that DH

this isn't my particular field of physics so always willing to learn :)

so, I assume, we aren't even talking about rest mass of a photon, its purely the heating effect caused by the transfer of energy by the absorption of the photon ?

Dave

 

[Drakkith]

thanks for that DH

this isn't my particular field of physics so always willing to learn :)

so, I assume, we aren't even talking about rest mass of a photon, its purely the heating effect caused by the transfer of energy by the absorption of the photon ?

Dave

Exactly.

 

[D H]

so, I assume, we aren't even talking about rest mass of a photon

Correct.

its purely the heating effect caused by the transfer of energy by the absorption of the photon ?

Incorrect. There's also chemistry. Photosynthesis is an endothermic reaction. The sugars created by photosynthesis are more massive than the masses of the compounds that went into forming those sugars; it's a consequence of an endothermic reaction.

 

[Dale]

and further to that ... aren't photons supposed to be massless ?
so isn't it irrelevant to discuss their coming to and going from the Earth causing an addition or loss of mass of the Earth ?

The statement that a photon is massless means that its energy equals its momentum in units where c=1. I.e. The formula for mass in such units is m^2=E^2-p^2. So, if you have an object with m=1 at rest (p=0 and E=1) and it absorbs a photon with E=1 (m=0 and p=1) then by conservation of momentum and energy after the absorption it has E=2 and p=1, which gives m=1.7 So even though a photon is massless another object can still gain mass when it absorbs one.