In book "Motion Mountain-an adventure in physics"; I read about mass increase due to absorption of one green photon 3.7 * 10^(-31) kg.

 

means on absorption of green photon mass of the object or body increases.

Please tell me more about it.

Mass is a form of energy. If an object absorbs energy, its mass will increase.

 

Standard physics separates the kinetic term, in order to be able to transform between reference frames.

 

E²=m²c⁴ + p²c²

 

m here is the rest mass

I would've thought that the object would get warmer rather than heavier. Is this just a theoretical discussion, or does this sort of thing actually happen?

No, it's very real

 

http://blogs.scienceforums.net/swansont/archives/278

 

An isomer (long-lived excited state) of Fe-65 was discovered because its mass is greater than that of the ground state, by an amount that is E/c^2. So the atom, absorbing a photon of that energy, increases in mass.

Swansont: At the end of the post you linked to you mention the quadrupole moment. What relation does this have to the material you posted?

 

I understand it was a joke but does it have any significance to the material?

Swansont: At the end of the post you linked to you mention the quadrupole moment. What relation does this have to the material you posted?

 

I understand it was a joke but does it have any significance to the material?

 

It's related to the title of the post, not the material. (The various repsponses one might give to Have you put on weight?)