Einstein's Theory of Mass-Energy Conversion: True or False?

[RAD4921]

According to Einstein's theory, during the process of fusiom some of the mass of the element(s) gets converted to energy, therefore the over all mass of the obnject is less due to the mass to energy convertion. This is true yes?

 

[mathman]

Yes. Example (all numbers are atomic mass units).
neutron 1.0086649
H¹ 1.007825
He⁴ 4.0026032
Add up 2 neutrons and 2 H and get 4.0329798, leaving a difference (converted to energy) of .0303766.

 

[RAD4921]

To mathman

Thanks for your reply.
Another question: Outside of the big bang are there any examples where energy gets converted to mass?

 

[geometer]

Thanks for your reply.
Another question: Outside of the big bang are there any examples where energy gets converted to mass?

Sure, lots. Another nuclear example: In nuclear fission (as opposed to fusion), a neutron is absorbed by a fissionable nucleus such as u-235, or pu-239. The resulting nucleus is unstable and splits, generally into two large fragments and releases some more neutrons. The sum of the masses of the fragments and the released neutrons is less than the mass of the nucleus and the absorbed neutron before the reaction. This "mass defect" is converted to energy. This is how a nuclear weapon works and how a nuclear power plant generates energy.

 

[pervect]

According to Einstein's theory, during the process of fusiom some of the mass of the element(s) gets converted to energy, therefore the over all mass of the obnject is less due to the mass to energy convertion. This is true yes?

Yes, though the energy has to get radiated away before the mass will actually decrease.

 

[pmb_phy]

According to Einstein's theory, during the process of fusiom some of the mass of the element(s) gets converted to energy, therefore the over all mass of the obnject is less due to the mass to energy convertion. This is true yes?

The sum of the rest mass of the individual particles change. But the total mass remains unchanged. See http://www.geocities.com/physics_world/sr/nuclear_energy.htm

The conservation of mass holds true whether you think of mass as relativist mass or as invariant mass. In the case of the later the invariant mass equals the energy in the inertial frame divided by c^2. Since energy is conserved then so too does the invariant mass. In the former case the total mass is the sum of the masses.

Note: Relativistic mass is the m in p = mv. Given this definition it can be shown that this is a conserved quantity and to show this one does not need to rely on the conservation of energy.

Pete

 

[mathman]

Outside of the big bang are there any examples where energy gets converted to mass?

Pair production (gamma ray to electron-positron pairs) is an absorption mechanism used in shielding against gamma rays.