  We discuss the derivation of Newtonian potentials in the framework of quantum
field theory. We focus on two particular points: on long range forces i.e.
forces which fall off as $1/r^n$ being mediated by light quanta like neutrinos
or Goldstone bosons and on possible temperature dependence of such forces
arising in situations when the exchanged quanta are in a thermal heat bath.
Examples of the latter are cosmic relic photons and relic neutrinos. Among
other things, we will show that the existence of cosmic relic neutrinos
modifies the long tail of the two-neutrino exchange Feinberg-Sucher force
drastically. Results concerning the potential mediated by two Goldstone bosons
are also presented.
