How we can change a proton into neutron and a neutron into proton? Is it possible?
A weak interaction converts proton into neutron.. Proton is not a fundamental particle neither is neutron. Proton is made up of two up quarks and one down quark , neutron is made up of two down quark and one up quark. In weak interaction one up quark become down quark causing this reaction
proton -> neutron +electron + neutrino + Energy
this being very slow process therefore it takes a long time for stars like Sun to burn because this process is required for H to He conversion through fusion