When a nucleus is placed inside an external magnetic field, it aligns itself parallel to the field, as that is the most stable position for it to be in. In more technical terms: it acquires an alpha spin. When you shine radio waves at this nucleus, it absorbs energy and flips over anti-parallel to the external magnetic field. It acquires a beta spin. It then releases energy and flips back to the alpha spin state, parallel to the external magnetic field. My question is simply: why? Why does the nucleus flip over when you give it radio wave energy? Why not just stay in the stable position? What does the nucleus benefit by doing this? I am never getting a straight answer to this question. My chemistry textbook, ChemGuide, KhanAcademy, Youtube, etc. all say the same thing: that the nucleus "now has enough energy to be in the unstable beta spin state". Never explaining why that occurs. Like, we just have to accept it without question. I have high school level physics/chemistry knowledge. A+ grades. Wikipedia is not an option for me at all; I tried my hardest to read Wikipedia but it's just too ridiculously difficult to understand.