because the coldness in the ice cream and the suns gamma rays are hitting the ice cream and then it will start to melt. and that is why ice cream melts.

Why are very high temperatures and pressures required for fusion to occur? to generate the neutrons that are needed to break the nuclei o to overcome the repulsion between the protons in the nuclei that join to maintain the proper conditions to keep the chain reaction going to keep the uranium fuel separate from the control rods