# Nuclear fusion difficulties

What is it that make nuclear fusion so difficult at low temperatures? There is plasma existing at low temperatures, so what does it make for fusion to be so difficult to reach at ambient temperatures?

• – Peter Diehr May 3 '18 at 13:11

Basically, what needs to happen in a fusion reaction is that two nuclei approach each other very close. They don't want to do that mainly because of their extremely strong electrostatic repulsion - both nuclei are positively charged. The force of repulsion grows quadratically with decreasing separation ($\frac{1}{r^2}$), and the distances required for the strong force to bind nuclei together are extremely short.