Helium-2,, also known as a diproton, is an isotope of helium, which according to theoretical calculations would have been stable had the strong force been 2% greater.
Helium-2 or, also known as a diproton, is an extremely unstable isotope of helium, which consists of two protons without any neutrons. According to theoretical calculations it would have been stable had the strong force been 2% greater.