For example, a piece of uncooked spaghetti has a persistence length on the order of 10 18 m (taking in consideration a Young modulus of 5 GPa and a radius of 1 mm). Double-helical DNA has a persistence length of about 390 ångströms. Such large persistent length for spaghetti does not mean that it is not flexible. It just means that its stiffness is such that it needs 10 18 m of length for thermal fluctuations at 300K to bend it.