Neutron Stars

[petrushka]

As per the Uncertainty principle the position and velocity of an electron cannot be ascertained simultaneously. Then how an electron's orbit decay and the electron combine with a neutron during the formation of neutron stars. (Since for this to happen position is known and velocity is zero).?

[incitatus]

You are mixing metaphors. The uncertainty principle isn't absolute, but restrains the accuracy of measurement of the two factors to a small 'fuzzy' probability space. If the probability spaces of the two particles coincide they can coalesce regardless of the uncertainty principle. Think of them as fuzzy clouds rather than marbles. Also no particle has a zero velocity as this would require zero energy ... and inside a neutron star is far from that.