radiohaloes and differing masses

jar writes:One way is by looking at rings produced when various elements radioactively decay. The energy level produced by the decay of a given mass of an element determines the energy level of the particle produced and that energy level determines how far the particle travels before it gets absorbed. The fact that particle emitted by a given isotope of a given element always travels the same distance before being absorbed so that concentric shells are formed is evidence that the energy level of that reaction has remained constant throughout the time involved to create the rings.When we look at a uranium or radon halo from 1.5 billion years ago it is identical to a uranium or radon halo created today.The idea that the physical laws were different at anytime during the existence of the Earth has simply been refuted.

foreveryoung writes:If the sub atomic particles of a uranium or radon atom were of less mass in the distant past, why would their respective radiohaloes be of a different size?