If we are to replace the Linear No Threshold theory of radiation harm, we must have a replacement. The purpose of this piece is to present the Sigmoid No Threshold dose-harm model and compare it with LNT. The piece requires a bit of background, at a minimum reading LNT is Nonsense. You will need to know that dose, the amount of radiation energy deposited in a kilogram of tissue, is measured in milligrays (mGy).