The pH scale measures how strongly acidic or alkaline ... Stomach acid turns universal indicator paper a strong red colour. This indicates a pH value of 0, the strongest value of acid.
This means that the pH values of strong acids are lower than that of weak acids, which explains why the rate of reaction of strong acids with substances (such as metals, metal carbonates etc ...
(Gravity is so weak as to be entirely irrelevant on these scales.) The fact that it is insignificant on larger scales is the paradoxical effect of an odd strong-force quirk. The photon, which ...