Professor Jemimah Normal of Warwick University has published proof that dog faeces get progressively heavier after they have been ejected from the dog. "There has been much speculation about this and a certain amount of anecdotal evidence," the Professor told us. "We have known for some time that although dog owners generally collect and bag their animal's mess, they are inclined to carry it only a short distance before leaving on a wall, wedging it behind a lamppost or hanging it from a tree. We posited that the waste matter gains mass upon exposure to air, becoming too heavy to carry. But it is only now that we have observed this in the laboratory."
Professor Normal - whom we would be calling a professional 'poo-ologist' right now, if such a thing existed - has spent many years in a moderately well-ventilated laboratory, making careful measurements of fresh dog excrement. Professor Normal has few friends and doesn't get out much.
"The really disturbing thing," the Professor continued, "is that the process does not appear to end. Molecules of canine ejecta continue to increase in mass, apparently indefinitely. What this means for the planet, I cannot say - but the possibility that the Earth might one day be knocked off its axis by the sheer weight of crap is a very real one. And you can take that from me as a professional poo-ologist."