B.eng.(Hons.), Ph.D. and B.Sc.(Hons.) geology, Tas Walker used measuring cylinder to illustrate how scientific dating works. A picture showed water tap dripping into the clearly marked cylinder. The audience could see that it held exactly 300 ml of water. The diagram also showed that the water was dripping at a rate of 50 ml per hour. He asked, ‘How long has the water been dripping into the cylinder?’ immediately someone called out, “Six hours.” dividing the amount of water in the cylinder (300 ml) by the rate (50 ml per hour).” He said, Every dating method that scientists use works exactly the same way. It involves measuring something that is changing with time.” “The problem is that six hours is the wrong answer.” the water has only been dripping for one hour. Someone called out, “The tap was dripping faster in the past?” another said “The cylinder was nearly full when you started?” “Maybe. But can you see what you are doing?” He asked. “In order to calculate an age you made assumptions about the past. You assumed the rate had always been 50 ml per hour and that the cylinder was empty when it started. Based on those assumptions you calculated the time of 6 hours.” Then, when he told them the correct answer, they quickly changed their assumptions about the past in order to agree with the age he told them.” Every scientist must first make assumptions about the past before he can calculate an age. If the result seems okay then he will happily accept it. But if it does not agree with other information then he will change his assumptions so that his answer does agree. In a nutshell, Is scientific dating a way of measuring or a way of thinking!