The Professor began his class by holding up a glass with some water in it. He held it up for all to see & asked the students “How much do you think this glass weighs?” ’50gms!’….. ’100gms!’ …..’125 gms’ … the students answered. “I really don’t know unless I weigh it,” said the professor, “ but , my question is: What would happen if I held it up like this for a few minutes ? ‘Nothing’ …. . the students said. Ok what would happen if I held it up like this for an hour?’ the professor asked. ‘Your arm would begin to ache’ said one of the student “You’re right, now what would happen if I held it for a day?” “Your arm could go numb; you might have severe muscle stress & paralysis & have to go to hospital for sure!” ….. Ventured another student & all the students laughed “Very good . But during all this, did the weight of the glass change?” Asked the professor . ‘ No’ Was the answer. “Then what caused the arm ache & the muscle stress ?” The stud