A philosophy professor stood before his class with items on the table in front of him. When the class began, he picked up a very large and empty jar and proceeded to fill it with rocks. He then asked the students if the jar was full. They agreed that it was.
So the professor then picked up some pebbles and poured them into the jar. He shook the jar lightly. The pebbles of course rolled in to the open areas between the rocks. He then asked the students again if the jar was full. They agreed it was.
The professor picked up some sand and poured it into the jar. Of course, the sand filled up everything else. He then asked once more if the jar was full. The students responded with a unanimous “yes.”
The professor then produced two cans of beer from under the table and proceeded to pour their entire contents into the jar- effectively filling the empty space between the sand. The students laughed. “Now,” said the professor as the laughter subsided, “I want you to recognise that this jar represents your life. The rocks are the important things; Your life, Your health, Your family, things that if everything else was lost and only they remained, your life would still be full. The pebbles are the other things that matter- like your job, your home, your career. The sand is everything else- the small stuff which seems important but is not really that necessary. If you put the sand into the jar first, there is no room for the pebbles or the rocks. The same goes for your life. If you spend all your time on the small stuff, you will never have room for the things that are important to you. Pay attention to things that are critical to your happiness. But if you put the rocks in first; the things that really matter in your life, than your life will be a lot more fulfilling and happier. Set your priorities; the rest is just sand.”
One of the students raised their hand and enquired what the beer represented? The professor smiled, “I am glad you asked. It goes to show, no matter how full your life may seem, there is always room for a couple of beers.”
Porosity: The science
Porosity (p) in sediment dynamics is the ratio of the volume of voids, to the total volume. For non-cohesive sediments such as sand, p= 0.3 to 0.4. Well-graded and poorly sorted sediments have a large standard deviation of the mean, with p= 0.3. Poorly graded and well sorted sediments have a small standard deviation of the mean with large porosity, with p=0.4. Coastal engineers often take p=0.35 when the actual value is unknown.
This is a story I heard from David Basco, Old Dominion University, Virginia, USA, during his lectures in Coastal Hydrodynamics and Sediment Transport. In Plymouth, I had the opportunity to meet him and his wife in person, and share with him this photograph of our outreach activity at the National University of Ireland, Galway, a jar full of oranges, marbles and maerl.