Wednesday, 16 March 2011

12 Apostles vs. 1 Newton

 I was thinking about Jesus and his walk on water.  It is considered to be one of the miracles of Jesus in the Gospels.  I should just say that you can believe whatever you want, there is no right and wrong answer but I am merely providing a physical answer to a biblical miracle.  Accounts of this miracle appear in the Gospels of John (John 6:16–21), of Matthew and of Mark.  This is what it says: Jesus sent the disciples in a boat, ahead of him, to Bethsaida.  When they were half way across the Sea of Galilee, Jesus walked over the lake water and met them.  I like many have tried to walk on water like say a water strider.  Physically it does not work. So I started trying to understand the properties of water and other fluids further.  The surface tension (easy), the tensile and compressile strength and finally the viscoscity were understood. 

To reiterate from previous posts surface tension is the property of the liquid at the water air interface the tension here that resists force.  The tension here is due to different forces mainly hydrogen bonding as in the rest of the liquid.  Its properties change mostly from the temperature or from the addition of specific chemicals (like soap).  Both will decrease the surface tension by changing the bonding between the water molecules.

The tensile and compressive strength also relates to the bonding in the water.  The bonding here more relates to the bonding underneath the surface between other water molecules.  Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. 

Viscoscity relates to the shear rate whereby the liquids resistant can be deformed or moved.  This is caused by the friction between the molecules.  Viscocity properties however change depending on the type of fluid: Newtonian and Non-Newtonian.  (This is of course named after Isaac Newton who developed classical mechanical theories).  A Newtonian fluid react to forces in a linear manner.  However, non-Newtonian fluid, the relation between the shear stress and the shear rate is different, and can even be time-dependent. Therefore a constant coefficient of viscosity cannot be defined.  For example the polymer that you put on your French Fries, Ketchup, is stable at rest but becomes fluid when agitated.  Other Non-Newtonian fluids like clay (thixotropic - time dependent fluid viscosity decreases with increased stress) or cornstarch independent (dilatant - time independent viscoscity increases with increased stress).  Viscosity is thus about movement and the shear rate on a particular substance being newtonian or non-newtonian. 

To summarize, what property in water water would allow Jesus to walk over water?
Surface tension: The boat would be floating due to surface tension
Compressive strength: probably not since he would most likely sink under normal gravity
Viscoscity or shear: This would probably be the property of water that would allow someone to walk on it if water were a non-Newtonian fluid in particular a thixotropic non-Newtonian fluid.  One that becomes harder when you step on it. 

So we can subtly rewrite the story accounted in John with some classical mechanical physical principles added  (I wonder if anybody has written The Physics of the Bible?).  Jesus saw that his disciples in the boat were freaking out because of some storm or earthquake.  Jesus obviously wanted to help them but he did not have a boat.  An earthquake or volcanic eruption in the region could have caused the bedrock beneath the Galilee Sea to shift. Layers of sediment at the bottom of the lake began to rise, mixing with water and turning it into a gel-like thixotropic fluid.

At the time of chaos and panic, no one would pay much attention to the thixotropic properties of the water.  However, Jesus was pretty smart (and may have learned something about physics somewhere) and probably wanted to set an example for his followers (like Dr. Albert Hofmann did with LSD which fair enough will also allow you to walk on water) and waded out into the deeps only to discover that he could actually walk on water due to the thixotropic fluid supporting him.  The boat on the other hand would be still floating due to the surface tension of the water.  Yes science is magic and can even be considered a miracle.  I would imagine it would look something like this (except with a thixotropic clay and not a dilatant cornstarch like fluid).