Non-Newtonian Fluids

I had a friend recently introduce me to the wonderful world of non-newtonian fluids.  (Stick with me here; this is cool.)

Non-newtonian fluids are fluids that change their properties when presented with different forces.  One classic example is a mixture of corn starch and water.  Try this at home: mix 2 cups of corn starch in 2 cups of water in a small bowl.  (Disclaimer: I have not actually tried this at home myself, but I have experienced the end result when someone else did the mixing.  If you try this, comment below and let me know how it goes.)

Now the fun part!  If you are not playing along at home, picture a bowl with a goopy tan mixture.  Take your hand and slowly sink it into the bowl.  Your fingers will slide through the fluid like sinking into soupy mud.  Nothing unusual about that.  But now, remove your hand.  This time, put your hand quickly into the bowl with some gusto.  Your finger tips will break through the surface and – wham!  It’s like you hit a rock.  Keep tapping away quickly, and your fingers move across what feels like a solid layer just beneath the surface.  Hesitate for just a few seconds and you will feel your fingers sliding once more into soupy mud.  (Now you want to try this at home, don’t you?)

This crazy phenomenon is a property of non-newtonian fluids.  This is what scientists or engineers mean when they say these fluids behave differently under different pressures or under different forces.  In the case of corn starch and water, greater pressure makes it feel more like a solid, while lighter pressure makes it feel more like a liquid.  As long as you move quickly and with enough force, you will not sink.  If you had a small swimming pool and enough corn starch, you could make a non-newtonian fluid that you could literally run across. 

Yes, that’s right.  You could literally run across a non-newtonian fluid!  You, too, could walk on water (or at least water and cornstarch).  But here’s the catch.  It only works if you go quickly and with gusto.  Stop moving, and you sink to the bottom.

This shouldn’t come as too much of a surprise, I suppose.  After all, Peter and Jesus already demonstrated this for us (Matthew 14:22-33).  Only for them, it wasn’t in a giant swimming pool of corn starch and water; it was in the stormy Sea of Galilee.  (Which, just for the record, is NOT a non-newtonian fluid.)

After the feeding of the five thousand, Jesus sent his disciples on ahead of him in a boat.  “During the fourth watch of the night, Jesus went out to them, walking on the lake… “Lord, if it’s you,” Peter replied, “tell me to come to you on the water.”  “Come,” He said.  Then Peter got down out of the boat, walked on the water and came toward Jesus (Matthew 14:25,28-29).  Just like skipping quickly across a pool of non-newtonian fluids!  I see such purpose in Peter’s strides.  Despite the wind and the waves and the late hour and the exhaustion of the previous day, Peter is moving without hesitation.  Jesus called and Peter went… walking across the water.

But when he saw the wind, he was afraid and, beginning to sink, cried out, “Lord, save me!” (Matthew 14:30).  Why is it Peter could be walking across the water just fine one minute, and sinking the next?  Well, just like that bowl of non-newtonian fluids, as soon as Peter hesitated, he began to sink. 

There are certainly times in life when it is wise to proceed with caution.  But there are far more often times when God is calling and it is our job to simply go.  We are not supposed to stop and measure the wind or ponder the waves.  We are not supposed to identify just how that liquid is going to be turned into a solid.  When Jesus calls, we need to climb out of the boat and go with gusto.  Because it is only when we are moving forward that the fluid will remain solid beneath our feet.   (And that’s something worth trying at home, too.) 

“Come,” He said.  Then Peter got down out of the boat, walked on the water and came toward Jesus (Matthew 14:29). 

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