Did Jesus walk on water? Cornflour effect explained



Updated: September 27, 2009


This article includes a cool movie!

One of the miracles that Gospels attribute to Jesus is that of him walking on the surface of the Galilee Sea. As a man of science, I do not buy easily into religion, especially not the stories that border on supernatural or miraculous. However, this time, I am tempted to say that there might be a shred of truth in this story, because it can in fact be backed by science.

Walking on water is possible - provided it is thixotropic. Read on.

Teaser

Thixotropy

You might be a little lost there, but thixotropy is the property of non-Newtonian, pseudo-plastic fluids that show a time-dependent change in viscosity. Namely, the viscosity of thixotropic fluids reduces the longer they are exposed to shear stress. In other words, thixotropic fluids are lazy. They take time to react to changes in pressure before reaching the viscosity equilibrium. This laziness can be exploited for all sorts of things.

Examples

There are quite a few examples of thixotropic fluids in nature: honey, lava, connective tissue in human bodies, and others. Of course, no one does it better than Brainiac. If you're interested, you can watch a scientifically abused piece from the show where John Tickles demonstrates walking on water - mixed with custard.

The keyword here is: cornflour. This little bugger does all sorts of wonders. I've even made a little demonstration of my own, would you believe it.

See Dedoimedo cornflour experiment on Youtube!

I've uploaded a short video demonstration showing the mind-boggling thixotropic properties of cornflour. Just mix it with water in 50:50 ratio and start enjoying non-Newtonian fun all the way. My wife assisted in the experiment. She's the voice behind the bogus Russian narrator, as we all know that Russians are THE people you want for funky scientific experiments. Plus, she's the one doing all the hard work, while I'm merely pointing the lens.

Alternatively, here's the URL: Dedoimedo cornflour experiment on Youtube.

A few stills:

Demo 1

Demo 2

Demo 3

Demo 4

Damn, that's almost a miracle! Apropos miracles ... Back to the miracle of walking on water ... So, let's try to rationalize the miracle. Did Jesus really walk on water? Well, there are several options here.

1) Jesus did really walk on water

Well, it did happen the way it's described in the holy books ... no comment there ... Least likely of all ...

2) Jesus was familiar with cornflour

I an not sure if they had corn in Judea two thousand years ago, but they might have had something similar, which when mixed with water, exhibits thixotropic properties. Someone close to Jesus or maybe Jesus himself may have experimented and made this little discovery. Afterwards, creating the first FX effect in the history of mankind would not have been difficult.

They could have created a long, narrow trough and placed it just below the water surface. While outside the trough, you'd have normal, semi-polluted water of the Galilee Sea, inside the trough, you'd have a mix of water and thixotropic substance, which would allow a casual demonstrator to appear as if walking on water.

This would surely amaze the crowds, especially if performed in the evening hours when the subtle details of the performance are less obvious.

3) Natural disaster

Thixotropy is evident in lava and mud slides. Something similar might have taken place back then. My theory goes for an earthquake in the region, which caused the bedrock beneath the Galilee Sea to shift. In turn, this would cause layers of sediment at the bottom of the lake to rise, mixing with water and turning it into a gel-like substance.

At the time of chaos and panic, no one would pay much attention to the thixotropic properties of the water, unless they were keen of mind and action, as Jesus obviously was. A simple reason for wandering into the deeper water would have been to salvage lost fishing boats. The earthquake could have torn off their mooring and cast them offshore.

Poor fishermen would probably have been very afraid to attempt rescuing their boats, especially if the water was turbid and misbehaving. However, a brave man determined to set example for his followers would have waded out into the deeps - only to discover that he could actually walk on water.

You'd have a sea rescue operation turned into miracle, all by accident.

Man on water

Of course, later on, other people would try to do the same thing, but by now, the sediment would have settled back down onto the lake floor, forever wiping away the evidence of thixotropy. And thus the myth would have been born.

BTW, the Gospels do mention disciples, in the boat. It is likely that they might have tried to wade the lake, only to find themselves stuck in the gel, when Jesus came to their rescue. It kind of fits into my earthquake theory.

Even better, the Gospels also mentioned Peter coming after Jesus. But he was afraid and hesitant, which might explain why he failed. If he'd moved too slowly, he would have negated the thixotropy effect and simply sank, whereas someone walking at a firm, brisk pace would have stayed afloat.

Man, I'm a genius.

Other ways

Walking on water can also be achieved in normal water, sans any starch. For example, certain insects, like water striders, are known to stay afloat. But this is because of the water surface tension rather than thixotropy. What more, humans tend to be bigger and heavier than most insects, so this does not seem like the best way to achieve miracles.

Strider

Note: image taken from Wikipedia and is distributed under CC-BY-SA license.

Likewise, if you walk fast enough - or rather run - you'll manage to stay afloat. This is something you see all sorts of animals do, including humans when waterskiing. But this hardly constitutes as walking, now does it?

So this one is probably out of the question, as humans cannot run fast enough to manage the glide effect. It's all about displacing a body of water that exceeds your impulse (the change of momentum integrated over time). If you manage to meet the headfront with short enough bursts of pressure against the surface, you'll manage to create an illusion of being lighter than water and thus maintain the flotation effect. Humans can't really change their density, unless they swallow really, really large quantities of Helium, but they can definitely control their speed. In the older days, this was not really possible, so we can rule this one out, too.

Which brings us back to thixotropy, it's the only reasonable way.

Conclusion

Thixotropy sounds like a lot of fun. It's a very interesting physical property, especially since it allows people to wade into cornflour-flavored liquids and have all sorts of gravity-defying pranks. It may have even formed the cornerstone of the larger religion in the world.

There you go, a miracle explained in simple, scientific terms.

Cheers.

Update, March 2011

One of my readers, a guy called Andrew sent me a long and detailed email explaining how I got it wrong. It's not thixotropy we're talking about here, it's dilatancy. He has compiled a mile-long explanation, so here it is. Many thanks to Andrew and my apologies for mixing up such delicate issues pertaining to non-Newtonian fluids. But my video still remains fly. Here's the reply, as is, no polishing the verbiage.

I read your article on thixotropy. The shear-thickening behaviour you described is
actually dilatancy, and not thixotropy. For proof, google "dilatancy" and "corn flour". Also
see the article entitled "dilatant" in Wikipedia.

I do not have a Master's degree in electrical engineering. But I do have Honours in
chemistry and applied chemistry. And I worked in the paint and resin industry for 30
years.

Thixotropy (shear thinning) is generally good for wall paints. The thixotropic
structure of the paint is broken down by the application of shear from the brush or roller. This
temporary reduction in viscosity makes the paint easy to spread. A few seconds after the paint
has been applied, the thixotropic structure returns. The viscosity increases, which is
good, because it reduces the tendency for the film of paint to drip or sag on vertical
surfaces.

Dilatancy (shear thickening) is undesirable for paints. You need arms like a gorilla
to apply the paint, because the viscosity increases as you apply it. Then, a few seconds
after you apply the paint, it sags and runs and drips.

During my career, I have made many batches of resin that have gelled, either due to
runaway reactions, or due to improper formulation. While the resin is a Newtonian
fluid, there will be a funnel shaped depression in the surface of the resin near the stirrer,
because the impeller is pumping resin away from the stirrer shaft. When the resin
begins to gel, it will start to climb up the stirrer shaft. It does this because it becomes
dilatant. The resin close to the shaft is sheared at a higher rate than the resin further away, so
it has a higher viscosity, and will wrap around the stirrer shaft.

There are many possibilities. Perhaps I am the only person to have read the article.
Maybe there were other readers, but they were ignorant of the difference between  
thixotropy and dilatancy. There could even have been readers who were aware of the
difference, but did not bother to inform you. It is even possible that some readers
have informed you, but you have chosen not to correct the article.

You can do one of three things:

You can leave the article as it is, (which is the wrong thing to do)
You can correct the article, (which is the right thing to do)
You can remove the article (which is the cowardly thing to do)

So which is it to be?

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