Non-Newtonian fluids

It helps to know what a Newtonian fluid is before you start thinking about non-Newtonian fluids.  Conveniently, just about every fluid you can think of is Newtonian.  When you push on a fluid, it moves out of the way.  Some move fast, some move slow (this is quantified as viscosity), but when a fluid seizes up and stops,,when it becomes like a solid in response… That goes against Newton!

Obleck bounding on a speaker
Non-Newtowning fluids are better with food coloring

Perhaps the most common non Newtonian fluid people run across [foreshadowing] is cornstarch and water. It’s used to thicken gravy and other sauces (because of viscosity). But when making gravy, you are cautioned to mix the corn starch in cold water first and then add that to your hot liquid that needs to be thickened to avoid clumps. This is because the corn starch on the outside will mix with water first and be agitated (pressed on) by the hot liquid and turn solid, preventing even distribution of the inner cornstarch. But if you mix it with child water first all of the corn starch will be able to mix with the hot water.

5 kids mixing conrstarch and water by hand in a 15 gallon bucket
A hands-on experience

So we mixed it 50lbs bag of corn starch with water, and learned that if you put water into cornstarch it will mix on the surface, and further attempts to mix in more water will cause the outer cornstarch solution to turn solid. Preventing further mixing…. Much like cornstarch dumped directly into hot water. The right way to mix large batches is to add the corn starch slowly into water until the desired thickness is achieved.

You can then put that on a speaker and play a time of just the right frequency to see the corn starch turn solid, be thrown in the air and turn liquid again on the way down

Or you can jump in a big tub of it and see if you can start running before you begin to sink. It’s harder than it looks.

Or you can cut to the chase and just build a trough that you can run across… Or stop and sink into.

Making liquid dance on a speaker is pretty cool, and visually memorizing, but hands on (or feet in) is really the best way to experience and believe in the properties of Non Newtonian fluids.

kids gather around and playing with obleck in a speaker

No matter what you do though, make sure you leave lots of time for cleanup.

Solar Eclipse in Clemson

Enlarge Cereal Box Solar Eclipse viewer
Joshua’s solar eclipse view

We travelled to Clemson for the total solar eclipse. We threw a few simple, random building materials I the car as we we’re heading out. And when we got there we had a little bit of time… So we made a cereal box viewer, sans the cereal box… And way better. Josh gave lots of demos and explained how it worked and some of the more interesting properties. So much so that we were interviewed for and included in a book!

One of the neat things about the book was that Marie Harris, one of our favorite librarians from “The Loft” (a cool teen only space at Imaginon – the Children’s Library) in Charlotte – send me an email after she read the book. We’re quoted talking about Baily’s Beads which was truly the most amazing thing that I got to see being in totality.


Brian makes three great tackles in a row while injured.

Brian (gray sleeves, red socks) is injured at the start of this play (on the ground protecting his head). He’s trying to get get subbed off the field… but the play comes his way. So he does the only thing he can think to do – he makes the tackle. And then he does it again and again. The play finally moves away from him and he can limp away… but he keeps checking to make sure his team doesn’t need him. Fortunately his injuries were temporary and he was able to rejoin the game after a short break.

Rugby Tackle
Brian in hot pursuit from a lineout on the far side of the pitch.

Life U Rugby Camp

Rugby tackle
Brian makes a tackle a the the Life University summer rugby camp.

Playing rugby at the Life University rugby camp. It’s unthinkable that so few kids know about the Life camp. The best college players in the country (many from outside the US) run a week long overnight clinic for high school kids. There is just not a better place to have a clinic.

Las Vegas Sevens

Kids playing rugby - white player running with ball with green player in pursuit
Brian running for a try at the Vegas Sevens

Every year the Rugby world lays siege to every hotel and parking space in Las Vegas. Rugby Sevens is the fast past version – 7 minute half, 7 a side, of the regular version. The national teams from around the world play in the evening and the middle school through college kids play during the day.