Water and cornstarch make a non-Newtonian fluid when mixed: messy but great fun!

Fast-forward fifteen years to the beginning of the present school year and the Internet has given us all a huge leg-up in finding hands-on ways to learn science. These are demonstrations rather than experiments–an important difference for those entering a fair. Nevertheless, I have included two of my favorites below.

Homemade Oobleck:

Pay tribute to Dr. Seuss's book Bartholomew and the Oobleck by whipping up this mixture that is both solid and liquid at the same time! The simplest version is listed below, but adding a few more bells and whistles can increase the demonstration's awe-factor a bunch.

What to do: You need a mixing bowl, water, and cornstarch. Fill the mixing bowl with about 1 cup of cornstarch, and add roughly an equal volume of water. Mix, incrementally adding cornstarch or water until the mixture attains an appropriate blend of goopiness and firmness. Enjoy the fluid's bizarre properties by squishing and kneading it with your hands.

What's going on? Nearly all fluids have some intrinsic flow resistance. This property, called viscosity, is the reason water flows more easily than honey and at least partly why Usain Bolt can run 100 meters in under 10 seconds while it takes Michael Phelps well over a minute to swim the same distance. Our water/cornstarch mixture has a very special viscosity, making it easy to dip your hand into the mixture slowly, but quite hard to push it in quickly. (Technically, this is an example of a non-Newtonian fluid.) Science class will teach you that almost all matter can be classified into either a solid, liquid, or gas, but this is at least one example where the distinctions blur.

Bernoulli's Hair Dryer:

In 1738 the mathematician Daniel Bernoulli (pronounced Ber-NEW-lee) published a theory of fluids that has influenced the designs of airplane wings and sailboats ever since. Exploit this concept to suspend a balloon or ping-pong ball precariously in mid-air with a hair dryer.

What to do: You need a hair dryer and a small round balloon (or a ping-pong ball, depending on the hair dryer's strength). Turn the hair dryer on, point it upward, and place the balloon in the vertical column of air. If the ceiling is not too high, you should be able to balance the balloon in mid-air this way. Now begin to tilt the hair dryer and watch the balloon stay suspended almost magically.

What's going on? Everyday experience helps us understand why the balloon or ball stays suspended when the hair dryer is pointed vertically: air blowing upward pushes on the balloon, and this in turn counteracts gravity. But why doesn't the balloon fall off to the side when we begin to tilt the hair dryer? The answer lies in Bernoulli's principle, which states that, all other things being equal, a fluid loses pressure as it picks up speed. The air coming out of the hair dryer is moving faster than the room's air so its pressure is lower. This pressure difference helps keep the balloon suspended, even when you tilt the hair dryer.

Water and cornstarch make a non-Newtonian fluid when mixed: messy but great fun!

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After some cajoling from the wife, I trekked down to the library to check out the science section. I was amazed at the bevy of great pop science books. Most are accessible, quick reads on pretty much every science topic under the sun. However, I'm a social creature, I wanted to discuss science books with peers.

A few quick searches and voila! Science book clubs exist right here in the Bay Area (one of them hosted by myself so I'd have more control on book selection). Lively discussion and science books, it's a good combination.

Down to a Science Book Club

Book: "How We Decide" by Jonah Lehrer

When: Monday, May 25th, 7-9 PM

Where: Books Inc, 601 Van Ness @ Turk, 2 blocks north of SF City Hall

Details: Ever had a experience of option paralysis? Like when you are looking at the 11 different types of Cheerios in the cereal aisle? If you're anything like me, decision making is an "interesting" process. Jonah Lehrer tackles the neurobiology of decision making and points out a few ways you may be able to overcome that paralysis. Watch Jonah discuss decision making at the Commonwealth Club or listen to him discuss Choice on RadioLab.

California Academy of Science Book Clubs

Teens Talk Books: Underwater Explorations

Book: Shark Life: True Stories about Sharks and the Sea by Peter Benchley

When: June 6th, 11:00 am in Education Classroom

Where: California Academy of Sciences

Coming face to face with the jaws of a great white shark.  Chasing leaping orcas near Vancouver.  Swimming with hoards of hammerheads in the Sea of Cortez.  Benchley, the author of Jaws, shares his many underwater adventures with sharks and other marine creatures, while helping the reader learn more about these majestic creatures, how to swim with them safely, and why it is vital for us to protect our oceasn.  Join us for a discussion of Benchley's fascinating read!

Reservations: Free with admission to the museum, but participants should call the Naturalist Center at 415-379-5494 to reserve a space.

Bookworms (Adult Book Group): Why Do Oceans Matter?

Book: Sea Change: A Message of the Oceans by Sylvia Earle

When: June 16th, 6:30 pm in the Naturalist Center

Where: California Academy of Sciences

Details: In recognition of World Ocean Day this month, the group will read and discuss noted marine biologist Sylvia Earle's book which is both a plea for ocean conservation and a very personal story of her own lifelong exploration of life in the deep.

Reservations: Free.  Reserve a space by calling 415-379-5494.

This Week In Science Online Book Club – Hosted by TWIS.org

An Ocean of Air: Why the Wind Blows and Other Mysteries of the Atmosphere

Details: Most of the time we hardly notice that we're moving through air. But when a storm system whips it into a whirling mass that grows into a tornado or a hurricane, then the air around us makes headlines. Science consultant Walker (Snowball Earth) presents a lively history of scientists' and adventurers' exploration of this important and complex contributor to life on Earth, from Galileo's early attempts to show that it has weight to the explorations by 20th-century scientists Oliver Heaviside and Edward Appleton of the ionosphere, which acts as a giant mirror bouncing radio waves from one side of the globe to another. Walker provides readers with easy-to-follow discussions of the science behind the discovery that carbon dioxide levels are rising exponentially.

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