Category Archives: Science

Mentos Geysers

I guess that by now everybody knows that you can build a very sticky geyser by dropping Mentos into a bottle of Coke. Some of my students and I even had a lot of fun – um, I meant we did some very serious scientific experiments with carbonated beverages and mints with a porous surface in a science class just before the summer break last year. However, our experiments were quite tame compared to these…

Fritz Grobe and Stephen Voltz have taken the experiment to the next level – “with over 250 geysers of soda. And this time they’re linked together in one giant chain reaction! A clever mechanism harnesses the power of one geyser of Diet Coke to drop the Mentos into the next bottle. So just like dominos, all they have to do is start the first one, and the rest is Diet Coke & Mentos history!” Watch it here.

(Siehe auch hier im Archiv.)

Non-Newtonian fluids, again.

Ask MetaFilter: Liquid Bounce.

“At the University of Texas, researchers have produced some amazing videos and photos of liquid bouncing on liquid. This was one of nature.com’s Images of the Year for 2007 (picture number 6, in the upper-right corner). The project report, along with pictures and videos, is found on their bouncing jet page, and it’s quite extraordinary both for the counter-intuitive nature of the phenomenon and the extremely low-tech production methods. You can even do it at home with little more than a lazy Susan and some silicone oil.”

Includes a link to vibrated shear thickening fluids.

(Previously: February 17, 2008, April 22, 2007.)

Non-Newtonian Fluids

Non-Newtonian fluids are fluids whose visosity changes according to the force which is applied to them. Stick your finger in slowly, and it behaves like a liquid, but bang it with a fist, and it behaves like it’s solid. Like in this film: Non-Newtonian fluid (Youtube link).

Or, more spectacularly, you can even walk on the liquid, like in this movie: Walking on a cornstarch-water-mixture (noisy Youtube link, in Spanish).

Of course, the best-known non-Newtonian fluid is Silly Putty, at least to Americans. By the way, I’ve never seen it for sale in Germany, but John VanDyk was kind enough to send me some years ago. Hi, John!

Non-Newtonian fluids have some interesting properties (the following are all Youtube links, except where noted):

Kaye Effect: Pour a thin stream of shampoo into a container, and a stream of shampoo might jump back up. This effect became famous when it was explained by a group of Dutch scientists last year, who produced a stunning video of the Kaye effect. See also Leaping Shampoo and the Stable Kaye Effect (PDF).

Fano Flow: the fluid can be syphoned tubeless – it seems to move upwards unsupported.

Weissenberg Effect: The fluid climbs up a rotating rod. You know this one from beating egg-whites with an electric mixer.

Barus Effect (aka Merrington Effect, Die Swell, and Extrudate Swell): After passing a small orifice the diameter of the liquid stream increases.

Liquid Rope Coil Effect: When the poured liquid reaches the surface, it seems to coil like a rope. You can demonstrate this one fairly easily with honey.

Chernobyl

It’s been a little over 21 years now since the nuclear power plant in Chernobyl blew up. I wrote about it on the 20th anniversary and a few years earlier, but the MetaFilter thread Chernobyl – 20 years later has some new (at least to me) links on the topic.

My Journey to Chernobyl: 20 Years After the Disaster is an article with photos by Mark Resnicoff, who traveled to the contamination zone in June 2006. There also is a discussion about his essay.

Chernobyl Legacy by Paul Fusco:

On April 26th, 1986, Chernobyl’s Reactor No. 4 unleashed a thoroughly modern plague that emptied cities, condemned entire regions, and seeped invisibly into the bodies of those exposed to its destructive presence.

Photographer Paul Fusco faces the dark legacy of Chernobyl, focusing on the horrifying human consequences of the event that is now 20 years in the past. Fusco’s work forces us to remember an important nightmare that we would forget at the peril of our morality and our future.

It takes a while for the site to load, but it’s worth the wait. At least look at and listen to “Chernobyl legacy” from the menu.

Karol Lasia has a collection of black-and-white photos from the area. Lasia was born in 1986 and traveled to Chernobyl and Pripyat in the summer of 2006.