By Wendy Langhans
Toothpaste – part of the morning bathroom ritual. You open the tube and turn it down at an angle, but nothing flows out of it until you squeeze it. Then the toothpaste just sits there, a colorful blob on your toothbrush. Did you ever wonder why it doesn’t flow off your toothbrush?
Believe it or not, it has to do with physics, specifically viscosity. Viscosity can be described as “a fluid’s internal resistance to flow”. Newton (of the falling apple fame) has an equation for it, which you can read about here. Some fluids, like motor oil, are Newtonian. Others, like toothpaste, are not. Toothpaste is known as a “shear-thinning fluid”, which means it “behave like a fluid when worked or agitated and then settle(s) into a nearly solid state when at rest.” That’s why you have to squeeze the tube to get the toothpaste to come out.
And some snake venom behaves in a similar way, for a similar reason.
Here in California, we are familiar with rattlesnakes, who bite their prey using syringe-like hollow fangs. But worldwide, only 1 out of 7 venomous snakes use hollow fangs. Most snakes or other poisonous reptiles use twin fangs, and many of these fangs are grooved.
The venom clings to the inside the of concave groove, like honey on a stick. But when the snake bites it’s prey, the 3-sided groove and the victim’s tissue become a 4-sided tube. The increase in surface area increases the amount of surface tension. Because snake venom behaves as a shear-thinning fluid, this increase in the force from surface tension decreases the venom’s viscosity and increases the flow rate into the victim, at about 1 cm per second.
So, unlike our local rattlesnakes, which strike at lightening speeds, (.5 seconds, start to finish), these “groovy” snakes often hold onto their prey and strike several times. It reminds me a bit of the “59th Street Bridge Song”:
Slow down, you move too fast.
You got to make the morning last.
Just kicking down the cobble stones.
Looking for fun and feelin’ groovy.”
I just may try humming that the next time I brush my teeth.
Upcoming Outdoor Events:
Saturday, March 12 – Sunday, May 29, SCV Search & Rescue Trail Challenge 2011: 12 Weeks/12 Hikes.
Saturday, May 21, 8 – 10 AM, Early Morning Bird Hike at Towsley Canyon. Will you be able to identify the birds you find? Don’t worry, Volunteer Naturalist Roger has plenty of experience to help you out. Let your eyes spy the many birds at Towsley Canyon on this easy walk. Binoculars optional. Meet at the Towsley Canyon front parking lot. For directions and trail maps, click here.
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org for time and place.
Wednesday mornings, May 4, 11, 18, 25.
Saturday mornings, May 14, 28.
For a glimpse of our local flowering plants, check out the Facebook page, “90 Days of Santa Clarita Valley Wildflowers”.
You can listen to stories like this every Friday morning at 7:10 a.m. on “The SCV Outdoor Report”, brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
For the complete MRCA hike and activity schedule and for trail maps, click here or go to www.LAMountains.com.