Feeling pressured? Not as much as you will be after climbing inside a 55-gallon trash bag and having all the air sucked out of it.
“It feels like there’s a linebacker lying on top of you,” says Eric Muller, Senior Science Educator at the Exploratorium in San Francisco.
The Feeling Pressured activity shows you how to achieve the effect: you need the trash bag, of course, along with an industrial-strength vacuum (10 to 12 amps), and at least three people. The one who’s going to be in the bag needs to weigh at least 100 pounds.
“Could you combine two 50-pound kids to get the 100 pounds?” we asked Eric.
“It’s got to be one person,” says Eric. “And I wouldn’t do this with young kids. Air pressure is pretty powerful stuff.”
Pretty powerful, indeed. Eric reminds us that the average person walking around at sea level has in the neighborhood of 40,000 pounds of force pushing on his or her body. “That’s almost 15 pounds per square inch (psi),” Eric says. When the vacuum is turned on, the pressure inside the bag is reduced. And the higher air pressure outside the bag pushes on all on the bag’s exterior surface.
“People are surprised,” says Eric. “They feel it’s hard to breathe. You can’t move—it’s like being in a straitjacket.” And it’s an experience that the bagged person (and those working the vacuum) is unlikely to ever forget.
“It brings home that there’s an invisible substance [air] around us that actually exists and does something,” says Eric. “It’s invisible, but it’s not nothing.”
Going further
“It’s a great gateway activity to teach kids about the atmosphere, an important part of climate literacy. After kids get that air pressure exists, they start thinking about what causes it,” Eric points out.
This leads to thinking about the composition of atmosphere; some activities that can extend Feeling Pressured are the Atmosphere Composition Model, the Percentage of Oxygen in the Air, and Skin Size, in which learners calculate the surface area of someone’s skin and the amount of atmospheric force pushing on it.
Eric didn’t invent "Feeling Pressured," but he’s been an enthusiastic disseminator since he stumbled on the idea at a conference in Jamaica in 1994. “I’ve probably put several hundred people in the bag,” Eric says, “and have helped those people get thousands of others in there.”
Pedagogical protagonist
When I asked Eric to describe what he does, not just with trash bags but in general, he threw out half a dozen possibilities in under a minute. “Funny you should ask,” he began, sipping his decaf (full strength coffee would put his already high energy level through the roof). “I need to get a new business card made up, and I was thinking of putting my job down as ‘cog.’ Educational Cog.”
“I also call myself a Teacher of Teachers. And of course, a Science Educator. Oh, and I think there’s ‘Coordinator of Technology’ in my title as well.”
“But most of all," he laughs, "I'm a Pedagogical Protagonist.”
That may be, but watching Eric in action, convincing people to climb into bags, teaching about Hot Spot Island Formation with ketchup, or using chocolate to demonstrate how lava cools, you have to conclude that he’s really more of a live science action figure.
Note to parents and educators: The "Feeling Pressured" activity is best for learners over 14. Even then, you might want to supervise—as Eric Muller says, air pressure is powerful stuff.
Photos:
1. Feeling Pressured activity
2. Skin Size activity
3. Resident Exploratorium Pyro/Teacher Eric Muller takes a blow torch to sugar, just to see what will happen.