By The Metric Maven

Split Bulldog Edition

Adam Savage has returned with a new version of Mythbusters, titled Mythbusters Jr. Adam hosts a number of wunderkind who address a number of myths—-for science! In 2012, when asked about why the Mythbusters did not use the metric system in their show, the answer was:

“We try, we do both sometimes. But we’re both fully inculcated with the English system, sad to say. That’s how we think.”

Adam has now taken on the responsibility to educate a new generation in the adventures of myth-busting. During his sabbatical did he muse on measurements?—-and try to inform himself about them?—well, I’m sure this won’t be much of a spoiler—but no…. not at all it appears. Worse, it’s clear he is passing on American measurement prejudice and hubris that decreases our scientific literacy.

In a segment titled Space Scream, the team examines, if in space: “no one can hear you scream.” To investigate this assertion, they build a vacuum chamber, and then use a pump to pull a vacuum. A gauge is shown which has KPa, and also inches Hg. One of the impressionable students reads out “five inches of mercury.” Adam Savage then states: “Now the numbers you’re hearing are inches of mercury. Ten inches of mercury! They’re a standard unit of measurement for atmospheric pressure—and it goes back to one of the earliest tests on vacuum which is how far up a tube can you draw liquid mercury. Eighteen inches of mercury—and it turns out 29.92 inches is as far as you’ll ever get. That is as close to a perfect vacuum as you can get here on Earth.”

What might have been useful is explaining the other scale, the Kilopascal scale. That a pascal is a newton of force per square meter, or a force that exists over an area, like pounds per square inch, but metric. But this is a quibble compared to their metric blindness in a segment called Spider Silk vs Steel. The segment starts out astonishingly metric, but with introduced confusion about micron versus micrometer. Dr Todd Blackledge, a professor at the University of Akron, when asked how thick the spider silk is, stated it is about 3 microns. Once again, academic metric ossification in the US concerning the metric system is still on display.

The myth they examine is whether spider silk is stronger than steel. The spider thread used is estimated at 3 microns in thickness. I cringed, and thought the word micrometer clearly and unambiguously expresses the value of length. Then Mythbuster Jr. Allie makes me proud: “We got our hands on some pretty thin steal thread. It’s about 30 micrometers thick. We looked at our spider silk underneath a microscope, and it was about 3 micrometers thick.” The voice over narrator then quashes my metric hope, by re-introducing microns, and equating them with micrometers. Overall, still not bad for a US television program. They even show the computations! This is not kid stuff! It might have been useful for Mythbusters Jr. to have pointed out that a human hair is about 100 micrometers thick for comparison. The steel thread is about three times smaller than a human hair and the spider silk is about 30 times smaller than a human hair. Measurement expression and clarity, is clearly not Adam’s thing. He’s too inculcated in the “English System” to change.

First, a steel thread is connected between a pair of posts on upright columns. A wire hook is placed at the center. One-by-one, washers and paperclips are added to the bottom hook of the double hook, which slowly stretches the steel thread. The added mass in grams is called out. Adam spoils the metric mood by pointing out the stretch of the filament is about four inches. The total mass added when the steel fiber fails is 39.305 grams. One might question the youthful readout to 5 micrograms. That’s quite a scale. The voice-over narrator continues to use microns.

Next, 500 threads of spider silk is connected between the two connection points, and the process repeated. The amount of paper clips and washers was 83 grams when the spider silk failed. The spider silk clearly was stronger than the steel thread.

Coarsely labeled container used to stress the steel wire and spider silk

To check this result, 25 000 strands of spider silk will be placed across the two posts. Adam tells us it’s 9.5 miles of silk, or 15.2 Kilometers for refined people. The test fixture is modified by connecting a graduated container at the bottom of the test hook. This container will be filled with water until the thread under test fails. They will then have the weight in water which caused thread failure. The container is coarsely graduated in both liters and quarts.

They use a 28 gauge steel wire for the initial test, but never indicate what its diameter is, as if 28 gauge means something. They use 40 pounds of water in the reservoir and allow gravity to slowly convey it to the rectangular container stressing the steel wire. The group then weighs the water to find out what mass of water precipitated the failure. It’s 12.5 pounds. They switched to pounds?—of course they did.

The 25 000 strands of spider silk is then prepared, and water allowed to flow. They helpfully show that the spider silk has passed the steel wire snap value, which occurred when a volume of 5.9 quarts, with a “mass” of 12.5 pounds, was in the container. The camera shows the water approaching the 8 quart mark. We next see it approach 10 liters, which is between 8 and 12 quart marks. Then failure occurs. Adam weights the water and measures 26 pounds.

Well, from a metric standpoint this is a serious cold mess. The first test with 500 spider silk threads was essentially metric, even if the long retired and meaningless micron was used. The second test used water. Adam looked at the value in quarts, and then weighted it, to determine the value in pounds. This is true metric blindness. If one has 500 mL of water it will weigh 500 grams. Each liter of water (i.e. 1000 mL) has a mass of 1 Kilogram (i.e 1000 grams). They could have used a container with mL, and read-off the value also as an estimated mass in grams. This would have been very, very educational for the youth participating in this experiment, but American metric blindness kept them from seeing this simplification. There is no instant equivalence between quarts and pounds of water like there is with liters and Kilograms. There is an expectation of complication and de-correlation of units for the “English System,” with which Adam is inculcated.

We could only see the 10 liter mark during the segment, which indicates 10 Kilograms or about 22 pounds at that point. The final value measured was 26 pounds which works back to 11.81 Kg, or 11.81 liters of water, or 11 810 mL, or 11 810 grams. Had some thought been put into the measurement involved, both experiments could have been expressed with the same metric units. In the first case, they had 39 grams for the steel and 83 grams for the spider silk. In the second experiment we have 5682 grams and 11 810 grams. It could have been all the same units.

An American audience could have learned the simplicity of using water to measure mass, and how its volume could be used as a check when weighed. 1000 mL is 1000 grams. The two values should ideally be equal, but Mythbusters Jr. has metric blindness. I have written this blog for over six years now, and written to the original Mythbusters program. What Mythbusters and Mythbusters Jr. seem to have proven to me is, that in Cyberspace, no one can hear your metric scream.