If only they had used Mathcad

[RichardJ]

We all know the benefits of units in Mathcad, and the Mars Climate Orbiter and the Gimli Glider have been cited numerous times on the forums as examples of why units matter. Here's a couple of lesser known ones though:

The Vasa warship:

In 1628, crowds in Sweden watched in horror as a new warship, Vasa, sank less than a mile into her maiden voyage, with the death of 30 people on board. Armed with 64 bronze cannons, it was considered by some to be the most powerful warship in the world. Experts who have studied it since it was raised in 1961 say it is asymmetrical, being thicker on the port side than the starboard side. One reason for this could be that the workmen were using different systems of measurement. Archaeologists have found four rulers used by the workmen who built the ship. Two were calibrated in Swedish feet, which had 12 inches, while the other two measured Amsterdam feet, which had 11 inches.

Stonehenge model:

In the 1984 mockumentary This is Spinal Tap, the members of a fictional rock group order a model of a Stonehenge megalith for their stage show - but the note written on a napkin mistakenly asks for a model 18 inches tall, instead of 18 feet. Curiously, and probably coincidentally, the British rock band Black Sabbath had experienced the opposite problem during its Born Again tour in 1983. Its replica of Stonehenge was so big, it got in the way of the band, and very few of the "stones" would fit on the stage. One version of the story says there was a mix-up between metres and feet.

Both courtesy of the BBC: http://www.bbc.com/news/magazine-27509559

Why don't we have "Amsterdam feet" as a unit in Mathcad?

[PhilipOakley]

My googling of "units mistakes" also gave

On January 26, 2004 at Tokyo Disneyland's Space Mountain, an axle broke on a roller coaster train mid-ride, causing it to derail. The cause was a part being the wrong size due to a conversion of the master plans in 1995 from English units to Metric units. In 2002, new axles were mistakenly ordered using the pre-1995 English specifications instead of the current Metric specifications.

http://spacemath.gsfc.nasa.gov/weekly/6Page53.pdf

and from http://mentalfloss.com/article/25845/quick-6-six-unit-conversion-disasters

SOHO, the Solar Heliospheric Observatory, a joint project between NASA and the ESA (European Space Agency), lost all communications with Earth. After about a week of trying various things, communication was restored and everyone breathed a sigh of relief. Among the problems thought to have caused the sudden blackout?

• There was an error in the spacecraft’s navigation measurements of nearly 100 km, which resulted in a much lower altitude than expected and led to the vehicle’s break-up in the atmosphere.

• The conversion factor from English to Metric units was erroneously left out of the AMD files.

• Interface Specification required that the impulse-bit calculations should be done using Metric Units.

the Institute for Safe Medication Practices reported an instance where a patient had received 0.5 grams of Phenobarbital (a sedative) instead of 0.5 grains when the recommendation was misread. A grain is a unit of measure equal to about 0.065 grams… The Institute emphasized that only the metric system should be used for prescribing drugs.

An aircraft more than 30,000 pounds overweight... In 1994, the FAA received an anonymous tip that an American International Airways (now Kalitta Air, a cargo airline) flight had landed 15 tons heavier than it should have. The FAA investigated and discovered that the problem was in a kilogram-to-pounds conversion (or lack thereof).

Even Columbus had conversion problems. He miscalculated the circumference of the earth when he used Roman miles instead of nautical miles, which is part of the reason he unexpectedly ended up in the Bahamas on October 12, 1492, and assumed he had hit Asia. (Maybe he should have waited for Mathcad 😉

And there are more 😉 (as you know)

http://lamar.colostate.edu/~hillger/unit-mixups.html US metric association

Philip

[ValeryOchkov]

Not units but as temperature relation scales:

In the past was a bridge across the Rhine built. On one side the Germans started and on the other side the Swiss started to build it. When both side met, they recognized that the height difference is about a half meter. The reason for the error was that the German standard of the construction zero height is the average level of the North Sea, and in Switzerland the average level of the Mediterranean Sea.

[ValeryOchkov]

Valery Ochkov wrote:

Not units but as temperature relation scales:

In the past was a bridge across the Rhine built. On one side the Germans started and on the other side the Swiss started to build it. When both side met, they recognized that the height difference is about a half meter. The reason for the error was that the German standard of the construction zero height is the average level of the North Sea, and in Switzerland the average level of the Mediterranean Sea.

Now we have same errors with temperature units when we use old reference books:

[ValeryOchkov]

Valery Ochkov wrote:

Not units but as temperature relation scales:

In the past was a bridge across the Rhine built. On one side the Germans started and on the other side the Swiss started to build it. When both side met, they recognized that the height difference is about a half meter. The reason for the error was that the German standard of the construction zero height is the average level of the North Sea, and in Switzerland the average level of the Mediterranean Sea.

See please http://communities.ptc.com/message/244432