Imperial Measurements With Matt Parker

[jakeXT]

[Enthusiast]

1. Try engineering something with that system.

[Locut0s]

2. I'll do one better. NASA lost a $653 million dollar mission due to an imperial snafu...

http://en.wikipedia.org/wiki/Mars_Climate_Orbiter

"
However, on September 23, 1999, communication with the spacecraft was lost as the spacecraft went into orbital insertion, due to ground-based computer software which produced output in non-SI units of pound-seconds (lbf×s) instead of the metric units of newton-seconds (N×s) specified in the contract between NASA and Lockheed. The spacecraft encountered Mars at an improper angle, causing it to incorrectly enter the upper atmosphere and disintegrate.
"

In more detail:

"
On November 10, 1999, the Mars Climate Orbiter Mishap Investigation Board released a Phase I report, detailing the suspected issues encountered with the loss of the spacecraft. Previously, on September 8, 1999, Trajectory Correction Maneuver-4 was computed and then executed on September 15, 1999. It was intended to place the spacecraft at an optimal position for an orbital insertion maneuver that would bring the spacecraft around Mars at an altitude of 226 kilometers on September 23, 1999. However, during the week between TCM-4 and the orbital insertion maneuver, the navigation team indicated the altitude may be much lower than intended at 150 to 170 kilometers. Twenty-four hours prior to orbital insertion, calculations placed the orbiter at an altitude of 110 kilometers; 80 kilometers is the minimum altitude that Mars Climate Orbiter was thought to be capable of surviving during this maneuver. Final calculations placed the spacecraft in a trajectory that would have taken the orbiter within 57 kilometers of the surface where the spacecraft likely disintegrated because of atmospheric stresses. The primary cause of this discrepancy was engineering error. Specifically, the flight system software on the Mars Climate Orbiter was written to take thrust instructions using the metric unit newtons (N), while the software on the ground that generated those instructions used the Imperial measure pound-force (lbf). This error has since been known as the "metric mixup" and has been carefully avoided in all missions since by NASA.[16]

The discrepancy between calculated and measured position, resulting in the discrepancy between desired and actual orbit insertion altitude, had been noticed earlier by at least two navigators, whose concerns were dismissed. A meeting of trajectory software engineers, trajectory software operators (navigators), propulsion engineers, and managers, was convened to consider the possibility of executing Trajectory Correction Maneuver-5, which was in the schedule. Attendees of the meeting recall an agreement to conduct TCM-5, but it was ultimately not done.
"

[Bernardo de La Paz]

4. Really foul misnomer to call it "metric mixup". Better to call it "imperial mixup".

Best to call it a "measurement system mis-match". Perhaps some anti-metric troglodyte dubbed it the "metric mixup" (as it appears in the article). Of course it was not the fault of the metric system.

[Enthusiast]

7. OMG!

Amazing!

[krispos42]

18. We've decimalized the imperial system

I work for a precision machining shop. We make small parts for a variety of companies. Let me put it this way... some of our stuff is, as I type this, roving around Mars.

Anyway, I work in decimal inches for everything except machined threads. Everything that comes in is measured to either 3 or four decimal places. And I'm talking things that go into space and into nuclear submarines and airliners.



The imperial system was a much better system for an agrarian society, as the actual units reflected the capacities and capabilities of the people and animals and land. A furlough, for example, is 220 yards, or about as long as a team of oxen could pull a plow continuously.

In modern usage, we have sloughed off unnecessary unit groupings, such as rods and chains and furlongs, and typically only use three: mile, foot, and inch. Compare this to the metric system, with the kilometer, meter, centimeter, and millimeter.

Measuring and making things in the real world gets you strange numbers anyway. I stare at small precision parts all day, and to get the geometry the engineer that designed it needs, you get strange numbers whether it's metric or English. You're taking angles, chords, tangents, hypotenuses, etc., so whatever convenience you get from using metric goes away almost immediately.

The metric system is much better for science, due to its latecomer status: it has the advantage of base units being interrelated and consistent. But out in the "everyday" world, it simply doesn't matter, as long as the units are consistent. I want a pool for my house.... does it matter if I buy a 15' diameter, 5'-foot deep pool, or a 4.5 meter, 1.5 meter deep pool?

I'm really thirsty, does it matter if my drink is a quart or a liter?

Yeah, there are still some strange units out there... bullets and powder charges are still weighed in grains, for example, but that's a market we dominate.

[Jim Lane]

19. Metric would still be an advantage for the non-decimalized parts

The other day I needed to convert miles per hour into feet per second. I had to start by multiplying by 5,280 instead of just moving a decimal point. (Granted, with either system I'd still have to divide by 3,600, but at least metric would have eliminated one of the steps that required a calculator.)

[krispos42]

21. Add 50% to the MPH number.

5280/3600=1.467, so if you just add half, you're in the ballpark.



Reality is messy. Anything you measure in real life winds up being in fractions of a base unit anyway.

I'm not saying metric is worse than imperial, but once you've decimalized the imperial units, they become as easy to use as metric units for pretty much every day-to-day need.

If I had to give distances in miles, furlongs, rods, chains, feet, and inches... ugh. But once I can simply write the distance in decimal, it doesn't matter much if it's kilometers or miles.

[Jim Lane]

24. I've sometimes used 60mph = 88fps

This works well because a speed is often rounded to the nearest 10mph so factoring 60 is easy. The particular occasion that came up last week, though, was one where I couldn't use approximations or shortcuts.

There are other such questions that come up. How many football fields laid end-to-end would make a mile? This one is easy if you happen to know that a mile is 1,760 yards but not everyone knows that. How far away is the Moon in relation to the height of a human? I don't cook so I've gotten a little hazy over the years about the teaspoon-tablespoon-cup-pint-quart conversions that I knew in elementary school.

Decimalizing as you describe it helps somewhat, but it's not the universal standard. I'd be hesitant to write "5.8 feet" for fear that it would be misread by someone as 5' 8". The error is less than two inches but that could be important.

[jakeXT]

20. The only advantage I see is in calculating the volume (liter vs gallon), if you want to know how

much water you'll need or which pumps to buy.

I want a pool for my house.... does it matter if I buy a 15' diameter, 5'-foot deep pool, or a 4.5 meter, 1.5 meter deep pool?

[krispos42]

22. Ah,but there's still geometry involved.

pi dee squared, all over 4

And there's about 7½ gallons in a cubic foot.


It would be easier. Sometimes. It's just that the ease is not worth the disruption, particularly for the end user.

I have a pump; I'll stick it in the pool and run it until it drains. I'm in no rush, after all. Probably take hours anyway. Maybe a day or two. Conversely, when it's time to fill it up again I'll stick the garden hose in the and run it until it's full.


Where is really matters is with engineers designing things, but they have the knowledge and the tables to get all this stuff done in a very precise, mathematical way anyway.

[Bernardo de La Paz]

3. It's impossible to be progressive without advocating metric measurement

Here is a map of all the countries using the imperial system of measurement which (in addition to the points of the video) is based on the King's thumb and foot. Remember, conservatives love British royalty!

If Obama wants to make a legacy, and drive the Tea party so far around the bend they disappear into their own anatomy, he would push through proper metrification in 2015 after we get out the vote in 2014 to make a Democratic majority.

If metric is good enough for the US Army and schoolchildren, it is good enough for the USA. Or we comfort ourselves that at least we have Burma among advanced countries with us.

[Locut0s]

5. This would be very cool to see...

How likely do you think it is though?

[BumRushDaShow]

6. I remember back in the '70s

when I was in school learning the metric system, I had been told that the U.S. would be converting to being all-metric by the early '90s....

I guess the attempts using products like the "2 liter" soda, "325 mg" aspirin, "5K" (5 kilometer) race, and "100s" (100 mm cigarette) didn't quite go far enough to convince anyone....

But then again many Brits still use "stones" for weight.

[tjwmason]

8. The large majority of us Brits still think in imperial.

Whilst I was entirely educated in metric, as soon as I started to use measurements for real-life things (in my case mostly cooking) the imperial system just seemed to fit better.

We still use imperial for quite a bit of stuff - milk and beer are still sold in pints, and road signs are all in miles.

[Doc_Technical]

9. When Canada heard that the U.S. was converting to the metric system..

it figured that Canada should also convert so they just went ahead and did so.

The comedy group The Frantics made light of this conversion:

[progressoid]

13. Hahahaha

excellent

[Wounded Bear]

10. Hey! We got Liberia, too!

USA! USA! USA!

[CanSocDem]

11. More evidence...

...of the influence of corporate money on government services.

Business has successfully argued that Americans aren't intellectually flexible enough to accept a totally new measurement system, when in fact, the real reason is that it is the corporations who are too "inflexible" to change.

Everything a name brand corporation is, is fundamentally, an illusion. They have everything invested in that illusion. They're not about to give it up easily.



.

[Bernardo de La Paz]

15. The US has to run two measurement systems. That costs corporations.

Ultimately, the short term costs of converting to metric are dwarfed by the savings.

US companies have to export in metric, mostly. US cars need metric tools because it is too stupid to make cars with imperial bolts for the US and export a different version to the civilized world.

Beware of denigrating branding too much. The Democratic Party is a brand.

[CanSocDem]

16. Didn't mean to denigrate 'branding'...

...it is everything in a free market economy. Which is to say, without it, the 'free market' wouldn't exist.

And I'm not for one minute suggesting that without a carefully crafted "brand", the "Democratic Party" wouldn't exist.



.

[Bernardo de La Paz]

17. Cool. Now we need branding for metric :P . . nt

[CanSocDem]

23. They didn't waste their time in Canada.

One or two provinces started by including metric distances on highway mileage signs. After a year or so it was only metric. Then all the provinces jumped in with total immersion. As for "branding", they just said it would make us "world class". We always wanted that so it was an easy sale.

At the time I was driving a transport truck between metric and non-metric jurisdictions and had my rudimentary math skills put to the test. Soon, like others have mentioned, it becomes more of a concept and less of an actual measurement. A "brand" if you will....


.

[panader0]

12. I've worked construction all my life.

About twenty years ago, someone decided to have the plans for a large, headquarters building on the local Army base done in metric measurements. It caused havoc. All building materials are in inches and feet in the US. Plywood is 4'X8', a block is 8"x8"X16", etc.
As a foreman, I bought a metric convertor, but it was still a SNAFU. The idea of plans in metric was quickly dropped.
If the US is to change over to metric, most building materials would have to change too.

[Bernardo de La Paz]

14. Yes, materials would change. But you have to get started on change or be left behind.

The US market is getting smaller as a share of the global market. The US is getting more provincial to the extent that it follows conservative policies.