Helium Shortage has ended ...

[StefinSB]

The problem is deeper than just doing unit conversions, or getting used to decimal multiples and submultiples.
The problem is that the US metric system is physically incoherent, as the base units are Length, Time and Force.
1 Lb is a unit of force, not of mass as it is 1 kg...
The SI unit, instead, is physically coherent, as the base units are length, time and mass.
Using an incoherent measurement system requires to "patch" physical formulas adding a dummy factor, usually called gc, and numerically equal to the Earth's gravity acceleration for converting force to mass.
Example:
The first Newton law says that the force applied to a body is equal to the product of the mass of the body multiplied by its acceleration.
In SI we write this as:
F=M*a.
Force is in Newton, mass is in kg and acceleration is in m/(s^2).
In the US system, force is in lb-force and acceleration is in feet/(s^2).
If also the mass is expressed in lb-mass, the above formula becomes dimensionally wrong.
You fix it this way:
F=M*a/gc
The units of gc is lb-mass*m/(s^2)/lb-force and its numerical value is the same as g=32.17405 ft/s^2.
You can understand how the need of writing the formulas differently is a mess.
So it is not just matter of converting lb in kg, or ft to m, which is trivial.
All the formulas in your textbook need to be revised, for making them physically coherent...

You “argument” is pointless as the overwhelming majority of science in the US is carried out in the SI system. Besides, with the steady globalization, metric is slowly creeping in.

 

[formernuke]

Actually it was used in the production of nuclear weapons so once the cold War ended production of helium went way down.

 

[Degenerate]

Back on topic: please stop wasting helium on open circuit! (while blaming party balloons)

I went through 3600L of 18/45 today on open circuit.
Sorry not sorry.

 

[fsardone]

Actually it was used in the production of nuclear weapons so once the cold War ended production of helium went way down.

To be precise, helium is an element and cannot be produced (short of nuclear fusion which opens another class of issues), only extracted.
Also being so light (2 protons and 2 neutrons) once free in atmosphere tends to migrate to higher layers and once in thermosphere, due to thermodynamic speeds, acquire escape energy and leave the earth gravitational pit.
Lost forever. Helium will be exhausted (sooner or later on earth at least, no chance in the universe).
There is a big sour e close by though ... 150 * 10^9 meters or 1 AU just to remain in the discussion on units. AU is accepted in the SI except its symbol is ua

 

[Graeme Fraser]

I deal with pounds and kilos due to working in international shipping, also some metric for shipment dimensions. US Customs even uses kilos for HS codes that require weight to be reported. I listen to BBC Radio a lot so I have a fair idea of the C to F conversion. What makes me laugh though is when wind speed is reported in miles per hour on the BBC weather forecasts. Guess they’re still hanging onto that part of the imperial system.

Yep, our weights and measures are all over the show. Can't really make up our mind one way or the other. I think we're roughly 75% metric, or possibly closer to 9/16".

For example:
Longer distances = miles
Shorter distances = metres
Speed = MPH
Vertical distance = metres underwater (except in air which is feet)
Pressure = bar (except tyres which are PSI)
Weight = Kilos (except humans and hamsters, which are measured in Stone / pounds
Fluid = litres (except beer which is always pints)
Fuel = purchased in litres, but only understood in MPG
Temperature = Celsius, except when above 100° F

Quite simple really, apart from every 3rd Wednesday of the month when we swap it round just to be awkward.

 

[Marie13]

Yep, our weights and measures are all over the show. Can't really make up our mind one way or the other. I think we're roughly 75% metric, or possibly closer to 9/16".

For example:
Longer distances = miles
Shorter distances = metres
Speed = MPH
Vertical distance = metres underwater (except in air which is feet)
Pressure = bar (except tyres which are PSI)
Weight = Kilos (except humans and hamsters, which are measured in Stone / pounds
Fluid = litres (except beer which is always pints)
Fuel = purchased in litres, but only understood in MPG
Temperature = Celsius, except when above 100° F

Quite simple really, apart from every 3rd Wednesday of the month when we swap it round just to be awkward.

Ah, thanks for that. Very helpful!

 

[BRT]

The problem is deeper than just doing unit conversions, or getting used to decimal multiples and submultiples.
The problem is that the US metric system is physically incoherent, as the base units are Length, Time and Force.
1 Lb is a unit of force, not of mass as it is 1 kg...
The SI unit, instead, is physically coherent, as the base units are length, time and mass.
Using an incoherent measurement system requires to "patch" physical formulas adding a dummy factor, usually called gc, and numerically equal to the Earth's gravity acceleration for converting force to mass.
Example:
The first Newton law says that the force applied to a body is equal to the product of the mass of the body multiplied by its acceleration.
In SI we write this as:
F=M*a.
Force is in Newton, mass is in kg and acceleration is in m/(s^2).
In the US system, force is in lb-force and acceleration is in feet/(s^2).
If also the mass is expressed in lb-mass, the above formula becomes dimensionally wrong.
You fix it this way:
F=M*a/gc
The units of gc is lb-mass*m/(s^2)/lb-force and its numerical value is the same as g=32.17405 ft/s^2.
You can understand how the need of writing the formulas differently is a mess.
So it is not just matter of converting lb in kg, or ft to m, which is trivial.
All the formulas in your textbook need to be revised, for making them physically coherent...

You state in the first part of your statement that pounds cannot be converted to Kilograms because they don't measure the same thing, In the last part you state that converting pounds to kilograms is trivial. Which is it?

 

[Angelo Farina]

As said, it is not trivial. It SEEMS trivial..
If you search on the Internet, you easily find unit converters, which state that 1 kg = 2.20462 lb
So apparently it is just matter of multiplying or diving by that factor.
The problem is that in SI you need to enter the MASS in kg in the formulas for doing calculations, while in the US system the pound is a measure of FORCE, not mass. So, apart converting the numerical value of lb to kg or vice versa, YOU NEED TO MODIFY THE FORMULAS, as they are dealing with different physical quantities.
If you are just purchasing a beef steak at the butcher, the change from mass to force is inconsequential: if you make the unit conversion correctly, you will come out with the very same beef steak you wanted to buy.
But whenever the mass/weight has to be used in a formula for doing calculations (as it often happens for scuba diving calculations), you must take into account that the two quantities measure different physical properties, and hence they must be used in different formulas...

 

[Manatee Diver]

As said, it is not trivial. It SEEMS trivial..

It is trivial. You are making things harder than they need to be.

Force Calculator F = ma

This isn't the 19th century, in the rare instances that a normal person needs to calculate things like that, they can pull up a calculator.

For the people that do it as part of their job, they likely either already have a calculator or they are already working in metric. As most scientific fields in the US use metric.

 

[Angelo Farina]

It is trivial. You are making things harder than they need to be.

Force Calculator F = ma

This isn't the 19th century, in the rare instances that a normal person needs to calculate things like that, they can pull up a calculator.

For the people that do it as part of their job, they likely either already have a calculator or they are already working in metric. As most scientific fields in the US use metric.

They can pull up a calculator if they have Internet access. Hard to do while diving...
I agree that the solution is to use the SI, where all these calculations are much simpler. Scientists are used to it. But "normal people" in US still think in the Imperial units, and it is not so easy for them.
Said that, luckily the SI is slowly penetrating also in the normal usage, and I hope that finally the imperial units will be abandoned entirely.
The real problem with technical equipment, for us divers, is threads: there are of 5 or 6 different "flavours". In whatever way your measure pitch and diameter, if you match threads which are not compatible you can get very dangerous leakages.
Last point. many people here write "metric" instead of SI. They are not the same. Before the SI became mandatory (around 1980) we were using the metric system, called ST or TS (Technical System), but it was INCOHERENT, exactly as the US Imperial system. The kg was a unit of force, not of mass...
We were used to a pressure unit which was kg/cm^2 (which again is roughly 1 bar or 1 atm). Of course this disappeared with the SI.
My old diving manual, dated 1975, was all written in that metric but incoherent system... And again the formulas were WRONG if used with mass instead of force...