Metric versus Imperial System for Diving?

[mrdre]

So much confusion within imperial system, eh? You won't hear these conversations between "metric" people. force is force, mass is mass. different measures, different names. no need for some "assumptions" that just cause further confusion.

 

[dfx]

Yes it was, because measurements of distance and weight were connected. It was chosen in such a way that 1 cubic centilitre (a cube of 1x1x1 centimetre) of pure fresh water weighs 1 gram. One cubic liter is therefore 1 kilogram and so forth. As a nice side effect of this connection between units of distance and the weight of water, 10 metres is spot on 1 bar.

Fixed it for you. The coincidence is that 1 atm is roughly equal to 1 bar.

 

[Diver0001]

Ah yes. I stand corrected. Thanks.

 

[mrdre]

It's actually not a "neat coincidence" at all. In a really goofy, roundabout way (and I can't remember the proof for it)....it was defined that way, kinda-sorta.

It was coincidence, because meter was chosen to be 1/10000000 of half of Earth meridian. It just so happened that 10 meters of water presses roughly as one atmosphere, "roughly" - not exact. But the approximation is good enough for practical reasons.

 

[oszillodrom]

It's actually not a "neat coincidence" at all. In a really goofy, roundabout way (and I can't remember the proof for it)....it was defined that way, kinda-sorta.

Actually, this works out due to a few coincidences:

- the kilogram used to be defined as the mass of a liter of water, for practical reasons
- Earth's gravity is close to 10 m/s^2
- the air pressure at sea level (atm) happens to be close to 100 kPa

I hadn't realized that before, it was fun to think about it. So that's quite an undeserved win for us metric proponents.

 

[Diver0001]

So much confusion within imperial system, eh? You won't hear these conversations between "metric" people. force is force, mass is mass. different measures, different names. no need for some "assumptions" that just cause further confusion.

I don't see confusion either way. Both systems are standardized baselines for communicating. Nothing more, nothing less. What normally happens in these kinds of discussions is that people make value judgement about things that they have never used and don't fully understand. It goes both ways.

There is no need for a value judgement here. Everyone is going to have a personal preference and it's perfectly understandable to me that people would prefer to use what they know.

Aside from the happy side-effect that the metric system makes the numbers come out round for diving, this is really a non discussion. I've used both systems extensively for diving and they both work fine.

I have trouble understanding why people get defensive about this. It's really a non-issue.

R..

 

[mrdre]

I don't see confusion either way. Both systems are standardized baselines for communicating. Nothing more, nothing less. What normally happens in these kinds of discussions is that people make value judgement about things that they have never used and don't fully understand. It goes both ways.

There is no need for a value judgement here. Everyone is going to have a personal preference and it's perfectly understandable to me that people would prefer to use what they know.

Aside from the happy side-effect that the metric system makes the numbers come out round for diving, this is really a non discussion. I've used both systems extensively for diving and they both work fine.

I have trouble understanding why people get defensive about this. It's really a non-issue.

R..

The key difference is that metric system is decimal, while imperial is not. In metric systems calculations often involve moving decimal point left or right. Anybody can tell how many meters are in 1 kilometer. Ask how many feet are in 1 mile? With metric system you measure everything from atoms to stars. Can't do that with Imperial.

It's non-issue and not big of a deal for diving. I'm just commenting. For everyday life it really doesn't matter. People hardly add or subtract. This becomes an issue when you do scientific research, use in military, etc.

Actually I find it very ironic, that the US initially helped and supported the French to develop and adopt the metric system.. Centuries later in 2015 the US will remain the only country in the world that didn't adopt the metric system. Just an irony.

 

[DiveNav]

Unfortunately the imperial system does not make this distinction clear at all, as they use the pound for two completely different things.

Pound (mass) - Wikipedia, the free encyclopedia
Pound (force) - Wikipedia, the free encyclopedia

You forgot the Pound currency

---------- Post added October 23rd, 2014 at 02:58 PM ----------

..... It was chosen in such a way that 1 cubic centilitre (a cube of 1x1x1 centimetre) of pure fresh water weighs 1 gram. .....

At what temperature?

 

[oszillodrom]

At what temperature?

At 4°C.

 

[Diver0001]

With metric system you measure everything from atoms to stars. Can't do that with Imperial.

Well... at the risk of sounding nit-picky, you can, actually. You wouldn't want to for obvious reasons but you can.

Actually I find it very ironic, that the US initially helped and supported the French to develop and adopt the metric system.. Centuries later in 2015 the US will remain the only country in the world that didn't adopt the metric system. Just an irony.

The UK did a poor job of transitioning too and they're system is even worse because people talk in hybrid.

It's an expensive operation to adopt a new system of measurement. Just think about the the cost alone of having to replace every single road sign in the country that has a distance or a speed on it..... School books, computer programs, product labels... you name it. This is the reason the UK failed to make the transition and I think their example is a good one. If you don't have the money to do it right then you're probably better off not doing it.

To my way of thinking the US missed the window in which they could have made the transition without incurring astronomical costs for a project that would, for all intents and purposes, deliver a zero-sum benefit.

If I had to make the decision I wouldn't do it either and certainly not now when you're up to your lips in debt and deficit and there are bigger fish to fry.

R..