Some random thoughts on teaching buoyancy… one of the six skills


I have to be a bit pedantic here… in the real world outside of diving where there exists some semblance of respect for the constructs of everyday science, there is a place where there is no neutral, positive or negative buoyancy. It is a happy place and I like it there.

Neutral, Negative, Positive. These are outcomes and not states of buoyancy. I know it is a hard habit for divers to break – like referring to the Gas Laws as physics when they belong in the realm of chemistry – but I would suggest at this level you should understand the distinction.

Things float, things sink, things maintain their position in the water column: Which of these outcomes corresponds to our state as a diver, depends on the balance between gravity and buoyancy.

It will help us understand this skill more completely, I believe, if we first understand that balance is the variable while gravity and buoyancy are the constants.

So just to recap, there is no such thing as negative buoyancy; that is like saying a color is whitish black or a cup of coffee is Hot Cold.

Positive buoyancy is redundant term at best. But it could also mean that a buoyant force is optimistic; which is just plain wrong.

Neutral buoyancy assumes some all-powerful entity has suspended the Laws of Physics.

Any questions?

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5 thoughts on “Some random thoughts on teaching buoyancy… one of the six skills

  1. Well, if we believe the Collins English Dictionary definition nr. 2 for the word buoyancy to be true, then it all makes sense, doesn’t it? Negative, positive, neutral… all versions of it. The sign of the force can surely be both positive or negative, depending on the frame of reference? Usually it’s defined as negative being towards the center of Earth, I think. Which is a troublesome direction for a diver running out of breathing gas, but otherwise as good a direction as any of the pysical (or chemical) directions.

    Collins says:
    buoyancy (‘bɔɪənsɪ) n
    1. the ability to float in a liquid or to rise in a fluid
    2. the property of a fluid to exert an upward force (upthrust) on a body that is wholly or partly submerged in it

    Cheers, Otto.

    • Ok, replying for myself.

      I can see what mean now, saying buoyancy is always positive. Of ourse it is, as a force induced by the water pressure, as ooposed to gravity. I was being immersed (no pun intented) in my physics gradute student frame of reference with the previous comment. In that sense, I think negative buoyancy would indeed require some antigravity… Ok, I’ll shut up now.

      Thanks for the inspiring writing!

      Otto.

  2. I know that languages evolve. In some cases there are terms which just don’t make sense. For example, irregardless. The word regardless means “to have no regard”. Prefixing a word with ir- negates the word, as in irrelevant means “not relevant”. Thus irregardless means “not to have no regard”. Utter nonsense.

    However, I can see “negative buoyancy”, “neutral buoyancy” and “positive buoyancy” being used. Positive buoyancy is really “having buoyancy”, negative buoyancy is really “lacking buoyancy” and neutral buoyancy is really “neither having or lacking buoyancy”. It is when we introduce neutral buoyancy we can see some savings. It would make sentences less wordy.

    Was it proper grammar ten years ago? Not really. Will it become proper grammar? Probably. Languages evolve.

    “This river I step in is not the river I stand in” — an ancient Greek philosophy on change.

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