Physics Rant: The Truth to Buoyancy in Diving

[bfw]

First off, let me admit that, as Scott Adams put it, I have 'The Knack'. I'm an aerospace software engineer, and I was always the kid in science class that would mess up the curve for everybody else.

Blah, blah, blah, been there, done that, got the t-shirt. I've done software and hardware for machine vision, motion control, automated stress analysis, non-contact wafer oxide characterization, magnetic resonance RF optimization and gradient control, and industrial automation, AND I know a dozen phrases in Klingon. Loosen up that sphincter and learn to enjoy life a little. For starters, I've been working in dive training for 20 years and I've NEVER, EVER, heard or read the compound noun "negative buoyancy." I HAVE seen the adjective phrase "negatively buoyant" which does NOT denote a force or vector, but rather the state of an object, and is perfectly acceptable.

Beyond that, you claim that you are intensely bothered by misuse of technical terms, then go on to call gravity a MAGNETIC force. Kettle to pot, color check, over. You also used the word "always" redundantly in the sentence about correcting movies, so stick that in your Stunk & White. If you're going to play the OCD card, at least get it right.

In a nutshell, lighten up, Francis.

 

[Hoomi]

...so stick that in your Stunk & White. If you're going to play the OCD card, at least get it right.

In a nutshell, lighten up, Francis.

Stunk & White? Stunk & White?!?

BLASPHEMY!!!!

The Elements of Style was written by William Strunk Jr. and E. B. White. Why, to reduce the name to a common past tense of "stink" is akin to saying radio was invented by Nikola Teste.

:shocked2:

(Yeah, yeah; there are some word-dorks out here too... )

 

[SteveAD]

Stunk & White? Stunk & White?!?

BLASPHEMY!!!!

The Elements of Style was written by William Strunk Jr. and E. B. White. Why, to reduce the name to a common past tense of "stink" is akin to saying radio was invented by Nikola Teste.

:shocked2:

(Yeah, yeah; there are some word-dorks out here too... )

Radio was Marconi

Tesla was the loser of the electricity war Edisons AC beat out Teslas DC

 

[Scubagolf]

Time Evolution of Negative Buoyancy of an Oceanic Slab Subducting With Varying Velocity

References and further reading may be available for this article. To view references and further reading you must purchase this article.

R. Mahatsente and G. Ranalli Corresponding Author Contact Information, E-mail The Corresponding Author

Department of Earth Sciences and Ottawa-Carleton Geoscience Centre, Carleton University, Ottawa, Ont., Canada K1S 5B6

Received 11 February 2004;
Revised 20 April 2004;
accepted 17 May 2004.
Available online 20 July 2004.

Abstract

The negative buoyancy of a subducting oceanic slab is estimated based on thermal models and various kinematic boundary conditions. Both temperature and negative buoyancy are time-dependent and are computed subject to time-varying subduction rates. The magnitude of the negative buoyancy increases with increasing depth of penetration of the slab and subduction velocity. For mature oceanic lithosphere, the buoyancy of a slab reaching the base of the mantle transition zone is approximately 5 Ž× 1013 N m−1 for a peak subduction rate of 5 cm a−1. In all cases considered, the rate of increase in negative buoyancy depends on the convergence rate at a particular period of time during subduction. If the velocity increases exponentially in the initial stages of subduction, the maximum rate of increase is observed when the slab subducts with the peak subduction velocity. If subduction continues with a constant velocity, the rate of increase in thermal buoyancy begins to decrease as the slab penetrates the lower mantle, and the buoyancy approaches an asymptotic value for increasing time. If the velocity decreases exponentially in the last stages of subduction, the negative buoyancy begins decreasing while the slab is still sinking, as its thermal anomaly decreases. After subduction stops, the slab achieves thermal equilibrium with the surrounding mantle in approximately 10?0 Ma depending on its past history.

Author Keywords: Subduction; Oceanic Lithosphere; Temperature in subducting slab; Negative buoyancy

 

[b1gcountry]

Yes! This is now my most popular post ever! Now if we could just get someone to mention Hitler...

Tom (OP)

 

[Hoomi]

Radio was Marconi

Tesla was the loser of the electricity war Edisons AC beat out Teslas DC

You might want to double-check your history there.

Tesla developed many of the concepts that Marconi used to produce the radio. The actual invention, however, was Tesla's. The biggest reason Marconi ended up with credit is that his family had the financial wherewithal to move ahead with production, and secure support. Without Tesla's ideas, however, it is doubtful Marconi would have had a working radio anywhere near as soon as he did.

Edison was a HUGE proponent of DC, and in fact, proved to be a ruthless bastard by traveling the country, electrocuting animals at shows and fairs, to prove how dangerous AC was. The real "battle" for AC household electric versus DC was between Westinghouse, who championed AC, and Edison, who promoted DC.

AC vs. DC

Edison and electrocution

Tesla and radio

 

[tfsails]

The Elements of Style was written by William Strunk Jr. and E. B. White. Why, to reduce the name to a common past tense of "stink" is akin to saying radio was invented by Nikola Teste.

I would think that Nikola Teste would be some sort of nut, wouldn't you??


Sorry--the devil made me do this...

 

[Hoomi]

I would think that Nikola Teste would be some sort of nut, wouldn't you??


Sorry--the devil made me do this...

If I'd been on the ball, I'd have thought of it first.

( <--- I think they're coming for us... )

 

[SDiggy]

Yes! This is now my most popular post ever! Now if we could just get someone to mention Hitler...

Tom (OP)

Hilter dove with a jacket style BC with Air2, wore split fins/blade fins (take your pick...) and put his mask on his forehead.

made me do it, I couldn't resist. send the after me!