Ummmmm… me when I have on a weight belt and a bouyancy compensator adjusted correctly when I’m scuba diving.
Even better you can prove it to yourself by following the procedure outlined here.
http://www.sme.org/memb/neweek/actbuoy.htm
My husband and I have done experiments like this in our hot-tub with perrier bottles on numerous occasions. It just takes a lot of patience and a bit of wine.
You and your husband are way ahead of the scientific curve, I think a partially filled wine bottle (3rd or 4th) will disprove this “law” too!
Oops. Of course, what was I thinking. Anyways, the globes in such thermometers will often sit midway up the tube for long periods of time, clearly achieving neutral bouyancy.
(Phew…saved myself. :p)
Setting Sun
Can you give a website stating the “law” of neutral buoyancy being impossible?
So far it seems, you are the only one who has said there is such a law.
No, no, no you misunderstood. The wine goes into PictsiePat and MrPict. Neither we nor the wine float under the water. You add enough water to the perrier bottle, seal it up and it will float under water. Too much water and it will sink, too much air and it will float partially submerged. The patience comes in when trying to getting just the right amount or air/water. Wine helps with this.
Fortunately we are both engineers and explore many scientific principles in the hot tub. Our most recent explorations have involved vortices (forced vs free) and the eternal question of which way the sprinkler turns if the water goes in rather than out.
One of the questions better answered in the library.
Yes water does compress but it takes a lot of pressure to get much change in volume.
http://van.hep.uiuc.edu/van/qa/section/Underwater_and_in_the_Air/Pressure/20030603113030.htm
Their example is water at 150 atmospheres (one mile down) loses about 1% volume.
I also don’t see what’s so impossible about neutral bouyancy. So long as your mass equals the mass of the water you displace you’ve got the same density as the water itself and there’s no reason for you to sink or float. If neutral bouyancy didn’t exist I think it’d be hard for liquid water to exist, all the molecules would constantly be flying all over the room.
Ok, I finally read the link. What it is saying is that they couldn’t achieve neutral bouyancy with a submarine. This does not mean that neutral bouyancy does not exist. What it means is that on the large scale (submarine size) in a non-steady state environment (the ocean is not a steady state place, what with currents and all not to mention temperature gradients that affect water density) it would be very difficult if not impossible to achieve neutral bouyancy.
Neutral bouyancy can be achieved in a static system (ie steady state). The point of the vibration dampers in Koon’s exhibit is to replicate a steady state environment.
Again I urge you to perform the experiment in the link I posted. That is what science is all about.
Not wanting to be a nitpicker here but I did go to that site previously and found this quote" True “neutral buoyancy” is impossible to obtain."
Yes, it is in a paragraph titled “Archimede’s Law and Submarines” but just how did that website author come to that conclusion? I do not think Archimedes specifically said that.
Why did the OP choose to ignore this post? I think that it answers the question posted. There is no law stating neutral bouyancy is impossible. The website cited by the OP deals with submarines being unable to float submerged while not moving. Somewhere along the way, whoever wrote this website confuses a solvable control problem with a physical law.
Submarine at surface, flood tanks. It starts to sink, gaining momentum. You now stop filling the tanks. You then start purging the tanks well before you achieve your desired depth. This acts to slow your descent. All it takes is trial and error tweaking or a nice computer program to determine the proper actions. It was likely not doable in the 1800s, but I’d be willing to bet it is now.
And why does the OP ignore the first hand evidence stated about scuba divers floating submerged? If you make up a physical law, and then ignore all examples given that break this “law”, you are unlikely to be convinced that it is not true.
OK, I guess that the last 2 posters made most of these points. Drat. Gotta learn to make it short and sweet.
We’ll definitely try your experiment in our hot tub. As I said previously, I think you and your hubby are on the right track, but I’ll use, both, a partially filled bottle of Perrier and a partially filled bottle of (cheap) wine. We’ll see which one hovers underwater? Based on the the wine consumption, we might still prove Archimedes and his 2,200 years old law “old”.
Sorry, I thought I was posting directly after SettingSun.
Seems a few Message Board members got their posts in between there.
And I agree with Valgard and Pictsie, neutral buoyancy is not impossible.
Setting Sun as I’ve said before, I think you are the only one in this thread who thinks it is impossible.
Sorry, I tend to agree with Mangetout. Just can’t prove it is true.
A few years ago I saw a soft drink (forget the name now), that had little red BB-sized balls suspended in it. The soda was clear and the little balls–edible gummy things–were suspended throughout: neutrally buoyant. You could shake the stuff and they just stayed where they were, neither rising nor sinking. It was quite intriguing.
I couldn’t resist and bought a few bottles. When you put ice cubes in it, eventually the balls would start to sink. I figured out that as the ice melted and diluted the soda, it became less dense than the undiluted water/sugar solution, and therefore the balls, being more dense, sank.
I haven’t seen the stuff in a while, but I haven’t looked, either.
Ok, let’s say I am the only one postulating this, e.g. the “New Archimedes” 
, provided an example that contradicts my postulate …
Man, leave off with a pithy reply, have dinner and look what happens.
SettingSun, here’s Archimedes Principal, notice it’s a principla and hardly a law.
to put it more simply F[sub]b[/sub]=p[sub]l[/sub]gV[sub]object[/sub] where p is the density of the liquid. When F[sub]b[/sub] = p[sub]object[/sub]gV[sub]object[/sub] (here p is density of the object) the object will be at rest. So long as the density of the object matches that of the liquid in which it resides the object will not move.
For a diver the V[sub]object[/sub] changes with inhalation, as does p[sub]object[/sub] making it much harder to maintain neutral buoyancy. Likely the suits used by astronauts in buoyancy tanks minimize the change in volume and so makes it more useful than it might otherwise be.
Now, if you want to become wildly nitpicky you could argue that the minute differences in density of the liquid due to temperature changes, or 2nd order effects due to lunar gravity will cause an oscillation, knock yourself out.
Not a pithy reply at all, give me the example and the cite. Thanks …
Those making claims need to provide evidence. Otherwise I’m the Second Coming. Prove me wrong.
I have never held an object under water that didn’t float to the surface or sink to the bottom. Have you?