What's wrong with this

[MarkE]

That one is kind of a nit pick,, important as it may be, but still,, the intent is showing a high pressure and a low pressure.

I tend to agree.  I think Tinman meant gauge pressure and just didn't think much about the value.

That one also raises one of those strange questions,, "what if" you can have a negative pressure?

What would a negative pressure be?  Proximity of attractive particles?

Would the only problem be that the scale we use would need to change?

It requires a concept that something in the environment pulls in all directions.

Would that mean that you could suck the atoms apart?

That all depends on how strong this unknown pulling force is and what it acts on.

Is there any data from actual tests to see if indeed the mass and its interaction with gravity is indeed the same regardless of its state?

There are countless tests.  The ice melting experiment is a common grammar / middle school science demonstration.

[MarkE]

not sure, it is one of those things I do actually think about from time to timeSo far as I know we only have forces that work in one direction,, but that might not be the case.indeed,, and just how that might work.
That test has a volume change,, so not really a good example.

No, there is no volume change:  Fill a plastic bottle mostly with crushed ice, seal the cap and add marks to the bottle or add a scale to it so you can track the water line outside.  When the ice melts, the air pressure inside will change a bit, but the bottle should not deform unless it is really weak.  If the bottle deforms the experiment is no good.

I was just thinking Tinmans test over,, and it takes time to heat up the contents of the sphere,, a metal sphere,, could it be that that heat source also heats up the water in the container so that it expands ever so slightly reducing the mass density of the water in the vessel??

I don't think so.  I suspect weak seals result in gas being driven out when he heats his sphere, and cold gas being drawn in when he cools and condenses.

Not sure if that could happen or not, but water does have a lot of other things, including gasses, dissolved within it.

Heating the water enough to drive out dissolved gasses would tend to lower the density of the water and make the sphere sink.  That's the opposite of what Tinman reports.

[TinselKoala]

I tend to agree.  I think Tinman meant gauge pressure and just didn't think much about the value.

But he refers to "one atmosphere" of pressure in two of the spheres. That's 14.7 psi absolute or zero psi gauge pressure. So I can buy that +20 psi might refer to +20 psig, or even +20 psi absolute, which is +5.3 psig. But -20 psig would be.... -5.3 psi absolute. So how can you have a negative absolute pressure? That means that you have to put _in_ 5.3 psi to get to zero psi absolute (i.e.  vacuum) . It makes no sense either way, as far as I can tell.

What would a negative pressure be?  Proximity of attractive particles?It requires a concept that something in the environment pulls in all directions.That all depends on how strong this unknown pulling force is and what it acts on.There are countless tests.  The ice melting experiment is a common grammar / middle school science demonstration.

Another common demonstration is to boil some water in a can, then seal the can with a tight seal, then cool the can by splashing cold water onto it. The steam inside the can condenses back to water, leaving a partial vacuum behind. Ambient air pressure then crushes the can... which changes its volume. Maybe it will sink then!

The only way I know of to change an object's buoyancy is to change its density. This can be done by changing its displacement volume, or changing its mass, or both (assuming external conditions, like the density of the fluid it is in, don't change.) The stipulated conditions are that the displacement volume of the rigid steel sphere does not change. Phase change of any material does not change its mass. A kilogram of water inside a rigid container, changed to steam, still masses a kilogram, and if the container's displaced volume doesn't change, then its density does not change, so its buoyancy cannot change.

One might here like to review the Cartesian Diver and explore just how it is made to rise and sink by application of pressure to the outer container of fluid it floats in. The Diver is _not rigidly sealed_ and the pressure change on the outer container changes the volume of the Diver, which changes its density, thus changing its buoyancy.

[Qwert]

What i know is what i see in front of me.
Let me ask you this Qwert. If you seen something happen right before your sober eyes,and then read in a text book,or had others tell you that it's not possable,which would you believe?.

I would learn first how to properly measure such a "something" since my experience tells me that my eyes not always tell me the truth. And that might be only my interpretation what I see. There is lot of "somethings" that I don't see and they still exist. There are also possibilities that others say something exist and that is only a lie or their mis-interpretation.

[MarkE]

But he refers to "one atmosphere" of pressure in two of the spheres. That's 14.7 psi absolute or zero psi gauge pressure. So I can buy that +20 psi might refer to +20 psig, or even +20 psi absolute, which is +5.3 psig. But -20 psig would be.... -5.3 psi absolute. So how can you have a negative absolute pressure? That means that you have to put _in_ 5.3 psi to get to zero psi absolute (i.e.  vacuum) . It makes no sense either way, as far as I can tell.

I think he just threw the -20psi value up as an example value.  I don't think too much of it.  To tell what he really meant you will have to ask him.

Another common demonstration is to boil some water in a can, then seal the can with a tight seal, then cool the can by splashing cold water onto it. The steam inside the can condenses back to water, leaving a partial vacuum behind. Ambient air pressure then crushes the can... which changes its volume. Maybe it will sink then!

That's a fun demonstration, but alters the envelope.  Tinman says that he is holding his envelope constant.

The only way I know of to change an object's buoyancy is to change its density. This can be done by changing its displacement volume, or changing its mass, or both (assuming external conditions, like the density of the fluid it is in, don't change.) The stipulated conditions are that the displacement volume of the rigid steel sphere does not change. Phase change of any material does not change its mass. A kilogram of water inside a rigid container, changed to steam, still masses a kilogram, and if the container's displaced volume doesn't change, then its density does not change, so its buoyancy cannot change.

That is what I have said to Tinman a couple of times now.  In order to alter the buoyancy, one or more of the following must change:

1) Total mass of the vessel and its contents.
2) Total volume of the vessel.
3) Density of the surrounding fluid.

One might here like to review the Cartesian Diver and explore just how it is made to rise and sink by application of pressure to the outer container of fluid it floats in. The Diver is _not rigidly sealed_ and the pressure change on the outer container changes the volume of the Diver, which changes its density, thus changing its buoyancy.

I think that the crux of the matter is that Tinman believes that the average density of material inside the vessel changes when density of some of the material inside the vessel changes.  I admire Tinman's willingness to conduct experiments and his honesty with his experiments.  I have no doubt that ultimately Tinman will observe and accept the truth.