UA vs Denpressure

Quote from: Rayzor on January 28, 2017, 05:38:13 AM

Quote from: sceptimatic on January 28, 2017, 05:26:25 AM

Quote from: onebigmonkey on January 28, 2017, 04:44:57 AM

Quote from: sceptimatic on January 28, 2017, 04:02:49 AM

Quote from: onebigmonkey on January 28, 2017, 03:49:08 AM

How much water would a cubic metre of mercury displace?

Try it next time you have some spare.

The density of mercury is 13.56. So one cubic metre of mercury will weigh 13.56 tonnes.

How much water will it displace when submerged?

13.56 tonnes.

Bzzzt.. wrong  which is a bit sad since I gave you the correct answer already.

One cubic meter of mercury will displace exactly one cubic meter of water,  which is a volume of 1000 liters or approximately 1000 kg  ( depending on temperature )

Yes it will displace one cubic metre of water when just submerged in shallow water but that's not the real truth of the matter.
Allow the mercury to sink to its level and it will displace exactly what I said.
The major problem with that is, we cannot measure it like that for obvious reasons.
The best way we can do it is to displace the water by creating a resistance against it.
How?
Easy.
We simply place the block on a floating platform and measure the overspill, which would be?

Yep, 13.56 tonnes.

Whatever you do,  don't go into ship building,  you are failing to understand the difference between floating and sinking.    Archimedes figured it out over 2000 years ago.

Betty the Destroyer would understand,  and cats don't even like water.

Quote from: sceptimatic on January 28, 2017, 06:28:42 AM

Quote from: Rayzor on January 28, 2017, 05:38:13 AM

Quote from: sceptimatic on January 28, 2017, 05:26:25 AM

Quote from: onebigmonkey on January 28, 2017, 04:44:57 AM

Quote from: sceptimatic on January 28, 2017, 04:02:49 AM

Quote from: onebigmonkey on January 28, 2017, 03:49:08 AM

How much water would a cubic metre of mercury displace?

Try it next time you have some spare.

The density of mercury is 13.56. So one cubic metre of mercury will weigh 13.56 tonnes.

How much water will it displace when submerged?

13.56 tonnes.

Bzzzt.. wrong  which is a bit sad since I gave you the correct answer already.

One cubic meter of mercury will displace exactly one cubic meter of water,  which is a volume of 1000 liters or approximately 1000 kg  ( depending on temperature )

Yes it will displace one cubic metre of water when just submerged in shallow water but that's not the real truth of the matter.
Allow the mercury to sink to its level and it will displace exactly what I said.
The major problem with that is, we cannot measure it like that for obvious reasons.
The best way we can do it is to displace the water by creating a resistance against it.
How?
Easy.
We simply place the block on a floating platform and measure the overspill, which would be?

Yep, 13.56 tonnes.

Whatever you do,  don't go into ship building,  you are failing to understand the difference between floating and sinking.    Archimedes figured it out over 2000 years ago.

Betty the Destroyer would understand,  and cats don't even like water.

Yeah I bet he did. Pencil and A4 paper I think, wasn't it?

Quote from: onebigmonkey on January 28, 2017, 06:47:49 AM

I use what i have. I guarantee that it will work with any size water container. Absolutely 100% guarantee it.

Feel free to provide your own demonstration. You'll need your own cat.

Or are you too pussy?

Swidt?

Me? How?

Geddit?

Now you know I can't emulate the real experiment. It's way lout of mine and your power.
It has to be done another way to see what's happening.

You see, just like atmosphere being stacked, so is water.
It isn't incompressible, it just resists compression a lot better than atmosphere, because it's more dense, obviously.

The more a block sinks by it's own density and attempted crushing by the water pressure, the water pressure becomes much higher due to that dense block displacing it by that crush or attempted crush.

This would be transferred UP and out as further spillage to create a water weight that matches the block. A little beaker or barrel won't solve this issue with your mercury.

You seem to be saying that by sinking further, the mercury will eventually displace an amount of water equal to its own weight. But for that to happen the density of the water would have to increase to equal the density of mercury. It doesn't get anywhere close to that, even at great depths:

Quote from: sceptimatic on January 28, 2017, 07:01:14 AM

Quote from: onebigmonkey on January 28, 2017, 06:47:49 AM

I use what i have. I guarantee that it will work with any size water container. Absolutely 100% guarantee it.

Feel free to provide your own demonstration. You'll need your own cat.

Or are you too pussy?

Swidt?

Me? How?

Geddit?

Now you know I can't emulate the real experiment. It's way lout of mine and your power.
It has to be done another way to see what's happening.

You see, just like atmosphere being stacked, so is water.
It isn't incompressible, it just resists compression a lot better than atmosphere, because it's more dense, obviously.

The more a block sinks by it's own density and attempted crushing by the water pressure, the water pressure becomes much higher due to that dense block displacing it by that crush or attempted crush.

This would be transferred UP and out as further spillage to create a water weight that matches the block. A little beaker or barrel won't solve this issue with your mercury.

You seem to be saying that by sinking further, the mercury will eventually displace an amount of water equal to its own weight. But for that to happen the density of the water would have to increase to equal the density of mercury. It doesn't get anywhere close to that, even at great depths:

How do you know?

Water is just an extension of atmosphere. It can be compressed but is much more difficult.
To compress it you need something that is much less buoyant,
Basically a large block of dense metal, like gold or lead or whatever.

This sinks down and compresses heavy water and causes that compression to displace more of the heavy water which is transferred to the top and would be measured by more overflow....if it was possible to do it and see the results.

It's the opposite of where we are at sea level and looking up. It's as if we are the ocean bottom feeders. We are the compressed on the atmospheric bed, if you like.

We displace out own dense mass of atmosphere but if we were to be pushed up into less atmosphere, we expand to equalise the more expanded, less dense atmosphere.
Now imagine if we lived up there and that was our ocean, yet we could step off to the side onto another ledge (as an instance).

Now think about that block of metal lying next to us. We throw it in the water (upper atmosphere) which, as we know is under much less pressure.
We let the block drop down into more dense and more dense atmosphere until it reaches the bottom (our real sea level) and you'd see that it's displaced more dense atmosphere which it has compressed up and pushed much more up than it would if it was just dropped on a small ledge that only covered it by a few feet at the top of out atmosphere.

Let's see you get your head around that.

Quote from: Pineal on January 27, 2017, 05:19:26 PM

I know the earth is accelerating.

You claim that you "know the earth is accelerating".

To claim that you know something seems to imply that you have irrefutable evidence for it - where is this irrefutable evidence?

The earth is accelerating in the round earth theory as well.

Now you know I can't emulate the real experiment. It's way lout of mine and your power.

If you have no experimental evidence to support your claims, then how did you reach these conclusions?

Quote from: rabinoz on January 27, 2017, 05:59:42 PM

Quote from: Pineal on January 27, 2017, 05:19:26 PM

I know the earth is accelerating.

You claim that you "know the earth is accelerating".

To claim that you know something seems to imply that you have irrefutable evidence for it - where is this irrefutable evidence?

The earth is accelerating in the round earth theory as well.

In what way do you claim that the Globe (not round earth, your flat earth is also round) is accelerating.
I agree that the surface is subject to very slight centripetal acceleration as it rotates and
the earth as a whole is subject to a much smaller centripetal acceleration due to its orbiting the sun.

But this has no connection with gravitation, so what acceleration are you referring to.

Quote from: razor

Archimedes figured it out over 2000 years ago.

 Yeah I bet he did. Pencil and A4 paper I think, wasn't it?

Actually legend has it that it was a bathtub, and he ran down the street shouting eureka after he realised that floating things displace their exact WEIGHT in water.   While sinking things displace their exact VOLUME.

It's all about density you know....     WEIGHT divided by VOLUME.

Here is the "true" story of Archimedes.






I figure sceptimatic might like cartoons better,  well,  because,  you know,  don't make me say it....   

OP-wise, the question's incomplete. UA and denpressure don't standalone, because they aren't meant to. There's more to both models: in UA you either have to deal with celestial gravitation or the accelerator penetrating the Earth, to say nothing of aspects of the accelerator itself. With denpressure, you need to understand molecules and the dome. Only with all of that together can you compare the two mechanisms, without all of that they're just not complete.

Personally, I'd go for denpressure. I don't think either fully works, but denpressure is at least interesting.

Because liquid mercury is very dense and does not absorb atmosphere, readily. It's excellent at repelling atmospheric pressure upon it, just like everything else does, because denpressure is how it all works.

Can I ask about the nature of repelling atmospheric pressure? The explanation I've seen previously seemed to be based more on just not accepting atmosphere into it, rather than actively repelling it. Was this just a quirk of phrasing, or is there more to it?
Though I'll understand you might not want to get into it here if there's more to it, I remember how these discussions could go.

Quote from: Pineal on January 28, 2017, 10:47:18 AM

Quote from: rabinoz on January 27, 2017, 05:59:42 PM

Quote from: Pineal on January 27, 2017, 05:19:26 PM

I know the earth is accelerating.

You claim that you "know the earth is accelerating".

To claim that you know something seems to imply that you have irrefutable evidence for it - where is this irrefutable evidence?

The earth is accelerating in the round earth theory as well.

In what way do you claim that the Globe (not round earth, your flat earth is also round) is accelerating.
I agree that the surface is subject to very slight centripetal acceleration as it rotates and
the earth as a whole is subject to a much smaller centripetal acceleration due to its orbiting the sun.

But this has no connection with gravitation, so what acceleration are you referring to.

The earth's orbit follows a continuous elliptical shape. As the earth hurdles through space, the direction of travel constantly changes due to the sun's gravity. Since the earth is changing directions constantly, it is also changing velocity. 

Since acceleration is defined as a change in velocity, one would be correct in saying that the earth is constantly accelerating as it moves about its orbit.

You seem to be saying that by sinking further, the mercury will eventually displace an amount of water equal to its own weight. But for that to happen the density of the water would have to increase to equal the density of mercury. It doesn't get anywhere close to that, even at great depths:

As per the above graph water IS in fact compressible to a very small degree. I can't verify the accuracy of the graph and why it reaches a limit of 1.028 but according to this source, and for the sake of this argument, let's say that at a depth of 1 mile density of water increases by 1%

https://water.usgs.gov/edu/compressibility.html

Imagine you have a >1 mile deep body of pure water (density 1000kg/mł). Now take a non porous, non compressible solid object of exactly 1mł, with a density of 1010kg/mł, and drop it in. It will sink, as we all know. But once it reaches 1 mile in depth, where the density of the surrounding water is the same as itself, it will stop sinking and be neutrally buoyant.

It is still displacing the same volume (1mł). BUT at that depth, that volume contains not 1000kg, but 1010kg of water. It's simply pushing more water molecules aside, as they are packed in tighter.

All the way up at the surface, if say you were in a tall graduated cylinder and could measure the displacement, it would still be exactly 1mł and not 1.01mł, as less molecules are pushed aside as you get closer to the surface again and the density decreases.

Correct as this principle may be, to try and apply it to how our atmosphere acts on things thousands of times denser than itself in order to explain "denpressure", is pure idiocy.

Quote from: rabinoz on January 28, 2017, 02:29:00 PM

In what way do you claim that the Globe (not round earth, your flat earth is also round) is accelerating.
I agree that the surface is subject to very slight centripetal acceleration as it rotates and
the earth as a whole is subject to a much smaller centripetal acceleration due to its orbiting the sun.

But this has no connection with gravitation, so what acceleration are you referring to.

The earth's orbit follows a continuous elliptical shape. As the earth hurdles through space, the direction of travel constantly changes due to the sun's gravity. Since the earth is changing directions constantly, it is also changing velocity. 

Since acceleration is defined as a change in velocity, one would be correct in saying that the earth is constantly accelerating as it moves about its orbit.

I do believe that is what I said, but it is not the cause of the gravity we experience on earth.
The centripetal acceleration at the equator due to the earth's rotation is about 0.03 m/s²
and that due to our orbiting the sun is about 0.005954 m/s².

These are both small compared to gravity, and that due to our orbiting the sun is quite negligible except for extremely precise measurements.

Correct as this principle may be, to try and apply it to how our atmosphere acts on things thousands of times denser than itself in order to explain "denpressure", is pure idiocy.

I've been hoping someone would address the issue of relevance. At extreme pressures you would get some different results but how does that relate to denpressure which is about equivalent to the pressure from 10 m of water? As far as I know density, buoyancy and displacement are all very consistent at depths of 10 m or less. And that's double the air pressure at sea level.

Quote from: MaxPen on January 28, 2017, 09:03:45 PM

Correct as this principle may be, to try and apply it to how our atmosphere acts on things thousands of times denser than itself in order to explain "denpressure", is pure idiocy.

I've been hoping someone would address the issue of relevance. At extreme pressures you would get some different results but how does that relate to denpressure which is about equivalent to the pressure from 10 m of water? As far as I know density, buoyancy and displacement are all very consistent at depths of 10 m or less. And that's double the air pressure at sea level.

You're fighting a losing battle with Sceppy. He simply does not believe any of the usually properties of fluids and gases in particular.

The most important of these in this case is that by definition a fluid cannot support any static shear stress.
This implies that pressure is non-directional (a scalar quantity) and the direction of a force on a surface is always at right-angle's (normal) to that surface.

The outcome of this is that static pressure alone cannot cause a nett force on an object (up down or any other way). Any force is caused by pressure difference (pressure gradient).

Since amospheric pressure falls with increasing altitude the force under an object is greater than the force on top, so we get buoyancy.
And it's exactly the same in a liquid.
All of this relies on gravitation to cause the atmospheric or water pressure.

Now there in no reason why we could be in a pressurised vessel (divers in a diving bell are), but this increased pressure will not cause any extra downward force, all it will do is to provide a little more buoyancy due to the denser air.

But Sceppy with his expanding molecules will have none of this. The trouble is that his hypothesis has no explanation for why one particular direction is down.

Best of luck you'll need it.  Read some of Lewis Carol's writings first might get your might on the right frame of mind. 

I realised about 50 pages ago on the air pressure/gravity thread that it's a losing battle, I don't think anyone else thinks otherwise yet here we all are lol. At one stage I thought he was on the right track with understanding the reality of density. Then, as if it couldn't get any more farcical, along comes expanding molecules.

Expanding molecules, and if I understood him right he thinks if you went deep enough the water would compress and become as dense as mercury!?

But earlier he agreed with me that fluids don't really compress(significantly). Hydraulic systems wouldn't work very well if they did.

I'm not sure what to think anymore. (You've inspired me to change my sig again)

Quote from: sceptimatic on January 28, 2017, 07:32:30 AM

Quote from: razor

Archimedes figured it out over 2000 years ago.

 Yeah I bet he did. Pencil and A4 paper I think, wasn't it?

Actually legend has it that it was a bathtub, and he ran down the street shouting eureka after he realised that floating things displace their exact WEIGHT in water.   While sinking things displace their exact VOLUME.

It's all about density you know....     WEIGHT divided by VOLUME.

Here is the "true" story of Archimedes.






I figure sceptimatic might like cartoons better,  well,  because,  you know,  don't make me say it....   

Here's another fantasy for you.


Once upon a time a man named Eratosthenes phoned his mate up and said "oi, I'm doing an experiment with a big hole and the sun and I want you to ram a stick in the ground outside your house when I tell you, then ring me back with the angle of the sun, then I can triangulate it all and find out how big this big ball of spinning Earth is."

Land line, naturally.

I can tell you many stories like this. How many do you want to use as part of your real life today?

Can I ask about the nature of repelling atmospheric pressure? The explanation I've seen previously seemed to be based more on just not accepting atmosphere into it, rather than actively repelling it. Was this just a quirk of phrasing, or is there more to it?
Though I'll understand you might not want to get into it here if there's more to it, I remember how these discussions could go.

If an object does not readily accept atmosphere into it, it resists it. It repels it by the entire density and area, meaning the atmosphere exerts and equal push back onto that object by that displacement.
It's what makes a man made scale plate measurement of the object.

This is why mercury is better for barometers because they absorb very little atmosphere which means it can repel atmospheric absorption into it.

Take this barometer.
It's self explanatory in itself but it shows that the mercury being so dense, does not allow seepage of atmosphere through it and into the gap in the tube at the top. This means it keeps that gap at an extreme low pressure and allows the atmosphere to push up the mercury to compress the more expanded atmosphere trapped inside.

People are under the impression that the space at the top is vacuum but it's not.
If that mercury was less dense, then the atmospheric push down onto it would force up a little at a time and basically render the barometer useless as an accurate measurement.

As a side note, take a good look at this barometer dish and think on how I mentioned tides working on a circular Earth.

Mercury makes a better barometer because it requires less of it. Water makes a perfectly acceptable barometer, you just need a ridiculously big tube.

No-one who understands how it works believes that the space in the top of the barometer. The existence of the air in the barometer is what makes it work.

No-one is denying that atmosphere exerts a pressure. What is being denied is that it is the cause of everything else.

Until you grasp that your understanding of the nature of your environment is fundamentally flawed and that the cart is not only before the horse it is somewhere in the next town you will never get anywhere.

It's self explanatory in itself but it shows that the mercury being so dense, does not allow seepage of atmosphere through it and into the gap in the tube at the top.

People are under the impression that the space at the top is vacuum but it's not.

You do know how you make such a barometer right? With the tube full of mercury (ie no empty space whatsoever) it is inverted while the open end is still under the bigger container of mercury. So if mercury doesn't allow seepage of atmosphere through it, and neither does the glass, what then fills the space at the top?? Nothing!! it's a vacuum. Which atmospheric pressure tries to push the mercury back up into.

Mercury makes a better barometer because it requires less of it. Water makes a perfectly acceptable barometer, you just need a ridiculously big tube.

No-one who understands how it works believes that the space in the top of the barometer. The existence of the air in the barometer is what makes it work.

No-one is denying that atmosphere exerts a pressure. What is being denied is that it is the cause of everything else.

Until you grasp that your understanding of the nature of your environment is fundamentally flawed and that the cart is not only before the horse it is somewhere in the next town you will never get anywhere.

Until you change from being a parrot to a thinker, you'll only every mimic what you're comfortable and safe, mimicking.
Outside of the box will never exist to people like you.

Quote from: sceptimatic on January 28, 2017, 11:56:18 PM

It's self explanatory in itself but it shows that the mercury being so dense, does not allow seepage of atmosphere through it and into the gap in the tube at the top.

Quote from: sceptimatic on January 28, 2017, 11:56:18 PM

People are under the impression that the space at the top is vacuum but it's not.

You do know how you make such a barometer right? With the tube full of mercury (ie no empty space whatsoever) it is inverted while the open end is still under the bigger container of mercury. So if mercury doesn't allow seepage of atmosphere through it, and neither does the glass, what then fills the space at the top?? Nothing!! it's a vacuum. Which atmospheric pressure tries to push the mercury back up into.

If there is no empty space whatsoever then why is there an empty space at the top of the tube?

Think carefully about what you're saying.

Quote from: MaxPen on January 29, 2017, 12:13:31 AM

Quote from: sceptimatic on January 28, 2017, 11:56:18 PM

It's self explanatory in itself but it shows that the mercury being so dense, does not allow seepage of atmosphere through it and into the gap in the tube at the top.

Quote from: sceptimatic on January 28, 2017, 11:56:18 PM

People are under the impression that the space at the top is vacuum but it's not.

You do know how you make such a barometer right? With the tube full of mercury (ie no empty space whatsoever) it is inverted while the open end is still under the bigger container of mercury. So if mercury doesn't allow seepage of atmosphere through it, and neither does the glass, what then fills the space at the top?? Nothing!! it's a vacuum. Which atmospheric pressure tries to push the mercury back up into.

If there is no empty space whatsoever then why is there an empty space at the top of the tube?

Think carefully about what you're saying.

The tube is full at the point of inversion. Atmospheric pressure can't support the full weight of the mercury so it drops creating a vacuum at the top. The mercury will drop until it reaches a point where the atmospheric pressure equals the weight of mercury.

Quote from: sceptimatic on January 29, 2017, 12:39:27 AM

Quote from: MaxPen on January 29, 2017, 12:13:31 AM

Quote from: sceptimatic on January 28, 2017, 11:56:18 PM

It's self explanatory in itself but it shows that the mercury being so dense, does not allow seepage of atmosphere through it and into the gap in the tube at the top.

Quote from: sceptimatic on January 28, 2017, 11:56:18 PM

People are under the impression that the space at the top is vacuum but it's not.

You do know how you make such a barometer right? With the tube full of mercury (ie no empty space whatsoever) it is inverted while the open end is still under the bigger container of mercury. So if mercury doesn't allow seepage of atmosphere through it, and neither does the glass, what then fills the space at the top?? Nothing!! it's a vacuum. Which atmospheric pressure tries to push the mercury back up into.

If there is no empty space whatsoever then why is there an empty space at the top of the tube?

Think carefully about what you're saying.

The tube is full at the point of inversion. Atmospheric pressure can't support the full weight of the mercury so it drops creating a vacuum at the top. The mercury will drop until it reaches a point where the atmospheric pressure equals the weight of mercury.

That makes no sense at all. Try again.

If there is no empty space whatsoever then why is there an empty space at the top of the tube? Think carefully about what you're saying.

There is no empty space in the tube before it's inverted while submerged under more mercury. It's completely full of mercury.

Now think carefully and answer my question. What is in the empty space at the top of the tube after the tube is inverted, and how does it get in there. Through the mercury? Through the glass? How?

Quote from: Rayzor on January 28, 2017, 05:03:58 PM

Quote from: sceptimatic on January 28, 2017, 07:32:30 AM

Quote from: razor

Archimedes figured it out over 2000 years ago.

 Yeah I bet he did. Pencil and A4 paper I think, wasn't it?

Actually legend has it that it was a bathtub, and he ran down the street shouting eureka after he realised that floating things displace their exact WEIGHT in water.   While sinking things displace their exact VOLUME.

It's all about density you know....     WEIGHT divided by VOLUME.

Here is the "true" story of Archimedes.






I figure sceptimatic might like cartoons better,  well,  because,  you know,  don't make me say it....   

Here's another fantasy for you.


Once upon a time a man named Eratosthenes phoned his mate up and said "oi, I'm doing an experiment with a big hole and the sun and I want you to ram a stick in the ground outside your house when I tell you, then ring me back with the angle of the sun, then I can triangulate it all and find out how big this big ball of spinning Earth is."

Land line, naturally.

I can tell you many stories like this. How many do you want to use as part of your real life today?

But you don't disagree with the results of Archimedes' experiment. Your claim is that if he did it at greater depths he would get different results. So why do you call it a fantasy?

Quote from: sceptimatic on January 29, 2017, 12:39:27 AM

If there is no empty space whatsoever then why is there an empty space at the top of the tube? Think carefully about what you're saying.

There is no empty space in the tube before it's inverted while submerged under more mercury. It's completely full of mercury.

Now think carefully and answer my question. What is in the empty space at the top of the tube after the tube is inverted, and how does it get in there. Through the mercury? Through the glass? How?

It was already there in the first place in a minute amount.
That minute amount of atmosphere compresses quite easily by the external atmospheric push on the mercury below it, because it has a glass separator between that small amount of atmospheric pressure at the top and the external atmospheric pressure upon it.

It is not a vacuum.

Quote from: MaxPen on January 29, 2017, 01:00:13 AM

Quote from: sceptimatic on January 29, 2017, 12:39:27 AM

If there is no empty space whatsoever then why is there an empty space at the top of the tube? Think carefully about what you're saying.

There is no empty space in the tube before it's inverted while submerged under more mercury. It's completely full of mercury.

Now think carefully and answer my question. What is in the empty space at the top of the tube after the tube is inverted, and how does it get in there. Through the mercury? Through the glass? How?

It was already there in the first place in a minute amount.

How do you know this? The barometer is designed and constructed specifically and deliberately such that there is nothing but mercury in the tube. If you assert otherwise then you need to justify your assertion.

It is not a vacuum.

Strictly speaking, that's correct. It is a Torricellian vacuum, which is to say mercury vapour at a very low pressure.

Quote from: sceptimatic on January 29, 2017, 02:01:06 AM

Quote from: MaxPen on January 29, 2017, 01:00:13 AM

Quote from: sceptimatic on January 29, 2017, 12:39:27 AM

If there is no empty space whatsoever then why is there an empty space at the top of the tube? Think carefully about what you're saying.

There is no empty space in the tube before it's inverted while submerged under more mercury. It's completely full of mercury.

Now think carefully and answer my question. What is in the empty space at the top of the tube after the tube is inverted, and how does it get in there. Through the mercury? Through the glass? How?

It was already there in the first place in a minute amount.

How do you know this? The barometer is designed and constructed specifically and deliberately such that there is nothing but mercury in the tube. If you assert otherwise then you need to justify your assertion.

Quote from: sceptimatic on January 29, 2017, 02:01:06 AM

It is not a vacuum.

Strictly speaking, that's correct. It is a Torricellian vacuum, which is to say mercury vapour at a very low pressure.

I've just explained. Take heed or don't.

Quote from: Copper Knickers on January 29, 2017, 02:28:18 AM

Strictly speaking, that's correct. It is a Torricellian vacuum, which is to say mercury vapour at a very low pressure.

I've just explained. Take heed or don't.

Copper Knickers just explained that above the mercury there is nothing but mercury vapour.
The vapour pressure of mercury at room temperature is about 0.002 mmHg. Normal air pressure is about 760 mmHg,
so the pressure above the mercury in a mercury barometer i's only 1/380,000 of normal air pressure.

in industrial standards this would be not quite good enough to be called a high vacuum.

Sceppy, you really think that you are the only person in the world that understands a vacuum but
you know hothing compared to the experts that make untra-high vacuum equipment for industry.
For example, what do you know about turbomolecular, diffusion and ion vacuum pumps  and over what pressure range would use each?