Hi Guys, a little question that is a little deeper than it looks.

When you take a 5 lt bottle and vacate it so that it's contents are in a state of low pressure ( Vacuum ) say we reduce the inner pressure by say 1000 atmospheres.

1. What has happened to the space in the bottle?

2.Has the space expanded or contracted Or has it stayed the same?

If yu continue to reduce the pressure until the bottles perosity allows leakage ( our imaginary bottle being so strong!!!)

3. What would you call the force that holds a piece of paper to the side of the bottle. Keeping in mind that the outer atmospheric pressure is determined by the gravity effecting that atmosphere.

Say, you take this bottle out into space and do the same thing being reduce the inner pressure by 1000 atmospheres say from ambient pressure (vacuum ) to 1000 times that less.

What would be the force that you have created? What would you call it?

uummm....... suction? hell if i know. 8th grade conceptual physics only goes so far man.

Quantum Quack,

When you take a 5 lt bottle and vacate it so that it's contents are in a state of low pressure ( Vacuum ) say we reduce the inner pressure by say 1000 atmospheres.


Question: Are you on Jupiter? If you reduce the pressure in your bottle by 1 atmosphere you have a perfect vacuum. :bugeye:

Err... wouldn't its just be called a pressure gradient?

When you take a 5 lt bottle and vacate it so that it's contents are in a state of low pressure ( Vacuum ) say we reduce the inner pressure by say 1000 atmospheres.

MacM is right. If the initial pressure is 1 atm, then you can only reduce it by that amount.

1. What has happened to the space in the bottle?

It has less molecules of gas in it than it did before. Other than that, no change.

2.Has the space expanded or contracted Or has it stayed the same?

Stayed the same.

If yu continue to reduce the pressure until the bottles perosity allows leakage ( our imaginary bottle being so strong!!!)

3. What would you call the force that holds a piece of paper to the side of the bottle. Keeping in mind that the outer atmospheric pressure is determined by the gravity effecting that atmosphere.

Atmospheric pressure force ?

so you guys are saying that if I keep vacating the bottle there is a limit to how much I vacate ie 1 atmosphere........This doesn't sound right at all.

You have a pump that just keeps pulling on the bottle irrespective of ambient pressure. How loooowwww can you go?

"It has less molecules of gas in it than it did before. Other than that, no change."

The volume that is being vacated also consists of space as well as molecules
How can the bottles inner space stay the same?
The molecules removed also took up space in the bottle and now they don't??

quantum

Vacuum has no matter therefore no pressure Its the preasure on the outide of the bottle that creates the force. Consider a soda can under water it contains nothing inside it will be squashed from the force of the water.

Now if you start with a bottle that has 1 atmosphere inside it and you take 1 atmosphere out you have an empty bottle. In this case its completely empty even the optimist must agree that the bottle is empty but its still a nice bottle and did not crush :).

After some thought I thnk the point I am trying to suggest is that we need to think of the universe as variable Vacuum and not variable pressure......

Just tossing an idea around....hope you dont' mind

FNG2k4, The ouside pressure is created by the effect of gravity on the atmosphere.

If there was no gravity there woudl be no pressure.

Gravity attracts particles or matter to it the strength of that attraction determines the pressure.

What is Gravity?

pressure can also be explained with kenitic energy. Particles collide with each other and bounce around causing the pressure. The less particles the less they can bounce off of each other also the less tempature the less the particles move and the less pressure.

I dont know what Gravity is but I know what it does. By the way how is that relevant to the perfect vacuum inside your bottle?

The universe as a variable vacuum huh. I knew life sucked but I didnt think it was a universal thing.

Its an intresting view but what would the benifits be? What does looking at it like a partial vacuum and not particles colliding help?

FNG2k4, ha ha......it certainly would explain why life suks.....ha

Well it's just that the reason the particles are in proximity is becasue they a held there by ambient gravity. Take away the gravity from the particles and around the particles and there are no collisions etc.thus less vacuum ( or less pressure depending on your POV.)

If you look at the earths atmosphere, it is held to the earth by the attraction of gravity. beyond the atmosphere there is less attraction thus less pressure thus more vacuum.......... as you travel farther away beyond the moons orbit I think you'll fine ther is even more change in the intensity of the vacuum.....maybe gravity is harmonically inclined, afterall if one studies the ocean one knows of inversion layers and sudden shifts in pressure and temperature.

I bet if you could work out the harmonic formula for gravity you will have gone along way to explain it.
I don't know, but if you look at the way mass ( the earth) is layered in it's core to mantle then extraplulate into the atmosphere and beyond it would be interesting math.

The sun and the position of planets etc could all suggest gravitational harmonics

yeah space really isnt that empty it just seems that way compared to a planets lack of "elbow room". Gravity waves alright im cool with that.

Why not everything is moving and warping space so the wave maybe more like the surface of the water. Take a motion less pool of water and place a resting floating object in it obj A and place a second one in moving in the water obj B. The movement of obj B will cause a movement on obj A. which then causes a change in both objects does it settle into a nice pattern? Eventually yes it could or else we wouldn't be here.

Does it have to?

With three objects it just gets confusing. soo all objects are messing with the paths of all objects and that change is really random depending on where they start. It obeys defined rules but predicting what happens with those three items is a lot of math.

FNG2k4, The ouside pressure is created by the effect of gravity on the atmosphere.

If there was no gravity there woudl be no pressure.

Gravity attracts particles or matter to it the strength of that attraction determines the pressure.This is quite true, at least on earth. But gravity isn't necessary for gas pressure. You could have a tank of compressed gas floating through the void of outer space where it wouldn't experience any significant gravity, and there would still be pressure.

and no doubt because of the container it would stay at the same pressure yes?

Or if it was in a balloon then the gas will expand until it equalises assuming the balloon is very elastic it would expand considerably.

But the real question is why is the container able to keep the pressure in side. If it wasnt for the Stick in the atomic structure it would fly apart. What is this sticky stuff that holds it all together do you think?

The strength of the sticky stuff determines how much pressure the container can hold.
There fore the sticky stuff determines the pressure of the gas yes?
Again Gravity or inverse force comes to mind.....and I wonder why?

By sticky stuff are u talking about in the container? If u are then u have to remember that different substances act differently at different temperatures. Some are gases, some are liquids and some are solids. Solids always have greater strength (molecular bonding) than the other two and this is why they stay together up to a certain pressure of the gas. Obviously the molecules of the gas would have to be different to the molecules in the side of the container for this to work! The 'sticks' u talk about (presumably from chemistry models) represent the molecular bonding forces and are electrostatic in nature.

some one once talked about an interesting pheno that occurs between two plates held close together in a vacuum, Ican't remember the name of the effect. Any one?

I think the effect is that the plates move towards each other.....?????

John thanks for your input but can you explain what you mean by electrostatic?

By electrostatic force I mean the forces holding molecules together. In a solid the apparent force is quite strong because the individual atoms don't have much energy and the atoms are tighter. There is effectively zero ES force between molecules in a gas but they can apply a pressure on a solid (due to particle collisions) up to the point in which the pressure is greater than the ES force holding the container together. Then rupture occurs.

I forgot to mention that the ES force by its name comes from differences in charge on the atoms. Unlike charges attract and all that.....

Quantum Quack,

some one once talked about an interesting pheno that occurs between two plates held close together in a vacuum, Ican't remember the name of the effect. Any one?

I think the effect is that the plates move towards each other.....?????

ANS: "Casmir Effect"

Um i kinda started typin half way through readin the posts, so some of my answers are already answered. just a reminder.


Ok, quantum quack, i may only be in highschool, but i still think i can answer u questions, in a more understandable fasion.

ur question about the vacume thing.
1) If u have air molecules inside your bottle, and u remove them, u have a vacume.which means no molecules inside a certain given space.

ur question about electrostatic.
its like static electricity, it attracts things. Its how particales and molecules stay together, they attract each other with a sort of static. The static also gives off a magnetic field, which may also be another reason y they have a tendensy to stay together but i think its mostly because of the static.

U also have to remeber that each molecular structure has a different, how would u put this, static strength. The different static strengths give each thing its different durability or strength.

ur gravity question
1)gravity is a force that keeps u stuck to the planet. That would be a definition taht easy to understand but as someone has already said, it is due to the fact that the earth rotates and that fact that we, and everything in the universe in attracted to a bigger mass, and seeing that the earth has a mass taht is about 10000000000 times bigger than our, we get attracted to it, jsut like all the air molecules.

Another reason y we get stuck to the earth, is the fact that the air pressuse(air has a density, mass and weight, so its like water in a big collum, there in more weight near the bottom than there is at the top because all the weight of the water is added up as u go deaper.) keeps us fixed to the ground, like the water example, it has a weight which pushes us to the ground.

basicly thats the best i could come up with, but hey, im only in grade 9, its not like i know everything. so, if anything is wrong, fuzzy, incomprehensible, or just plane stupid, tell me. And ill try to fix it or let someone else fix it for me. ;)

Thanks Wanted that was really good of you. When you publish your first book can you let me have a copy?

Quantum Quake you are thinking of the Casimir Effect, truly a great demonstation that "empty space" is filled with a sea of virtual particals. It is strong enough that some nanotech MEMS are having to account for it in the forces between small devices. A whole bunch of folks are trying to figure out how to make some use of it. (investors beware.)

if you take two sheets of glass they "appear" not to be attracted to each other.
But when you drop the ambient pressure significantly enough the relative attraction between the glass increases. The glass has within it a significant vacuum and when the ambient pressure is lowered the attraction to each other increases...
My thoughts....
Vacuum is by nature attracted to itself.....is the thinking