Ultra vacuum.

You have some strange thoughts Oomsarael. Some thing must give a true vacuum is is a very powerful force to over come. My guess is either the sphere collapses or the piston gives up. A vacuum can never be perfect because particles can always travel through. As to anti matter how does this connect with a vacuum? Too much to contemplate right now. Good to see you are still out there. How is you digging going have you got started yet?

Hi BW. Glad to be back knowing I was missed!

I don't know much about vacuums I must confess. All I can guess that it is not the vacuum that will make the sphere to collapse but the air pressure around it, right... I was just wondering, if you have an empty space that expands even more how it will affect the reading of that vacuum. In other words does that reading have a limit? The limit could be when the air pressure around the enclosed space are high enough to make whatever sphere is used collapse... Imagine the sound of such an implosion. Isn't that what makes the sound of lightning thunder? The lightning burns and displace the air, then after the electrical discharge the air around rushes back into the empty space and makes the thundering sound. As far as anti-matter goes, I don't really know what it is but I read somewhere that it got something to do with black holes. I don't think that it is something we would want with us here on earth...

Have I started digging yet? No... But after my neighbour had an outburst about me grinding in my backyard I had to go work in an industrial area. I really would like to work from home rather, so I am really thinking. Maybe I could use a vacuum between a double wall all around my workshop... That will kill the noise!

Hello (01:30 BST) Yes the air pressure on the outside will crush with an equal force to the hardness of the vacuum. (the harder the vacuum the better) It is like when a can gets crushed by deep water pressure. If you try to force the situation were by a greater degree of suction is applied then some thing just has to give either the sphere or the piston a vacuum is non elastic. Take a plastic bottle and pour in so boiling water (make sure it can stand the heat) then carefully pour out the water and fasten the top now cool it under cold water it will crush in by the exact volume of air displaced by the removal of the hot air. Both the out side atmospheric pressure and the partial vacuum act together because of the un equal pressure gradient. the greater this is the harder the crush effect. So in your case it would indeed be a very violent event.

Ref the lightning situation it is both the very rapid heating and expansion of the air and its rapid cooling that make for the thunder. It is then the difference in the speed of light versus the speed of sound that makes for the delay in hearing thunder occurring at a distance you can count five seconds per mile of distance. 3 seconds per kilometer

You will no get more than 100% vacuun, you can not take anything to nothing , but to pull the piston you have to be strong enougth to overcome the atmosferic presure about 10.13 N per each cm2 of your piston.

CIRO

Yes, there is a very practical limit to the vacuum you can create. The offset of the local atmospheric pressure is that limit, so really the pressure is not that great on the outside of a vessel that has a 100% vacuum. My work place is at about 5000' above sea level so a "perfect" vacuum here is just under 25" Hg or 12.70 psig. After you create that much vacuum in a vessel you could rig up all the crazy contraptions you want and you will get no more than 25".

WyoPatriot

A perfect vacuum, assuming you could make one, is simply a space with no atoms, molecules, ions, etc. 'flying' around. Adding more volume to that space changes nothing in the original space.

If you remove all the air then in theory you have achieved a perfect vacuum- If I remember correctly that can only be done at absolute zero -that is the stopping of all atomic movement , aside from the collapse of the steel from the inward molecular migration and the outer atmosphere pressure the question of the creation of the vacuum by use of a pump seems too basic -that kind of pump efficiency don't exist so don,t worry about it unless you go into outer space!

Also remember that absolute zero will give you one bad case of frostbite so be careful

I understand that it is in the practical hard to remove all the molecules of gas ot of a vessel by means of a pump. But what if you have a very smooth piston top inside a very smooth cylinder at top dead center. When you pull on that and there are no leaks surely it would be a very close to nothing in that space.. I am yust thinking of all the metal atoms on the surface.... They would come loose and be floating around in the space. So, is it then really IMPOSSIBLE to have a space with absolutely nothing in it??? As far as the strenght of the vacuum, I understand now that to increase the strenght you will have to increase the pressure around it, but with the bigger space of vacuum, you will have a greater capacity of potential energy stored. Thanks for clearing this out guys. As far as anti -matter goes I will search CR4 and do some reading.

If you continue to increase the volume (by pulling the piston further out), then you will get closer and closer to a "perfect vacuum" in the sense that the few gas molecules present will be spread out over a larger volume. In practice, we can never achieve a perfect vaccum. Not even intergalic space is completely empty.

But hypothetically speaking, even if we could achieve a perfect vacuum, increasing its volume would not improve the vacuum. You can not have "less than zero" gas molecules in the container. By the way, Brainwave's insinuation that the sphere must collapse is nonsense. If the walls of the sphere are thick enough, it could withstand any outside pressure applied to (short of the pressure exerted by a neutron star or black hole). And regarding your last question: no, this has nothing to do with anti-matter.

There is a way to get a perfect vacuum. It happens in a liquid helium dewar. The inside tank gets very cold from the liquid helium so the remaining air from the evacuated chamber freezes to the inner wall. After a while all of the air is frozen to the tank, and none is left to bounce back and forth to the outer wall. The dewar still gains some heat from the neck, so the helium still boils off in a few weeks.

You would never find a piston that would not leak air inside, though.

Cryo pumps work that way. Whenever a particle strikes the cryo array, it loses its kinetic energy and sticks to it.

Yeah, It seems that when the required vaccum is approaching zero the wall thickness approaches infinty.

But what is this caption???

"A closed mouth gathers no foot"

I think it is "A closed mouth gathers no food"

But what is this caption???

"A closed mouth gathers no foot"

I think it is "A closed mouth gathers no food"

LOL! Both statements are true.

Hi Oomsarel. Sticking to your original thought experiment (and neglecting to admit certain elements of practical reality), when you pull on the piston you will simply have more volume containing 100% vacuum. When you push the piston back, you will have less volume containing 100% vacuum. Either way, you have 100% vacuum.

In practice your vessel's walls will outgas for a time, introducing a small amount a gas into the vessel, and even the best seals leak a little. To maintain the vacuum, you will need to continually pump the volume of your chamber. At those low pressures, pumping becomes something of a statistical process as flow in the conventional sense ceases. This is because the mean free path of the gas molecules approaches that of the dimensions of the vessel itself. Chances are (good chances, like close to 100%) there will always be a few rogue gas molecules/atoms which haven't yet found their way into the (typically a cryo) pump, so your vacuum will never be entirely perfect.

In the quantum sense, you will never, ever have a perfect vacuum, as space itself is seething with virtual particles which flicker in and out of existence continually - including anti-particles. But they don't persist. Then you have the Higgs field and related esoterica which permeates spacetime. "Empty" space is a Classical myth.

In the quantum sense, you will never, ever have a perfect vacuum, as space itself is seething with virtual particles which flicker in and out of existence continually - including anti-particles.

Good point. But note that these transitory virtual particles (the "quantum foam") occur at all points in space-time, whether or not a vacuum exists there. This is what I meant when I replied that Oomsarel's thought experiment has no relation with anti-matter.

Answer #4 and #5 nail it.

The forces of "absolute" vacuum in engineering terms is only equal to the air pressure surrounding it. Those are not large forces when you consider 12 to 15 PSI versus 2000+ PSI in a compressed gas cylinder.

Except for a few mercury vapor atoms in your average mercury barometer you have pulled essentially a perfect vacuum, and that is supported by a glass wall possibly only .05 inches thick. Air pressure will only support 30 inches or so, and a longer tube is equivalent to pulling your piston out. It still only has the 15 psi, yet the evacuated volume has increased.

Why antimatter? A vacuum is only the absence of matter. I think you are musing too deeply.

Ok. I realize that to comment on antimatter was a silly thing to do, wasn't thinking clearly... I did some reading on antimatter and found it very interesting. Thanks.

With Steel you can create at vacuum to some level which depends on strength of the vessel and the force you apply. Suppose if we use a stronger vessel and greater force we can create more vacuum.

I don't think that the absence of air means that there is nothing inside. Even if you remove air completely then also, I think, electromagnetic wave propagates in side. What is making them to propagate? There some media through which it is propagating that is other than air. What is that media? I guess those are free electrons protons and neutrons without any atomic structure.

What do you say?

I welcome other members also to comment on my idea...

You can have an EM field without matter. You are still not getting any more "pressures" or forces of any significance. The pressure you observe is only 1 atmosphere, and that is because of the air pressure around the vacuum you created. If you dropped your vacuum chamber to the bottom of the ocean then you would have very significant forces. Put it in space and the forces go towards zero.

Think about it, what is trying to fill the void? It is only the air at one atmosphere around you. It is not very significant from a strength of materials point. A diver going down 32 ft experiences the same pressure change.

I understood that you are adding the topic of relative pressure.

Ok, If we take our vessel to the space, what is the guarantee that our vessel if completely empty with out any air molecule? There might be another place in space where the pressure is relatively lower than your current position in space.

I strongly belive that there is something which is beyond our knowledge that is letting the EM waves to propagate space. Since EM waves are related to electric charge,I think that the space is packed with elements like electrons through which EM wave is propagating.

EM waves propagate in free space in the form of photons. Other particles are not required. Some interesting questions might be "why is the speed of light what it is, and not faster or slower?" "What is it about space that limits the maximum velocity of light?" "What is an electric field (in the deep sense)?" "What is electric charge?"

Btw, your avatar is the same one used by English Rose - a delightful member of this forum whose wit and wisdom is always appreciated...

It is not same avtar... Just now I checked it.

Yes, his threads seems to be interesting.

You are correct, there are so many things that are yet to be discovered.

May be all our engineers and scientists are satisfied with present knowledge on EM wave propagation.

Not all.

I am sorry. Not all engineers and scientists.

There a thing called 'ether' which is there in the gaps between atoms or molecules.

Yoga experts believe that, ether is more subtle than air and it is present even when it seems that there is nothing.

The existence of the ether has been debated on and off for over a century. My opinion (and it is only an opinion) is that spacetime needn't be permeated by a "something" in addition to spacetime that allows for EM waves to propagate, but that this "something" - an ether, if you will - is not in addition to spacetime but is intrinsic to the fabric of spacetime itself.

Look into 'ether' on Google or one of the other search engines and review its scientific history.

The comments about how difficult it is to achieve a perfect vacuum are right, if you look at specs for vacuum equipment in the 10-9 torr range they are defined not by pressure but by their leak rates. Cleanliness is paramount, even a stray fingerprint on a component in hard vacuum significantly increases the pumping time. Once at vacuum, the materials used to make the chamber will continue to outgass or give off molecules hence the need to continuously pump with a cryo pump.