I just cant imagine how vacum can really exist, please help.

[Laminal Cockroach]

how can vaccum actually exist because there just cannot be nothing somewhere, i understand the theories sometimes. but i still think that there has gotto be some kind of matter in between the particles maybe some massless particles like gluons that carry strong forces between quarks, please somebody answer

[Kristophe]

how can vaccum actually exist because there just cannot be nothing somewhere

Why not?

but i still think that there has gotto be some kind of matter in between the particles

Why?

maybe some massless particles like gluons that carry strong forces between quarks

What about outside of atomic nuclei? You'll find few gluons there.

If space is absolutely packed tight with particles, what are they moving through?

[antoniseb]

how can vaccum actually exist because there just cannot be nothing somewhere,

It really depends on what your standards are for a vacuum. If you think that the quantum foam makes space not a vacuum, then there is no vacuum. If you aren't concerned about that, but do think that photons, neutrinos, and virtual particles do count, then there are very tiny short-lived vacuums. If you count matter densities of a few nuclei per cubic centimeter as close enough, then the universe contains mostly gigantic vacuums between the galaxies.

[Laminal Cockroach]

i'm sorry but i dont understand what you mean by "If you think that the quantum foam makes space not a vacuum, then there is no vacuum" especially what you mean by quantum foam, is that something physical or virtual actually im only doin' AS levels at the moment

P.S- thaks for answerin'

[Robert Andersson]

Wikipedia: Quantum foam

[Laminal Cockroach]

Oh.... thanks Robert I think i do kindda understand now

[Enzp]

LC, without invoking quantum phenomena, if you just want to stick to conventional atoms and things, try this analogy.

You have a standard deck of playing cards and you spread them evenly out on a small table. They cover the top of the table. Now spread them out on a large table, gaps appear. Now spread them out on the floor of a gymnasium. You have mostly gaps and here and there a card. Now spread them out on the runway at a large airport. You would have to walk quite a ways between cards.

The vacuum of interplanetary space is like that airport runway. There are occasional atoms floating about, or other particles. But mostly there is empty space. That is a vacuum. There are still occasional atoms coming through now and then, but effectively there are almost none. SO it boils down to your definition of a vacuum.

Here on earth, our atmosphere is like the small table top. A lot of atoms in a small space. But in space the density trends toward zero. In any practical sense, that is a vacuum.

[antoniseb]

You have a standard deck of playing cards and you spread them evenly out on a small table.

Thanks Enzp, that's a great analogy. I'll have to use it in the future.

[Argos]

Space is full of energy. There is no vacuum in the Greek sense. Vacuum is just a displaced and misused word from an ancient epoch.

[Laminal Cockroach]

The vacuum of interplanetary space is like that airport runway. There are occasional atoms floating about, or other particles. But mostly there is empty space. That is a vacuum. There are still occasional atoms coming through now and then, but effectively there are almost none. SO it boils down to your definition of a vacuum.

Thanks that actually helps coz i always thought vaccuum is just vaccuum and nothing else i mean like ur concept of vaccuum being just large intermolecular spaces was never quite clear and so obvious to me before, but if i may also question, isnt it possible to have certain particle in place of those what we conventionally think intermolecular spaces??!!??

[Halcyon Dayz]

In physics, a vacuum is the absence of matter in a volume of space.

See Wiki article.

[Laminal Cockroach]

Yeah..... Thanks Guys

[simtom]

...I think what LC's trying to say is that what actually makes things move. For instance why does an electron move around a nucleus.. You might start saying something about forces, but have you ever thought about where these forces come from.. like gravity, it's easy to just say that every mass is attracted to other masses etc, but why? surely there are particles far smaller then quarks that we simply just don't know about.. that provide these forces.

another example is if there is nothing in a vacuum the light shouldn't be able to travel through it.. i guess what i'm trying to say is that there are definitly particles (if that's the right word for them) in any vacuum, but there are just way to small for us to actually think of them as masses, instead we just think of the way they act as a force and not realise that forces must come from somewhere also..

also sry for the bump

[Kaptain K]

...if there is nothing in a vacuum the light shouldn't be able to travel through it...

The "luminiferous aether" is so 19th century!

[Laminal Cockroach]

The "luminiferous aether" is so 19th century!

but i thought its a valid questions and more so i dont actually understand how?

[Ken G]

And keep in mind that vacuum is not really emptiness, in the sense that there are virtual particles appearing and disappearing all the time. It is empty of real energy-conserving matter, but you can violate energy conservation willy nilly on timescales shorter than given by the uncertainty principle. Check out the Casimir effect, amazing stuff.

[SolusLupus]

I have to wonder... what would happen if you could flood the universe with actual air? Let's just say that you use the same air we have on earth, minus pollution - just simple oxygen/nitrogen mix. Then you literally FLOOD the entire universe with it (let's say that you pull it out of another dimension or some other science-fictiony thingy). What would be the end result?

I find the answer hard to imagine. I mean, just the introduction of air that covers all in the universe wouldn't cause things to, say, fall - since air doesn't create gravity, right?

Or am I mistaken?

[Ken G]

All mass-energy generates gravity, air is just not very dense so you wouldn't normally notice the gravity there. But Earth's air is much denser than the critical density needed to close the universe, gravitationally. If you flooded the universe with air, you would introduce a dynamical collapse time on the order of 1 over the square root of G times the mass density, say about a month! Not a good thing.

[01101001]

[...] air doesn't create gravity, right?

Take a large plastic bag, the bigger the better. Wad it up into your hand and shake your fist. Learn how an empty bag feels -- like almost nothing. Now fill the bag with air and seal it. Shake it back and forth so it goes thump, thump. It will feel different from when it was wadded up. That difference is mainly the added inertia of the air inside the bag. The thumping comes from the air smashing against the bag as it changes directions.

Air weighs about a gram per liter. The air inside a small room weighs about 30 kg, the weight of an average 9-year-old child. Yes, it has mass. And with mass comes gravity.

[SolusLupus]

If you flooded the universe with air, you would introduce a dynamical collapse time on the order of 1 over the square root of G times the mass density, say about a month! Not a good thing.

Doesn't sound it. I must've touched on something interesting, 'cause it ALMOST went over my head. 1 over the square root of G times the mass density... G being based on what? The G of space? (Note: I'm not that well-learned in the more complicated aspects. I'm still taking algebra!)

Air weighs about a gram per liter. The air inside a small room weighs about 30 kg, the weight of an average 9-year-old child. Yes, it has mass. And with mass comes gravity.

Ahhh, right. That makes sense. I feel silly now

[Kaptain K]

G being based on what?

"G" is the gravitational constant: 6.67 x 10-11 N x m^2/kg^2

[SolusLupus]

Kaptain K, you have burst the insides of my brain. I hate you now. DARN YOU, AND DARN YOUR FRIGGIN ALGEBRA!


*cough* I'm calm now. I'll probably learn that in the physics class I'll supposedly be taking in about a year from now :P

[Ken G]

Or if you use grams and centimeters as your units, then G is about .00000007. Hang in there lonewolf, you'll soon see the power of that algebra you so readily denigrate! Take G, and multiply it by what 01101001 has told you is the density of air, which is a gram per liter, or in centimeter units, about .001. Now take the square root of the result, that is going to be roughly .000025 . Not so bad, use your calculator. Now take 1 over that number, i.e., take the inverse. You get about 4 million! That answer will be in the unit of time we're using here, which is seconds. 4 million seconds is about a month, which is very roughly the timescale for the complete collapse of your air-filled universe, because that's what the formula for gravity says. So you see, algebra is going to be really cool!

[SolusLupus]

den·i·grate
tr.v. den·i·grat·ed, den·i·grat·ing, den·i·grates

1. To attack the character or reputation of; speak ill of; defame.
2. To disparage; belittle: The critics have denigrated our efforts.


How exactly did I denigrate it? I'm just saying that my primitive mind can't handle such a complex and long equation without bursting. That's when I look at it with a cursory glance though. I can easily do the equation when I write it down and think it through

Though I will admit, sometimes I hate Algebra with the fury of 1000 suns. >.>

*Cough*

A complete collapse of the universe, eh? Sounds spiffy.

[Laminal Cockroach]

Well basically there are molecules in air and to the tinyest fraction there will gravity exerted on it right?