What is the density of space?

[brodykade]

Is there matter in every cubic foot?

 

[lunatio_gordin]

"Space doesn't have a density. Space doesn't really exist, or, perhaps more accurately, space is the absence of other things. One can't grab a handful of space and measure any properties of it."<br />Space is a Vacuum.

 

[igorsboss]

"Space doesn't have a density. Space doesn't really exist, or, perhaps more accurately, space is the absence of other things. One can't grab a handful of space and measure any properties of it."<br /><br />Space has the property of size. Space doesn't necessarily have anything in it, so yes, it may be a vaccuum.<br /><br />But even if it has nothing in it, it still has a density. The density of a perfect vaccuum is simply zero kg/m^3.<br /><br />But that wasn't the question... The question is whether every cubic foot of space had at least some matter in it.<br /><br />Somewhere across the universe, there might be a cubic foot which becomes a perfect vaccuum, and then a moment later, it becomes occupied by something. However, demonstrating it may be infeasable.<br />

 

[lunatio_gordin]

heh, I guess zero isn't always neglegible. <br />perhaps i should elaborate: A "perfect vacuum" is an area of space where there are no atoms or subatomic particles at all.

 

[brodykade]

In every vacuum, place or plane of space...is there always energy or a force acting?

 

[lunatio_gordin]

Well, there's a theory about "Vacuum energy", but this is pretty well disputed, so i'd have to say unknown at this time, though i can't answer this one off the top of my head.

 

[brodykade]

would you mind detailing the theory a bit for me?

 

[lunatio_gordin]

http://www.ldolphin.org/energetic.html <br />first page of the google search. this place seems to explain it well.

 

[brodykade]

Thanks for your thoughts and information.<br />Happy Trails.

 

[igorsboss]

<font color="yellow">In every vacuum, place or plane of space...is there always energy or a force acting?</font><br /><br />Energy is the ability to do work, which is force times distance. Force is mass times acceleration. Hence, the only way to observe Force or Energy is to observe its effect on some mass. But if you have mass, then you don't have a perfect vaccuum!<br /><br />However, there are force fields everywhere. Those fields are just unphysical mathematical models which predict what would happen to a particle if it were placed in such-and-such a position. But that doesn't imply that there actually is a particle there.<br /><br />Gravitational Force Field: If I drop an apple, I predict it will fall, even though I have no apple to drop just now.<br /><br />Gravitational Force, Gravitational Potential Energy: Look! That apple accelerate as it falls!<br /><br />Space is mostly empty. Density is an average quantity. If your box is big enough (ie. a cubic light century), there will always be something in the box. However, if your box is small enough (ie. a cubic plank length), there will almost never be anything in the box!<br /><br />The question is this: Is one cubic foot a big enough box to ensure that something (which has mass) is always in the box?<br /><br />My guess: Probably not. My proof: I have none at this time.

 

[majornature]

Great argument that space has density but also consider that space has mass and volume. It doesn't say anything about space being empty. The definition for Space is the expanse in which the solar system, stars and galaxy exist; universe. <br /><br />So is space really empty as we see it? <div class="Discussion_UserSignature"> <font size="2" color="#14ea50"><strong><font size="1">We are born.  We live.  We experiment.  We rot.  We die.  and the whole process starts all over again!  Imagine That!</font><br /><br /><br /><img id="6e5c6b4c-0657-47dd-9476-1fbb47938264" style="width:176px;height:247px" src="http://sitelife.space.com/ver1.0/Content/images/store/14/4/6e5c6b4c-0657-47dd-9476-1fbb47938264.Large.jpg" alt="blog post photo" width="276" height="440" /><br /></strong></font> </div>

 

[lunatio_gordin]

the way we're using "space" right now is more of a "Vacuum in which everything exists." we're sort of using space to describe the unoccupied regions of the universe.

 

[igorsboss]

<font color="yellow">consider that space has mass and volume</font><br /><br />I would say:<br />* Space has volume.<br />* Space may contain mass.<br />* Density models how tighly mass is packed into space.<br /><br />This is, of course, an overly simplified view.<br /><br />Space also exists in combination with time. That is to say, that two of the properties of space are:<br />* Volume, which controls how much stuff may be contained, and <br />* Time, which controls how rapidly the contained stuff vibrates.<br /><br />Mass has different properties<br />* It behaves as a multidimensional wave of stuff, with a particular frequency<br />* It demonstrates inertia, a resistance to being accelerated<br />* It warps the space around it<br /><br />The mystery is, what is the stuff that vibrates? It isn't Ether. It is probably tiny little whirlpools of energy called strings, each vibrating with more than 4 degrees of freedom.<br /><br />But the simplified view is sufficient for our present needs.

 

[rickstine]

Space has no actual time or any end it has no real shape or size.Space is a voide.Elements do exist,but you can't just measure the amount.So really one def.of space can't summeries it at all.<br />

 

[nexium]

The following is my educated guess: At any instant, a typical cubic foot of space has no mass; but the particles are fast moving, so it would be rare to have zero mass for a whole second, especially in our solar system, where the density of space is usually several times higher than in the voids between the galactic groups.<br /> Perhaps, one gram per cubic kilometer occurs in the least dense regions of the Universe. That would be a density of 10E-15 compared to water = water is a thousand times a million times a million more dense than 10E-15.<br /> Perhaps someone can estimate the average mass of virtual particles per cubic foot. I have not seen a guestimate. Could virtual particles account for the missing mass? I should think each virtual particle has mass, and thus gravity, while it lasts only a picosecond typically. I also have not seen an estimate of how long a virtual particle lasts.<br /> It is thought that photons/nuetrinos are very numerous, so a cubic foot with zero photons/nuetrinos for even a picosecond may be very rare. Some kinds of nuetinos are though to have a very small mass. Neil

 

[le3119]

The vacuum is nearly empty, but the atoms and virtual particles passing through it do so at a high velocity, therefore the kinetic energy is high but the vacuum is rather cold, close to Absolute Zero.

 

[emperor_of_localgroup]

For mass-density space must have mass (material). But at this time we do not know what space is made of. It sure doesn't have convetional mass we are accustomed to. This density is measured as Kg/m^3 (Kg/cubic meter).<br /><br />Does space have other form of mass? We dont know.<br /><br />If Zero Point Energy is correct, we may be able to describe density of space as J/m^3 (Joules/cubic meter or eV/m^3, i.e. energy/cubic meter).<br /><br /> <div class="Discussion_UserSignature"> <font size="2" color="#ff0000"><strong>Earth is Boring</strong></font> </div>