What is in Space???

[Denners]

Space is determined as empty but that's judged based upon human opinions but is their nothing?? or is there gases or certain particles that our equipment just aren't advanced enough to trace??

[Strange]

Space is not completely empty. The intergalactic medium if thought the be about 10 atoms per cubic metre. The interstellar medium is about 1 atom per cm³. This is mainly hydrogen. Then there are photons, neutrinos, and other particles flying around.

[Phi for All]

Space is determined as empty but that's judged based upon human opinions but is their nothing?? or is there gases or certain particles that our equipment just aren't advanced enough to trace??

 

Space isn't empty by scientific standards. It may be thought of as empty by people who are only counting planets and stars as "non-emptiness". It depends on the context in which you're speaking.

 

I suppose it depends on what you think is important. If you're trying to land your space ship to make repairs, space will seem incredibly empty. If you're trying to beef up the shielding on your ship, you're going to find out that it's full of stuff that's trying to penetrate your hull. It depends on your perspective, like so much else.

 

Also from a scientific perspective, opinion plays a tiny part. Empirical observation, noting what actually happens in reality, that's the difference between objective science and subjective opinion.

 

Your last question needs some clarification. Are you asking whether there are elements we know about but have no way to detect, or are you talking about elements we haven't discovered yet? The idea that there is a whole bunch of answers we're completely oblivious to is a popular one. I think it gives the hope of some wiggle-room for folks who have some wild hypotheses.

[StringJunky]

Space is not completely empty. The intergalactic medium if thought the be about 10 atoms per cubic metre. The interstellar medium is about 1 atom per cm³. This is mainly hydrogen. Then there are photons, neutrinos, and other particles flying around.

Is the IGM denser than the ISM?

[DimaMazin]

Expansion of space exists. And galaxy clusters feel its force.

[Strange]

Is the IGM denser than the ISM?

 

It is supposed to be a lot less dense. Let me find a source for the numbers ....

[StringJunky]

 

It is supposed to be a lot less dense. Let me find a source for the numbers ....

In your post you have IGM as 10 atoms to 1 atom in ISM. I haven't looked but thought it would be the other way round.

[Mordred]

It is the IGM is less dense than the ISM.

 

Wiki has a handy table for the average density per ISM regions.

 

http://en.m.wikipedia.org/wiki/Interstellar_medium

 

Wiki also places the IGM approx 6 protons per m^3.

 

 

http://en.m.wikipedia.org/wiki/Outer_space

[Strange]

In your post you have IGM as 10 atoms to 1 atom in ISM. I haven't looked but thought it would be the other way round.

 

Ah, but that was per cubic metre vs cubic centimetre. In other words the ISM is about 100,000 times denser. Interestingly, even the IGM is many times denser than the average density of the universe.

[StringJunky]

 

Ah, but that was per cubic metre vs cubic centimetre. In other words the ISM is about 100,000 times denser.

Ah, I see. Nothing like using different units to make a comparison clear as mud. ;p

[Strange]

Ah, I see. Nothing like using different units to make a comparison clear as mud. ;p

 

Just trying to keep you on your toes...

[KenBrace]

Space is determined as empty but that's judged based upon human opinions but is their nothing?? or is there gases or certain particles that our equipment just aren't advanced enough to trace??

 

This might shed some light...

 

https://www.youtube.com/watch?v=-EilZ4VY5Vs

If my understanding of physics is correct then space is indeed something though not exactly what you normally think of as "something". You have to abandon all Newtonian preconceptions and way of thinking when dealing with quantum mechanics.

Edited February 6, 2015 by KenBrace

[Sorcerer]

Is space smooth or made up of discrete points a planck length in diameter?

[Mordred]

Good question, this question troubled scientists, still does. Tests are showing that space is smooth, based on how different wavelength of light and neutrinos travel through space. A lumpy universe should affect certain wavelengths more than others.

 

They found that based on QM predictions, that they could not detect a lumpy universe, based on the Planck length, etc.

 

So it's still showing as smooth. The consensus is maybe it becomes lumpy on smaller scales, which QM doesn't allow.

 

http://m.phys.org/news/2012-08-spacetime-smoother-brew-knew.html

[MWresearch]

What space is physically made out of is a mathematically abstract medium that can only be quantified in terms of dimensions: the 3 special dimensions and time, sometimes more dimensions depending on the model. In recent science, new models of space are quantized. It is projected that there exists the smallest units of space and time travelable, the Planck length and Planck Time. Though it is not proven that these quantities possess the significance they are claimed to have, quantizing space, especially using Planck units solves many problems of infinitely small objects, limits the least and most amount of energy particles can have, allows particles to cross into the event horizons of black holes and gets rid of infinitely divisible space. In that sense, space exists more like pixels on a computer.

[hoola]

what is space? space devoid of normal matter and energy is a sea of virtual particles, as shown by the casimir effect...the deeper questions are what are virtual particles made of, why are they there and how do they relate to normal matter and energy ?

[Graeme M]

I know I am gonna regret asking this question, but hey. I always understood 'space' to not be a thing as such - that is, the various physical particles that make up the universe at either macro or micro scales are simply there. For example, the 'space' between earth and moon is just that - space, or distance. There may be all sorts of other things in that space, such as tiny particles and of course various energies. But they are discrete things, space is not.

 

However the sense of some of the above replies suggests it IS a thing, eg a 'sea of virtual particles'. I guess I don't grasp that idea due to having a limited understanding of the physics of it all. But am I am to understand from those replies that yes, space is a thing, as opposed to being just... well... space?

[Mordred]

Actually, the way you described it is accurate. Space is volume filled with the energy contents of the universe. This includes virtual particles.

[GeneralDadmission]

 

Ah, but that was per cubic metre vs cubic centimetre. In other words the ISM is about 100,000 times denser. Interestingly, even the IGM is many times denser than the average density of the universe.

 

So the average density of the universe factors DM in? Does that imply DM is in a low mass-high density state?

Actually, the way you described it is accurate. Space is volume filled with the energy contents of the universe. This includes virtual particles.

 

Could virtual particles be described as the potential density of the universe?

Edited February 26, 2015 by GeneralDadmission

[zapatos]

Expansion of space exists. And galaxy clusters feel its force.

Since you say a galaxy cluster 'feels' the force of expansion, that force is something that should be able to be measured. I would also take that to imply the force could move the galaxy through space, while my understanding is that the galaxy clusters are not moving through space due to expansion.

[Mordred]

Look at expansion as an ideal gas relationships. All particle and force interactions contribute to the energy density to pressure relations described by the ideal gas laws.

 

Dark energy being w=-1. Negative vacuum. Vacuum is a pressure term.

 

Matter doesn't exert a measurable pressure, neither does dark matter. However local gravity affects exert pressure via the stress energy tensor.

 

 

http://en.m.wikipedia.org/wiki/Equation_of_state_(cosmology)

 

Here is a basic article I wrote

http://cosmology101.wikidot.com/universe-geometry

page two with the distance to FLRW metrics in 2d,3d,4d

http://cosmology101.wikidot.com/geometry-flrw-metric/

 

I mentioned the stress energy tensor of the Einstein field equations.

 

http://en.m.wikipedia.org/wiki/Stress%E2%80%93energy_tensor

 

Notice the pressure and energy density terms in the matrix.

 

 

 

[latex]T^{\mu\nu}=(\rho+p)U^{\mu}U^{\nu}+p \eta^{\mu\nu}[/latex]

 

http://www.th.physik.uni-bonn.de/nilles/exercises/ss04/gr05.pdf

 

for the metric tensor portion above.

 

http://en.m.wikipedia.org/wiki/Metric_tensor_(general_relativity)

 

Virtual particles contribute in the same fashion. If you are at a state of thermal equilibrium and in a state that can be completely described as a vacuum the last formula on the wiki ideal gas law link can be used. Ie nothing but virtual particles as one example.

See scalar modelling

 

http://en.m.wikipedia.org/wiki/Equation_of_state_(cosmology)

Edited February 26, 2015 by Mordred

[hoola]

do the galactic clusters "feel" the force? Isn't it the space that is expanding, and carrying the clusters away from each other, like moving sidewalks. If the rate of expansion doesn't change, per galaxy, no force is felt by anything, right? Space is the active element...and wouldn't the speed of expansion depend on the amount of curvature?

[Mordred]

Ps the Higgs field also uses the scalar modelling formula (derivitive of)

do the galactic clusters "feel" the force? Isn't it the space that is expanding, and carrying the clusters away from each other, like moving sidewalks. If the rate of expansion doesn't change, per galaxy, no force is felt by anything, right? Space is the active element...and wouldn't the speed of expansion depend on the amount of curvature?

Pressure is force per volume. So yes it's the force exerted by pressure on galaxies.

 

Curvature is an energy density pressure distribution relation curve.

 

Gravity can only affect mass in order to have mass you need energy/mass density. So gravity can only affect particles as energy is a property of particles.

When you think about the following statements.

 

1) mass is equivelent to energy (e=mc^2)

2) energy is a property of particles.

3) gravity only affects mass

4) space time is any metric coordinate system that includes time as a coordinate.

 

The statement "space time curvature is a geometric coordinate descriptive of the influence gravity has on the particles that occupy the volume of space" becomes apparent.

(PS, all the four forces are described in geometric interaction relations.) Hence the importance of differential geometry in physics.

 

 

The term space itself is just the amount of volume.

Edited February 26, 2015 by Mordred

[Robittybob1]

Pressure is force per volume.....

I thought pressure was force per unit area.

[MWresearch]

However, there are problems with using both relativity and higgs fields. If you explain gravity through bosonic interactions, then there is no need for curvature. Yet, the equations in special and general relativity remain extremely accurate when treating time and space as dimensions with changing metrics. The combination of relativity and quantized bosonic models of gravity have not been completed.

 

You also stated the topography of the universe as a function of energy density. While it may make sense at first when you consider that matter and energy appear to distort space, those distortions are only local. They are not the inherent curvature of dimensions and their measurement depends on the frame of reference. A spherical universe would imply non-local effect on the non-orthoganlity of dimensions, independent of position and time. This difference is important because in a universe distorted by a large amount of mass, emitted light beams in opposite directions will not necessarily converge.