Dark Matter

[Earl]

Could Dark matter be the mass generated by the virtual particles constantly cycling through existing and not existing hence been dark as they don't actually exist but on a cosmological scale there mass would be large

[Nexus 6]

Well what ever it is a definate explanation of what it is would be a big step in answering some questions that still need resolving

[FraserClarke]

Could Dark matter be the mass generated by the virtual particles constantly cycling through existing and not existing hence been dark as they don't actually exist but on a cosmological scale there mass would be large

But then it should be spatially homogenous across the Universe (because a virtual particle can be created at any point in space-time), not cluster like is observed.

[noakesy]

does dark matter have a speed like light ,,,

[cotterless45]

It is matter and there's a 400 times more of it than " normal " matter. It has a tangeable effect in giving more speed than expected to the edges of galaxies.It provides the "missing" mass to stars.

I think it's the physical skeletal structure/glue that holds the Universe against accelerating expansion. Wherever there is gravity there is dark matter.Perhaps it has a quantum gravitational effect.

I think we'll find out pdq it's a WIMP (Weakly Interacting Massive Particle).

[WayBig]

If it was truly dark, we'd see it....can we call it transparent matter instead...I'll start up a facebook group to get supporters for the idea and see if I can change physics!

[Earl]

But then it should be spatially homogenous across the Universe (because a virtual particle can be created at any point in space-time), not cluster like is observed.

Could you provide a link to some more info on the cluster like?

[FraserClarke]

Could you provide a link to some more info on the cluster like?

Well it has to be spatially inhomogenous, or it wouldn't have any net gravity to affect dynamics of other things -- there would be equally as much stuff pulling you to the right as pulling you to the left; and we'd all be left stuck here in the middle (as Stealer's wheel so elegantly put it).

A couple of observational points to consider;

The effect you see on the dynamics of galaxies requires a (roughly) 1/R^2 profile to explain it. e.g. Rotation curves of spiral galaxies and dark matter

The Bullet cluster is some of the best evidence for dark matter around -- try getting someone to explain that observation with MOND; Bullet Cluster - Wikipedia, the free encyclopedia

[Earl]

cheers some good reading ill work through it

[JohnnyD333]

There is something holding galaxies in place, and gravity is not it. If you take the theoretical dark matter out of the equation, galaxies would just disperse and nothing would hold together. I do like the idea of "transparent matter" lol.

[George Jones]

Could Dark matter be the mass generated by the virtual particles constantly cycling through existing and not existing hence been dark as they don't actually exist but on a cosmological scale there mass would be large

Wrong dark stuff . There is speculation that this is dark energy.

But then it should be spatially homogenous across the Universe (because a virtual particle can be created at any point in space-time)

[Earl]

Wrong dark stuff . There is speculation that this is dark energy.

I see, this would always be growing as there is ever more nothing all the time?

[Earl]

Am I correct in thinking:

a) Nothing (space) is growing at an ever increasing rate. expansion rate is not accelerating but there is constantly more to expand so more expansion occurs.

Visible Matter is always getting less due to it been converted into forms of energy.

If these are correct how massive is this?

If space is infinite then an infinite amount of space is brought into existence all the time due to it expanding.... i think i have popped a brain cell at this point.

now i see the last part of "A Universe from Nothing" in the fact that there has to be and infinite number of universes in existence and coming into existence all the time...

but if that is not the case then does not infinity exist?

all because of the Dark Stuff's.

[WayBig]

[quote=Earl_UK;179958

... there has to be and infinite number of universes in existence and coming into existence all the time...

that's one of the interpretations of superposition in quantum physics - the super imposed wave functions being the interference between 2 universes, and the interference ending when an observation is made and the wave function collapses....or something like that

[George Jones]

I see, this would always be growing as there is ever more nothing all the time?

Yes, and this together with a hand-waving argument involving the first law of thermodynamics and quantum uncertainty is a possible explanation for the acceleration of the expansion of the universe.

[Earl]

Yes, and this together with a hand-waving argument involving the first law of thermodynamics and quantum uncertainty is a possible explanation for the acceleration of the expansion of the universe.

Am i right in thinking that if infinity expands it expands infinitely all the time?

[George Jones]

Am i right in thinking that if infinity expands it expands infinitely all the time?

Only if space is infinite (open universe). Space, however, could be finite (closed universe).

Yes, and this together with a hand-waving argument involving the first law of thermodynamics and quantum uncertainty is a possible explanation for the acceleration of the expansion of the universe.

This hand-waving argument follows. It uses some maths, and should probably be binned. It also uses two letters that look very similar p and ρ, the Greek letter rho. p is pointed at the top while ρ is smooth at the top.

When a gas of pressure p undergoes a volume change ΔV, a work (energy) equal to pΔV is required. This comes from the (internal) energy E of the gas, so the energy of the gas changes by an amount ΔE. Conservation of energy gives

0 = ΔE + pΔV

Consequently, the change in energy of the gas

ΔE = -pΔV (equation *)

is negative if the gas expands. This means that the gas loses energy as it expands; this energy goes into expanding the gas.

Now consider a "material" that still obeys conservation of energy

0 = ΔE + pΔV

and

ΔE = -pΔV

as it expands, but that keeps its energy density ρ = E/V constant as it expands. Because E = ρV and energy density ρ is constant, the change in energy ΔE is related to the change in volume ΔV by

ΔE = ρΔV

Combining this with (equation *) above gives

ρΔV = -pΔV

which is only true if p = -ρ. If a material that maintains constant (positive) density expands, it must have negative pressure!

Does any such "material" exist? The quantum vacuum probably has these properties. Because of the Heisenberg uncertainty principle, the quantum vacuum has non-zero energy density (the virtual particles of the original post in this thread). Also, as the universe expands, there is more vacuum, but it's the same type of vacuum with the same energy density. Just as two gold bars have the same density as one gold bar, doubling the volume of the(quantum) vacuum doesn't change its energy density.

Putting everything together, a positive energy quantum vacuum has negative pressure, and this negative pressure repulsion causes the expansion of the universe to speed up. This is dark energy.

[GerryTheBlob]

I'm sure that once upon a time before the term 'Dark Matter' became popular the unseen material that held the universe in balance was refered to as the Ether...

[spider72]

Ether was a virtual medium, which in theory allowed light waves to propagate through vacuum of space before the nature of light was discovered and later explained by Einstein's theory of special relativity. Ether existance was disproved by The Michelson-Morley Experiment.

[GerryTheBlob]

I stand corrected and enlightened, what I'm getting at though is the term 'Dark Matter'. It does little to describe the phenomena and yet the media continue to propagate the term. I agree that 'Transparent Matter' is more like it but sadly not catchy enough for the media. I'm sure that there is a better term that this group could come up with. How say you....