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Offline StealthPhy

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The nature of dark matter?
« on: 04/10/2015 08:12:23 »
I have an idea on the nature of dark matter which I wanted to share on this forum. I do not have the capabilities to test the idea myself, having not been a professional physicist since completing my PhD 22 years ago, so I’d really welcome any comments or feedback from the scientific community on whether the idea has any merit. I’ve described it below, starting with the background information that the idea is based on.

Dark matter is the name given to the mechanism needed to explain the large scale gravitational behaviour of the universe. For example, the rotational dynamics of spiral galaxies imply that there is a halo of “dark matter” that extends beyond the visible limits of each spiral galaxy. The mass of this halo would need to be many times greater than the mass of the galaxy it surrounds to explain the observed rotational behaviour of the galaxy. The halo’s only effect is its gravitational pull – it has not been observed by any mechanism other than the effect its gravity has on the galaxy it surrounds.

Similarly, observed gravitational lensing of light by galaxies is greater than would be caused by the mass of “visible” material contained in the galaxy – again implying an abundance of dark matter around the galaxy exerting its gravitational influence.

As far as I’m aware, two main theories are currently being pursued to explain these effects. The first assumes the existence of dark matter – a type of matter particle which does not interact with other material in the universe in any way except through its gravitational influence. The second is a modification of Newton’s Law of Gravity, proposing that the law requires a correction factor that becomes measurably large at very large distances.

I’d like to propose a third line of enquiry and would welcome the opinions of the scientific community on whether it is worth pursuing.

The theory of general relativity states that gravity is the result of the curvature of spacetime in the vicinity of massive objects where the magnitude of this curvature is proportional to the mass of the object. An object distorts the spacetime around it so that other objects moving through this curved space appear to be deflected from a straight path. This deflection is attributed to the force we call gravity.

So, for example, the Earth moves in a straight line through the curved spacetime surrounding the Sun, ending up in the same place it started after one year. This is similar to a person walking in a straight line on the curved surface of the Earth ending up where they started having walked all the way around the Earth. As far as I know, physicists have not yet described the actual physical mechanism that causes a massive object to bend the spacetime around it.

The implication of the previous paragraph is that in the absence of any objects - in empty space - spacetime is not curved. Instead it is completely undistorted and “flat”. Objects moving through empty, undistorted spacetime are not deflected and continue to move in a straight line.

My suggestion is that this may not be the case – that empty space can contain tiny ripples of spacetime distortion, remnants of the slightly inhomogeneous structure of the early universe immediately after the big bang. These ripples exist throughout the universe but occur at higher concentrations around collections of matter – around galaxies. 

The effect of each individual ripple is immeasurably small – smaller than the gravitational effect of the smallest sub-atomic particle. But when they occur in large numbers around galaxies their aggregate effect – integrated over intergalactic distances – is large enough to explain the effects attributed to dark matter.

This “ripple theory”, proposing the existence of tiny distortions in spacetime even in the absence of matter, could perhaps explain the observed effects of gravity without visible matter to cause it. It relies on breaking the causal relationship of massive objects causing the curvature of spacetime. In fact it may reverse it – distorted spacetime creates the energy needed for the existence of massive objects – but that is a separate discussion in itself.

I would very much welcome the views of anyone working in this field on whether this idea is worth further investigation, or whether it has been proposed and rejected previously.


 

Online jeffreyH

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Re: The nature of dark matter?
« Reply #1 on: 04/10/2015 14:02:06 »
If there exists a hypothetical force carrier for the gravitational field it could be considered that gravity is not after all inherent to mass. Mass simply interacts with the field. In which case the ripples in spacetime could be the cause of the effects attributed to dark matter within galaxies. I am no physicist so you will need expert opinion from other sources. I do think your idea is worth pursuing though.
 

Offline unstman

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Re: The nature of dark matter?
« Reply #2 on: 04/10/2015 16:45:42 »
I do not wish to appear ignorant on the said subject, but, who is to say that Dark Energy/Matter was created by the Big Bang?

What if Dark Energy/Matter existed before, during and after the Big Bang?

What if Dark Energy/Matter was the cause of the Big Bang.

If, I am to believe, Dark Energy/Matter makes up 96% of the Universe, who is to say the creation of matter (as we perceive it) was not created by Dark Energy/Matter rather than created at a central point because everything appears to be moving away from our point in space? 

If this was the case, could this be reason to believe the creation of Multiple Universes?
 

Offline evan_au

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Re: The nature of dark matter?
« Reply #3 on: 04/10/2015 23:20:09 »
Quote from: StealthPhy
My suggestion is ... that empty space can contain tiny ripples of spacetime distortion, remnants of the slightly inhomogeneous structure of the early universe immediately after the big bang.

Most mainstream Physicists do think that "space contains tiny ripples of spacetime distortion, remnants of the slightly inhomogeneous structure of the early universe immediately after the big bang". A major part of the Plank satellite mission and ongoing data analysis is to measure the impact of these ripples on the Cosmic Microwave Background Radiation.

However, these distortions are not present in empty space, but are due to the presence of matter in the universe which was almost-but-not-quite evenly spread throughout the early universe.

Quote
These ripples exist throughout the universe but occur at higher concentrations around collections of matter – around galaxies.
While the early universe was very homogenous, as it cooled, it "clumped" into structures like atoms, gas clouds, galaxies, stars and planets. So gravitational inhomogeneity is more pronounced around galaxies.

It seems to me that this proposal is suggesting that the extent of these ripples in spacetime deviate slightly from what Newton or Einstein would calculate. This puts it in the category of "Modified Newtonian Gravity".

In any case, for a snapshot of the current list of "possibly feasible" theories for Dark Matter, have a look at: https://en.wikipedia.org/wiki/Dark_matter#Alternative_theories
 

Offline acsinuk

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Re: The nature of dark matter?
« Reply #4 on: 09/10/2015 12:27:02 »
There are lots of alternative ideas but if you magnetise a galaxy it will spin the stars without the need for dark matter.  The youtube magnoflux spin presentation demonstates the effect using a CRT or salt cell
 

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Re: The nature of dark matter?
« Reply #4 on: 09/10/2015 12:27:02 »

 

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