Macro View Makes Dark Matter Look Even Stranger | Universe Today
Categories: CosmologyDark Matter

Macro View Makes Dark Matter Look Even Stranger

We know dark matter exists. We know this because without it and dark energy, our Universe would be missing 95.4% of its mass. What’s more, scientists would be hard pressed to explain what accounts for the gravitational effects they routinely see at work in the cosmos.

For decades, scientists have sought to prove its existence by smashing protons together in the Large Hadron Collider. Unfortunately, these efforts have not provided any concrete evidence.

Hence, it might be time to rethink dark matter. And physicists David M. Jacobs, Glenn D. Starkman, and Bryan Lynn of Case Western Reserve University have a theory that does just that, even if it does sound a bit strange.

In their new study, they argue that instead of dark matter consisting of elementary particles that are invisible and do not emit or absorb light and electromagnetic radiation, it takes the form of chunks of matter that vary widely in terms of mass and size.

As it stands, there are many leading candidates for what dark matter could be, which range from Weakly-Interacting Massive Particles (aka WIMPs) to axions. These candidates are attractive, particularly WIMPs, because the existence of such particles might help confirm supersymmetry theory – which in turn could help lead to a working Theory of Everything (ToE).

According to supersymmetry, dark-matter particles known as neutralinos (aka WIMPs) annihilate each other, creating a cascade of particles and radiation. Credit: Sky & Telescope / Gregg Dinderman.

But so far, no evidence has been obtained that definitively proves the existence of either. Beyond being necessary in order for General Relativity to work, this invisible mass seems content to remain invisible to detection.

According to Jacobs, Starkman, and Lynn, this could indicate that dark matter exists within the realm of normal matter. In particular, they consider the possibility that dark matter consists of macroscopic objects – which they dub “Macros” – that can be characterized in units of grams and square centimeters respectively.

Macros are not only significantly larger than WIMPS and axions, but could potentially be assembled out of particles in the Standard Model of particle physics – such as quarks and leptons from the early universe – instead of requiring new physics to explain their existence. WIMPS and axions remain possible candidates for dark matter, but Jacobs and Starkman argue that there’s a reason to search elsewhere.

“The possibility that dark matter could be macroscopic and even emerge from the Standard Model is an old but exciting one,” Starkman told Universe Today, via email. “It is the most economical possibility, and in the face of our failure so far to find dark matter candidates in our dark matter detectors, or to make them in our accelerators, it is one that deserves our renewed attention.”

After eliminating most ordinary matter – including failed Jupiters, white dwarfs, neutron stars, stellar black holes, the black holes in centers of galaxies, and neutrinos with a lot of mass – as possible candidates, physicists turned their focus on the exotics.

Ongoing experiments at the Large Hadron Collider have so far failed to produce evidence of WIMPs. Credit: CERN/LHC/GridPP

Nevertheless, matter that was somewhere in between ordinary and exotic – relatives of neutron stars or large nuclei – was left on the table, Starkman said. “We say relatives because they probably have a considerable admixture of strange quarks, which are made in accelerators and ordinarily have extremely short lives,” he said.

Although strange quarks are highly unstable, Starkman points out that neutrons are also highly unstable. But in helium, bound with stable protons, neutrons remain stable.

“That opens the possibility that stable strange nuclear matter was made in the early Universe and dark matter is nothing more than chunks of strange nuclear matter or other bound states of quarks, or of baryons, which are themselves made of quarks,” said Starkman.

Such dark matter would fit the Standard Model.

This is perhaps the most appealing aspect of the Macros theory: the notion that dark matter, which our cosmological model of the Universe depends upon, can be proven without the need for additional particles.

Still, the idea that the universe is filled with a chunky, invisible mass rather than countless invisible particles does make the universe seem a bit stranger, doesn’t it?

Further Reading: Case Western

Matt Williams @https://twitter.com/storybywill

Matt Williams is the Curator of Universe Today's Guide to Space. He is also a freelance writer, a science fiction author and a Taekwon-Do instructor. He lives with his family on Vancouver Island in beautiful British Columbia.

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  • Nice article and thought provoking comments (with insightful commentary from Steve). Reminds me of my best times with UT. LC where are you - I hope you are well.

    It seems to me that with a greater undstanding of thr interplay of Bosonic matter (light / force carriers) and Fermionic matter (baryonic matter) we may one day solve the enigma of galactic rotation rates and cosmic expansion/acceleration. It strikes me that gravity waves have not yet been conclusively observed although there seems to be strong anecdotal evidence thus far.. Also scientists have yet to conclusively identify a graviton or explain precisely the speed at which gravitational force may travel.. I have heard many state it travels at the speed of light but I am left scratching my head at the gravity/light conundrum inherent in GR and SR...

    • You and me both! Have you read any of the recent research that'd suggests that gravity may in fact be a result of quantum entanglements?

      • No not really - Being only a science admirer, I rely on great sites like UT to bring forth the most exciting and groundbreaking research - I look forward to more great articles! Thanks Matt.

  • 'We know that dark matter/energy exists' because if it doesn't then the theories fall apart.
    Might it not be better to assume that it is the current assumptions wherein the problems exist and re-structure from there ?

  • I think "we know dark matter exists" overstates the present status of our science. We know that our current list of standard model particles doesn't account for the mass and dynamics of galaxies. We also don't have a good explanation for why the Universe expands, nor why its expansion is accelerating. That is the reason for the using the word 'dark' - we do not really understand (yet) what is going on out there.

    Turning that into "because we can't explain this, therefore we have discovered a mysterious something" is a logical fallacy.

    • Those words were not meant literally. They were meant to convey the scientific quandary we find ourselves in, which is that either space is filled with an invisible, mysterious mass, or we need to seriously rethink our understanding of it.

  • Ahem.. that is to sway... that either the universe is missing 95.4% of its mass OR perhaps we've somehow miscalculated or not properly included all the effects of quantum entanglement or 'strange action' at a distance? i.e. We live in a 'sticky multiverse'?

  • There is no Dark Matter the so called Missing 95.4% is all within the black holes in the centre of all the galaxies black holes are far more dense than we give them credit for and there is a weight gravity equilibrium throughout the cosmos why complicate this by inventing dark matter it makes more sense without it....KISS also the Universe is expanding because gravity from other Universes are pulling each other together which I believe will continue until they collide ...then BANG the whole thing starts again...:) B Crane

    • The pattern of it's dispersion through the Cosmos is easily seen indirectly in the form of space/time distortion and modeled as halos surrounding galaxies and clusters there-of. The centralized gravity of much more massive SMBH's wouldn't fit the observations. It's not just mass, it's the distribution pattern of it that needs to 'work' as well. And per the statement about other Universe's gravity's pulling ours, it's not the matter in our Universe that's expanding, it's the fabric of space-time itself. If the gravity of other Universes outside of our own WERE pulling ours into a larger shape, there's no way multiple 'objects' could be configured outside ours in such a way as to pull it perfectly in every direction at once. Math does come into play in these theories... they're not just wild conjectures made by the uneducated.

  • In reconsidering baryonic dark matter, astrophysicists are overlooking an even simpler baryonic-matter configuration that hasn't been excluded by microlensing studies and in a form, in which, we're already very familiar:

    Helium and molecular hydrogen near absolute zero are effectively invisible if the luminous stellar metallicity 'snows out' and collects in icy chondrules within primordial gravitationally-bound 'globules' in halo orbits.

    Bok globules, 'the coldest objects in the natural universe', are visible within giant molecular clouds (GMCs) due to their gaseous stellar metallicity, and gaseous metallicity lowers the speed of sound, promoting Jeans instability, forming stars.

    So if dark, primordial globules on disk-crossing halo orbits are trapped by the mass of GMCs in which they become visible and convert to stars, then astrophysicists have things exactly backwards: outgassing Bok globules (cometary globules and elephant trunks) create and sustain GMCs, helping to trap the next generation of halo (Bok) globules until the combined stellar radiation of the emerging star cluster dissipates the gas.

    Primordial globules may explain 'reionization' of the universe if the vast majority of hydrogen and helium within pre-existing gravitationally-bound proto-galaxies spontaneously condensed into gravitationally-bound globules, beginning 150 million years after the Big Bang, with endothermic reionization of hydrogen promoting gravitational collapse by isothermally clamping the temperature to around 2000 Kelvins. This endothermic ionization mechanism which promotes nearly-isothermal gravitational instability in protostars was discovered by Richard B. Larson in 1969 (Larson, 1969, Numerical calculations of the dynamics of collapsing proto-star). Then Population III stars are merely the largest globules in the range of 100 to 300 solar masses that continued to gravitationally collapse until they formed the first stars of the universe.

    And with baryonic dark matter globules, and perhaps chunks, there never was a 'cuspy halo problem' (which should preclude WIMP models) if globules convert to stars and luminous gas in globular clusters and galactic cores.

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