Cosmologists and particle physicists have over the last decade or so proposed the existence of Dark Matter. It’s so called because it cannot be seen or sensed directly. It is inferred from gravitational effects on visible matter. Together with it’s theoretical cousin, Dark Energy, the two were hypothesized to make up most of the universe. In fact, the regular star-stuff — matter and energy — of which we, our planet, solar system and the visible universe are made, consists of only a paltry 4 percent.
Dark Matter and Dark Energy were originally proposed to account for discrepancies in calculations of the mass of large objects such as galaxies and galaxy clusters, and calculations derived from the mass of smaller visible objects such as stars, nebulae and interstellar gas.
The problem with Dark Matter is that it remains elusive and for the most part a theoretical construct. And, now a new group of theories suggest that the dark stuff may in fact be an illusion.
[div class=attrib]From National Geographic:[end-div]
The mysterious substance known as dark matter may actually be an illusion created by gravitational interactions between short-lived particles of matter and antimatter, a new study says.
Dark matter is thought to be an invisible substance that makes up almost a quarter of the mass in the universe. The concept was first proposed in 1933 to explain why the outer galaxies in galaxy clusters orbit faster than they should, based on the galaxies’ visible mass.
(Related: “Dark-Matter Galaxy Detected: Hidden Dwarf Lurks Nearby?”)
At the observed speeds, the outer galaxies should be flung out into space, since the clusters don’t appear to have enough mass to keep the galaxies at their edges gravitationally bound.
So physicists proposed that the galaxies are surrounded by halos of invisible matter. This dark matter provides the extra mass, which in turn creates gravitational fields strong enough to hold the clusters together.
In the new study, physicist Dragan Hajdukovic at the European Organization for Nuclear Research (CERN) in Switzerland proposes an alternative explanation, based on something he calls the “gravitational polarization of the quantum vacuum.”
Empty Space Filled With “Virtual” Particles
The quantum vacuum is the name physicists give to what we see as empty space.
According to quantum physics, empty space is not actually barren but is a boiling sea of so-called virtual particles and antiparticles constantly popping in and out of existence.
Antimatter particles are mirror opposites of normal matter particles. For example, an antiproton is a negatively charged version of the positively charged proton, one of the basic constituents of the atom.
When matter and antimatter collide, they annihilate in a flash of energy. The virtual particles spontaneously created in the quantum vacuum appear and then disappear so quickly that they can’t be directly observed.
In his new mathematical model, Hajdukovic investigates what would happen if virtual matter and virtual antimatter were not only electrical opposites but also gravitational opposites—an idea some physicists previously proposed.
“Mainstream physics assumes that there is only one gravitational charge, while I have assumed that there are two gravitational charges,” Hajdukovic said.
According to his idea, outlined in the current issue of the journal Astrophysics and Space Science, matter has a positive gravitational charge and antimatter a negative one.
That would mean matter and antimatter are gravitationally repulsive, so that an object made of antimatter would “fall up” in the gravitational field of Earth, which is composed of normal matter.
Particles and antiparticles could still collide, however, since gravitational repulsion is much weaker than electrical attraction.
How Galaxies Could Get Gravity Boost
While the idea of particle antigravity might seem exotic, Hajdukovic says his theory is based on well-established tenants in quantum physics.
For example, it’s long been known that particles can team up to create a so-called electric dipole, with positively charge particles at one end and negatively charged particles at the other. (See “Universe’s Existence May Be Explained by New Material.”)
According to theory, there are countless electric dipoles created by virtual particles in any given volume of the quantum vacuum.
All of these electric dipoles are randomly oriented—like countless compass needles pointing every which way. But if the dipoles form in the presence of an existing electric field, they immediately align along the same direction as the field.
According to quantum field theory, this sudden snapping to order of electric dipoles, called polarization, generates a secondary electric field that combines with and strengthens the first field.
Hajdukovic suggests that a similar phenomenon happens with gravity. If virtual matter and antimatter particles have different gravitational charges, then randomly oriented gravitational dipoles would be generated in space.
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