Physics

Understanding Dark Matter



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Most of us never think about it or even know it exists, but it's everywhere! Billions upon billions of unseen particles that are constantly passing through us and everything that we see in the physical world, yet we can't see or feel these particles. It is the backbone in which all other luminous matter in the universe rests upon. What is it? It is dark matter. In fact, there are two unseen forces that scientists believe we can't see and they are the most powerful forces at work in the universe: dark matter and dark energy.

So what is dark matter and dark energy? First, it must be stated that scientists have searched for nearly 100 years, yet have no conclusive proof that these forces exist. So how do they know that these forces are out there? Because of their effect on luminous matter. Scientists cannot observe them directly so they must speculate. Dark matter makes up about 90% of known space. When you look into space, even with all of the billions upon billions of stars, there is far more space than physical matter. Dark matter is what scientists believe is giving structure and support to all matter in the universe but dark energy may eventually tear the universe apart. Paradoxically, right now dark energy is helping, along with gravity, to hold everything together. But that is changing. Titanic opposing forces working against each other? Perhaps.

Let's look more closely at dark matter. It affects the speed of galaxy clusters. What some scientists have observed in galaxies is that even with the amount of mass they possess, there is a force keeping their rotation speeds constant so that the galaxies don't break apart and fly off into space. Hundreds of galaxies have been observed that rotate far too quickly for their size and mass but are still being held together in place. So, scientists have concluded that this phenomenon is dark matter. Dark matter creates the structure of the universe behind the scenes on a magnificent scale! Dark matter gravitationally attracts normal, or luminous matter, and it is this luminous matter that astronomers see that forms the vast walls of galaxy clusters.

Dark matter is a web-like framework, or scaffolding as some would say, that normal matter can attach itself to and clump together to form the vast cosmic structures and objects that we see. It is the unseen, skeletal backbone of the universe. Scientists have come up with very interesting theories as far as what kinds of objects could be made of dark matter. Black holes have been proposed as dark matter objects, and also dark stars. Dark stars are dying and dead stars. These would be objects such as neutron stars, white dwarfs, black dwarfs and brown dwarfs. Brown dwarfs have many characteristics that are similar to the planet Jupiter. Dark matter objects can also come in the form of M.A.C.H.O.S. M.A.C.H.O.S stands for Massive Astrophysical Compact Halo Objects. Dark Matter also consists of weakly interacting, massive sub-atomic sized particles known as W.I.M.P.s. So, dark matter can consist of objects from one extreme of the cosmic spectrum to the other.

Dark energy, on the other hand, is what is pulling everything apart and scientists believe that eventually it will cause the universe to end in darkness and ice! The strange thing is that while the galactic structures of the universe are organized and held together while they are moving, they are also flying away from each other at faster and faster speeds and dark energy is the force behind the eternal expansion of the universe.

The activity of the galaxies in the universe suggest that the universe is "open" in that it will expand forever rather than contract and collapse which is what scientists once thought. This effect may be caused by what some scientists mystically speak of as The Great Attractor. Scientists have known for years that something seems to be pulling the galaxies in our local group and even our Virgo supercluster toward itself at amazing speed. A huge swath of space that includes the Milky Way and other super-clusters of galaxies is flowing towards this mysterious, gigantic unseen mass, The Great Attractor, which is 250 million light years away.

The gas and dust in our Galaxy obscures the light from The Great Attractor, and it is outshone by the stars and other objects in our Galaxy. Based on the differing velocities at these scales, the unseen mass inhabiting the voids between the galaxies and clusters of galaxies amounts to perhaps 10 times more than the luminous matter that we can see. Recent findings suggests these motions are the result of gravitational forces from two things: The Great Attractor, and a conglomerate of galaxies far beyond it. Could dark energy also be involved? Is The Great Attractor dark energy, or is it a dark matter object? Could it be a combination of both? I don't think these questions are all that far-fetched!

The universe as we see it contains only the stable relics and leftovers of its beginning. The unstable particles have decayed away over time but the structure of space remembers all the vast webs of particles and forces we can no longer see around us. Dark matter is mostly made up of these decayed particles and dark energy. The universe is not slowing down while expanding but speeding up which seems unnatural and strange. The repulsive effect that dominates gravity is dark energy. The amount of mass and matter that dominates the volume of space is dark matter. These two forces, scientists believe, help lay the foundation and hold together the cosmic structures we see. One the Nurturer and the other the Destroyer of the luminous matter in our universe.

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