Dark matter and dark energy are the two most vexing problems in science today. Together they control the universe, and contain 96 percent of all the mass and energy in it - but no one knows who is who
By: Alon Zaevi, Israeli Astronomical Society
The dark matter first saw the light of day several decades ago, with the aim of answering the question of why galaxies remain in a cohesive structure. Given only normal matter, the galaxies may never have formed, and may now be moving away from each other. Therefore, there must be some mysterious invisible substance that plays the role of 'gravitational glue'.
On the other hand, dark energy entered the picture only in the late 90s, when astronomers discovered that the universe is not only expanding and spreading - but it is also accelerating its speed while 'running away'. Just then, it was thought that there must be some hidden force, a kind of anti-gravity, that pushes the galaxies and separates them from each other, and at an increasing speed.
Many theories have been put forward, and are still being put forward, in an attempt to get the scientists out of the darkness - of each of the difficulties. For example, to explain dark energy, theorists have reverted to the term 'cosmological constant' that Einstein first introduced as a makeshift factor in order to balance the force of gravity. After some time, Einstein changed his mind and considered this statement as the biggest folly of his life. But today, many theorists feel comfortable using the neglected constant, and this to attribute to it the effects of dark energy, even though it still does not define what the accompanying force is.
In the eyes of theorists, it is very tempting to consider the dark pair as the products of that unknown phenomenon. Sher, a professor of physics at Vanderbilt University, tries his luck, like many before him, at making the connection between dark matter and dark energy, and claims that one and only factor is behind everything and pulling the strings. 'It is quite perplexing for scientists that there are two different unknown sources for the most prominent forms of mass and energy in the universe. On the other hand, this is the nature of things - we are prevented from choosing the universe we live in', Sher said during an interview with him.
In order to explain everything in one fell swoop, Sher brings to life a rare form of expression of energy: a scalar field. Although this field is directionless, like an electric or magnetic field, it combines energy, pressure and magnitude. A scalar field is considered to precede the 'inflation', the period of time that lasted less than one second after the big bang, when the speed of expansion and expansion of the universe was a billion times even before it began to slow down towards a more reasonable growth rate. Sher relies on the findings of the work of several scientists from different universities, which predicted a unique type of second generation for a scalar field, known as essence/essence driven by kinetic energy or for short, 'essence-.'k
The problem that arises as a result of Sher's idea is that we live in a very special moment on the timeline where both the density of dark matter and the density of dark energy are roughly equal. In addition to this, Mario Liyo, a senior scientist at the Space Telescope Science Institute, believes that: 'The model needs fine-tuning, since its dark matter is not permanent but temporary.
In the past, quite a few attempts were made to find a single explanation for dark matter and dark energy, the theories mainly dealt with modified gravity. Once they tried to unite all the forces in the universe into a 4-dimensional plane known as a membrane or 'brain', and it is compressed between other 'brains', like in a sandwich. As a result, gravitation escapes into a fifth dimension, perpendicular to the general plane. Then, the dark matter effects are actually the gravitational effects of the other 'Brains' on our 'Brain' (Universe/Plane)'. In any case, Mario Liuyo concludes with a note of warning: 'Despite the sympathetic tendency to bridge dark matter and dark energy, it is very possible that these two things should not be linked at all.'
The string theory (String Theorie) for its many issues, claims that the dark matter is actually supersymmetric particles, without any connection to the dark energy that remains alone without a decent explanation. The scientists are looking forward to the year 2007, during which an experiment will be carried out which may shed serious light on dark matter, when a special particle collision accelerator (Large Hadron Collider - LHC) will reach the desired energy levels to produce supersymmetric particles, assuming they exist at all.
Dark matter, which many good scientists say will remain a mystery for a long time (at least a few more decades), may involve an external factor called 'vacuum energy' that works in accordance with the universe. In addition to this, quite a few theorists believe and suspect that this is one of the many surprises that await us in the scientific future...
