Tuesday, 25 May 2010
Of Dark Matter, Quintessence, Aether and Ether (Expanded)
What is it like out there in the tremendous void between stars in our Milky Way galaxy? According to a recent article , there are about one million atoms (mostly hydrogen) per cubic meter, so it is not completely desolate. But get into the space between galaxies, and there are only 10 atoms/m3. That is a far better vacuum than anything we can achieve on Earth.
But imagine that you are in a space vehicle (an impossible dream because of the huge amount of energy it would take to get there), staring off into space through a porthole window. What will the “sky” look like? It would be lit up with billions of tiny stars. In other words, that cubic meter of lonely, practically empty space, is crisscrossed by a fantastic number of photonic outputs of the universe -- the visible as well as ultraviolet, infrared, and so forth. All of it is electromagnetic radiation.
Recently, cosmologists have been calling our attention to another ingredient in the void between stars in the Milky Way galaxy – Dark Matter. It is not electromagnetic radiation, so we can’t “see” it. It is a mysterious substance – different from ordinary matter. Actually, Dark Matter refers to an effect that fits into the "nothing new under the universe" category, because it was proposed, way back in 1933, by Fritz Zwicky . According to his calculations at that time, which are remarkable in view of the relatively flimsy data upon which they were based, the stars in the galaxies should be flying apart: Given the mass of a typical star and the vast distances to its nearest neighbors, gravitational attraction is insufficient to hold the star in a circular or spiral orbit around the center of the galaxy. Zwicky suggested that "missing matter" was responsible. Eventually, the missing mass came to be called Dark Matter.
In addition to Dark Matter, since 1998, we have Dark Energy. Here is how Linda Rowan and Robert Coontz introduced The Dark Side, Science, 20 June 2003: "Dark stars, the dark age, dark matter, and dark energy are the major components of the dark side of the universe: 96% of the universe consists of mass and energy we can't see and don't really understand. Fortunately, the badly outnumbered 4% of luminous matter feels the dark side through gravity and other forces." In this brief Chapter, Dark Energy is completely avoided; Dark Matter, on the other hand, is something that we can "feel"; it interacts with us via gravitational attraction.
It is no trivial or fly-by-night phenomenon; in fact, cosmologists estimate that the mass of Dark Matter is from five to 10 times that of the luminous material ! This is mind-boggling and ego-crushing; it should completely reverse our perspective and be worthy of headlines in the popular as well as scientific press. In other words, the galaxy consists of a huge blob, cloud, or halo of Dark Matter within which are 100 billion relatively insignificant specks -- or stars -- of ordinary matter. The ordinary matter flies along stream lines that are determined by gravitational interaction with the Dark Matter in which it is immersed.
...Although its density is insubstantial, the Dark Matter is spread out over such a huge volume that its total influence is equivalent to that of a gravitationally massive substance. Furthermore, because the Milky Way is not unique, we must assume that each of the 100 billion galaxies in the universe is immersed, similarly, in a cloud of massive Dark Matter.
But the matter, Dark or otherwise, is far from being ended, for Dark Matter is reminiscent of the aether. Once upon a time (1864), James Clerk Maxwell and his contemporaries "invented" the aether, which is approximately analogous to our atmosphere. It filled all of empty space; that is, space that is devoid of mass such as neutrons, protons, and electrons. It was invented because a medium is needed in which an electromagnetic field (EMF) wave can propagate, just as sound cannot travel in a vacuum. Eventually, especially in the United States, the spelling was changed to "ether," which causes minor irritation if one is looking up aether or ether in an index. Major irritation was caused in the 1920s, however, because the "big shots" of physics abandoned the aether. They couldn't measure its motion with respect to the earth, so they declared that it doesn't exist; that electromagnetic fields somehow propagate in a perfect vacuum.
There is no way an EMF can propagate in a vacuum. But in 1887, Albert A. Michelson and Edward W. Morley showed that the aether, if it exists, is traveling with the earth. On the other hand, star aberration data  received with telescopes indicate that it is not being dragged along by the earth: Picture a star at the zenith (overhead): When its light exits from the Milky Way’s aether on the way to being captured by the earth’s aether, the light should be bent by an angle of 0.0001 radians (20.5”), which represents the earth’s rotation around the sun (3 X 104 m/s) relative to the velocity of light (3 X 108 m/s). After capture, the star’s light should travel vertically, relative to the earth beneath. This does not happen at all; instead, a telescope has to be tilted at an angle of 20.5” to compensate for the earth’s rotation. The 20.5” is the “aberration of starlight.” If a telescope is pointed directly upward for a year, its star images will appear as tiny circles, 41” in angular diameter.
How can we explain the fact that the earth’s aether is dragged along by the earth, while aberration data indicate that starlight does not encounter the earth’s aether? Here it is my turn to say “Somehow, by relativistic effects which are described below, and by the curvature of space.”
Let’s consider another aspect of the earth dragging its aether along. Since the earth travels around the sun at a speed 0.01% as fast as the velocity of light, there must be a transition zone, in front of the earth, where the aether is compressed as one goes from the earth's aether to that of the sun. Similarly, behind the earth, there must be a transition zone of expansion.
...If we send out a spaceship to measure the velocity of light in the “compression” or “expansion” zones, it will always measure 300 million m/s. Over 100 years ago, it was known that the velocity of light is always 300 million m/s, independent of whether the source is moving towards us or away from us, provided the measurement is made at an inertial (not accelerating) platform. (There is a radial acceleration of the earth around the sun, and of an object around the center of the earth, but these effects are relatively small.) The correct scenario is depicted in Fig. 2(b), where the uniform spacing signifies constant measured velocity of light. In 1905, Albert Einstein explained this with his theory of special relativity: space and time are not the same to all observers; and space can curve.
....In Model 1, a photon is analogous to a minuscule projectile. It carries a certain amount of energy (for a “green” photon, 3.4 X 10-19 joule). This blob of energy leaves its source and flies through space, sometimes for billions of years, at the speed of light, until it encounters a material object. Then it deposits 3.4 X 10-19 joule of energy (usually in the form of heat). What happens if two of these photon “projectiles” hit each other? Nothing much. They act as if they have zero diameter, so they pass “through” each other unscathed. But projectiles with zero diameter don’t make much sense. Also, how does it turn out that the speed of a projectile, regardless of its launching platform or frequency, is 300 million m/s?
In Model 2, a photon is analogous to a wave on the surface of a lake: The ripple is transmitted from one molecule of water to the next. All of us have experienced the energy carried by a water wave. But how is the ripple of a photon transmitted from one “molecule” of vacuum to the next? The answer, it seems to me, is that the “vacuum” is actually filled with that mysterious “substance” called the aether. Furthermore, if a photon is a ripple in the aether, we expect its velocity to be independent of the source or frequency, just as the speed of a sound wave is independent of the loudspeaker or the audio frequency.
...More recently, however, the vacuum has been dignified with additional properties: subatomic particles randomly appear and disappear. It is therefore confusing to call empty space a "vacuum" while so much is going on. But our physicists and cosmologists came to the rescue, in 1998, with a fashionable new word – quintessence . (Actually, it is only a new application, because it appears in old dictionaries.) Now, empty space is permeated with quintessence (Dark Energy). So, since the aether was rejected, and the "vacuum" is misleading, let's all jump on the "quintessence" bandwagon. Well, not so fast: The latest descriptions of DarkMatter reveal that it is a "dark horse"; it could be the aether, after all!"
by Sid Deutsch