Monday, May 17, 2010

Way too short a summary of "Traditional" Cosmology

In fact there is nothing traditional about current cosmology. The fact that the universe is more than only our own Milky Way Galaxy was only discovered in the 1920ties by Edwin Hubble. The same Edwin Hubble discovered in 1929 that the distance to far away galaxies was proportional to their red shifts (increase in wavelength of electromagnetic radiation such as radio, light, x-rays etc. due to the Doppler effect) indicating that all very distant galaxies and clusters have an apparent velocity directly away from our vantage point. The farther away, the higher the apparent velocity. From this observation it could be logically assumed that earlier in time those galaxies and clusters were closer together. Fred Hoyle is credited with coining the phrase Big Bang in a radio broadcast back in 1949. When in 1964 the cosmic microwave background radiation was discovered and analyzed , most scientists were fairly convinced by the evidence that some Big Bang scenario must have occurred.

Black holes (objects so massive even light can not escape its gravity) were thought about as far back as 1783. In 1915, with the help of Einstein's freshly developed theory of general relativity, it was shown that black holes could exist in theory. It was not until the 1960ties that the term “black hole” emerged. A defining feature of a black hole is its event horizon. This is a boundary in spacetime beyond which events can not affect an outside observer. At the center of a black hole lies a singularity. This is a point in spacetime where matter is crushed to infinite density, the pull of gravity is infinitely strong, and spacetime has infinite curvature. This means that a black hole's mass becomes entirely compressed into a region with zero volume called a gravitational singularity. In such singularities our current laws of physics break down. It is expected that there will emerge a theory of quantum gravity that will unite general relativity with quantum mechanics.

It is speculated that there is a singularity at the beginning of cosmic time (Penrose-Hawking singularity theorems) but as the Big Bang model is likely to be refined in the future, solutions that do not require a singularity may win favor.

Several models exist regarding the future of the universe. The discovery that cosmological expansion is accelerating instead of decelerating, has somewhat caused a stir. What causes the acceleration? It was already theorized that dark matter must exists to account for unexplained gravitational effects and that the matter we can observe is only a tiny part of all the matter in the universe. Still gravity looses the tug it seems. So dark energy was conceived. Dark energy, it is thought, is an hypothetical energy that tends to increase the rate of cosmological expansion. Ironically, dark energy has renewed interest in the cosmological constant, a modification of Einstein's original theory of general relativity to achieve a stationary universe. He later abandoned the idea calling it his greatest mistake. Now it seems convenient to introduce it again.

So, mankind has found the time to contemplate the beginning and ending of time and space in an effort to try and understand how we got here and where we are going.

Lately, with the ever increasing popularity of popular science on tv (Discovery Channel, National Geographic Channel, History Channel etc.), “normal” people are getting acquainted with and interested in these matters. The grandness of the subject naturally fascinates us. Quite often though it seems to me that such programs focus a bit too much on the cataclysmic doom scenarios in order to create a spectacular program and provoke fear rather than thought.

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