Refining the Theory Of Big Bang
July 25th 2008 13:40
Astronomers continue to make new observations that are also interpreted within the framework of the big bang theory. No major problems with the big bang theory have been found, but scientists constantly adjust the theory to match the observed universe. In particular, a “standard model” of the big bang has been established by results from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), launched in 2001 (see Cosmology). The probe studied the anisotropies, or ripples, in the temperature of cosmic background radiation at a higher resolution than COBE was capable of. These ripples indicate that regions of the young universe were very slightly hotter or cooler, by a factor of about 1/1000, than adjacent regions. WMAP’s observations suggest that the rate of expansion of the universe, called Hubble’s constant, is about 71 km/s/Mpc (kilometers per second per million parsecs, where a parsec is about 3.26 light-years). In other words, the distance between any two objects in space that are separated by a million parsecs increases by about 71 km every second in addition to any other motion they may have relative to one another. In combination with previously existing observations, this rate of expansion tells cosmologists that the universe is “flat,” though flatness here does not refer to the actual shape of the universe but rather that the geometric laws that apply to the universe match those of a flat plane.
To be flat, the universe must contain a certain amount of matter and energy, known as the critical density. The distribution of sizes of ripples detected by WMAP show that ordinary matter—like that making up objects and living things on Earth—accounts for only 4.4 percent of the critical density. Dark matter makes up an additional 23 percent. Astoundingly, the remaining 73 percent of the universe is composed of something else—a substance so mysterious that nobody knows much about it. Called “dark energy,” this substance provides the antigravity-like negative pressure that causes the universe's expansion to accelerate rather than slow down. This “accelerating universe” was detected independently by two competing groups of astronomers in the last years of the 20th century. The ideas of an accelerating universe and the existence of dark energy have caused astronomers to substantially modify previous ideas of the big bang universe.
For me, one thing is for sure. Doing research is not an easy task. But I'm happy of sharing what I've known. I hope that these informations will help for those who are in need of these...
To be flat, the universe must contain a certain amount of matter and energy, known as the critical density. The distribution of sizes of ripples detected by WMAP show that ordinary matter—like that making up objects and living things on Earth—accounts for only 4.4 percent of the critical density. Dark matter makes up an additional 23 percent. Astoundingly, the remaining 73 percent of the universe is composed of something else—a substance so mysterious that nobody knows much about it. Called “dark energy,” this substance provides the antigravity-like negative pressure that causes the universe's expansion to accelerate rather than slow down. This “accelerating universe” was detected independently by two competing groups of astronomers in the last years of the 20th century. The ideas of an accelerating universe and the existence of dark energy have caused astronomers to substantially modify previous ideas of the big bang universe.
For me, one thing is for sure. Doing research is not an easy task. But I'm happy of sharing what I've known. I hope that these informations will help for those who are in need of these...
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