NASA released the image of the earliest universe in the beginning of 2003. The image shows the stunning details that may be the most important scientific results of the recent few years. Scientists used Wilkinson Microwave Anisotropy Probe (WMAP) to capture the cosmic portrait that reveals the afterglow of the big bang, i.e. the cosmic microwave background radiation.
This is a full-sky map of the oldest light in the Universe. The red spots show warmer speckles while the blue flecks show the cooler portions. The oval shape projection of the full sky is similar to global map. The universe is being bathed in an extraordinary uniform microwave light which translates into a frigid average of 2.73 Kelvin (degrees above absolute zero, or -273 ¢XC). The temperature variation throughout this void is extremely small. But WMAP, with its ability to resolves slight temperature fluctuations down to millionths of a degree, is still able to detect these minute differences and produces the finest full sky thermogram of the cosmic background.
According to big bang theory, the early Universe is a hot, dense and opaque fluid of electrons and protons. This hot plasma constantly emits, scatters and reabsorbs photons and is the source of the cosmic background radiation. As the universe continued to expand, the temperature of the cosmic soup finally dropped below 2,967 Kelvin. Electrons began to combine with protons to form neutral hydrogen. Since hydrogen is almost completely transparent to electromagnetic wave, cosmic radiation could then propagate freely through the universe. In the beginning, the background radiation was more energetic than gamma rays. Following the expansion of the Universe, the wavelength of the radiation is also being stretched and is now reaching us in the form of microwaves. The cosmic microwave background radiation we see today is from the era just before the temperature was low enough to allow neutral hydrogen to form. In other words, we are seeing the Universe 380,000 years after the big bang, or over 13 billions years ago. The infinitesimal patterns of this radiation reveal the matter distribution of the early Universe, which were the seeds of today's clusters of galaxies. It grew gradually to the vast structure as we see today.
By carefully studying the polarity of the background radiation, scientists concluded that the first generation of stars in the universe first ignited to shine at only 200 million years after the big bang, much earlier than expected.
WMAP provides valuable data to support and strengthen the big bang and the inflation theories, and help us to answer a bunch of age-old questions. What is the age of the Universe? How much dark matter in the universe? How much "dark energy" in the universe? How they play role in determining the geometry of universe?
Now we can say with confidence that the Universe contains 4% of ordinary matter that we are all made of, 23% of unknown types of dark matter that we name them as "cold dark matter" and 73% or even more of mysterious "dark energy". Scientists still know very little about "dark energy" except it is anti-gravity and is responsible for the acceleration of the Universe expansion. One of these possibilities for the dark energy is the "cosmological constant" that was introduced by Albert Einstein. In fact, the amount of dark matter and dark energy dominate the geometry of the universe. If the density of matter and energy in the universe is less than the critical density, the space curvature (Wo) will be negative. The space geometry is open and negatively curved as a saddle. If the density equals to the critical density exactly, the space is flat as a sheet of paper. If the density is greater than the critical density, the space geometry is closed and positively curved as a ball. If the universe has a ball-like geometry, light emitted will diverge and eventually converge back to the point of origin.
As an extension of the big bang theory, inflation theory predicts the universe density is rather close to the critical density. Thus, the universe is flat. Within the limits of instrument error, WMAP confirms this prediction.
Scientists compare and combine the WMAP data with the other diverse cosmic measurements, including clusters of galaxies, Lyman-a cloud clustering and supernovae. Eventually, the scientists have reached a unified understanding of the universe. We can describe the Universe as follows:
The universe is 13.7 billion years old with only a 1 percent margin of error.
The first stars ignited about 200 million years after the big bang.
The WMAP portrait shows the light from 380,000 years after the big bang.
The ingredients of the Universe are 4% ordinary matter, 23% cold dark matter, 73% dark
Expansion rate (Hubble constant) value Ho = 71 km/sec/Mpc with only 5 percents margin of
The fate of the universe is expansion forever.
Photo credit: NASA