How does the change in temperature of the universe provide evidence for the universe expansion that supports the big Bank theory?
The change in temperature of the universe, specifically the observation of the cosmic microwave background radiation (CMB), provides strong evidence for the expansion of the universe and supports the Big Bang theory. Here's how:
1. The Big Bang theory explains that the universe originated from a hot, dense, and highly energetic state around 13.8 billion years ago. As the universe expanded, it cooled down, allowing matter and energy to form.
2. The CMB is the afterglow of this hot, dense state that is still detectable today. It is an almost uniform background radiation that permeates the entire universe. The CMB was discovered in 1965 by Arno Penzias and Robert Wilson.
3. The temperature of the CMB is incredibly uniform in all directions, with a measured temperature of about 2.7 Kelvin (-270.45 degrees Celsius or -454.81 degrees Fahrenheit). This uniformity is surprising because if the universe were not expanding, different regions would have different temperatures due to the dissipation of heat over time.
4. The most compelling evidence supporting the expansion of the universe comes from the observation of the CMB's temperature fluctuations. Satellite missions like the Cosmic Background Explorer (COBE), Wilkinson Microwave Anisotropy Probe (WMAP), and Planck have mapped these fluctuations with unprecedented detail.
5. These temperature fluctuations in the CMB correspond to slight variations in the density of matter at different regions of the early universe. These density variations are crucial for understanding the seeds of structure formation that led to the formation of galaxies and galaxy clusters.
6. The key insight is that these tiny density fluctuations were imprinted in the CMB when the universe was just about 380,000 years old. By studying these fluctuations, scientists can gain insights into the conditions of the early universe and its evolution over time.
7. Analysis of the CMB fluctuations shows anisotropies or variations in temperature at different scales that match the predictions of an expanding universe. These fluctuations are consistent with the early universe undergoing a period of rapid expansion called inflation, which is a component of the Big Bang theory.
8. Additionally, the observed redshift of distant galaxies (the stretching of light towards longer wavelengths) also supports the idea of the expanding universe. The further away a galaxy is, the more its light is redshifted, indicating that space itself is stretching and causing the wavelength to lengthen.
In summary, the change in temperature of the universe, as observed through the CMB and its fluctuations, is strong evidence for the expansion of the universe, aligning with the predictions of the Big Bang theory.