The Big Bang Theory Is Probably True

I. The Homogeneity of the Universe The Big Bang Theory (BBT) rests on only two assumptions. One is that the laws of the universe are the same throughout space and time. This is an implication of the theory of special relativity. The other is that the universe is homogeneous and isotropic. This has been observed. "A major prediction of the Big Bang is that the universe is homogeneous. At small scales, just as in the solar system, this is obviously not true, but if we look at the largest scales of the universe, this is true. As an example, consider the plot below showing galaxies from the Las Campanas Redshift Survey. Each dot represents a galaxy (about 20,000 in the total survey) where they have measured both the position on the sky and the redshift and translated that into a location in the universe"[1]: An even stronger case for the homogeneity of the universe can be made in the Cosmic Microwave Background Radiation (CMBR), in that it is virtually homogeneous and isotropic being isotropic (the same) to roughly one part in 100,000, further. This spectrum has been redshifted by the expansion of the universe, and today corresponds to approximately 2.725 K. [2]: Now, universal homogeneity and isotropy and not indicators of the big bang, but the observation of it validates one of the theories assumptions. Further, the CMBR can only be explained through the BBT. "In the absence of BBT, there would be no reason to expect a uniform, long-wavelength background radiation in the universe. "[1] In addition to the overall isotropy of the CMBR, there are the small anisotropies in it as well. "The recent discovery of the previously predicted acoustic peaks in the power spectrum has established a working cosmological model: a critical density universe consisting of mainly dark matter and dark energy, which formed its structure through gravitational instability from quantum fluctuations during an inflationary epoch. "[6] "The angular power spectrum of the anisotropy of the CMB contains information about the formation of the Universe and its current contents. .. The graph above [shown below] shows the angular power spectrum measured by WMAP and several balloon-borne and ground-based experiments. These data are perfectly consistent with a flat Universe that is dominated by a vacuum energy density of cosmological constant which provides 73 percent of the total density of the Universe. Another 23 percent of the density is dark matter. Only 4 percent of the density is ordinary matter made of protons and neutrons. " Notice the almost perfect prediction of the Lambda-CDM model on the angular power spectrum. It is clear that the BBT matches up with predictions very well. "With 5 years of WMAP data, and improved ground-based and balloon-borne experiments, the consistency with Lambda-CDM [sic] remains excellent. "[11] The BBT is remarkably close to observations, II. Galatic Evolution The BBT predicts that earlier formed galaxies will look different than recently formed galaxies. "As one would expect, the morphology of the few nearby galaxies in these images [of various sections of the universe] is quite a bit different from the very high redshift galaxies. "Galaxies that formed relatively recently appear very different from galaxies formed at similar distances but shortly after the Big Bang. "Observations of star formation, galaxy and quasar distributions and larger structures agree well with Big Bang simulations of the formation of structure in the Universe. " No other theory can explain why more redshifted galaxies look different than less redshifted galaxies. In addition, no other theory can explain why galaxies evolve, and, as follows, the way they do evolve. [1][3][4] III. Abundance of Elements There is an abundance of light elements that can only be explained by the BBT. "The fact that helium is nowhere seen to have an abundance below 23% mass is very strong evidence that the Universe went through an early hot phase. This is one of the cornerstones of the Hot Big Bang Model. " Further, the abundance of light elements over heavy elements is a further confirmation. ". .. as one examines older and older objects, the abundance of most heavy elements becomes smaller and smaller, asymptoting to zero. By contrast, the abundance of helium goes to a non-zero limiting value. "[1][5] Here is a graph showing the abundance of elements in the universe. Notice how the abundancies fall asymptotically to zero, as predicted by the BBT: In addition to the abundance of light elements themselves, there is the variation in different light element ratios. For example, consider the ratio of helium to deuterium (a hydrogen atom with two protons. "Because deuterium has a nucleus that is very weakly bound compared with most nuclei, it is very sensitive to the conditions in which it is formed (as we have just seen): if the temperatures are too high, deuterium breaks apart, and it can only be formed when there are free neutrons to combine with protons. Detailed analysis of the deuterium abundance gives very strong support to the hot big bang picture. ""Indeed there is no obvious reason outside of the Big Bang that, for example, the young universe should have more helium than deuterium or more deuterium than 3He, and in constant ratios, too. "[2][10] Fianlly, there are the primordial gas clouds. These are clouds of gaseous elements no larger than hydrogen and deuterium, formed in the first few minutes after the big bang. The composition of these gas clouds matches the composition predicted from Big Bang nucleosynthesis. "The composition of the gas matches theoretical predictions, providing direct evidence in support of the modern cosmological explanation for the origins of elements in the universe. "[12] IV. Hubble's Law Hubble's Law states that v = H0*D where: v is the recessional velocity of the galaxy or other distant object, D is the comoving distance to the object, H0 is Hubble's Constant, measured to be 70.4 (errors +1.3, -1.4) km/s/Mpc The only plausible explanation for this is the expansion of the universe, which we are currently experiencing. It is one of the cornerstones of the Big Bang Theory, and very much helps prove it. Again, while not a proof of the BBT, it's finding underlies the entire basis of the BBT itself. [2][7] Further, the expansion of the universe has been found to be accelerating, which indicates the existence of dark matter, or a negative pressure that counteracts the force of gravity throughout the universe. This is a part of the Lambda-CDM model of the BBT, and there is no other cosmological theory that can plausibly and reliably explain why this is occurring. [8] V. Stellar Age If the BBT were to be true, there should be no stars older than approximately 13.5 billion years. The oldest stars known fit nicely into this model: "The globular cluster NGC 6397, Panquini found an age of 13.4 billion years, plus or minus 800 million years. Other studies like Krauss and Hansen obtained similar results with related methods: 12.2 and 12.1 billion years, respectively, with errors on order 1 to 2 billion years. "[1][9] In addition, we should see differentiations in different stellar generations. Stars create the denser materials. If so, newer stars should have more metallicity the younger they are. This is indeed observed. Generally, the youngest stars, the extreme Population I, are found farther in and intermediate Population I stars are farther out, etc, as shown here: This organization is observed in galaxies throughout the universe, and is another important proof of the BBT. Conclusion "[The] big bang picture is too firmly grounded in data from every area to be proved invalid in its general features. " - Lawrence Krauss Sources [1]: . http://www.talkorigins.org... [2]: . http://en.wikipedia.org... [3]: . http://arxiv.org... [4]: . http://www.atnf.csiro.au... [5]: . http://astro.berkeley.edu... [6]: . http://background.uchicago.edu... [7]: . http://www.pnas.org... [8]: . http://www.physicsoftheuniverse.com... [9]: . http://arxiv.org... [10]: . http://csep10.phys.utk.edu... [11]: . http://www.astro.ucla.edu... [12]: . http://www.sciencedaily.com...