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Is the Big Bang Theory valid?

  1. Dec 8, 2011 #1
    I think Big Bang theory is valid because of Inflation theory, it states that universe expanded faster than a light(right?) and that theory can solve the problems that Big Bang had: the Flatness and the Horizon problem. Another reason is Cosmic Microwave Background Radiation, which is first predicted to exist by scientists who support the Big Bang theory, and later was discovered by Hubble.

    Are my arguments correct?

    Is there any more evidence that support the Big Bang theory??
  2. jcsd
  3. Dec 8, 2011 #2
    Fuzzles, a bit of a clarification...

    Inflation does not "validate" the Big Bang Theory, it is an adjunct to the theory which explains the issues you noted in your post. The "validation" of the Big Bang theory comes from multiple, independent observations. Typically, these are known as the four pillars of the Big Bang theory:

    1) The evidence that the Universe is expanding via observation of progressively red-shifted galaxies at further distance scales.

    2) The evidence that the Universe has evolved in time (which also disproves Steady State) by observation of evolution of galaxies and large scale structure. The early Universe did not look the same as it does now. For example, quasers were prevalent in the early Universe (high red-shifts).

    3) The existence and observation of the Cosmic Microwave Background Radiation, as well as it's particular black-body spectrum and temperature.

    4) The relative abundance of light elements as observed in our Universe correlates directly with the models of Big Bang Nucleosynthesis.

    So, in conclusion, the strength of the Big Bang theory lies in these four major, independent observations...whereas Inflation theory is a separate aspect of the Standard Cosmological Model, which answers some of the early questions / problems that were seen with the very early (naive) Big Bang model. The inclusion of Inflation Theory model within the central Big Bang cosmology has brought about a concordance which matches very, very well with the observed homogenity and relative isotropy of our Universe.
  4. Dec 8, 2011 #3
    The CMBR wasn't discovered by Hubble, it was discovered by accident by 2 physicists in the 1960's.
  5. Dec 8, 2011 #4
    Yeah. The two guys who lucked out got the Nobel. The two guys who predicted the CMBR couldn't get anyone to do the experiment and got bupkis.
  6. Dec 8, 2011 #5
    It was later confirmed by the COBE satellite and more recently, the WMAP satellite.
  7. Dec 8, 2011 #6
    I might use the expression "later COBE and WMAP" put much greater precision into the measurements. The original Penzias and Wilson discovery was corroborated by hundreds, if not thousands of individual, seperate ground based radio-telescope observations made after the initial discovery. COBE and WMAP happen to be famous for their own discoveries, which augmented and expanded upon the original CMB discovery.
  8. Dec 8, 2011 #7


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    Penzias and Wilson were engineers working for Bell Labs. They had no interest or knowledge of 'big bang' theories. Check your facts before asserting unfounded conclusions.
  9. Dec 9, 2011 #8


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  10. Dec 9, 2011 #9
    Wow...slow down there, Chronos, are you replying to me? Penzias and Wilson made the discovery, got the credit for it, and the Nobel. I agree with you that they initially didn't know what they had discovered, nor where they involved in Cosmological research, but the fact remains that they discovered the CMB radiation (although it was predicted by others...including George Gamow).

    So, if you were replying to me, I don't know exactly where any of my facts or conclusions are unfounded?

    Besides, in my main reply to this thread, I didn't even mention Penzias and Wilson?? So I am a bit confused.
  11. Dec 9, 2011 #10
    Just out of curiosity has anyone ever tried looking at other wavelengths for other black body radiation which is flat in amplitude and from every direction like the main CMBR signal?
  12. Dec 9, 2011 #11
    Hello Tenelorn:

    Not sure exactly what you mean by "flat in amplitude". Did you mean uniform in distribution?

    In terms of the electromagnetic spectrum, the current 2.73K CMB radiation is the lowest temp / frequency we will be able to observe, as it is from the surface of last scattering at the Recombination era. The incandescent plasma was around 3000K, and has since cooled to 2.73K due to the expansion of space. As the earlier Universe (prior to Recombination) was opaque, we cannot get E/M observations from any earlier period.

    However, we should be able to get information from earlier times from cosmic background Neutrinos, and studies are underway. Another possibility for future observations is from Gravitational waves from the Early Universe...although this won't happen anytime soon.
  13. Dec 9, 2011 #12


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    Well, we've done all-sky surveys in a fair number of wavelengths. No, so far nothing like the CMB has been found. Nor would we expect to see anything like the CMB but at a different wavelength.

    The problem, basically, is twofold. As Deuterium2H notes, we can't observe any radiation from before the CMB was emitted, because our universe was opaque before then. And then after the emission of the CMB, the universe was too transparent for there to be any uniform stuff to emit anything. Basically, our best estimates of the transparency of the universe since the CMB was emitted are that about 92% of the light from the CMB reaches us. So there just isn't any way for there to be a uniform distribution of stuff that would emit a thermal spectrum since then.
  14. Dec 9, 2011 #13


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    You don't need an all-sky survey (the CMB wasn't found with one): everyone who has ever pointed a telescope of any kind at the sky is looking, primarily, for black body radiation.
  15. Dec 9, 2011 #14


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    Apologies, I was addressing the OP.
  16. Dec 13, 2011 #15

    Thanks Chalnoth and Deuterium. Thanks Russ, great site by the way.

    I fully understand the reason why there should not be any radiation like the CMBR radiation at other wavelengths, I was just asking if anyone had checked to be absolutely certain. It should be relatively easy these days to verify the RF radiation in all directions from KHz to visible. I am just wondering what else might be out there. eg. Would we perhaps see a red shifted Hydrogen emission line due to all the hot hydrogen atoms?

    Regarding the transition from opaque to transparent presumably it was a relatively slow transition, but not so slow as to cause different temperatures or redshifts to be observed? Or perhaps this might be the observed pattern on the WMAP pictures?

    I didnt know whether to start a new thread for this question: In a recent TV cosmology program they discussed how the universe started as pure energy which eventually condensed into matter. By energy do they mean photon energy and other force carriers? By matter do the mean perhaps a quark soup or perhaps protons neutrons and electrons? Also is there an estimate of the ratio of the numbers of elementary particles produced in the BB? It seems a happy coincidence that there were equal numbers of electrons as protons or do we think that there may be many ionised particles in space.
    Last edited: Dec 13, 2011
  17. Dec 13, 2011 #16


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    Yes, it's certainly the case that there's no other background it that range. The most significant gaps in our observations are at the high-energy end, but I think any high-energy black body source would have a broad enough spectrum that we would have seen it anyway.

    Yes, it was a bit slow. But since temperature is linear with redshift, the change in temperature over the expansion during the transition neatly cancels. So the primary effect is that instead of seeing a clear image of the CMB, we see a blurred image. This has the impact of suppressing small-scale power in the CMB power spectrum. Without this effect, the CMB power spectrum would be nearly flat (that is, the peaks would be of roughly the same level at all scales).

    I don't know. That doesn't make sense to me. The idea of "pure energy" has never made any sort of sense to me, not since I learned a bit about physics, anyway.

    But as for what was actually there, well, I don't think we know what specific particles were created, but the reason why protons and electrons exactly balance is simple: charge was exactly conserved.
  18. Dec 14, 2011 #17
    Chalnoth, Would there be any radiation produced by incandescence due to the vibration of hot hydrogen atoms?

    I just read that the main source of the CMBR is recombination:
    The baryonic matter in the universe consisted of ionized plasma, and it only became neutral when it gained free electrons during "recombination," thereby releasing the photons creating the CMBR. How much broadening is as a result of dopler shift and is the broadening significant compared to the width of the black body radation?

    At the time of the CMBR would there also have been a Hydrogen transition line emission at 1420MHz which would have been redshifted to 1.29MHz?
    I believe that Radio waves can propagate through ionized gases with less attenuation. Perhaps there is just too much interference in this band?

    I just found this although they are looking at lower red shift frequencies:

    In cosmology the line is of great interest in big bang cosmology because it is the only known way to probe the "dark ages" from recombination to reionization. Including the redshift, this line will be observed at frequencies from 200 MHz to about 9 MHz on Earth. It potentially has two applications. First, by mapping redshifted 21 centimeter radiation it can, in principle, provide a very precise picture of the matter power spectrum in the period after recombination. Second, it can provide a picture of how the universe was reionized, as neutral hydrogen which has been ionized by radiation from stars or quasars will appear as holes in the 21 centimeter background.

    However, 21 centimeter experiments are very difficult. Ground based experiments to observe the faint signal are plagued by interference from television transmitters and the ionosphere, so they must be very secluded and careful about eliminating interference if they are to succeed. Space based experiments, even on the far side of the moon (which should not receive interference from terrestrial radio signals), have been proposed to compensate for this. Little is known about other effects, such as synchrotron emission and free-free emission on the galaxy. Despite these problems, 21 centimeter observations, along with space-based gravity wave observations, are generally viewed as the next great frontier in observational cosmology, after the cosmic microwave background polarization.

    Source: http://en.wikipedia.org/wiki/Hydrogen_line
    Last edited: Dec 14, 2011
  19. Dec 14, 2011 #18

    I think they were probably talking about this point where the energy of the universe was dominated by photon energy:

    Photon epoch Between 10 seconds and 380,000 years after the Big Bang

    After most leptons and anti-leptons are annihilated at the end of the lepton epoch the energy of the universe is dominated by photons. These photons are still interacting frequently with charged protons, electrons and (eventually) nuclei, and continue to do so for the next 380,000 years.

  20. Dec 14, 2011 #19
    Yes Penzias and Wilson,if my knowledge is right.What confuses me is the theory of multiverses. If our universe was just one among many,then there must be a number of big bangs resulting in their own universes. That must mean that these expanding universes might stop expanding and lead to the so called 'Big Crunch'.Then,are these processes cyclic?Does one finally lead to the other and hence an 'oscillatory universe'???Would someone please clear my doubts?
  21. Dec 14, 2011 #20


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    Um, that emission line is for neutral hydrogen, due to a hyperfine transition splitting. And the light really wasn't emitted by the hydrogen in the early universe per se. Instead, the early universe was a diffuse plasma, and I'm pretty sure that the thermal emission from the plasma vastly outstripped any small amount of emission from the energy transitions of the gas as it was forming from that plasma.

    Additionally, the hyperfine transition emission is going to be minuscule compared to the Lyman and Balmer emission lines. The Lyman series lies between 2470THz and 3290THz, while the Balmer series lies between 457THz and 822THz. Redshifting these to the current time and you get 2260GHz-3020GHz and 419GHz-754GHz.

    The problem, however, is that at these wavelengths the dust in our own galaxy is quite bright, so I'm not so sure we could measure these emission lines in the first place.

    Yes, that's probing the universe after the emission of the CMB, looking for the very faint emission of the neutral hydrogen gas that remained.

    P.S. Oh, and please make it clear what your source is. It isn't obvious here that it's the Wikipedia article you previously mentioned.
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