Sufficient doses, of the idea that the Universe was created with a violent explosion of energy and matter, have been injected in the plebeian culture. The Big Bang theory has struck chords with millions of people, perhaps because of its close resemblance to many religious discourses on creation, but remains poorly understood. Anyone who accepts the Big Bang theory, with no protest or skepticism, has surely failed to grasp the central point of the theory.
We shall outline the evidences which have led the scientific consensus
on the Big Bang Theory, which was counter-intuitive to most brilliant scientists.
On the ‘compulsion’ of having a beginning
The first question to be asked by a novice while big-bang-theory-indoctrination
should be, “Was there a beginning?” This
question, though innocent, had (and perhaps still has) vicious philosophical
weight. The answer– ‘Of course! There has
to be a beginning’ arises from the obvious idea of ‘causation’. Causation, as
Hume said, is the cement of the universe, and lies at the heart of our conceptual
structure (Kistler, 2006) . To put the idea
briefly, if an event e has the cause d, and d has the cause c and so
on, one has to end at event a. One can argue that ‘has to end’, comes from the mere choice
of finite alphabets as event-labels, instead of infinite numbers.
Our intrinsic inability, to conceptualize an infinite
regress of events, makes us overlook the fact that not having a beginning is logically simpler. Avoiding a long drawn-out
argument on philosophical fallacies of having a First Cause on a scientific take on creation, we instead move on to the science behind The Big Bang
Theory.
The Big Bang Theory
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| Image credit: NASA / CXC / M. Weiss |
While an entire post can be dedicated on explaining even the basics of Big Bang theory, we will suffice this post with a short introduction to Big Bang theory. The idea of a beginning first came into scientific consideration in 1927, when a Belgian, Georges Lemaitre proposed, what is called, ‘Primeval Atom Hypothesis’. According to Lemaitre’s calculations, the universe began as a tiny speck of astounding density, a “primeval atom” as he would come to call it, which swelled over the vastness of time to become the observable cosmos (Greene, 2011). When he suggested this to Einstein, Einstein remarks were, ‘Your mathematics is correct, but your physics is abominable.’
Interestingly, it wasn’t the first time that Einstein was being suggested of an expanding Universe. In 1921, Russian meteorologist Alexander Friedmann had come with a solution to Einstein’s equations (in General Theory of Relativity) which suggested that the space would stretch, causing the Universe to expand. Einstein had a deep seated belief that, the Universe had an eternal existence (which, as was pointed out before, was logically simpler) and at its largest scales– changeless. He refused to trust mathematics over his intuitions.
Einstein himself had found something unexpected with General Relativity (GR), when he had tried to apply it to the whole of the Universe. GR failed to produce a static Universe. GR, being a theory of attractive gravity, predicted that a large mass (like our universe) will either keep collapsing under its own weight or exhibit deceleration in its expansion rate if it was growing in size to begin with. In either case, a static universe was out of the question (Gupta, 2012). With Lemaitre’s and Friedmann calculations, it seemed that the Universe, at its largest scales (i.e. intergalactic voids), is in a state of steady (though 2011 Nobel Prize in Physics was awarded to S. Perlmutter, A. Riess and B. Schimdt for discovery that the rate of expansion of the universe is increasing with time) expansion.
It would be worthy to digress from the topic a little, to mention some similarities between the Big Bang theory in cosmology and Darwinian Theory of Evolution in Biology. Just like theory of evolution is about how life evolved after the creation of DNA, the Big Bang theory explains the evolution of the universe after the moment of creation. It’s crucial to understand that the Big Bang theory is not about the bang at all. It’s the story after time t=0. To take the analogy a step further, its domain is (0,t], where ‘t’ is the present time. Just as Natural selection is the engine that drives evolution of life, General Theory of Relativity drives the evolution of the Universe.
Evidences Supporting Big Bang
Hubble’s discovery of receding Galaxies
In 1929, an American astronomer Edwin Hubble while studying the spectra of radiation from galaxies, discovered that spectroscopic lines were shifted to the red end as though there was some kind of a Doppler redshift (he formulated a relationship based on these observations, which bears his name). He correctly interpreted that, the Doppler shift (this was later to be defined as cosmological redshift, which we will discuss in subsequent posts) was due to the Galaxies moving away from us, rather than a lateral movement. If one extrapolates this backward in time, one gets the ‘primeval atom’ which Lemaitre had posited. Though there have been changes to the theory proposed by Lemaitre in subsequent decades, the discovery of receding galaxies was enough to discard the static outlook for the Universe, and establish Big Bang Theory at helm of general evolution of the Universe.
Discovery of Cosmic Microwave Background Radiation
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| WMAP image of the cosmic microwave background radiation |
Another prediction of Big Bang was the existence of a uniform radiation background in the microwave range. If the theory were correct, then space everywhere should now be filled with remnant photons from the creation event, whose vibrational frequencies are determined by how much the universe has expanded and cooled during the billions of years since they were released. Detailed calculations showed that this radiation of photons should be in the range of microwave radiation.
A uniform microwave background was indeed discovered (accidentally) radiation in 1964 by Arno Penzias and Robert Wilson at Bell Labs. This came to be known as cosmic microwave background radiation (CMBR). The reason of its existence and its nature, are indeed interesting topics to discuss, and will be taken up in subsequent posts.
We have cited the evidences (quite superficially) that there
was indeed a beginning. We haven’t touched upon many aspects of the Big Bang
theory (most important of them is perhaps the Inflationary model) and subsequent course of evolution of Universe
(which is what the theory is about). Food for thought– what was there before Big Bang? We will start the next post with an
answer to this question and a more detailed outlook on the Big Bang theory.
Citations
Greene, B. (2011). The Hidden Reality. New
York: Alfred A. Knopf.
Gupta, P. D. (2012, March). General Relativity and
the Accelerated expansion of the Universe. Resonance, pp. 258-259.
Kistler, M. (2006). Causation and Laws of Nature.
New York: Routledge, Taylor & Francis Group.
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