Preface• The general theory of relativity, predicts that space-time began at the big bang singularity and that it will come to an end either at the big crunch singularity (if the whole universe recollapsed), or at a singularity inside a black hole (if a local region, such as a star, were to collapse).• However when quantum effects are taken into account in the study of these singularities results vary.
“Hot Big Bang Model”• First put forward by: – George Gamov & Ralph Apher (in 1948).• States that: – The universe expanded from a singularity and that it is still expanding today.• It’s supported by: – Hubbles law and the expansion of space – Cosmic microwave background radiation – Abundance of primordial elements – Other
Questions Left Unanswered• Why was the early universe so hot?• Why is the universe so uniform on a large scale?• Why did the universe start out with so nearly the critical rate of expansion?• Why, despite the fact that the universe is so uniform and homogeneous on a large scale, it contains local irregularities, such as stars and galaxies?• What were the universe’s initial “boundary conditions”?
Chaotic Boundary Conditions• Assume that: – Either the universe is spatially infinite or that there are infinitely many universes.
Anthropic Principle• “We see the universe the way it is because we exist.”
Fundamental Numbers (Ex. from “Martin Reess Six Numbers”)• N≈1036 - ratio of the fine structure constant to the gravitational coupling constant. N governs the relative importance of gravity and electrostatic attraction/repulsion in matter.• ε≈0.007 - the fraction of the mass of four protons that is released as energy when fused into a helium nucleus.• Ω ≈ 0.3 - the ratio of the actual density of the universe to the critical (minimum) density required for the universe to eventually collapse under its gravity.• λ ≈ 0.7 - The ratio of the energy density of the universe, due to the cosmological constant, to the critical density of the universe.• Q ≈ 10– 5 - The energy required to break up and disperse an instance of the largest known structures in the universe, namely a galactic cluster or supercluster, expressed as a fraction of the energy equivalent to the rest mass m of that structure, namely mc2• D = 3 - the number of macroscopic spatial dimensions.
Inflation• First put forward by: – Alan Guth (in 1980)• States that: – The universe underwent extremely rapid exponential expansion at an early stage. • Factor of at least 1078 in volume. • It lasted from 10−36 seconds after the Big Bang to sometime between 10−33 and 10−32 seconds.• It’s supported by (it accounts for): – A model of the universe in which many different initial configurations could have evolved to something like the present universe – The homogeneity and isotropy of the observable universe. – The amount of matter and energy in the universe. – Observations in the cosmic microwave background. – Other
Corrections to some misconceptions about Inflation• Inflation is not necessarily driven by dark energy. – Guth proposes, it can be driven by a strong energetic state caused by the symmetry of the fundamental forces in the early space-time.• Inflation does not begin or stop with the formation of our universe.
The search for a unified field theory• Some features it should incorporate: – Feynman’s proposal to formulate quantum theory in terms of a sum over histories. – Einstein’s idea that the gravitational field is represented by curved space-time
Hawking’s Proposition• “maybe time and space together form a surface that is finite in size but that does not have any boundary or edge”
New findings• 1988 – “A Brief History of Time” is published• 1998 – Adam Riess, Saul Perlmutter and others discover the cosmic acceleration.• 2003 – Full-sky detailed pictures of the cosmic microwave background radiation confirm Inflation.• Present – String Theory (notably M-Theory) is being researched and developed.
Current model debate• Inflationary Big Bang Model• The Steinhardt–Turok model
The Steinhardt–Turok model• For more info. check – “Inflationary Cosmology on Trial” – in YouTube • http://www.youtube.com/watch?v=IcxptIJS7kQ&featur e=g-like&context=G250e6fbALT2EwdgADAA – “The Endless Universe: Beyond the Big Bang” by Paul Steinhardt and Neil Turok