„Inflation takes advantage of this possibility… to let gravity be the repulsive force that drove the universe into the period of expansion that we call the Big Bang. In fact, when one combines general relativity with conventional ideas, now, in particle physics there really is a pretty clear indication, I should say, not quite a prediction… that at very high energy densities one expects to find states of matter which literally turn gravity on its head and cause gravity to become repulsive.“

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— Alan Guth

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

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Alan Guth

US-amerikanischer Physiker 1947

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„The miracle of physics that I'm talking about here is something that was actually known since the time of Einstein's general relativity; that gravity is not always attractive. Gravity can act repulsively. Einstein introduced this in 1916… in the form of the cosmological constant, and the original motivation of modifying the equations of general relativity to allow this was because Einstein thought that the universe was static, and he realized that ordinary gravity would cause the universe to collapse if it was static. …The fact that general relativity can support this gravitational repulsion, still being consistent with all the principles that general relativity incorporates, is the important thing which Einstein himself did discover..“

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— Alan Guth American theoretical physicist and cosmologist 1947

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

„Inflation is a prequel to the conventional Big Bang theory. …It does provide a theory of the propulsion that drove the universe into this humungous episode of expansion which we call the Big Bang.“

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— Alan Guth American theoretical physicist and cosmologist 1947

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

„A positive pressure produces an attractive gravitational field… Positive pressures are just sort of normal pressures and attractive gravity is normal gravity, so normal pressures produce normal gravity, but it is possible to have negative pressures, and negative pressures produce repulsive gravity, and that's the secret of what makes inflation possible.“

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— Alan Guth American theoretical physicist and cosmologist 1947

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

„The gravitational repulsion created by this small patch of repulsive gravity material would be, then, the driving force of the Big Bang and it would cause the region to undergo exponential expansion… there is a certain doubling time, and if you wait the same amount of time it doubles again, and if you wait the same amount of time it doubles again… and it's because these doublings build up so dramatically, it doesn't take very much time to build the whole universe. In about 100 doublings this tiny patch of 10-28 cm can become large enough, not to be the universe, but to be a small marble-sized region which will then ultimately become the observed universe, as it continues to coast outward after inflation ends.“

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— Alan Guth American theoretical physicist and cosmologist 1947

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I
The Early Universe (2012)

„When two identical 3He atoms collide… the interference is destructive. Particles that behave like 3He atoms are called fermions, short for "particles obeying Fermi–Dirac statistics."… while bosons imitate one another… the "identity force" between fermions acts like a repulsion, and the probability of finding a fermion at some point in space is reduced if some of its identical siblings are nearby…. It is the repulsive identity forces between electrons that support white dwarf stars… against their own gravity.“

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— Frank Wilczek physicist 1951

Longing for the Harmonies: Themes and Variations from Modern Physics (1987)

„What it takes to produce a gravitational repulsion is a negative pressure. According to general relativity, it turns out… both pressures and energy densities can produce gravitational fields, unlike Newtonian physics, where it's only mass densities that produce gravitational fields.“

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— Alan Guth American theoretical physicist and cosmologist 1947

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

„It turns out that the energy of a gravitational field—any gravitational field—is negative. During inflation, as the universe gets bigger and bigger and more and more matter is created, the total energy of matter goes upward by an enormous amount. Meanwhile, however, the energy of gravity becomes more and more negative. The negative gravitational energy cancels the energy in matter, so the total energy of the system remains whatever it was when inflation started—presumably something very small. …This capability for producing matter in the universe is one crucial difference between the inflationary model and the previous model.“

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— Alan Guth American theoretical physicist and cosmologist 1947

"A Universe in Your Backyard," in Third Culture: Beyond the Scientific Revolution (1996) ed. John Brockman, p. 279.

„Laws never become theories! The theory of gravity includes a number of Newtonian laws. There is not one law of gravity; there are several laws included within the theory. The same goes for Relativity and even for evolution for that matter.“

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— Aron Ra Aron Ra is an atheist activist and the host of the Ra-Men Podcast 1962

Patheos, Orwellian Legislative Duplicity on HB 1485 http://www.patheos.com/blogs/reasonadvocates/2017/05/05/orwellian-legislative-duplicity-hb-1485/ (May 5, 2017)

„Combine general relativity and quantum theory into a single theory that can claim to be the complete theory of nature. This is called the problem of quantum gravity.“

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— Lee Smolin American cosmologist 1955

The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next (2007)

„Inflation is a simple idea: imagine that the universe begins in a tiny patch of space dominated by the potential energy of some scalar field, a kind of super-dense dark energy. This causes that patch to expand at a terrifically accelerated rate, smoothing out the density and diluting away any unwanted relics. Eventually the scalar field decays into ordinary matter and radiation, reheating the universe into a conventional Big Bang state, after which things proceed as normal.“

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— Sean Carroll American theoretical cosmologist 1966

[The Eternally Existing, Self-reproducing, Frequently Puzzling Inflationary Universe, Preposterous Universe blog, 21 October 2011, http://www.preposterousuniverse.com/blog/2011/10/21/the-eternally-existing-self-reproducing-frequently-puzzling-inflationary-universe/]

„Einstein showed us how to find all the possible universes that were consistent with the laws of physics and the character of gravity, how to reconstruct their pasts and predict their futures. But actually finding them was no easy task.“

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— John D. Barrow British scientist 1952

Preface
The Book of Universes: Exploring the Limits of the Cosmos (2011)

„The conventional Big Bang theory does not say anything about what caused the expansion. It really is only a theory about the aftermath of a bang. In the scientific version of the Big Bang, the universe starts with everything already expanding, with no explanation of how that expansion started… So the Scientific version of the Big Bang theory is not really a theory of a bang, it's really a theory of the aftermath of a bang.“

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— Alan Guth American theoretical physicist and cosmologist 1947

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

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— John C. Baez American mathematician and mathematical physicist 1961

[2008, http://www.edge.org/q2008/q08_5.html#baez, Should I be thinking about quantum gravity? (essay at the World Question Center), edge.org]

„Some of the effects predicted by the theory [of loop quantum gravity] appear to be in conflict with one of the principles of Einstein's special theory of relativity… that the speed of light is a universal constant. …Photons of higher energy travel slightly slower than low-energy photons. …the principle of [general] relativity is preserved but Einstein's special theory of relativity requires modification. …A photon can have an energy-dependent speed without violating the principle of [general] relativity!“

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— Lee Smolin American cosmologist 1955

"Loop Quantum Gravity," The New Humanists: Science at the Edge (2003)

„So it was better to think of formulations which could explain the creation of matter without violating the law of conservation of matter…For that we used what is called as negative energy, which at that time was considered unrealistic. There was a good example of negative energy, mainly Newtonian gravity. Newtonian gravity is a negative energy system because gravitational potential energy is negative and we i. e, Fred Hoyle and me, worked out a fairly consistent method of describing this whole thing. Today what people call phantom fields, an idea which is catching up with people trying to explain some problems of the big-bang, these phantom fields are what we had proposed way back in the 1960’s.“

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— Jayant Narlikar Indian physicist 1938

An Exclusive Interview with Prof. Jayant Vishnu Narlikar

„The incompatibility between gravity and quantum coherence represented by black holes should be solved by a consistent quantum theory that contains gravity as superstring theory. Despite many encouraging results in that sense, I question here the general feeling of a naive resolution of the paradox. And indicate non trivial physical possibilities towards its solution that are suggested by string theory and may be further investigated in its context.“

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— Daniele Amati Italian physicist 1931

[The information paradox, arXiv preprint arXiv:hep-th/0612061v2, 14 December 2006, http://arxiv.org/abs/hep-th/0612061] (See also Thorne-Hawking-Preskill bet.)

„The conventional Big Bang theory says nothing about where all the matter came from. The theory really assumes that for every particle that we see in the universe today, there was, at the very beginning, at least some precursor particle, if not the same particle, with no explanation of where all those particles came from.“

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— Alan Guth American theoretical physicist and cosmologist 1947

Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)

„One of the evident facts about the world is the stability of empty space-time. In classical general relativity we can explain this as a consequence of the positive energy theorem… the positive energy theorem must extend in some suitable form to any viable quantum theory of gravity.“

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— Lee Smolin American cosmologist 1955

"Positive energy in quantum gravity" arXiv (Jun 10, 2014)