Quantum Gravity Quotes & Sayings

Change is ubiquitous. Only: elementary processes cannot be ordered along a common succession of instants. At the extremely small scale of the quanta of space, the dance of nature does not develop to the rhythm kept by the baton of a single orchestral conductor: every process dances independently with its neighbours, following its own rhythm. The passing of time is intrinsic to the world, it is born of the world itself, out of the relations between quantum events which are the world and which themselves generate their own time. — Carlo Rovelli

Whether you can go back in time is held in the grip of the law of quantum gravity. — Kip Thorne

Relativity. Gravity. Quantum. Electrodynamics. Evolution. Each of these theories is true, whether or not you believe in them. — Neil DeGrasse Tyson

Quantum mechanics as it stands would be perfect if we didn't have the quantum-gravity issue and a few other very deep fundamental problems. — Gerard 't Hooft

...a useful coorective to the triumphalism of some scientists. For example, Maddox went out of his way to emphasise the provisional nature of much physics - he referred to black holes as 'putative' only, to the search for theories of everything as 'the embodiment of a belief, even a hope' and stated that the reason why the quantum gravity project is 'becalmed' right now is because 'the problem to be solved is not yet fully understood' and that the idea that the universe began with a Big Bang 'will be found to be false'. — Peter Watson

Time sits at the center of the tangle of problems raised by the intersection of gravity, quantum mechanics, and thermodynamics. — Carlo Rovelli

The extreme weakness of quantum gravitational effects now poses some philosophical problems; maybe nature is trying to tell us something new here: maybe we should not try to quantize gravity. — Richard P. Feynman

communication between each universe is impossible because we're glued to our own three-dimensional membrane by the physical forces of quantum mechanics like a fly is glued to flypaper. Only gravity, which is responsible for the warping of space-time, can make the jump into other universes." "How far away are they?" "Maybe closer than you think. A lot closer than you think. One set of calculations concerning gravity says that other universes can be as close as a millimeter away from us. — Glenn Cooper

Three of the four forces (excluding gravity) are therefore united by quantum theory, giving us unification without geometry, which appears to contradict the theme of this book and everything we have considered so far. — Michio Kaku

What those two young physicists did remains the most important step yet made in the search for quantum gravity. They gave us two general and simple laws, which were the first physical predictions to come from the study of quantum gravity. They are: Unruh's law. Accelerating observers see themselves as embedded in a gas of hot photons at a temperature proportional to their acceleration. Bekenstein's law With every horizon that forms a boundary separating an observer from a region which is hidden from them, there is associated an entropy which measures the amount of information which is hidden behind it. This entropy is always proportional to the area of the horizon. — Lee Smolin

The most important single thing about string theory is that it's a highly mathematical theory, and the mathematics holds together in a very tight and consistent way. It contains in its basic structure both quantum mechanics and the theory of gravity. That's big news. — Leonard Susskind

An event horizon is also called the point of no return. In a sense of general relativity, it's the point at which the gravitational pull becomes so great escape is impossible. Some theorize quantum gravity effects become significant in the vicinity of such an occurrence. — Karen Marie Moning

Over the last three decades, theorists have proposed at least a dozen new approaches. Each approach is motivated by a compelling hypothesis, but none has so far succeeded. In the realm of particle physics, these include Technicolor, preon models, and supersymmetry. In the realm of spacetime, they include twistor theory, causal sets, supergravity, dynamical triangulations, and loop quantum gravity. Some of these ideas are as exotic as they sound. — Lee Smolin

Of course, even without my help, other forces would keep the cosmos chugging along. Many different belief systems powered the revolution of the planets and stars. Wolves would still chase Sol across the sky. Ra would continue his daily journey in his sun barque. Tonatiuh would keep running on his surplus blood from human sacrifices back in the Aztec days. And that other thing - science - would still generate gravity and quantum physics or whatever. — Rick Riordan

Both loop quantum gravity and string theory assert that there is an atomic structure to space. In the next two chapters we shall see that loop quantum gravity in fact gives a rather detailed picture of that atomic structure. The picture of the atomic structure one gets from string theory is presently incomplete but, as we shall see in Chapter 11, it is still impossible in string theory to avoid the conclusion that there must be an atomic structure to space and time. In Chapter 13 we shall discover that both pictures of the atomic structure of space can be used to explain the entropy and temperature of black holes. — Lee Smolin

We're going to need a definitive quantum theory of gravity, which is part of a grand unified theory - it's the main missing piece. — Kip Thorne

Surprisingly now, over a half a century later, time symmetric approaches to electromagnetism, quantum mechanics, gravity, and cosmology might be consonant with the kind of eschatology that a theist such as Pannenberg supports. — Robert John Russell

I do feel strongly that string theory is our best hope for making progress at unifying gravity and quantum mechanics. — Brian Greene

In the froth, space doesn't have a definite structure. It has various probabilities for different shapes and curvatures. It might have a 50 percent chance of being in one shape, a 10 percent chance of being in another, and a 40 percent chance of being in a third form. Because any structure is possible inside the singularity, we say the singularity is constructed from probabilistic foam, or quantum foam. Quantum gravity governs the probabilities for the various foam structures. — Clifford A. Pickover

As we discussed in Chapter 7, we physicists still haven't found a mathematical structure that can describe all aspects of reality, including gravity, but so far, there's no indication that string theory or any of the other most actively pursued candidates for such a description are any less mathematical than quantum field theory. — Max Tegmark

Every string theory that's been written down says the speed of light is universal. But other ideas about quantum gravity predict the speed of light has actually increased. — Lee Smolin

So we may now pose a question which could be answered only if we have a quantum theory of gravity. What is the nature of the information trapped in a quantum black hole? Keep this in mind as we go ahead and explore the different approaches to quantum gravity, for a good test of a theory of quantum gravity is how well it is able to answer this question. — Lee Smolin

Einstein comes along and says, space and time can warp and curve, that's what gravity is. Now string theory comes along and says, yes, gravity, quantum mechanics, electromagnetism - all together in one package, but only if the universe has more dimensions than the ones that we see. — Brian Greene

It is likely that space as we know it ceases to exist and is replaced by some form of chaotic quantum 'foam', where gravity plays a new role in fashioning the forms of energy that can exist. — Anonymous

Reality had briefly slid aside one of its black, opaque panels, to give him a glimpse of the gears that ticked behind it. Saunders had discovered a universal constant, like gravity or the quantum nature of light. No matter where you went - no matter how ancient the traditions, no matter how grand the history, no matter how awe-inspiring the landscape - there was always a market for a cheap Happy Meal. — Joe Hill

Because both quantum theory and Einstein's theory of gravity are united in ten-dimensional space, we expect that the question of time travel will be settled decisively by the hyperspace theory. As in the case of wormholes and dimensional windows, the final chapter will be written when we incorporate the full power of the hyperspace theory. — Michio Kaku

Perhaps the most energetic and persistent advocate of the claim that time is illusory is the British physicist Julian Barbour. Impressively, Barbour has managed to do interesting research in physics for decades now without any academic position, publishing dozens of papers in respected journals. He has supported himself in part by translating technical papers from Russian to English - in his spare time, tirelessly investigating the idea that time does not exist, constructing theoretical models of classical and quantum gravity in which time plays no fundamental role. — Anonymous

One readon why it has taken so long to construct a quantum theory of gravity is that all previous quantum theories were background dependent. It proved rather challenging to construct a background independent quantum theory, in which the mathematical structure of the quantum theory made no mention of points, except when identified through networks of relationships. The problem of how to construct a quantum theoretic description of a world in which space and time are nothing but networks of relationships was solved over the last 15 years of the twentieth century. The theory that resulted is loop quantum gravity, which is one of our three roads. — Lee Smolin

In a famous hoax, physicist Alan Sokal submitted an article to a leading journal of cultural studies purporting to describe how quantum gravity could produce a "liberatory postmodern science." The article, which parodied the convoluted style of argument in the fashionable academic world of cultural studies, was promptly published by the editors. Sokal announced that his intention was to test the intellectual standards of the discipline by checking whether the journal would publish a piece "liberally salted with nonsense." Sokal, "A Physicist Experiments with Cultural Studies," April 15, 1996, — Dani Rodrik

The resulting, stable singularities now carry the name BKL in honor of Belinsky, Khalatnikov, and Lifshitz. A BKL singularity is chaotic. Highly chaotic. And lethal. Highly lethal. — Kip S. Thorne

The Planck satellite may detect the imprint of the gravitational waves predicted by inflation. This would be quantum gravity written across the sky. — Stephen Hawking

One of the most exciting things about dark energy is that it seems to live at the very nexus of two of our most successful theories of physics: quantum mechanics, which explains the physics of the small, and Einstein's Theory of General Relativity, which explains the physics of the large, including gravity. — Adam Riess

There was a long history of speculation that in quantum gravity, unlike Einstein's classical theory, it might be possible for the topology of spacetime to change. — Edward Witten