Quotes from Lee Smolin

The dark-matter hypothesis is preferred mostly because the only other possibility—that we are wrong about Newton's laws, and by extension general relativity—is too scary to contemplate.

These two discoveries, of relativity and of the quantum, each required us to break definitively with Newtonian physics. However, in spite of great progress over the century, they remain incomplete. Each has defects that point to a deeper theory. But the main reason each is incomplete is the existence of the other.

What we have, in fact, is not a theory at all but a large collection of approximate calculations, together with a web of conjectures that, if true, point to the existence of a theory.

To understand what we mean when we say that space is discrete, we must put our minds completely into the relational way of thinking, and really try to see and feel the world around us as nothing but a network of evolving relationships. These relationships are not among things situated in space - they are among the events that make up the history of the world. The relationships define the space, not the other way around.

On the way, I shared the backseat of Feyerabend's little sports car with the inflatable raft he kept there in case an 8-point earthquake came while he was on the Bay Bridge.

There certainly is a tension between the relativity of simultaneity and non-locality in quantum theory, but it's not strong enough to add up to a falsification of either side by itself.

General relativity predicts that time ends inside black holes because the gravitational collapse squeezes matter to infinite density.

How we think about the future and the past determines everything about how we think about our situation as human beings.

If string theory is a mistake, it's not a trivial mistake. It's a deep mistake and therefore kind of worthy.

But in spite of the obvious effectiveness of mathematics in physics, I have never heard of a good a prioriargument that the world must be organised to mathematical principles.

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.

The search for the meaning of temperature and entropy of matter led to the discovery of atoms. The search for the meaning of the temperature and entropy of radiation led to the discovery of quanta. In just the same way, the search for the meaning of the temperature and entropy of a black hole is now leading to the discovery of the atomic structure of space and time.

The loop approach to quantum gravity is now a thriving field of research. Many of the older ideas, such as supergravity and the study of quantum black holes, have been incorporated into it. Connections have been discovered to other approaches to quantum gravity, such as Alain Connes's non-commutative approach to geometry, Roger Penrose's twistor theory and string theory.

I understood Einstein's general theory of relativity, which meant that I knew how to demonstrate every essential property of it in a page or less of concise and transparent work. It seemed to me that if you understood a theory, it shouldn't take weeks of calculations on an art pad to check its basic properties.

the logic of life is continual change, continual motion, continual evolution.

The key question for a quantum theory of gravity is then the following: Can we extend to quantum theory the principle that space has no fixed geometry? That is, can we make quantum theory background-independent, at least with regard to the geometry of space? If we can do this, we will automatically merge gravity and quantum theory, because gravity is already understood to be an aspect of dynamical spacetime geometry.

Some of its proponents like to say that string theory is a piece of twenty-first- century mathematics that has, by our good fortune, fallen into our hands in the twentieth century.

Thus, the double unification given by the equivalence principle becomes a triple unification: All motions are equivalent once the effects of gravity are taken into account, gravity is indistinguishable from acceleration, and the gravitational field is unified with the geometry of space and time. When worked out in detail, this became Einstein's general theory of relativity, which he published in full form in 1915.

THE GREEK PHILOSOPHER HERACLITUS left us a lovely epigram: Nature loves to hide. It is so often true. There is no way Heraclitus could have seen an atom. No matter how much his fellow philosophers speculated about them, to see an atom was beyond any technology they might have imagined.

There is no meaning to space that is independent of the relationships among real things of the world. [...] Space is nothing apart from the things that exist. [...] If we take out all the words we are not left with an empty sentence, we are left with nothing.

A quantum state is a useful tool because it can do just that. This is our next principle: Given the quantum state of an isolated system at one time, there is a law that will predict the precise quantum state of that system at any other time. This law is called Rule 1. It is also sometimes called the Schrödinger equation. The principle that there is such a law is called unitarity.

One of the hardest lessons to learn in academic life—and for me one of the most disconcerting—is the speed with which a radical insurgency can become orthodoxy. In just a few years a generation of students championing a dangerous new idea are elevated by an initial success into professorships. From these positions of influence they form a powerful network of academic power brokers, which they use to ensure the continuation of the revolution.

When we make a measurement on a system, we disturb it, typically by forcing it to interact with a measuring instrument. So Rule 1 does not apply to measurements. This is true not only of measurements, but of any interaction between the system and outside forces. So is there anything special about measurements? Measurements are special because they are where probabilities enter quantum theory.

laws they share some aspects of cosmological natural selection. One reason that cosmological scenarios with evolving laws succeed in making real predictions is that they don't rely on the anthropic principle—which states that we can live only in a universe