You have a row of dominoes set up; you knock over the first one, and what will happen to the last one is that it will go over very quickly.

Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe?

There is no physical law precluding particles from being organised in ways that perform even more advanced computations than the arrangements of particles in human brains.

Nothing exists from whose nature some effect does not follow.

If you are in a spaceship that is traveling at the speed of light, and you turn on the headlights, does anything happen?

There are children playing in the streets who could solve some of my top problems in physics, because they have modes of sensory perception that I lost long ago.

Science is beautiful when it makes simple explanations of phenomena or connections between different observations. Examples include the double helix in biology and the fundamental equations of physics.

Working out another system to replace Newton’s laws took a long time because phenomena at the atomic level were quite strange. One had to lose one’s common sense in order to perceive what was happening at the atomic level.

Resistance is usually ascribed to bodies at rest, and impulse to those in motion, but motion and rest, as commonly conceived, are only relatively distinguished; nor are those bodies always truly at rest, which commonly are taken to be so.

The missing link in cosmology is the nature of dark matter and dark energy.

The greatest progress is in the sciences that study the simplest systems. So take, say, physics – greatest progress there. But one of the reasons is that the physicists have an advantage that no other branch of sciences has. If something gets too complicated, they hand it to someone else.

My father was a research scientist in tropical medicine, so I always assumed I would be a scientist, too. I felt that medicine was too vague and inexact, so I chose physics.

An object in motion tends to remain in motion along a straight line unless acted upon by an outside force.

Let me show you how it’s done… Loser!

I went to Princeton specifically to study physics.

There could be no fairer destiny for any physical theory than that it should point the way to a more comprehensive theory in which it lives on as a limiting case.

It now appears that the way the universe began can indeed be determined, using imaginary time.

Organized murder is war, and though we demonstrate against a particular war, the nuclear, or any other kind of war, we have never demonstrated against war.

The United States was seriously defeated in Iraq by Iraqi nationalism – mostly by nonviolent resistance. The United States could kill the insurgents, but they couldn’t deal with half a million people demonstrating in the streets.

Quarks came in a number of varieties – in fact, at first, only three were needed to explain all the hundreds of particles and the different kinds of quarks – they are called u-type, d-type, s-type.

Man can be understood only by ascending from physics, chemistry, biology, and geology. In other words, he is first of all a cosmic problem.

Consequences are unpitying.

The drawing teacher has this problem of communicating how to draw by osmosis and not by instruction, while the physics teacher has the problem of always teaching techniques, rather than the spirit, of how to go about solving physical problems.

It was Einstein’s dream to discover the grand design of the universe, a single theory that explains everything. However, physicists in Einstein’s day hadn’t made enough progress in understanding the forces of nature for that to be a realistic goal.

My background educationally is physics and economics, and I grew up in sort of an engineering environment – my father is an electromechanical engineer. And so there were lots of engineery things around me.

M-theory is the unified theory Einstein was hoping to find.

It should be possible to explain the laws of physics to a barmaid.

Time can behave like another direction in space under extreme conditions.

In this day and age, when you can use a machine or computer to simulate or emulate what people can do together, it still can’t replace the magic of four people in a room playing.

Before 1915, space and time were thought of as a fixed arena in which events took place, but which was not affected by what happened in it. Space and time are now dynamic quantities… space and time not only affect but are also affected by everything that happens in the universe.

All the evidence, experimental and even a little theoretical, seems to indicate that it is the energy content which is involved in gravitation, and therefore, since matter and antimatter both represent positive energies, gravitation makes no distinction.

Chance is a word void of sense; nothing can exist without a cause.

In the past, there was active discrimination against women in science. That has now gone, and although there are residual effects, these are not enough to account for the small numbers of women, particularly in mathematics and physics.

I think equation guessing might be the best method to proceed to obtain the laws for the part of physics which is presently unknown. Yet, when I was much younger, I tried this equation guessing, and I have seen many students try this, but it is very easy to go off in wildly incorrect and impossible directions.

Shallow men believe in luck. Strong men believe in cause and effect.

Peoples do not defy repression and death, nor do they remain for nights on end protesting energetically, just because of merely formal matters.

Persuasion is clearly a sort of demonstration, since we are most fully persuaded when we consider a thing to have been demonstrated.

I tell you the solemn truth, that the doctrine of the Trinity is not so difficult to accept for a working proposition as any one of the axioms of physics.

I think we all change each other’s paths. I don’t know which law idea that is in physics, but I don’t think any of us can live without affecting one another.

Politics is a science. You can demonstrate that you are right and that others are wrong.

If a projectile were deprived of the force of gravity, it would not be deflected toward the earth but would go off in a straight line into the heavens and do so with uniform motion, provided that the resistance of the air were removed.

I am above the weakness of seeking to establish a sequence of cause and effect, between the disaster and the atrocity.

Everything starts somewhere, although many physicists disagree.

Understand: any phenomenon in the world is by nature complex. The people you deal with are equally complex. Any action sets off a limitless chain of reactions. It is never so simple as A leads to B. B will lead to C, D and beyond.

It is now quite lawful for a Catholic woman to avoid pregnancy by a resort to mathematics, though she is still forbidden to resort to physics or chemistry.

What goes up must come down.

OK, so what’s the speed of dark?

There happen to be a lot of people around who spent an hour on the Internet and think they know a lot of physics, but it doesn’t work like that… There’s a reason there are graduate schools in these departments.

Today, all physicists know from studying Einstein and Bohr that sometimes an idea which looks completely paradoxical at first, if analyzed to completion in all detail and in experimental situations, may, in fact, not be paradoxical.

Philosophers have not kept up with modern developments in science. Particularly physics.

We are the product of quantum fluctuations in the very early universe.

I think you should always bear in mind that entropy is not on your side.

With the exception of gravitation and radioactivity, all of the phenomena known to physicists and chemists in 1911 have their ultimate explanation in the laws of quantum electrodynamics.

From the point of view of basic physics, the most interesting phenomena are, of course, in the new places, the places where the rules do not work – not the places where they do work! That is the way in which we discover new rules.

We get the exciting result that the total energy of the universe is zero. Why this should be so is one of the great mysteries – and therefore one of the important questions of physics. After all, what would be the use of studying physics if the mysteries were not the most important things to investigate?

My first popular book, ‚A Brief History of Time,‘ aroused a great deal of interest, but many found it difficult to understand.

There is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics.

I hope I have helped to raise the profile of science and to show that physics is not a mystery but can be understood by ordinary people.

The observer, when he seems to himself to be observing a stone, is really, if physics is to be believed, observing the effects of the stone upon himself.

I tend to approach things from a physics framework. And physics teaches you to reason from first principles rather than by analogy.

To every action there is always opposed an equal reaction.