Stephen Hawking is a British physicist and author who studies black holes and who wrote A Brief History of Time.

Quotes by Stephen Hawking in Time One

If one takes the positivist position, as I do, one cannot say what time actually is.

Cosmology cannot predict anything about the universe unless it makes some assumption about the initial conditions.

There ought to be something very distinctive about the theory that describes the Universe.

[T]he Anthropic Principle … can be paraphrased as ‘Things are as they are because we are.

This renormalization procedure has never been put on a very firm conceptual or mathematical basis.

(E)ven if we find a unified theory, we may be able to make only statistical predictions.

The universe is what it is because it was what it was.

If gravity had been sometimes attractive and sometimes repulsive, like electrodynamics, we would never notice it at all because it is about 10⁴⁰ times weaker. It is only because gravity always has the same sign that the gravitational force between the particles of two macroscopic bodies like ourselves and the Earth add up to give a force we can feel.

The only way to have a scientific theory is if the laws of physics hold everywhere, including at the beginning of the universe.

Although there have been suggestions that spacetime may have a discrete structure, I see no reason to abandon the continuum theories that have been so successful.

The unpredictable, random element [of quantum theories] comes in only when we try to interpret the wave in terms of positions and velocities of particles. But maybe that is our mistake: maybe there are no positions and velocities, but only waves.

[B]y predicting that [when] the universe began … the density of the universe and the curvature of space-time would have been infinite, the theory of general relativity predicts that there is a point in the universe where the theory itself breaks down, or fails. Such a point is an example of what mathematicians call a singularity.

[A]t some time in the past (about 13.75 billion years ago), the distance between neighboring galaxies must have been zero. In other words, the entire universe was squashed into a single point with zero size, like a sphere of radius zero.

In a way this attitude is similar to that of those who in earlier centuries discouraged scientific investigation by saying that all natural phenomena were the work of God and should not be inquired into. I think that the initial conditions of the Universe are as suitable a subject for scientific study and theory as are the local physical laws.

(M)ost scientists .... separate the problem into two parts. First, there are the laws that tell us how the universe changes with time. … Second, there is the question of the initial state of the universe. Some people feel that science should be concerned with only the first part; they regard the question of the initial situation as a matter for metaphysics or religion.

It ... now takes enormous machines and a great deal of money to perform an experiment whose results we cannot predict.

I wanted to understand how the universe began.