If the rate of expansion one second after the Big Bang had been smaller by even one part in a hundred thousand million million, it would have recollapsed before it reached its present size. On the other hand, if it had been greater by a part in a million, the universe would have expanded too rapidly for stars and planets to form.

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

Because there is a law such as gravity, the universe can and will create itself from nothing.

What goes on inside a star is better understood than one might guess from the difficulty of having to look at a little dot of light through a telescope, because we can calculate what the atoms in the stars should do in most circumstances.

Most people don’t have time to master the very mathematical details of theoretical physics.

The centre of the system of the world is immovable.

It’s a pity that nobody has found an exploding black hole. If they had, I would have won a Nobel prize.

Einstein’s gravitational theory, which is said to be the greatest single achievement of theoretical physics, resulted in beautiful relations connecting gravitational phenomena with the geometry of space; this was an exciting idea.

Observations indicate that the universe is expanding at an ever increasing rate. It will expand forever, getting emptier and darker.

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

They say the universe is expanding. That should help with the traffic.

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?

Religion is part of the human make-up. It’s also part of our cultural and intellectual history. Religion was our first attempt at literature, the texts, our first attempt at cosmology, making sense of where we are in the universe, our first attempt at health care, believing in faith healing, our first attempt at philosophy.

Although almost every theoretical physicist agrees with my prediction that a black hole should glow like a hot body, it would be very difficult to verify experimentally because the temperature of a macroscopic black hole is so low.

Science predicts that many different kinds of universe will be spontaneously created out of nothing. It is a matter of chance which we are in.

According to ‚M‘ theory, ours is not the only universe. Instead, ‚M‘ theory predicts that a great many universes were created out of nothing.

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

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

Some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter.

Only black holes of very low mass would emit a significant amount of radiation.

Cosmology is a rapidly advancing field.

It is theoretically possible to warp spacetime itself, so you’re not actually moving faster than the speed of light, but it’s actually space that’s moving.

Our minds work in real time, which begins at the Big Bang and will end, if there is a Big Crunch – which seems unlikely, now, from the latest data showing accelerating expansion. Consciousness would come to an end at a singularity.

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

The radiation left over from the Big Bang is the same as that in your microwave oven but very much less powerful. It would heat your pizza only to minus 271.3*C – not much good for defrosting the pizza, let alone cooking it.

Imaginary time is a new dimension, at right angles to ordinary, real time.

The cyclic universe theory predicts no gravitational waves from the early universe.

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

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

Mediocre theoretical physicists make no progress. They spend all their time understanding other people’s progress.

I want to know why the universe exists, why there is something greater than nothing.

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.

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.

Theoretical physics is one of the few fields in which being disabled is no handicap – it is all in the mind.