Quotes from Stephen Hawking

Why do we remember the past but not the future? The

a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation.

On the observational side, by far the most important development has been the measurement of fluctuations in the cosmic microwave background radiation by COBE (the Cosmic Background Explorer satellite)

Up to now, most scientists have been too occupied with the development of new theories that describe what the universe is to ask the question why. On the other hand, the people whose business it is to ask why, the philosophers, have not been able to keep up with the advance of scientific theories.

why it is that we and the universe exist. If we find the answer to that, it would be the ultimate triumph of human reason – for then we would know the mind of God.

Equações são mais importantes para mim, pois a política existe para o presente, ao passo que uma equação existe para a eternidade.

In other words, the theory of relativity put an end to the idea of absolute time!

Parece que en la naturaleza hay un cierto nivel de aleatoriedad o incertidumbre, que no se puede eliminar por muy buenas que sean las teorías. Eso se puede resumir en el Principio de Incertidumbre, formulado en 1927 por el científico alemán Werner Heisenberg.

t is generally recognized that women are better than men at languages, personal relations and multitasking, but less good at map-reading and spatial awareness. It is therefore not unreasonable to suppose that women might be less good at mathematics and physics. It is not politically correct to say such things....But it cannot be denied that there are differences between men and women. Of course, these are differences between the averages only. There are wide variations about the mean.

So, one can regard the pair of particles as a single particle moving on a closed loop in space-time. When the pair is moving forward in time (from the event at which it appears to that at which it annihilates), it is called a particle. But when the particle is traveling back in time (from the event at which the pair annihilates to that at which it appears), it is said to be an antiparticle traveling forward in time.

Traditionally these are questions for philosophy, but philosophy is dead. Philosophy has not kept up with modern developments in science, particularly physics.

Cuando te enfrentas a la posibilidad de una muerte temprana, te das cuenta de que hay muchas cosas que quieres hacer antes de que tu vida termine.

In fact, according to quantum physics, each particle has some probability of being found anywhere in the universe.

We must accept that time is not completely separate from and independent of space, but is combined with it to form an object called space-time.

According to Feynman, a system has not just one history but every possible history.

it seems that we are no more than biological machines and that free will is just an illusion.

simplicity is a matter of taste.

was generally thought that all knowledge of the world could be obtained through direct observation

In modern science laws of nature are usually phrased in mathematics. They can be either exact or approximate, but they must have been observed to hold without exception—if not universally, then at least under a stipulated set of conditions. For

you remember every word in this book, your memory will have recorded about two million pieces of information: the order in your brain will have increased by about two million units. However, while you have been reading the book, you will have converted at least a thousand calories of ordered energy, in the form of food, into disordered energy, in the form of heat that you lose to the air around you by convection and sweat.

When I was in the Far East, I was asked not to mention the Big Crunch, because of the effect it might have on the market. But the markets crashed, so maybe the story got out somehow. In Britain, people don't seem too worried about a possible end twenty billion years in the future. You can do quite a lot of eating, drinking and being merry before that.

Our modern picture of the universe dates back to only 1924, when the American astronomer Edwin Hubble demonstrated that ours was not the only galaxy. There were in fact many others, with vast tracts of empty space between them.

We foresee great peril if governments and societies do not take action now, to render nuclear weapons obsolete and to prevent further climate change.

There might be one history in which the moon is made of Roquefort cheese. But we have observed that the moon is not made of cheese, which is bad news for mice. Hence histories in which the moon is made of cheese do not contribute to the present state of our universe, though they might contribute to others. That might sound like science fiction, but it isn't.