Freeman Dyson

Gödel's theorem shows conclusively that in pure mathematics reductionism does not work. To decide whether a mathematical statement is true, it is not sufficient to reduce the statement to marks on paper and to study the behavior of the marks. Except in trivial cases, you can decide the truth of a statement only by studying its meaning and its context in the larger world of mathematical ideas.

Rutherford's discovery was the beginning of the science that came to be called nuclear physics. ... The projectiles that he used to explore the nucleus were particles produced in the disintegration of radium ... discovered by Marie Curie in 1898. The particles are helium nuclei that are emitted at high speed when radium atoms decay ... The twenty years between 1909 and 1929 were the era of tabletop nuclear physics. ... Small and simple experiments were sufficient to establish the basic laws of nuclear physics.

Black holes are not rare, and they are not an accidental embellishment of our Universe. They are a fundamental driving force of its evolution. They are a dominant source of energy. For every ounce of matter consumed, they yield more than ten times as much energy as the nuclear reactions of fusion and fission that cause our sun to shine and our hydrogen bombs to explode.

Astronomers have so far escaped the extreme specialization that has overtaken physicists. Telescopes are big, but they are not as complicated as accelerators. Observations with a big telescope can be carried out in hours rather than years.

I have to clear away a few popular misconceptions about space as a habitat … It is generally considered that planets are important. Except for Earth, they are not. Mars is waterless, and the others are, for various reasons, basically inhospitable to man. It is generally considered that beyond the sun’s family of planets there is absolute emptiness extending for light-years until you come to another star. In fact, it is likely that the space around the solar system is populated by huge numbers of comets, small worlds a few miles in diameter, rich in water and the other chemicals essential to life.

A good cause can become bad if we fight for it with means that are indiscriminately murderous. A bad cause can become good if enough people fight for it in a spirit of comradeship and self-sacrifice. In the end it is how you fight, as much as why you fight, that makes your cause good or bad.

Science as subversion has a long history. ... Davis and Sakharov belong to an old tradition in science that goes all the way back to the rebels Benjamin Franklin and Joseph Priestley in the eighteenth century, to Galileo and Giordano Bruno in the seventeenth and sixteenth. If science ceases to be a rebellion against authority, then it does not deserve the talents of our brightest children. ... We should try to introduce our children to science today as a rebellion against poverty and ugliness and militarism and economic injustice.

The progress of science requires the growth of understanding in both directions, downward from the whole to the parts and upward from the parts to the whole. A reductionist philosophy, arbitrarily proclaiming that the growth of understanding must go only in one direction, makes no scientific sense. Indeed, dogmatic philosophical beliefs of any kind have no place in science.

It is characteristic of all deep human problems that they are not to be approached without some humor and some bewilderment.

Over periods of 10,000 years the distinctions between Western and Eastern and African cultures lose all meaning. Over a time span of 100,000 years we are all Africans. And over a time span of 300 million years we are all amphibians, waddling uncertainly out of dried-up ponds onto the alien and hostile land.

A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering.

There is a great satisfaction in building good tools for other people to use.