Quotes About Physics

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.

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

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.

All the known particles in the universe can be divided into two groups: particles of spin ½, which make up the matter in the universe, and particles of spin 0, 1, and 2, which, as we shall see, give rise to forces between the matter particles.

The naive view of reality therefore is not compatible with modern physics. To deal with such paradoxes we shall adopt an approach that we call model-dependent realism. It is based on the idea that our brains interpret the input from our sensory organs by making a model of the world. When such a model is successful at explaining events, we tend to attribute to it, and to the elements and concepts that constitute it, the quality of reality or absolute truth.

Until the advent of modern physics it was generally thought that all knowledge of the world could be obtained through direct observation, that things are what they seem, as perceived through our senses. But the spectacular success of modern physics, which is based upon concepts such as Feynman's that clash with everyday experience, has shown that that is not the case. The naive view of reality therefore is not compatible with modern physics.

The microwave background indicated that the universe had had a hot, dense stage in the past.

the statement "All uranium-235 spheres are less than a mile in diameter" could be thought of as a law of nature because, according to what we know about nuclear physics, once a sphere of uranium-235 grew to a diameter greater than about six inches, it would demolish itself in a nuclear explosion. Hence we can be sure that such spheres do not exist. (Nor would it be a good idea to try to make one!)

Visible light has a wavelength of between only forty and eighty millionths of a centimeter. Even shorter wavelengths are known as ultraviolet, X rays, and gamma rays. Maxwell's theory predicted that radio or light waves should travel at a certain fixed speed.

to explain how the early universe

As Nathan Myhrvold of Microsoft (a former post-doc of mine) remarked: I have sold more books on physics than Madonna has on sex.

So the total energy of the universe is zero.

events before the big bang can have no consequences, so they should not form part of a scientific model of the universe.

an­ti­quarks? Why are there not equal num­bers of each? It is cer­tain­ly for­tu­nate for us that the num­bers are un­equal be ear­ly uni­verse and left a uni­verse filled with ra­di­ation but hard­ly any mat­ter. There would then have been no galax­ies, stars, or plan­ets on which hu­man life could have de­vel­oped.

In physics a system is said to have a symmetry if its properties are unaffected by a certain transformation such as rotating it in space or taking its mirror image. For example, if you flip a donut over, it looks exactly the same (unless it has a chocolate topping, in which case it is better just to eat it).

calculations show that a change of as little as 0.5 percent in the strength of the strong nuclear force, or 4 percent in the electric force, would destroy either nearly all carbon or all oxygen in every star, and hence the possibility of life as we know it. Change those rules of our universe just a bit, and the conditions for our existence disappear!

What is it that breathes fire into the equations and makes a universe for them to describe?

time and space are intertwined. It is something like adding a fourth direction of future/past to the usual left/right, forward/backward, and up/down. Physicists call this marriage of space and time "space-time," and because space-time includes a fourth direction, they call it the fourth dimension.

This is known as the twins paradox, but it is a paradox only if one has the idea of absolute time at the back of one's mind. In the theory of relativity there is no unique absolute time, but instead each individual has his own personal measure of time that depends on where he is and how he is moving.

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

can one have atoms in which the nucleus is a tiny primordial black hole, formed in the early universe?

In a sense the debate between Penrose and Hawking is a continuation of that earlier argument, with Penrose playing the role of Einstein and Hawking that of Bohr.

Though realism may be a tempting viewpoint, as we'll see later, what we know about modern physics makes it a difficult one to defend.