John Gribbin - Get a Grip on Physics

Copyright

Copyright 1999 by John Gribbin
All rights reserved.

Bibliographical Note

This Dover edition, first published in 2011, is an unabridged republication of Get a Grip on New Physics , originally published in 1999 by Weidenfeld and Nicolson, London.

Library of Congress Cataloging-in-Publication Data

Gribbin, John R.

[Get a grip on new physics]

Get a grip on physics / John Gribbin. Dover ed.

p. cm.

Originally published: Get a grip on new physics. London : Weidenfeld and Nicolson, 1999.

Includes bibliographical references and index.

ISBN-13: 978-0-486-48502-7 (alk. paper)

ISBN-10: 0-486-48502-1 (alk. paper)

1. PhysicsPopular works. I. Title.

QC24.5.G75 2011

530dc23

2011016863

Manufactured in the United States by Courier Corporation
48502101
www.doverpublications.com

CHAPTER 1
Atoms and Molecules

CHAPTER 2
Beyond Newton

CHAPTER 3
The Quantum World

CHAPTER 4
Even Newer Physics

CHAPTER 5
Back to the Future

CHAPTER 6
Tomorrows Physics

THE OLD PHYSICS

Modem physics - or, at least, the first phase of modern physics - began with Isaac Newton, in the second half of the 17th century. The most important thing Newton did was to spell out that the entire Universe is governed by simple rules, which also apply to things going on here on Earth. The most famous example of this is his LAW OF GRAVITATION , which explains both the way an apple falls to the ground from a tree and how the Moon stays in orbit around the Earth - and much more besides.

OLD AND NEW PHYSICS

Old physics is the stuff we learn in school, the kind of laws that apply to objects we can see and touch, like billiard balls or cars. New physics deals with things that are inaccessible to our senses, like atoms and black holes.

NEWTON AND GRAVITY

This law of nature is what is known as an INVERSE-SQUARE LAW the force of attraction between two objects depends on their two masses multiplied together, divided by the square of the distance between them . So if the same two objects are twice as far apart the force is reduced to a quarter, while if theyre three times as far apart it is reduced to a ninth. And so on.

But, for the moment, the law itself is less important than the fact that there is a unique law that describes the force of GRAVITATIONAL ATTRACTION operating between any two objects in the Universe between a pencil on my desk and the cat in the next room, between the Moon and the Earth, or between two galaxies on opposite sides of the Universe, or even between my cat and a distant galaxy.

BEFORE NEWTON

Before Newton came along, even scientifically minded people commonly believed the Universe was governed by rules devised by the gods, or God. When, in 1609, Johannes Kepler realized that something made the planets stay in orbit around the Sun, he called it the Holy Spirit Force, and nobody laughed at him for doing so. The Universe was seemingly at the mercy of mysterious and incomprehensible forces, which might change from day to day or from place to place .

KEY WORDS

GRAVITY:

the force of attraction between two masses

GRAVITATION:

the influence any object exerts on other objects in the Universe simply by having mass

Johannes Kepler (15711630)

German astronomer who discovered the laws of planetary motion, which helped Newton develop his theory of gravity. Kepler used observations of the planets compiled by Tycho Brahe (15461601). Before joining Brahe in Prague, he trained for a career in the Church, then worked as a teacher of mathematics at a Protestant seminary in Graz.

Isaac Newton (16421727)

Newton was active in many fields. He studied alchemy (still almost respectable at that time) and theology, and served as a Member of Parliament (his knighthood was for political work, not science) and as Master of the Royal Mint and President of the Royal Society. Newton was very secretive about his work, and often got involved in huge rows with other scientists about who had thought of an idea first (usually he had thought of it, but hadnt bothered to tell anyone!). His great work in physics was completed before he was 30, but only published in 1687, at the urging of Edmond Halley. In the 1690s Newton suffered a mental breakdown, and although he recovered sufficiently to lead a normal life, he did no more scientific work.

A CLOCKWORK UNIVERSE

After Newton, the Universe was perceived in a quite different way - as a kind of cosmic clockwork mechanism, running predictably in accordance with laws of physics that could be determined from experiments here on Earth. The laws might be God-given (Newton thought they were), but they were now seen as being the same everywhere and at all times.

FUNDAMENTAL LAWS

The predictability of the Newtonian Universe was based on three other fundamental laws discovered by Newton . Known as Newtons LAWS OF MECHANICS (or laws of motion), they are spelled out in his great book Philosophiae Naturalis Principia Mathematica ( The Mathematical Principles of Natural Philosophy ), usually referred to simply as the Principia.

These three laws formed the basis of physics for the next 200 years - and still suffice to explain the way things behave explained by them (such as the flight of a jet aircraft, or the journey of a space probe to the planet Jupiter) were undreamed of by Newton himself.

Newtons first law of mechanics

The first of Newtons three laws of mechanics immediately shows how physicists often have to discount common sense in order to get a grip on the way the world works. It Insists that any object - by implication, any object in the entire Universe - either stays still or keeps moving in a straight line unless some force is applied to the object . The standing still part is no problem, so far as common sense is concerned. Here on the surface of the Earth most things do stay still, unless they are given a push. But if given a push, they certainly dont keep moving in a straight line for ever. They slow down and come to a halt.