I. Introduction Where did the atomic bomb come from? In this paper, I will look at the development of the ideas needed to create an atomic bomb. Specifically, what did scientists need to know for them to theorize that a cataclysmic explosion would result when a critical mass of certain elements undergo a chain reaction of nuclear fission. However, I will only look at scientific ideas generally, as they progressed towards fission.
This development of ideas was propelled by genius, persistence and tenacity, coupled with flashes of insight into the nature of the universe. We see that this development is tied closely to the ability to free the teathers of erroneous paradigms and build better models of the universe in their place. We will be concerned, principally, with the development of physics. Einstein wrote the following on the definition of physics:
“What we call physics comprises that group of natural sciences which base their concepts on measurements; and whose concepts and propositions lend themselves to mathematical formulation.” (Weaver, 78)
Although physics today is more focused, this is the basis of all science. One of the first groups of people to freely think about the universe and make an attempt to explain their world scientifically were the Greeks.
II. The Greek Ideology The Greek’s investigation of science demonstrate that their minds were on par with the best of this era, specifically Aristotle (384 – 322 B.C.), who formed many brilliant theories. He, along with others, put the theories into sophisticated form that created the basis of scientific thought for close to two millennia. In his universe were four “elements”: Earth, Water, Air, and Fire. The Earth was the common center of all the solid materials and had a natural place as the center of the universe.
If all the solid material sought a location as close to the center as possible, then the Earth had to be a sphere. He had likewise ordered the other “elements” into spheres. Water had its natural place on the surface of the sphere Earth. Air had its natural place on the surface of the sphere Water. Fire had its natural place outside the sphere of Air. Observations corresponded to this view of the universe. However, he performed no experiments. He stated that heavier objects would want to move faster toward their respective spheres than lighter objects. It is regrettable that he did not perform any of a number of simple experiments to prove or disprove his ideas.
These Greek philosophers worked to explain the motion of matter. Their ordering of the universe defined what happened when an element found itself outside of its sphere. It simply sought its correct sphere. They also did well with basic types of motion, stating that when one object had contact with another it would create motion in that object. There were other types of motion they had trouble with. For instance, why does a ball keep rolling even after your hand no longer has contact with it?
Another problem that arises from the Aristotelian classification is how would two objects affect each other in a vacuum? Aristotle had theorized that vacuums would create difficulties, but in his day they were only considered a philosophical abstraction. The problem did not need to be dealt with seriously. Nevertheless, motion in the absence of the element Air was unthinkable. For them, Air had inherent physical properties. Also, it encompassed everything that could possibly have motion. The absence of Air meant the absence of motion.
Before we can answer these questions, however, we must look at when and how observation combined with experimentation.
III. Unifying Observation and Thought with Experimentation The Aristotelian universe was generally accepted for about 1600 years. During the late Middle Ages the view began to change slowly. Scholars began to view experimenting as a method of testing theories. The following passage explains the beginning of the change in ideas when scientists used experimentation methodically.
“Historically we may say the revolution in ideas began with Copernicus and his heliocentric theory of the solar system, but Kepler’s work is much closer to modern science than that of Copernicus, for in formulating his three laws of planetary motion, Kepler proceeded much the way the contemporary physicist does in constructing theoretical models of structures such as atoms, stars, or galaxies. Even so, Galileo and Newton were the initiators of modern science, for whereas Kepler’s work was primarily empirical, the work of Galileo and Newton has all the elements of what we now call physics. This work was an enormous step forward in that it revealed the relationship between the motion of a body and the forces acting on it.” (Weaver, 18)
Let’s back track slightly to Galileo Galilei (1564 – 1642). It was not until Galileo that the Aristotelian universe collapsed in a flurry of ingenious and conclusive experiments. Galileo did not invent experimentation, but he forever united it with science.
For a brief background of Galileo, we turn to Segre’s “From Falling Bodies to Radio Waves.””
“Galileo passed the first ten years of his life in Pisa, went to Florence around 1574, and was back in Pisa in 1581, registering as a student of medicine at the university. When he was nineteen years old he became acquainted with geometry by reading books and meeting the mathematician Ostilio Ricci (1540 – 1603). [It can very well be imagined] what a revelation the discovery of geometry must have been for the young man. He was studying something probably distasteful to him, and all of a sudden he found the intellectual for which he was born and which somehow had escaped him previously. Probably only passionate love can equal the strong emotion aroused by such an event.” (Segre, “From Falling…”, 16)
Galileo was the first person to create a shop for the pursuit of scientific study. Some experiments dealt with time-keeping, not an easy task four hundred years ago. He dripped water down inclined planes and achieved useful results. He also experimented with rolling balls of various weights on these inclined planes. It is not difficult to prove that the amount of time for the ball to traverse the plane is independent of the mass of the ball.
In other words, it requires an equal amount of time for two balls of different weights to roll down an inclined plane. From this, and other experiments, he made the generalization that all bodies fell through equal distances in equal times. There were other significant discoveries made. Aristotelian thought was proved incorrect. Or we may say the generalizations made by Galileo provides a base to explain more phenomena when compared to the Aristotelian universe.
After other people performed experiments and formed theories, and a hundred years passed, Sir Issac Newton (1642 – 1727) enters the stage.
Newton developed mathematical tools to help him solve the problems created by his scientific pursuits. The nature of the phenomena he was pursuing forced him to create calculus. The following passage fills in some of the details.
“Using the calculus, Newton deduced Kepler’s three laws of planetary motion. This changed the methodology of scientific research forever, for it showed that a correct physical law (Newton’s law of gravity) combined with logic (mathematics) can reveal new truths with relatively little effort and in a relatively short time. Kepler’s empirical formulation of the laws of planetary motion represents some sixty man-years of research (thirty years of Tycho Brahe’s observation and thirty years of Kepler’s arithmetic analysis), were as Newton’s derivation took only an hour or two.” (Jefferson, 19)
The development of the correct mathematical tools was an important event. When mathematics is combined with experimentation and thought, a new method of discovering the laws of nature is possible. The importance of this event can not be understated. Here is another example of the power of Newton’s laws, applying thought and using mathematics.
At the beginning of the 1800’s , Uranus was found to have perturbations in its orbit. These perturbations were different from the orbit calculated by Newton’s law of gravitation. This fact threatened to dismantle the Newtonian universe. Then in the 1840’s, John Couch Adams (1819 – 1892) and Jean Joseph Leverrier (1811 – 1877), believing Newton’s law to be correct, developed a theory which could account for the differences between the predicted location for Uranus and its actual location. This theory was that another planet’s gravitational influence was perturbing Uranus’s orbit. Subsequently, Neptune was discovered.
Still the difficulty of how objects affected each other remained. We return now to the different types of motion to appreciate the scientific problem facing people in the 17th century.