Leaves And Quarks

When I was a kid, I loved to hang out at the second-floor veranda of my grandparents’ house. There, different varieties of potted plants: bougainvilleas, ferns, cacti, orchids, roses and many others were neatly arranged, regularly watered and meticulously taken care of by my three unmarried aunts. Then I would pick a large leaf from among the plants and would start doing what had become a ritual to me. I would divide the leaf into two, toss away one of the halves and kept the other to be divided again into two. The cycle would go on for some time until the portion of the leaf left in my hands was too small to be divided further.

Then questions and possibilities would begin flooding my mind: If there’s a way of breaking down this leaf fragment further into smaller and still smaller pieces, would it come to a point where the remaining piece is no longer a leaf? What are leaves made of? What are the flowers and the trees made of? And the mountains? Then I would realize that my quest had come to a dead-end and my young mind would begin to wander elsewhere.

When I was already in grade school, our science teacher told us that everything---including us, is composed of matter. Anything that has weight and occupies space is matter: leaves, trees, rocks, water…Even the air which we cannot see is matter because it occupies space. But what is matter made of?

Two thousand four hundred years ago, the Greek philosopher Democritus was asking a similar question: Could matter be divided into smaller and smaller pieces forever, or was there a limit to the number of times a piece of matter could be divided? After spending countless hours and days (or perhaps years) pondering on this fundamental question, he came up with a theory: Matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained. This piece would be indivisible. He named the smallest piece of matter atomos, meaning, “cannot be cut.”

However only few learned Greeks of the time accepted Democritus’ position. Another school of thought championed by Aristotle supported the more intuitive and commonly held belief that all substance found in our world can be derived from or composed of the following four elements: earth (meaning, soil), water, fire and air. He contended that these four elements were not made of atoms but were continuous. Because Aristotle was more influential, his idea was widely accepted while Democritus’ unpopular treatise on “atomism” was forgotten and his scholarly works were consigned in the back shelves of the great libraries of the ancient world through the centuries.

As Renaissance transformed the cultural landscape of Europe starting on the 14^th century, the scientific world has also undergone its own renaissance especially after the invention of the microscope. There was a renewed interest in the study of atomism as preserved in the works of Democritus and that of his student Epicurus. Results of repeated and replicated experiments in leading laboratories at the time showed consistently that indeed, matter is made up of smaller components. Thinking that they have finally discovered the elemental component proposed by Democritus, they called that component “atom.” Thus Democritus was vindicated and the Aristotelian physics which reigned supreme in the centers of learning since the glorious days of the Greeks was unceremoniously dethroned. But Aristotle’s idea was not totally rejected. His four-element concept is now re-interpreted as the four states of matter: solid (earth), liquid (water), gas (air) and plasma (fire).

The discovery of the atom paved the way for fast advances in the fields of physics, chemistry and material science and led to greater understanding of electricity and magnetism. Intense experimentations and observations resulted to the discovery of different types of atoms. They discovered that atoms of different substances have different weights while atoms of one substance have uniform weights. The atomic weight, therefore, has become the identifying property of a substance. A substance which is composed of only one kind of atom is called “pure substance” or element while a substance that is composed of two or more different kinds of atoms is called “composite” or compound.

Several elements have been identified out of the common substances that man has been familiar with since the dawn of civilization. Iron, silver, copper and gold are among those identified to be pure and therefore they are elements. Some gases, too, have been identified to be elements: hydrogen, oxygen and nitrogen. The chemists and physicists started constructing an abstract table called periodic table where elements were placed in their logical order according to atomic weights and other characteristics. Today, you can see this periodic table prominently displayed on the walls of Chemistry classrooms and laboratories. You can also find it usually printed in the inside back cover of chemistry textbooks.

In 1807, English chemist John Dalton laid down 5 propositions describing the atom which later became known as the Dalton’s Law:

1. All matter is made of atoms.
2. All atoms of a given element are identical in mass (or weight) and properties.
3. Atoms are indivisible and indestructible.
4. Compounds are formed by a combination of two or more different kinds of atoms.
5. A chemical reaction is a rearrangement of atoms.

By this time, there was a budding field of study called Alchemy. Its adherents, which counted among them the notable Sir Isaac Newton, believed that there could be a formula to transform a base metal like lead or iron into gold. They tried and experimented on different procedures. Some even resorted to magic. There were so many false claims of iron turning into gold and the believers were fooled over and over again.

The proper understanding of the atom marked the end of alchemy. But not all results of alchemists’ researches and investigations went to naught.  Many of the chemists started as alchemists and many of their discoveries were reinterpreted in the light of the atomic theory. We can, therefore, safely say that the pseudoscience of alchemy was the precursor to the modern science of Chemistry.

By the late 1800s, Physics was now considered a mature science. There were those who believed there wasn’t much more to do than smooth out some rough edges in nature’s plan. There was a sensible order to things, a clockwork universe governed by Newtonian forces, with atoms as the foundation of matter.

 But then strange things started popping up in laboratories: x-rays, gamma rays, a mysterious phenomenon called radioactivity. Physicist J. J. Thomson discovered the electron. Atoms were not indivisible after all, but had constituents. Was the atom, as Thomson believed, a pudding, with electrons embedded like raisins? No. In 1911 physicist Ernest Rutherford announced that atoms are mostly empty space, their mass concentrated in a tiny nucleus orbited by electrons.

 There was a growing interest in the study of hydrogen---the lightest and the smallest among elements. Scientists discovered that the hydrogen atom has only one electron orbiting around the nucleus. The electron is a very small particle with a negligible mass and possesses a negative electric charge. They reasoned that since the electron is orbiting around the nucleus, this means that there is a force of attraction between the electron and whatever is residing in the nucleus. They cited as analogy the earth-moon system and the solar system in general, which was already well understood since Newton’s time. 

 The moon orbits around the earth because initially the moon was moving in the direction perpendicular to the center line between the moon and the earth. The attractive force between these two bodies causes the moon’s otherwise straight line of motion into a curve thus making it a circular motion around the earth. In the case of the earth-moon system, the attraction is due to the gravitational force; in the case of the hydrogen atom, the attraction is due to electric force.

 Since, like magnets, opposite electric charges attract while like charges repel, they reasoned correctly that the particle in the nucleus of hydrogen has positive charge with equal strength as the electron’s negative charge to make it balanced and stable, otherwise the hydrogen atom would have disintegrated long time ago. And since the mass of the electron is almost zero, the mass of the particle in the hydrogen’s nucleus accounts for the total mass of the hydrogen atom. They called that particle inside the hydrogen’s nucleus proton. The proton, therefore, is a particle with a positive electric charge and has a mass equal to that of the hydrogen atom. They assigned it a value of one atomic mass unit ( amu) and became a standard in measuring all the other atoms.

 Next, researchers discovered that Helium, the second lightest element in the periodic table, has two electrons orbiting around its nucleus. But when they measured the weight of Helium, it was found out to be 4 amus. That means that the Helium nucleus contains 4 proton-like particles but only two of these have positive charge to balance the negative charges of two electrons orbiting around it.

 In 1920, Ernest Rutherford, proposed the existence of a proton-like particle with no electric charge. He called it neutron. After years of experimentation, they were able to isolate and detect the neutron particle. The year was 1932. The discovery of the neutron solves the problem of seeming discrepancies between their theoretical calculations and experimental measurements. They introduced a new number designation to each element. They called it the atomic number which is equal to the number of protons in the nucleus (which is also equal to the number of orbiting electrons). The amu continued to designate the amount of mass of the atom which is the sum total of protons and neutrons. For hydrogen, both the atomic number and the amu is equal to 1. Helium has the atomic number 2 and the amu is 4. The heaviest naturally-occurring element, Uranium has atomic number 92 and atomic mass unit of 238 because its nucleus has 92 protons and 146 neutrons.

 

Figure shows the atom of the second lightest element, Helium, which has two protons (colored red) and two neutrons (colored green) in its nucleus and two electrons orbiting around it.

The discovery of the neutron led to the realization that the nucleus, after all, is composite and breaking it down into its component parts is a possibility. But before the scientists could take steps to break up the atom, they have to understand first what holds the nucleus together. They already learned in electricity and magnetism that like charges repel and opposite charges attract. Under normal condition, the positively charged proton within the nucleus should repel each other and should have disintegrated long time ago. The only possible explanation that a group of protons stick together in the nucleus is because they are being held there by a very strong force. They called it strong nuclear force.  It is logical, therefore, that to break up the atom is to bombard the nucleus with a force greater than the nuclear force that holds them together.

 In 1938, the German chemist Otto Hahn, a student of Rutherford, bombarded a uranium atom with neutrons and successfully split the heavy uranium nucleus into two lighter nuclei of approximately equal size. They called the process nuclear fission as an analogy to biological fission in living cells. In the process of breaking up the atom, the strong nuclear force that holds the protons and neutrons together is released and is converted into an unimaginable amount of energy. That’s how the atomic bomb acquire its destructive power. Today, nuclear fission is occurring everyday under a very controlled environment inside the reactors of nuclear power plants in many parts of the world for the purpose of generating electricity.

 The successful division of the atom into smaller components violated the third rule of Dalton’s 1807 proposition and the scientists realized that they have concluded too soon. The thing that they called atom is not the same “atomo” in the mind of Democritus. Nevertheless, they continue to call it atom since it had already been universally accepted but the search for the fundamental, indivisible component of matter went on.

 After the atom was successfully split, the scientific community thought that maybe, we have already found the fundamental components of matter in protons and neutrons. Surely, these particles are already too small to be broken further. But again, they spoke too soon. Not long after, researchers discovered that protons and neutrons are made up of still smaller particles called quarks.

 How did the scientists discover all these? By using similar techniques used by Thompson, Rutherford, Hahn and other physicists since the last century: smashing atoms and sub-atomic particles with other particles inside those devices called accelerators and taking inventory of all debris in the form of smaller particles and released energies that are detected by their instruments. The early experiments consist of trying to break up a heavy atom like uranium by bombarding it with protons and later, neutrons. A breakup is successful only when the energy of the oncoming particle is greater than the strong nuclear force that holds the nucleus together.

 Once they succeeded in breaking up the atomic nucleus into its component protons and neutrons, the next step was to determine whether the proton and neutron can be cracked, too. But breaking up the proton or neutron is a much more daunting task than breaking up the atom. Aside from the fact that the proton or neutron is much smaller and thus a more elusive target, the force that held the quarks together inside the proton is much stronger. To accomplish the breakup, the colliding particles must possess a much greater energy. It has long been established that speed is convertible to energy---the higher is the speed, the greater is the energy. So, to raise the energy level of the colliding particles, they should be traversing at very high velocities as they smash each other.

 To attain this extremely high velocities, the particles have to be positioned far from each other to give them sufficient time to accelerate. It is similar to a motorist driving on a city street and wanting to merge onto a high- speed interstate highway. The motorist has to increase its speed and sync with the highway motorists before merging otherwise he will be in danger of being bumped. To accomplish this, the highway builders construct ramps that connects a city street to the highway. The longer the ramp, the higher is the speed that is attained by the merging vehicle.

 In the case of the colliding particles, they traverse inside a specially designed tubes called accelerators surrounded with powerful magnets. Whereas the car’s acceleration is powered by its engine, the particles accelerate due to the action of electromagnetic force. The second function of the electromagnetic field is to keep the particles in their designated trajectories to ensure a hit.

 The first accelerator, called cyclotron was invented and patented by Ernest Lawrence of the University of California, Berkeley in 1932. It was so compact, it could fit in one’s pocket. But as experiments require longer and longer distances in order for particles to attain higher and higher velocities, larger and larger accelerators were constructed. Today, there are more than 30,000 accelerators in operation around the world of varying sizes and shapes. The second most powerful accelerator in the world with 3.9 miles in circumference is situated underground in Batavia, Illinois 27 miles west of Chicago and managed by Fermilab.

 With this worldwide effort to find the fundamental stuff that made up matter, they soon discovered that the sub-atomic space is inhabited with so many weird and exotic family of particles and anti-particles that they coined the term “particle zoo.” Whether one of these particles is the fundamental stuff that they have been looking for, they are not sure yet and many more experiments have to be conducted. At this level of smallness, scientists also discovered that the particles and the forces that are interacting on them are starting to become interchangeable; that is, beginning to merge and thereby losing their distinctions. One of the problems the particle physicists were tackling at the time was how come that in one family of particles with the same characteristics some have mass and the others have none.

 In 1964, Professor Emeritus Peter Higgs of the University of Edinburgh proposed a mechanism that purportedly explains this phenomenon. Higgs mechanism predicted the existence of a particle which gives mass to everything. The scientific world embraced Higgs’ proposal and named the yet-to-be-found particle Higgs boson. The mainstream media dubbed it the “God particle.”  Higgs explained that this particle permeates all space which gives rise to the idea of a Higgs field which, in layman’s term, we call Higgs ocean. If the existence of the Higgs particle is proven true, then “empty space” is not so empty after all. We are all immersed in the Higgs ocean which gives mass to our bodies just as the air in the earth’s atmosphere causes the drag of all moving objects like cars and golf balls.   

 To prove the existence (or non-existence) of the Higgs particle the European Organization for Nuclear Research, otherwise known by its acronym CERN, constructed the world’s largest and most powerful particle accelerator, 27 kilometers in circumference, in a tunnel as deep as 574 feet beneath the Franco-Swiss border near Geneva, Switzerland. They called it the Large Hadron Collider (LHC). The LHC, which is a collaborative project of CERN and hundreds of universities and laboratories around the world, is the most complex machine man has ever built. It took thousands of scientists, engineers and technicians decades to plan and build it at a cost of ten billion dollars.

 On July 4, 2012, after executing a carefully planned experiment or experiments using the LHC, CERN announced they have sufficient evidence to conclude that the Higgs boson had been found. In the years to follow, that experiment will be repeated and replicated to confirm that particle’s existence with certainty. In addition, scientists will continue to conduct other related experiments to determine that particle’s other properties. Those properties have already been predicted in the standard model of particle physics but they need experimental data to confirm the results of their mathematical calculations.

 Have we finally found the fundamental building block of the universe? Probably we have. But then, it might be too early to say. But one thing is sure, we have gone a long way since Democritus’ time. Personally, I have gone a long way from my innocent ponderings about leaves and flowers to what is beyond quarks and Higgs bosons and the meaning of reality. And as long as we will not lose our imagination, the world around us will continue to be a source of awe and wonder.