It was Antoine-Laurent Lavoisier, a French scientist and chemist, who revolutionised progress in chemistry, as a discipline within natural science, in the 18th century by discovering this law. He did a very precise measurement of reactants (substances or elements used in chemical reaction before the chemical reaction), end product (result of chemical reactions between reactants). He confirmed that the amount of reactants is equal to the amount of product, meaning that there was no loss or creation of matter. The only difference was that product was molecule of compound with a new physical or chemical property, which has the same amount of matter as sum of matter, which takes part in this reaction. In the above example, 2 hydrogen and 1 oxygen together, were equal in amount to the amount of one molecule of water.
The same applies to physical reaction. If we measure an amount of ice before melting and then the amount of water obtained after the ice is melted, we will find out that it is an equal amount, meaning no matter was lost or created.
The conservation of matter is also called conservation of mass. It means that mass and matter are interchangeable which is understandable as mass is a fundamental property of matter. But what is actually mass? How can it be defined?
The Encyclopedia Britannica offers a very nice definition of mass as a quantitative measure of inertia. What is measured is a resistance that body of matter offers to a change of its speed or position upon the application of a force. It is based on Newton’s first law of motion that states that every matter tends to remains in motion at a constant speed or stand still indefinitely unless it is acted upon by force. Law of inertia, Newton’s first law of motion.
An example is a parked car and a little child in a toy car next to it. Both are still, not moving. If we want to change their inertia, in other words, move them, then obviously it would be much harder to do it to the car, which has a larger mass, then to the child in the toy car with a much smaller mass. The same applies if we want to stop them or change their inertia of motion.
Definition of mass is very tricky and can be very confusing, particularly following Einstein’s theory of special and general relativity.
Basically, if we do not consider Einstein’s theory of relativity, we can say that mass can be manifested in two ways. Namely as:
Inertial mass, which can be measured when we apply the force to move body of matter.
Gravitational mass, which is a measure of mass proportional to the gravitational force of attraction between two bodies, making them move towards each other.
Weight is not the same as mass. It refers to a force experienced by the matter due to gravity and it could be interchangeable with gravitational mass.
An example of inertial and gravitational mass could be described in the following example:
Our weight will be 6 times less on the Moon than on Earth as gravitational force is 6 times less there than on Earth (gravitational mass). We will equally need more force on the Moon to move objects, like a bus compared with a motorbike, as is the case on Earth (inertial mass). Both of them will be, however, 6 times lighter on the Moon (gravitational mass).
When we take Einstein’s theory of relativity into account then we have to introduce two more concepts, which are:
Rest mass refers to the mass of a matter which is moving at the same speed as an observer.
What does this means?
It means that if my wife measures my weight on a train, which moves at a speed of 100 miles per hour, my weight will be 90 kg for both my wife and myself (and scale which is on the train) as we are moving at a speed of 100 miles per hour. My weight would be the result of gravitational mass.
Relativistic mass refers to a mass which is the sum of rest mass, and mass increased due to speed. In the above example, my mass is significantly increased for a person who is next to the train I am in and passing him by at a speed of 100 km per hour.
The average punch of a professional boxer is 400 kg and serves as another example. The average weight of this boxer can be 90 kg but it is the speed of his fists that adds to the rest mass, making an average mass to be around 400 kg.
Einstein has completely changed our awareness about the relation between mass and energy. This affects the definition of mass and energy conservation and the correctness of such a statement if we look at these laws separately, referring only to mass or energy.
Einstein’s famous equation defines so-called mass energy equivalence
E = mc2
The equation was derived from the special theory of relativity. The equation clearly states that energy is equivalent to the amount of mass. We know that c is the speed of light, which is constant and unchangeable. It is also squared, giving a very big number. This means that a very small mass has a very large amount of energy.
We can, for a moment, leave out c squared, as it is constant, unchangeable, and look at the relation between energy E and mass m. In this scenario, if we want to increase energy, we have an increase in mass. If we have less energy, we have less mass.
With mass energy equivalence derived from the special theory of relativity, we cannot any more formulate or state that conservation of mass means that mass cannot be created as an increase in energy increases the mass and a reduction in mass releases and reduces the energy, which was locked away in the mass. We therefore talk about mass-energy conservation.
With the development of nuclear physics we are able to measure very precisely the mass of reactants taking place in a chemical reaction and the mass of the product of this reaction. It is established that the sum of masses of reactants is slightly larger than the mass of newly created compound, product. The reason for this is a need for energy to be released from reactants, which will bind them together into a new molecule. The only place from where this energy can come is the mass of reactants that are involved in this particular chemical reaction. So when the binding energy is unlocked (released) from some of the mass of reactant, their masses are subsequently decreased, giving the mass of product to be slightly less than the sum of masses of reactant before the chemical reaction.
If we put this another way, we have to bring energy to separate atoms or reactants from the product of new molecules created in a chemical reaction.
Molecule of water + binding energy = hydrogens + oxygen
We need to do something to a molecule of water to separate atoms from the molecule. We need to bring energy back, which was released to bind them together in a molecule of water. By doing this we will succeed in reversing the reaction with the disappearance of binding between these atoms and the reversal of these brought energy to the mass of oxygen and hydrogen. Now separated, atoms of hydrogen and oxygen will have their masses again at the amount it was before they got involved in the reaction.
In this example the mass-energy is conserved but during the chemical reaction there was change or reduction of mass and its increase in the reverse process with subsequent reduction or release of energy from the mass and its increase and absorption into the mass respectively.
I will touch upon this topic once more at the end of the third chapter.
2
FOUR FUNDAMENTAL FORCES
Four fundamental forces in the universe are:
Strong nuclear force
Weak unclear force
Electromagnetic force
Gravitational force
Fundamental forces can be defined as fundamental interactions among particles of matter. These fundamental interactions are maintained by exchange of carrier between particles.
We have division of matter into two main categories: fermions and bosons. Fermions have a job to make up our matter while the boson’s job is to carry force and energy.
The fundamental interaction between fermions or matter, which binds them together, can be compared to football players, for example. The players are fermions who are bound together during play by throwing and catching a ball. The b
all carries force and energy from player to player. Therefore, the ball is a boson. The range of a particular fundamental force is determined by the mass of the boson which carries this particular force. The bigger mass the narrow range of this particular force or lighter the boson which carries this particular force, the longer range of this force.
The boson which carries an electromagnetic force is a photon which is massless. The boson which carries gravitational force, graviton, is also massless. Both gravitational and electromagnetic forces are therefore unlimited.
The weak nuclear interaction of weak forces is referred to as radioactivity of elements. Elements with a high nuclear mass such as Uranium’s isotops can be very unstable which makes them undergo spontaneous nuclear decay. During this process we can have radiation in the shape of beta emission or so-called beta decay. Weak nuclear interaction is caused by W (W stands for weak nuclear force) and Z bosons. They are among heavier elementary particles, their mass around 100 times heavier than a proton. With such a mass of W and Z bosons as a carrier of weak nuclear forces, the range of nuclear forces is low.
Strong nuclear forces or interactions have a massive carrier within the nucleus called the pion. The strong interaction has an unusual behaviour to grow in strength as the distance increases between particles or quarks. The gluon is a force carrier with the responsibility to hold quarks together. All the other three remaining forces are known to decrease in their strength with the distance but strong nuclear force does not. That could be understood if gluon, their carrier which attracts quarks together , is imagined as an elastic band which is placed among quarks in that way that one elastic band is attached between two quarks. When quarks are tightly located to each other, three of them, making proton or neutron, the elastic band (gluon, carrier of strong nuclear force) is relaxed and their existence is almost not noticable. If, however, three quarks want to separate, then the elastic band comes into force, getting tight, pulling quarks back together. Although the strong nuclear force is stronger with the distance, this refers only to small distances within the atomic nucleus.
The strong nuclear force is 100 times stronger than electromagnetic force. This is understandable as they need to keep together protons within the atomic nucleus and overcome electromagnetic force or the repulsion of protons against each other due to the fact they are the same charge.
The strong nuclear force is stronger than weaker nuclear force by factor 10 on power of 11 which is 10 000 000 000 0 times stronger than weak forces. However, a strong nuclear force is 10 on power of 41 stronger than gravitational force.
If we use the whole number, then strong force is stronger than gravitational force 10 000 000 000 000 000 000 000 000 000 000 000 000 000 0 times.
If we outline four fundamental forces in order from the weakest one to the strongest one then they can be written as follows:
Gravitational force < Weak nuclear force < Electromagnetic force < Strong nuclear force
I will outline these forces in order from the weakest to the strongest one.
GRAVITATIONAL FORCE
This is the weakest force but at the same time the long distance force. It is interaction between two bodies which have masses . Due to the fact that these bodies or matter have a mass , the gravitational force exists among these two bodies.This gravitational force is expressed by an attraction between these two bodies. The strength of this attraction depends on the product of these two masses divided by square of distance between these two bodies. If both bodies have a constant mass, then the force of gravitational attraction is inversely proportional to the square of the distance between these two bodies. If an object is positioned 1 km from Earth and a similar object with the same mass 10 km away from the Earth then an attraction of gravitational force to the object at the distance of 1 km will be 100 times stronger than on the object which is positioned 10 km away from the Earth.
Gravitational force is important at the level of the universe as it is the force that shapes the universe. It is thanks to gravitational force that all celestial bodies are created (stars,planets, satellites). It is force that holds the solar system together as much as galaxies.
Isaac Newton was the first scientist who become aware of the existence of gravitational forces. With his work on mechanics and gravitation through precise formulation of his three laws of motion, Sir Isaac Newton revolutionised physics. This opened a new chapter where the universe was to be understood more clearly through existence and the effect gravitational force has on a large scale. However, the final touch in adjusting the theory relating to gravitation to its perfection came from Albert Einstein with his work on the theory of relativity. He realised that space, which has a third dimension, has another, fourth dimention attached to it ,which is time. Time, as a fourth dimension, is in relation to the other three through the speed of light which has only an absolute value. Unlike classic physics which postulates that space and time are absolute and not changable, Albert Einstein made famous a mind experiment which led to the conclusion that light does not change its speed and is always 300 000 km per second regardless if it is measured from the spot which is at rest compared to the light coming, or if it is measured from the spot which is moving in relation to the speed of coming light. He also predicted that light, as a matter, is subject to the force of gravitation and as such it can be pulled when it passes near a large celestial object such as a star. In that case, light is bent which can be perceived as a shift of a place where a particular star is usually seen when her light comes to us with no bending. In other words, when light is not passing near a large celestial body or star, then there is no displacement of this star from where the light is coming as there is no bending. (This phenomenon of bending and subsequent shifting of the position of the star is called gravitational lensing, as reminded by the displacement of a background object when we put a lens between our eyes and background objects.) This particular prediction Einstein made was tested by English astronomer Arthur Eddington during an eclipse on 29th May 1919. He went to the island of Principe, off the coast of West Africa, where a total eclipse was expected to take place on 29th May 1919. The main principle of a measurement was to take a photograph of stars which are in the background of the Sun when the Sun is present ,and the pictures of the same stars when the Sun is not present, at night. Obviously, with the presence of the Sun it is only possible to take photographs of stars if the Sun is in a total eclipse, such as took place in this part of the world on 29th May 1919. Following the success in taking pictures of the Hyades constellation before and in the presence of the Sun, the measurement Arthur Eddington made showed that the Sun caused a deflection of 1.61 seconds of arc between the same stars in absence of the Sun and their position on the photographs when the Sun was present. This deflection was close to a deflection of 1.75 seconds of arc as Einstein predicted.
Hyades is a star cluster which is within the constellation of Taurus. It is easily spotted in the sky as a V shape but the V is more in a horizontal position. It has a giant red star called Aldebaran which does not belong to the Hyades cluster but is so large as it is placed much closer to us than the Hyades cluster. The Hyades cluster is otherwise closest to our solar system and is composed of hundreds of stars of the same age
Picture 2.01
WEAK NUCLEAR FORCE
Weak nuclear force or weak nuclear interaction is caused by the emmision or absorption of virtual particles or W and Z bosons.
Beta radioactive decay is a reaction which takes place as a result of a weak nuclear interaction. In this process the nucleus of an atom is decayed in a way that a neutron is transformed into a proton. During this process an electron is emitted from the nucleus as well as neutrino.
Virtual particles of weak nuclear forces have the ability to change the flavor of quarks. We know that quarks come in up or down flavors and that a neutron is composed of 2 down and 1 up quark while a proton is composed of 2 up and 1 down quark. W bosons can change d
own in up quark and vice versa. With such property, weak nuclear forces are important in radioactive decay such as beta decay and also in nuclear fusion of hydrogen atom to hellium. (Atom of helliun has 2 protons and 2 neutrons.) Therefore, in order for nuclear fussion of hydrogen atom to take place, it needs to be created deutherium atom or hydrogen isotop with neutron as an additional particle so that the final result of the fusion will be hellium with 2 neutrons and 2 protons in atomic nucleus. To have deiterium we need weak nuclear interaction to take place or bosons of weak nuclear interaction to change up quark in down one and in doing so transform 1 proton into a neutron.
Weak nuclear interaction has an important role in beta radioactive decay as well as in nuclear fusion (explained above) which takes place in a star. The nuclear fusion is the important fuel of a star, preventing the star from collapsing due to the powerful gravitational force of an enormous mass of which a star is usually made. As weak nuclear force plays an important role in radioactive decay or a type of radioactvity (beta decay), it is the right place to elaborate a bit on radioactivity.
Radioactivity
Radioactivity is a property of some matter to emmit subatomic particles or energy spontaneously.
It happens among those elements which have a high atomic mass or a large number of protons and neutrons in its nucleus. When the number of protons and neutrons increases above binding power which keeps them together within the nucleus, then this nucleus becomes unstable and will decompensate or decay into a more stable configuration.
The binding power which keeps protons and neutrons together in the nucleus is a remnant of the strong nuclear forces which keep quarks together in a proton or neutron. It could be described as a spillover of that power beyond boundaries of protons or neutrons, having 100 times stronger power than electromagnetic forces. As such, it easily overcomes the power of electromagnetic forces which tend to pull protons apart from each other. However, this strong nuclear interaction is powerful only for a short distance within the nucleus in a range or diameter which is not larger than the sum of 2 and a half protons diameter (Picture 2.02).
Journey Through Time Page 4
