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1 What are the key ideas of Quantum Mechanics? Does light behave as a wave or a particle? This question is central to quantum mechanics. In the 19th Century, most physicists agreed that light behaved like a wave. However, as the 20th Century began, the idea of light as a wave was called into question. Problem One: Light doesn’t need a medium to travel through Some scientists were confused, as waves like sound waves, need a medium, or substance to travel through. Sound waves can only travel through a medium, like air. For instance, a bell in a vacuum, where there is no air, will not make a sound. However, light can travel without a medium. We know this, as the light from the sun and other stars travels to us through empty space. Did this mean that light was made up of particles, which could travel without a medium? Problem Two: The prediction of ultraviolet catastrophe is wrong A black body is an object which absorbs all light it encounters. When a black body is cold, it appears black because it radiates no energy. However, a black body which is hot will emit visible wavelengths. The hotter the black body, the higher up the spectrum the light which is emitted. For example, a black body at room temperature will emit infrared energy, but as it gets hotter, we will see energy emitted which is red, then orange, then yellow, then white and then blue. Finally, at the hottest temperatures, ultraviolet energy is given out. Twentieth Century physicists predicted that a perfect black body would give out radiation of an infinite density when it reached thermal equilibrium (when the black body was absorbing the same amount of energy as it was giving off) This prediction was called the ‘ultraviolet catastrophe’. “If this were true, all objects should appear violet in colour.” (Alastair Rae) However, this is not the case; the ultraviolet catastrophe did not occur, which physicists found very hard to explain. 2 The Solution: Max Planck In 1901, Max Planck discovered that light did not flow in a continuous stream, but that it came in little packets called quanta. (‘Quanta’ is the plural for ‘quantum’ which is Latin for ‘amount). All of the quanta in a beam of light are of the same size and contain the same amount of energy. The energy of a quantum is determined by the following formula: Frequency of the wave x a constant number. This constant number is one of nature’s constants, like Newton’s law of gravity. As Planck was so influential in the formulation of quantum mechanics, this constant is termed ‘Planck’s constant’. To aid our understanding of the idea of ‘quanta’, Alister McGrath asks us to imagine a sand dune in an African desert. He states that from a distance, the sand dune appears to be smooth, but when we look at it more closely, we see that it is made up of tiny grains of sand. Similarly, energy, like light, appears to be a continuous wave, but in actuality, it is made up of little packets of energy. (Quanta) Albert Einstein Einstein’s ideas and experiments gave more weight to Planck’s argument that light is not only a wave. He stated that all electromagnetic energy contain photons, which should be treated like particles. Einstein’s Photoelectric Effect (1905) Einstein proved that when light hits a metal surface, the metal gives out electrons. This means that particles (or quanta / photons) of light containing energy, hit the metal and eject the electrons. Therefore, there must be packets of energy contained within the light. The amount of energy these ejected electrons contain is always equal to the amount contained within the light ‘quantum’ minus a fixed amount. (This amount is the amount of energy required to eject the electron from the metal and is called the ‘work function’.) 3 “Einstein’s brilliant theoretical account for the photoelectric effect suggested that electromagnetic radiation had to be considered as behaving as particles under certain conditions.” (Alister McGrath) “We therefore have evidence … that light is a wave, while the photoelectric effect indicates that it has the properties of a stream of particles. This is what is known as ‘wave-particle duality.’ (Alastair Rae) In the Twentieth Century, it was becoming clear that atoms did not behave in a normal way. It became accepted that light could behave as a wave and a particle, and the term ‘wave-particle duality’ was coined to explain this idea. Thus, it was no longer sensible to ask the question, “Is light a wave or a particle?” because it is both of these things at the same time. Whether light behaves as a wave or a particle at a particular time depends upon what type of experiment is conducted and how an observation is carried out. Is it only light which displays wave-particle duality? The Nature of the Electron Further experimentation on wave-particle duality, found that electrons also behave as both a wave and as a particle. All atoms contain electrons which are forced to remain in a small space by an electrical charge which links them to the centre of the atom, the nucleus. The Double Slit Experiment The Double Slit Experiment is used to show that energy, such as light and electrons, behave as both waves and particles. The experiment was originally done with light, but eventually it was used with electrons also. In the experiment, electrons are fired through two slits on a plate. There is a screen behind this plate. If electrons behave as particples, the number of electrons hitting the screen at the back of the plate should be equal to the sum of the electrons which are fired through BOTH slits. If electrons are fired through two slits, the wave 4 However, physicists found that this does not happen. The number of electrons which hit the screen is LESS than the sum of the electrons which pass through the two slits. This means that the electrons are behaving as a wave as well as a particle. When two waves which are out of step with each other meet, they ‘interfere’ with each other, or cancel each other out. Thus, when the waves of electrons pass through the two slits, ‘interference’ takes place and some of the electrons are cancelled out. This is why the number of electrons which reach the screen is less that physicists predicted. Therefore, electrons also have wave-particle duality. Einstein hated quantum mechanics. One of his famous quotes is, “God does not play dice with the universe.” He believed that everything in nature is determined and that laws can be found to explain everything that happens in the world and that these laws can be used to make predictions about future events. However, advances in quantum mechanics have shown that things do not always behave in a predictable manner. Paul Davies explains this by stating, “… two identical situations might produce different outcomes. For instance, imagine firing an electron directly at an atom: it may deflect either to the left or to the right with equal probability.” Therefore, in quantum mechanics there is a lot of uncertainty. Heisenberg’s Uncertainty Principle Heisenberg argued that it is impossible to predict the value of the position and the momentum of a particle at the same time. Thus an observer can predict where a particle is, or can make a prediction about its momentum, but these two measurements cannot be taken at the same time. The greater the certainty of the position, the lesser the certainty about the momentum and the greater the certainty about the momentum, the lesser the certainty about the position. It is the observer that causes this uncertainty. The observer’s measurement of the position of the particle affects its momentum in an uncertain way and his/her measurement of momentum affects the particle’s position in an uncertain way. This is known as ‘observer effect.’ 5 Therefore, it seems that the observer causes uncertainty, “What we observe, we influence” (Mel Thompson). This uncertainty is not down to a failure of scientific apparatus and will not disappear as science progresses. The uncertainty is fundamental to quantum physics and will never go away, “an object has no existence independent of our observation of it. We cannot get ‘outside’ our process of observation to see what is ‘really’ there – it makes no sense to speak in those terms.” (Mel Thompson) All physicists can do at quantum level is base ideas on probabilities, “Quantum theory cannot predict the action of individual particles, but describes the atomic world in terms of probabilities, based on observations of very large numbers.” (Mel Thompson) Fritjof Capra – “The Tao of Physics” Capra tried to show that quantum mechanics has several links with Eastern Mysticism. He stated that “Physicists do not need mysticism and mystics do not need physicists, but humanity needs both.” He believes that the views of quantum mechanics are very similar to the ideas which Eastern mystics have held for generations. For instance: Eastern mysticism holds that everything in the universe is interrelated and connected. Capra argues that, like the mystic, “…the modern physicist … has come to see the world as a system of inseparable, interacting and ever-moving components “ Capra states that Eastern mysticism has always been able to deal with the paradoxes of nature. He states that mystical ideas can help scientists to come to terms with the apparent paradox of waveparticle duality. For example, the Yin-Yang sign embraces opposites and brings them together as one whole. The central role of the human observer, Capra argues, is central to both mystical thought and quantum physics, “In Eastern mysticism, the universal interwoveness always includes the human observer and his or her consciousness, and this is also true in atomic physics.” The world of quantum physics is difficult for scientists to explain and they often do not understand why things at quantum level happen in the way that they do. Similarly, in mysticism, it is difficult for believers to describe mystical experiences of God. 6 What are the implications for religion? Science has often seen to be in conflict with religion. Many scientists see themselves as uncovering new ideas which get rid of religion and superstition and shrink the gaps left for God in the modern world. If the new ideas discovered by quantum physicists can be linked to mystical and religious thought, as Capra suggests, perhaps science has discovered evidence for religion. Capra argues that God could be a unifying force which binds the whole of nature together. Perhaps God is the ultimate essence which links everything together and allows things like light and electrons to be two things at once. Has science found proof of God? However, perhaps religious people are clutching at straws here. Have scientists really found evidence of God? Is putting God in as an explanation of wave-particle duality another example of ‘God of the gaps’? Do we really have evidence of a God recognisable by religious believers of traditions such as Christianity, Islam and Judaism? Jeremy Bernstein: “Science Observed” Bernstein argues that Capra has made very weak links between science and mysticism. “At the heart of the matter is Mr Capra’s methodology – his use of what seems to me to be accidental similarities of language as if these were somehow evidence of deeply rooted connections.” Leon M. Lederman: “The God Particle” Lederman argues that Capra is wrong to simplify all of the advances of quantum mechanics by stating that they have only discovered things which Eastern mystics have known for centuries. “Starting with reasonable descriptions of quantum physics, he constructs elaborate extensions, totally bereft of the understanding of how carefully experiment and theory are woven together and how much blood, sweat and tears go into each painful advance.” Eddington The quantum physicist Eddington argued that any form of ‘quantum mysticism’ is wrong to state that great God of classical theism can be found in quantum mechanics, “We should suspect an intention to reduce God to a system of different equations. That fiasco should be avoided.” Alister McGrath: “Science and Religion – An Introduction” McGrath argues that a parallel can be made between wave-particle duality of quantum physics and Christology. He states that Christianity has struggled to explain how Jesus can be both a human being and God at the same time, “The Christological issue of critical importance was that the biblical portrayal of Jesus of Nazareth at times suggested that he behaved or functioned as God, at others as a human.” 7 If science can hold that light, electrons etc can be both waves and particles at the same time, without being able to fully explain this phenomena, then this could, McGrath argues, help Christians to assert that Jesus was both God and a human being at the same time. Religion has often been challenged by advances in science. For example, Copernicus’ realisation that the sun was the centre of our galaxy, rather than the earth, greatly challenged Christian teaching at the time. However, religion has managed to survive these challenges from science. Some religions have attempted to incorporate science into their religion, for example, Liberal Christians accept the scientific ideas of the Big Bang and Evolution. Other religious groups have rejected scientific ideas, for example, Literal Christians, who still believe in the creation of the world by God in 6 days as presented in Genesis. Religious people may argue that they do not need to have agreement with science as they have faith. Science may dispute some of their ideas, but they believe in God and trust in His teachings and so this does not matter. Some religious believers may champion the efforts of those, like Capra, who try to make links between religion and science. They want their religion to be acceptable to modern people. Keith Ward states that, “There are millions of things we do not understand, including the fundamentals of quantum mechanics.” Perhaps God is behind the workings of quantum mechanics and that is why we cannot understand them properly. However, it could be said that trying to find God in quantum mechanics is another example of ‘God of the Gaps’ – pushing God in to explain something not yet understood by scientists. 8 As we have seen, Capra argues that developments in quantum physics have led to truth which has been known by Eastern mystics for generations. For example, the discovery of the behaviour of electrons on earth has led to the discovery of electron behaviour throughout the universe, suggesting that everything in the universe is unified – a teaching of Eastern mysticism. However, these attempts to link religion to quantum physics have been widely criticised. The physicists who worked so hard to make these discoveries about quantum mechanics are appalled at claims that they have just discovered something that was already known. (E.g. Lederman in “The God Particle”) They argue that the discoveries they have made have involved much experiment and observation and that likening the results to mysticism because of some accidental similarities in language is nonsensical. (Bernstein). Quantum mechanics is based upon empirical evidence gained of the physical world. All physicists can perform the same experiments to see the same (albeit bizarre) results. This is different from the subjective ideas of mystics which are not based on any evidence at all. Quantum physics uses the language and strict methodology of science, not the language of mysticism. 9 If the fundamentals of quantum physics can be linked to mysticism (Capra) and can be used to explain the human and divine nature of Christ (McGrath), does this mean that science, rather than being the enemy of religion, can now be said to be religious itself? Yes! Capra states that science and mysticism can work hand-in-hand to discover the truth behind the universe. Similarly, McGrath states that science can help Christians to explain how Jesus can be both human and divine at the same time. Quantum mechanics reveals that there are some things that science cannot, and will never be able to, understand. Scientists need to realise that there is another force working outside the world which has given it the regular laws of nature (Newton’s laws) as well as the strange laws of quantum mechanics. The reason that we cannot understand the workings of quantum physics is because this is where God can be found and God is too difficult to comprehend. Science needs to learn that it cannot explain everything, but needs a helping hand from religion “The whole of science proceeds on the assumption that a reason can be found for why things are as they are, that it is the end of science if one finds an ‘uncaused’ event, or one for which there is no reason at all.” (Keith Ward: “God, Chance and Necessity) 10 No! Wittgenstein states that religion and science are playing different ‘language games’. Just as the rules of rugby cannot be used to judge the game of football, so the language of science must not be confused with the language of religion. Therefore, science cannot be religious and religion cannot be scientific. Stephen Jay Gould argues that religion and science must remain separate. Science cannot comment on religion and therefore, science cannot be religious, “We can neither affirm or deny it: we simply can’t comment on it as scientists.” Dawkins believes that scientific advances have removed the need for God altogether. To look for God in quantum mechanics is an example of ‘God of the Gaps.’ Dawkins states that, “the alleged marriage between religion and science is a shallow, empty, spin-doctored sham.” Religious believers may argue that if science is taken as religious, ‘Reductionism’ may occur. If religion is ‘reduced’ to the links which can be made with science, then there is a serious risk that the essence of the religion may be lost. For example, Eastern mysticism involves a religious way of life and embodies ideas beyond the concept of unity which Capra argues can be found in quantum physics. Bernstein argues that the trial, error and constant revision involved in science means that Eastern mystics would probably not want their beliefs and philosophy of life compared to it, “…if I were an Eastern mystic the last thing in the world that I would want would be a reconciliation with modern science." (Bernstein) 11