Particles, fields and the four fundamental forces
The particle and the field
Particles can, and do, routinely pop into and out of existence, and in fact, as Dana Mackenzie suggests, the whole concept of a “particle” is now perhaps slightly outdated. These days, quantum physicists consider that the really fundamental concept is that of the field, and particles are regarded as merely the field’s local manifestation, a particle being simply a fluctuation in the quantum field that may be just temporary or longer lasting[1].
The forces
The universe is also governed by four fundamental forces:
The electromagnetic force is responsible for light, electricity and magnetic attraction. Maxwell's equations encapsulate a complete characterisation of electro-magnetism that among other things describes:
"Every electromagnetic form or radiation - visible light, x-rays, sunlight that heats the earth, radio waves, television waves, wifi signals, bluetooth signals, cell phone transmission, and GPS all consist solely of Electric and Magnetic Fields. And everything you need to know about how they propagate and interact with materials is completely determined by (Faraday's Law and Ampère's Law) - which were unified and explained originally by James Clerk Maxwell in the 1860s".[1.1]. Einstein later realised that Newton’s laws and Maxwell’s equations needed some adjustment to take into account the speed of light as a universal constant so that the laws of physics are the same in all reference frames: see the page on Special Relativity
The strong and the weak nuclear forces operate only on atomic and subatomic scales. The strong nuclear force, identified in 1932, is an attractive force between protons and neutrons that keeps the nucleus together and is thus responsible for nuclear fusion that causes the sun and the stars to shine. The weak nuclear force is responsible for the radioactive decay of elements like uranium and plutonium[2].
As Bill Bryson points out, despite its name, the weak nuclear force is ten billion billion billion times stronger than gravity, and the strong nuclear force is vastly more powerful, but their influence extends to only the tiniest of distances - only about 1/100,000 of the diameter of an atom in the case of the strong force. That's why the nuclei of atoms are so compacted and dense and why elements with big crowded nuclei tend to be so unstable: the strong force just can't hold on to all those protons.[3]
The forces exercise their influence through fields, and each has its own messenger particle working within that field. In the case of the electromagnetic field it is the photon. In the case of the gravitational field, it is - perhaps - the hypothetical graviton, not yet discovered experimentally. The particles of the strong force are known as gluons and those of the weak force are the W and Z particles[4].
Scientists believe that in the first billionth of a second after the big bang when the temperature of the universe was above 10 billion billion billion (1028) degrees), some thousand billion billion times the temperature at the centre of our sun, the universe was a mostly uniform soup of particles racing around at the speed of light without mass and the electromagnetic and weak nuclear forces were originally part of the one unified force - the electroweak force. However, in the microseconds following the bang, a cataclysmic transition in the rapidly cooling universe known as 'electroweak symmetry breaking' broke or obscured the underlying symmetry between these forces. [4.1] Gravity is thought to have separated from the other forces at the Planck time, 1 x 10-43 seconds after the big bang [5].
What caused this state of affairs to come about? The most likely suspect is suggested as the so-called Higgs field or ‘ocean’ (so named because it permeates the universe everywhere) in that it imbues particles with different amounts of mass according to how much they interact with it [6]. As Matthew Chalmers describes things, when this occurred the W and Z bosons grew fat and retreated to sub-atomic confines; the photon raced away mass-free[7]; the electromagnetic force gained its current infinite range; and the fundamental particles that make up matter (fermions - electrons and quarks) interacted with the Higgs field and acquired their mass too [8]. In other words, “an ordered universe with a set hierarchy of masses emerged from a madhouse of masslessness” [9].
More recently and writing after the discovery of the Higgs boson, Gavin Hesketh has identified another problem: a missing boson [10]: there should be a third W with no electric charge (W0). As regards the "fat" W and Z bosons, the W boson is naturally massless and the apparent mass of the W is not a property of the boson itself (which the symmetry does not allow) but the result of the interaction of the W boson with the Higgs field - something which he describes, in an admittedly imperfect analogy, as like dragging a spoon through a molasses like substance filling empty space.
In the meantime, the missing neutral W0 boson became entangled with the winding symmetry of another force akin to electromagnetism but with its own boson, B - in the process producing the massless proton we are familiar with, along with another very heavy particle like the charged W bosons: the Z0 boson (with zero charge) - the final piece of the Standard Model. By these means, the charged W bosons and the Z boson (a heavy photon) pick up their masses from the Higgs field, while the photon - actually a mix of two deeper things, the B and the W0, tied together by the Higgs mechanism (yes, that's right!) - remains massless. [10.1] You couldn't make this up, says Hesketh!
So, "the electromagnetic force is not after all a fundamental property of the universe, but emerges through this electroweak model" [11],which says that all particles acquire mass in this way – the electron, muon and tau and the quarks - and the Higgs mechanism is the key to them all. All this came to pass experimentally in 1983 when the Super Proton Synchrotron at CERN reached enough high energy to actually produce W and Z bosons in the laboratory.
Particles can, and do, routinely pop into and out of existence, and in fact, as Dana Mackenzie suggests, the whole concept of a “particle” is now perhaps slightly outdated. These days, quantum physicists consider that the really fundamental concept is that of the field, and particles are regarded as merely the field’s local manifestation, a particle being simply a fluctuation in the quantum field that may be just temporary or longer lasting[1].
The forces
The universe is also governed by four fundamental forces:
- the gravitational force (the weakest of the four) first described in theoretical terms based on observations made by Newton in 1687;
- the electromagnetic force, combining the hitherto separate forces of electricity and magnetism formulated by James Clark Maxwell in 1865;
- the weak nuclear force
- and the strong nuclear force.
The electromagnetic force is responsible for light, electricity and magnetic attraction. Maxwell's equations encapsulate a complete characterisation of electro-magnetism that among other things describes:
- how changing magnetic fields produce electric currents: like charges repel each other and opposite charges (i.e. positive and negative charge) attract (Gauss' law);
- magnetic monopoles do not exist. While we have Electric Charges (Electric Monopoles), the magnetic equivalent has never been found - magnetic charge or a magnetic monopole (Gauss' law for magnetism);
- how electric currents and changing electric fields produce magnetic fields (Faraday's Law); and
- how electric fields are produced. In essence, a changing magnetic field gives rise to a changing Electric Field; and a changing Electric Field gives rise to a changing Magnetic Field - which itself will produce a changing Electric Field which will give rise to ..... and so on (Ampère's Law)[1A].
"Every electromagnetic form or radiation - visible light, x-rays, sunlight that heats the earth, radio waves, television waves, wifi signals, bluetooth signals, cell phone transmission, and GPS all consist solely of Electric and Magnetic Fields. And everything you need to know about how they propagate and interact with materials is completely determined by (Faraday's Law and Ampère's Law) - which were unified and explained originally by James Clerk Maxwell in the 1860s".[1.1]. Einstein later realised that Newton’s laws and Maxwell’s equations needed some adjustment to take into account the speed of light as a universal constant so that the laws of physics are the same in all reference frames: see the page on Special Relativity
The strong and the weak nuclear forces operate only on atomic and subatomic scales. The strong nuclear force, identified in 1932, is an attractive force between protons and neutrons that keeps the nucleus together and is thus responsible for nuclear fusion that causes the sun and the stars to shine. The weak nuclear force is responsible for the radioactive decay of elements like uranium and plutonium[2].
As Bill Bryson points out, despite its name, the weak nuclear force is ten billion billion billion times stronger than gravity, and the strong nuclear force is vastly more powerful, but their influence extends to only the tiniest of distances - only about 1/100,000 of the diameter of an atom in the case of the strong force. That's why the nuclei of atoms are so compacted and dense and why elements with big crowded nuclei tend to be so unstable: the strong force just can't hold on to all those protons.[3]
The forces exercise their influence through fields, and each has its own messenger particle working within that field. In the case of the electromagnetic field it is the photon. In the case of the gravitational field, it is - perhaps - the hypothetical graviton, not yet discovered experimentally. The particles of the strong force are known as gluons and those of the weak force are the W and Z particles[4].
Scientists believe that in the first billionth of a second after the big bang when the temperature of the universe was above 10 billion billion billion (1028) degrees), some thousand billion billion times the temperature at the centre of our sun, the universe was a mostly uniform soup of particles racing around at the speed of light without mass and the electromagnetic and weak nuclear forces were originally part of the one unified force - the electroweak force. However, in the microseconds following the bang, a cataclysmic transition in the rapidly cooling universe known as 'electroweak symmetry breaking' broke or obscured the underlying symmetry between these forces. [4.1] Gravity is thought to have separated from the other forces at the Planck time, 1 x 10-43 seconds after the big bang [5].
What caused this state of affairs to come about? The most likely suspect is suggested as the so-called Higgs field or ‘ocean’ (so named because it permeates the universe everywhere) in that it imbues particles with different amounts of mass according to how much they interact with it [6]. As Matthew Chalmers describes things, when this occurred the W and Z bosons grew fat and retreated to sub-atomic confines; the photon raced away mass-free[7]; the electromagnetic force gained its current infinite range; and the fundamental particles that make up matter (fermions - electrons and quarks) interacted with the Higgs field and acquired their mass too [8]. In other words, “an ordered universe with a set hierarchy of masses emerged from a madhouse of masslessness” [9].
More recently and writing after the discovery of the Higgs boson, Gavin Hesketh has identified another problem: a missing boson [10]: there should be a third W with no electric charge (W0). As regards the "fat" W and Z bosons, the W boson is naturally massless and the apparent mass of the W is not a property of the boson itself (which the symmetry does not allow) but the result of the interaction of the W boson with the Higgs field - something which he describes, in an admittedly imperfect analogy, as like dragging a spoon through a molasses like substance filling empty space.
In the meantime, the missing neutral W0 boson became entangled with the winding symmetry of another force akin to electromagnetism but with its own boson, B - in the process producing the massless proton we are familiar with, along with another very heavy particle like the charged W bosons: the Z0 boson (with zero charge) - the final piece of the Standard Model. By these means, the charged W bosons and the Z boson (a heavy photon) pick up their masses from the Higgs field, while the photon - actually a mix of two deeper things, the B and the W0, tied together by the Higgs mechanism (yes, that's right!) - remains massless. [10.1] You couldn't make this up, says Hesketh!
So, "the electromagnetic force is not after all a fundamental property of the universe, but emerges through this electroweak model" [11],which says that all particles acquire mass in this way – the electron, muon and tau and the quarks - and the Higgs mechanism is the key to them all. All this came to pass experimentally in 1983 when the Super Proton Synchrotron at CERN reached enough high energy to actually produce W and Z bosons in the laboratory.
A parting query
And incidentally, why 1/137 for the strength of the electromagnetic force? The answer is that we don't really know. It is a so-called "free parameter" whose meaning may come clearer once we have a better understanding of these things, but once we have measured it, any number of equations can attest to its validity as a useful tool of measurement. It also serves as a tool for computing the value of the coupling constant (a) when two photons collide.: there is roughly a 1/137 likelihood that an electron will emit one photon when this occurs. [12]
[1] Dana Mackenzie, op cit, 173.
[1.1] Robert P.Crease, The Great Equations - Breakthroughs in Science from Pythagoras to Heisenberg, WW Norton, New York, London, 2010, 132. For a comprehensive and easy to read online explanation, see http://www.maxwells-equations.com/index.php#maxwells
[1A] http://www.maxwells-equations.com/index.php#maxwells
[2] For an analysis of the nature of the uranium atom and nucleus, see E=mc² in practice
[3] Bill Bryson, A Short History of Nearly Everything, Broadway Books, 2003, 147. The strong and the weak nuclear forces are also illustrated in he page on E=mc² in practice
[4] Using a perturbative technique called the unitarity method, under which the probabilities of all possible outcomes must add up to 100%, three American scientists claim to have discovered a way to incorporate gravity into this model, according to which its hypothetical particle, the graviton, behaves like a ‘double copy’ of the strong subnuclear force particle, the gluon, that binds the constituents of the nuclei together, and each graviton behaves like two gluons stitched together, or rather work together’ like contestants in a three-legged race’: Zvi Bern, Lance J Dixon and David A Kosower, “Loops, trees and the search for new physics”, Scientific American, May 2012, 20 esp at 23,26. See also Unifying gravity and the standard model with quantum mechanics
[4.1] As to this episode of spontaneous symmetry breaking when the weak force separated from the electromagnetic, see The standard and inflationary models
[5] Ben Best, The Standard Model of Particle Physics http://www.benbest.com/science/standard.html p 8; “The fundamental forces of nature”, http://csep10.phys.utk.edu/astr162/lect/cosmology/forces.html. Figures like those reproduced here are known as exponential notation, a form of mathematical shorthand. Thus 1028 is a 1 with 28 zeros after it. 1 x 10-43 is a very small fraction: a 1 divided by a 1 with 43 zeros after it. The whole process is described by David Christian in Maps of Time, University of California Press, Berkeley (2011), 36.
[6] Green (2005) Ch 9. Since the discovery of the Higgs boson, it is now generally conceded that the suspect has been properly identified as the culprit.
[7] Well, it didn’t quite at this stage. It was bounced back and forth by the by the electrically charged particles before the light could travel very far. This is also the subject of later elaboration.
[8] Matthew Chalmers’ language in “The Higgs Problem - what exactly is that particle?” New Scientist, 10 November 2012, 34, 35.
[9] Ibid.
[10] What follows is an edited summary of a somewhat complex elaboration appearing in The Particle Zoo - The search for the fundamental nature of reality, Quercus, Hachette, London, 2016, Chapter 6, pp 140-146.
[10.1] Ibid, 140-2.
[11] Ibid, 142.
[12] Ibid, 27-29.
* Source for graphic: http://hyperphysics.phy-astr.gsu.edu/hbase/Forces/funfor.html
And incidentally, why 1/137 for the strength of the electromagnetic force? The answer is that we don't really know. It is a so-called "free parameter" whose meaning may come clearer once we have a better understanding of these things, but once we have measured it, any number of equations can attest to its validity as a useful tool of measurement. It also serves as a tool for computing the value of the coupling constant (a) when two photons collide.: there is roughly a 1/137 likelihood that an electron will emit one photon when this occurs. [12]
[1] Dana Mackenzie, op cit, 173.
[1.1] Robert P.Crease, The Great Equations - Breakthroughs in Science from Pythagoras to Heisenberg, WW Norton, New York, London, 2010, 132. For a comprehensive and easy to read online explanation, see http://www.maxwells-equations.com/index.php#maxwells
[1A] http://www.maxwells-equations.com/index.php#maxwells
[2] For an analysis of the nature of the uranium atom and nucleus, see E=mc² in practice
[3] Bill Bryson, A Short History of Nearly Everything, Broadway Books, 2003, 147. The strong and the weak nuclear forces are also illustrated in he page on E=mc² in practice
[4] Using a perturbative technique called the unitarity method, under which the probabilities of all possible outcomes must add up to 100%, three American scientists claim to have discovered a way to incorporate gravity into this model, according to which its hypothetical particle, the graviton, behaves like a ‘double copy’ of the strong subnuclear force particle, the gluon, that binds the constituents of the nuclei together, and each graviton behaves like two gluons stitched together, or rather work together’ like contestants in a three-legged race’: Zvi Bern, Lance J Dixon and David A Kosower, “Loops, trees and the search for new physics”, Scientific American, May 2012, 20 esp at 23,26. See also Unifying gravity and the standard model with quantum mechanics
[4.1] As to this episode of spontaneous symmetry breaking when the weak force separated from the electromagnetic, see The standard and inflationary models
[5] Ben Best, The Standard Model of Particle Physics http://www.benbest.com/science/standard.html p 8; “The fundamental forces of nature”, http://csep10.phys.utk.edu/astr162/lect/cosmology/forces.html. Figures like those reproduced here are known as exponential notation, a form of mathematical shorthand. Thus 1028 is a 1 with 28 zeros after it. 1 x 10-43 is a very small fraction: a 1 divided by a 1 with 43 zeros after it. The whole process is described by David Christian in Maps of Time, University of California Press, Berkeley (2011), 36.
[6] Green (2005) Ch 9. Since the discovery of the Higgs boson, it is now generally conceded that the suspect has been properly identified as the culprit.
[7] Well, it didn’t quite at this stage. It was bounced back and forth by the by the electrically charged particles before the light could travel very far. This is also the subject of later elaboration.
[8] Matthew Chalmers’ language in “The Higgs Problem - what exactly is that particle?” New Scientist, 10 November 2012, 34, 35.
[9] Ibid.
[10] What follows is an edited summary of a somewhat complex elaboration appearing in The Particle Zoo - The search for the fundamental nature of reality, Quercus, Hachette, London, 2016, Chapter 6, pp 140-146.
[10.1] Ibid, 140-2.
[11] Ibid, 142.
[12] Ibid, 27-29.
* Source for graphic: http://hyperphysics.phy-astr.gsu.edu/hbase/Forces/funfor.html