The Energy of Different Kinds of Rays
Sufficiently energetic rays can collide and materialize. Like particles, electromagnetic waves also come in “lumps.” Rays are the track or trajectory of these energy lumps. Unlike atoms, electromagnetic waves in free space can be subdivided without losing their characteristics. Therefore, the lumps need a different name. The lumps or quanta of electromagnetic waves are called photons.
The word “photon” comes from the Greek word for light. The same word applies to the quanta of all kinds of electromagnetic waves, whether they are the kind that we can see or not.
We may say that photons are “particles” like electrons or protons or neutrons, but some of their characteristics differ. Electrons, protons, and neutrons are material particles, that is, they have mass whether they are moving or not. As they move faster, they become more massive because their kinetic energy adds to their mass. Photons have a mass equivalent to their energy, but they have that mass only because they move at the speed of light. Material particles occupy a certain amount of space and usually force other material particles to seek some other location. Any number of photons can fit together in the same space and they all tend to follow the same trajectory, without forcing other photons out of line. In this aspect rays are like lines. A geometric line has zero width. One can bundle many lines together without increasing the width at all.
Photons move along rays like traffic on a highway.
Highway traffic may be mixed, consisting of lightweight economy cars, sports cars, touring cars, heavy luxury cars, buses, light and heavy trucks, and tractor-trailer rigs with 18 wheels or more. These vehicles have a range of sizes and differ in the amounts of cargo they can carry.
Photons differ according to the energy they carry. From less energetic to more energetic these are the photons of radio waves, microwaves, millimeter waves, heat, light, ultraviolet rays, soft X-rays, and hard X-rays or gamma rays.
Traffic on a highway can be slack or intense depending on the time of day or night and on the type of day, whether it is a workday, weekend, or holiday. The intensity of traffic is distinct from the type of traffic. Parkways exclude trucks and buses, but the traffic still ranges in intensity. Similarly, rays may be weak even if their photons have high energy, or intense even if their photons have low energy, but the photons always go at the same speed, the speed of light.
A ray is a track of photons, and photons are packets of waves. Waves vibrate. Vibration means that something is going back and forth or around and around. A cycle is one complete back-and-forth movement or one complete circuit. The vibration rate is also called the frequency, the number of times per second that the movement goes through cycles. Physicists give rates of vibration in a unit named after Heinrich Rudolf Hertz (German physicist, 1857–1894). A cycle per second is called a hertz.
The energy of a photon is proportional to its vibration rate. To get a ray’s energy in watt-seconds or joules, multiply the vibration rate in hertz times Planck’s constant, 662.606 876 micro-micro-micro-micro-micro-microjoule-seconds.
Planck’s constant is a very small number. The vibration rate for electromagnetic waves is usually a large number of cycles per second, but Planck’s constant is so small that the product of the vibration rate and Planck’s constant is almost always a small number. This means that it takes many photons to make up an intense ray, even if the photons are very energetic.
Let’s compare vibration rates using units of one megahertz (MHz), which means one million vibrations per second. Radio waves vibrate relatively slowly. The range for AM radio is from 0.522 MHz to 1.620 MHz. The standard FM radio tunes between 88 MHz and 108 MHz. The waves in a microwave oven vibrate at 2 450 MHz. The only waves we can see are light waves. Their rate of vibration lies between 430 million and 750 million MHz. Gamma rays vibrate more rapidly than any other electromagnetic waves.
We often describe a wave by its length rather than its vibration rate.
The length is the distance between any identifiable feature of a wave and the next repetition of that feature. For instance, the wavelength is the distance from one crest or peak to the next crest or peak. One obtains the same wavelength measuring from one trough or valley to the next trough or valley. Things are a little more complicated if one measures from the midpoint between a crest and trough. The wavelength is the distance from one midpoint to the next on rising slopes, or from one midpoint to the next on falling slopes.
Wavelength and vibration rate are inversely related. The product of wavelength and vibration rate is the speed of the wave. Electromagnetic waves travel in free space at a speed we know as the speed of light. Wavelength is the speed divided by the vibration rate, and the vibration rate is the speed divided by the wavelength. Low-frequency radio waves have long wavelengths, and the high-frequency waves of gamma rays have short wavelengths. Photons have wavelengths ranging from long to short as the photon energy increases.
The Most Energetic Rays
Subatomic particles like protons, neutrons, or electrons can only come from collisions of rays that vibrate very rapidly, because each particle requires a large amount of energy to make it. By the mid-20th century there were accelerators powerful enough to produce pairs of particles from pure energy. The minimum energy for pair production is that required to produce an electron and a positron. The energy a ray can provide is directly proportional to its vibration rate, and inversely proportional to its wavelength. Let’s work with the wavelength, because it is the easier to visualize.
Only X- or Gamma-Rays Make Particles
The wavelengths of the rays that make subatomic particles must be very small. Obviously, subatomic particles are smaller than atoms. The rays that make them must likewise have wavelengths smaller than the size of atoms. We can get an exact maximum for the wavelengths we need to make subatomic particles by considering wave energy and particle mass.
Consulting the table in Appendix A, we find the wavelength of a ray that can make an electron, 2.4 micro-micrometers. To make a proton or neutron we need rays with a wavelength of 1.3 thousandths of a micro-micrometer, that is, 1846 times shorter, because the weight of a proton or a neutron is 1846 greater than the weight of an electron.
To see how much shorter these wavelengths are than those of visible light, let’s first choose a color for comparison, one whose wavelength is a convenient number near the middle of the visible light spectrum. Blue light has a wavelength of 470 thousandths of a micrometer and green light about 528 thousandths of a micrometer. Therefore, 485 thousandths of a micrometer corresponds to a greenish blue. The wavelength of an energetic X-ray or gamma ray that will make an electron is 200 000 times shorter than the wavelength of greenish-blue light. The X-ray or gamma ray is vibrating 200 000 times faster and is 200 000 times more energetic than greenish-blue rays.
Now multiply the proton or neutron wavelength by 2000 times 200 000, or 400 000 000. That gives a wavelength of 528 thousandths of a micrometer, the wavelength of green light. The energetic X-rays or gamma rays one needs to make a proton or a neutron are 400 000 000 times more energetic than rays of green light. It is clear that only very energetic X-rays or gamma rays can make particles by colliding.
In the above examples we have calculated the energy of the photon needed to make one particle. Of course we need another photon of equal energy in a colliding ray to make another particle, identical with the first but opposite in sign if the first particle carries an electric charge. This second particle is called the antiparticle of the first. The antiparticle of an electron is a positron. A proton’s antiparticle is an antiproton. A neutron is the antiparticle of another neutron.
We might think that we could use lower energies to make pairs of neutrinos, since these very lightweight particles have very little mass. An ultraviolet photon provides enough energy to materialize the mass of a neutrino. However, neutrinos do not come from pure energy reactions. They come from decaying nuclei. One type of decay ejects an electron and a neutrino and converts a neutron to a proton. Another type of decay ejects a positron and a neutrino and converts a proton to a neutron. Before and after the reaction takes place, there is always matter present, in the form of a proton or a neutron. Therefore, two photons, colliding in space far from any material, cannot produce neutrinos.
Gamma-ray wavelengths are very small. To interact, it is not enough for the paths of two gamma rays to cross. The photons must arrive at the interaction region at about the same time. This means that gamma-ray photons can travel long times and great distances in random directions before materializing.
Natural Particle Production
Light photons do not have enough energy to form subatomic particles by themselves. About 400 000 of them would have to collide simultaneously to create a pair of electrons. It is very unusual for more than two photons to collide at once. Making an electron-positron pair requires energetic X-rays or gamma rays. Rays that make protons or neutrons must be even more energetic, and higher in vibration frequency.
The First Particles
We now have enough background to understand the production of the first subatomic particles. A long investigation has shown that the initial dark phase of the universe was the beginning of particles, atoms, and everything material. NASA scientists who reviewed this research wrote:
It was natural to seek conditions during the early stages of the expansion of the universe in which the elements might have been formed.[i]
[i] Truran, J. W. and A. G. W. Cameron, Chapter 23, “Nucleosynthesis,” Introduction to Space Science Written by the Staff of Goddard Space Flight Center National Aeronautics and Space Administration, Greenbelt, Maryland, Second Edition, Revised and Enlarged, Wilmot N. Hess and Gilbert D. Mead, editors (New York: Gordon and Breach, Science Publishers, 1968), p. 984.
Simulating the Process
No one has yet photographed directly the production of the first particles. It occurred in the first few micro-micro-microseconds of the universe, and telescopes cannot yet see any moment earlier than 380 000 years after the beginning. However, we can simulate the process of particle production. Physicists regularly cause collisions between energetic X-rays in cyclotrons and liner accelerators. Subatomic particles materialize daily from X-rays in laboratories around the world. The pictures physicists take of the darkness of X-rays coming from cyclotrons and producing atomic particles are simulated pictures of the first evening.
We do not know how much time passed until the gamma rays collided. Therefore, we do not know how long the first evening lasted. We do know that a light wave completes one vibration in a thousandth of a micro-microsecond. Until that amount of time had passed there was no such thing as a complete light wave. The first evening must have lasted at least that long.
During the first evening the gamma rays collided with one another and materialized as atomic components. Fred Hoyle (English astronomer, 1915–2001) was right when he said that the universe did not begin with a “single huge explosion,” that is, a “big bang.”[i] This popular name for the beginning of the universe is misleading. It suggests that an explosion occurred at a point and the ejected materials flew out into empty space.
[i] Hoyle, Fred, The Nature of the Universe, American edition (New York: Harper & Brothers, 7 October 1950), p. 119.
Collisions are not explosions. Explosions are destructive, but the collisions made the particles. Therefore, the beginning of the material of the universe was not an accidental, meaningless event. When collisions between gamma rays occurred, there was often energy left over that was not used to produce particles. That leftover energy produced electromagnetic waves of longer lengths than gamma rays, such as X-ray waves, ultraviolet waves, light, heat waves, and radio waves. This is how light was produced, as God said in the Bible, “Let there be light.”
The word “photon” comes from the Greek word for light. The same word applies to the quanta of all kinds of electromagnetic waves, whether they are the kind that we can see or not.
We may say that photons are “particles” like electrons or protons or neutrons, but some of their characteristics differ. Electrons, protons, and neutrons are material particles, that is, they have mass whether they are moving or not. As they move faster, they become more massive because their kinetic energy adds to their mass. Photons have a mass equivalent to their energy, but they have that mass only because they move at the speed of light. Material particles occupy a certain amount of space and usually force other material particles to seek some other location. Any number of photons can fit together in the same space and they all tend to follow the same trajectory, without forcing other photons out of line. In this aspect rays are like lines. A geometric line has zero width. One can bundle many lines together without increasing the width at all.
Photons move along rays like traffic on a highway.
Highway traffic may be mixed, consisting of lightweight economy cars, sports cars, touring cars, heavy luxury cars, buses, light and heavy trucks, and tractor-trailer rigs with 18 wheels or more. These vehicles have a range of sizes and differ in the amounts of cargo they can carry.
Photons differ according to the energy they carry. From less energetic to more energetic these are the photons of radio waves, microwaves, millimeter waves, heat, light, ultraviolet rays, soft X-rays, and hard X-rays or gamma rays.
Traffic on a highway can be slack or intense depending on the time of day or night and on the type of day, whether it is a workday, weekend, or holiday. The intensity of traffic is distinct from the type of traffic. Parkways exclude trucks and buses, but the traffic still ranges in intensity. Similarly, rays may be weak even if their photons have high energy, or intense even if their photons have low energy, but the photons always go at the same speed, the speed of light.
A ray is a track of photons, and photons are packets of waves. Waves vibrate. Vibration means that something is going back and forth or around and around. A cycle is one complete back-and-forth movement or one complete circuit. The vibration rate is also called the frequency, the number of times per second that the movement goes through cycles. Physicists give rates of vibration in a unit named after Heinrich Rudolf Hertz (German physicist, 1857–1894). A cycle per second is called a hertz.
The energy of a photon is proportional to its vibration rate. To get a ray’s energy in watt-seconds or joules, multiply the vibration rate in hertz times Planck’s constant, 662.606 876 micro-micro-micro-micro-micro-microjoule-seconds.
Planck’s constant is a very small number. The vibration rate for electromagnetic waves is usually a large number of cycles per second, but Planck’s constant is so small that the product of the vibration rate and Planck’s constant is almost always a small number. This means that it takes many photons to make up an intense ray, even if the photons are very energetic.
Let’s compare vibration rates using units of one megahertz (MHz), which means one million vibrations per second. Radio waves vibrate relatively slowly. The range for AM radio is from 0.522 MHz to 1.620 MHz. The standard FM radio tunes between 88 MHz and 108 MHz. The waves in a microwave oven vibrate at 2 450 MHz. The only waves we can see are light waves. Their rate of vibration lies between 430 million and 750 million MHz. Gamma rays vibrate more rapidly than any other electromagnetic waves.
We often describe a wave by its length rather than its vibration rate.
The length is the distance between any identifiable feature of a wave and the next repetition of that feature. For instance, the wavelength is the distance from one crest or peak to the next crest or peak. One obtains the same wavelength measuring from one trough or valley to the next trough or valley. Things are a little more complicated if one measures from the midpoint between a crest and trough. The wavelength is the distance from one midpoint to the next on rising slopes, or from one midpoint to the next on falling slopes.
Wavelength and vibration rate are inversely related. The product of wavelength and vibration rate is the speed of the wave. Electromagnetic waves travel in free space at a speed we know as the speed of light. Wavelength is the speed divided by the vibration rate, and the vibration rate is the speed divided by the wavelength. Low-frequency radio waves have long wavelengths, and the high-frequency waves of gamma rays have short wavelengths. Photons have wavelengths ranging from long to short as the photon energy increases.
The Most Energetic Rays
Subatomic particles like protons, neutrons, or electrons can only come from collisions of rays that vibrate very rapidly, because each particle requires a large amount of energy to make it. By the mid-20th century there were accelerators powerful enough to produce pairs of particles from pure energy. The minimum energy for pair production is that required to produce an electron and a positron. The energy a ray can provide is directly proportional to its vibration rate, and inversely proportional to its wavelength. Let’s work with the wavelength, because it is the easier to visualize.
Only X- or Gamma-Rays Make Particles
The wavelengths of the rays that make subatomic particles must be very small. Obviously, subatomic particles are smaller than atoms. The rays that make them must likewise have wavelengths smaller than the size of atoms. We can get an exact maximum for the wavelengths we need to make subatomic particles by considering wave energy and particle mass.
Consulting the table in Appendix A, we find the wavelength of a ray that can make an electron, 2.4 micro-micrometers. To make a proton or neutron we need rays with a wavelength of 1.3 thousandths of a micro-micrometer, that is, 1846 times shorter, because the weight of a proton or a neutron is 1846 greater than the weight of an electron.
To see how much shorter these wavelengths are than those of visible light, let’s first choose a color for comparison, one whose wavelength is a convenient number near the middle of the visible light spectrum. Blue light has a wavelength of 470 thousandths of a micrometer and green light about 528 thousandths of a micrometer. Therefore, 485 thousandths of a micrometer corresponds to a greenish blue. The wavelength of an energetic X-ray or gamma ray that will make an electron is 200 000 times shorter than the wavelength of greenish-blue light. The X-ray or gamma ray is vibrating 200 000 times faster and is 200 000 times more energetic than greenish-blue rays.
Now multiply the proton or neutron wavelength by 2000 times 200 000, or 400 000 000. That gives a wavelength of 528 thousandths of a micrometer, the wavelength of green light. The energetic X-rays or gamma rays one needs to make a proton or a neutron are 400 000 000 times more energetic than rays of green light. It is clear that only very energetic X-rays or gamma rays can make particles by colliding.
In the above examples we have calculated the energy of the photon needed to make one particle. Of course we need another photon of equal energy in a colliding ray to make another particle, identical with the first but opposite in sign if the first particle carries an electric charge. This second particle is called the antiparticle of the first. The antiparticle of an electron is a positron. A proton’s antiparticle is an antiproton. A neutron is the antiparticle of another neutron.
We might think that we could use lower energies to make pairs of neutrinos, since these very lightweight particles have very little mass. An ultraviolet photon provides enough energy to materialize the mass of a neutrino. However, neutrinos do not come from pure energy reactions. They come from decaying nuclei. One type of decay ejects an electron and a neutrino and converts a neutron to a proton. Another type of decay ejects a positron and a neutrino and converts a proton to a neutron. Before and after the reaction takes place, there is always matter present, in the form of a proton or a neutron. Therefore, two photons, colliding in space far from any material, cannot produce neutrinos.
Gamma-ray wavelengths are very small. To interact, it is not enough for the paths of two gamma rays to cross. The photons must arrive at the interaction region at about the same time. This means that gamma-ray photons can travel long times and great distances in random directions before materializing.
Natural Particle Production
Light photons do not have enough energy to form subatomic particles by themselves. About 400 000 of them would have to collide simultaneously to create a pair of electrons. It is very unusual for more than two photons to collide at once. Making an electron-positron pair requires energetic X-rays or gamma rays. Rays that make protons or neutrons must be even more energetic, and higher in vibration frequency.
The First Particles
We now have enough background to understand the production of the first subatomic particles. A long investigation has shown that the initial dark phase of the universe was the beginning of particles, atoms, and everything material. NASA scientists who reviewed this research wrote:
It was natural to seek conditions during the early stages of the expansion of the universe in which the elements might have been formed.[i]
[i] Truran, J. W. and A. G. W. Cameron, Chapter 23, “Nucleosynthesis,” Introduction to Space Science Written by the Staff of Goddard Space Flight Center National Aeronautics and Space Administration, Greenbelt, Maryland, Second Edition, Revised and Enlarged, Wilmot N. Hess and Gilbert D. Mead, editors (New York: Gordon and Breach, Science Publishers, 1968), p. 984.
Simulating the Process
No one has yet photographed directly the production of the first particles. It occurred in the first few micro-micro-microseconds of the universe, and telescopes cannot yet see any moment earlier than 380 000 years after the beginning. However, we can simulate the process of particle production. Physicists regularly cause collisions between energetic X-rays in cyclotrons and liner accelerators. Subatomic particles materialize daily from X-rays in laboratories around the world. The pictures physicists take of the darkness of X-rays coming from cyclotrons and producing atomic particles are simulated pictures of the first evening.
We do not know how much time passed until the gamma rays collided. Therefore, we do not know how long the first evening lasted. We do know that a light wave completes one vibration in a thousandth of a micro-microsecond. Until that amount of time had passed there was no such thing as a complete light wave. The first evening must have lasted at least that long.
During the first evening the gamma rays collided with one another and materialized as atomic components. Fred Hoyle (English astronomer, 1915–2001) was right when he said that the universe did not begin with a “single huge explosion,” that is, a “big bang.”[i] This popular name for the beginning of the universe is misleading. It suggests that an explosion occurred at a point and the ejected materials flew out into empty space.
[i] Hoyle, Fred, The Nature of the Universe, American edition (New York: Harper & Brothers, 7 October 1950), p. 119.
Collisions are not explosions. Explosions are destructive, but the collisions made the particles. Therefore, the beginning of the material of the universe was not an accidental, meaningless event. When collisions between gamma rays occurred, there was often energy left over that was not used to produce particles. That leftover energy produced electromagnetic waves of longer lengths than gamma rays, such as X-ray waves, ultraviolet waves, light, heat waves, and radio waves. This is how light was produced, as God said in the Bible, “Let there be light.”