
What is Light?
The concept of light enjoys a long, fascinating history as the focal point of philosophy, metaphysics, religion and mythology in addition to its place at the center of the natural sciences. In ancient cultures and religions, light was understood, studied and appreciated as a symbol of goodness, beauty and even divinity.
Then in the 1600's, with the research of Sir Isaac Newton and Christian Huygens, the real science of light started to take shape as it evolved from the realms of philosophy and religion to pure scientific study. Early on, however, scientists diverged in their opinions on how to describe it. Newton, for instance, viewed light more as a particle with his corpuscular theory of light, while physicist Christian Huygens considered it through the prism of his his wave theory. This presented a dilemma. Certainly, light could not be both a wave and a particle, could it?
In 1801m Thomas Young's double slit experiment cemented the notion in the scientific community that light was indeed a wave. This was followed by Maxwell's electromagnetic theory, which seemed to be the clincher. He believed light was not only a wave, but an electromagnetic wave or electromagnetic radiation with well-defined properties - which we will look at next.
Under most circumstances, the properties of light can be derived from the theory of classical electromagnetism, perfectly summarized in Maxwell's equation. All the sciences of electricity and magnetism come from Maxwell’s equation, including Coulombs law, Ohms law, our detailed understandings of magnetic fields, and much more. Let's take a brief look at these beautiful equations.
The concept of light enjoys a long, fascinating history as the focal point of philosophy, metaphysics, religion and mythology in addition to its place at the center of the natural sciences. In ancient cultures and religions, light was understood, studied and appreciated as a symbol of goodness, beauty and even divinity.
Then in the 1600's, with the research of Sir Isaac Newton and Christian Huygens, the real science of light started to take shape as it evolved from the realms of philosophy and religion to pure scientific study. Early on, however, scientists diverged in their opinions on how to describe it. Newton, for instance, viewed light more as a particle with his corpuscular theory of light, while physicist Christian Huygens considered it through the prism of his his wave theory. This presented a dilemma. Certainly, light could not be both a wave and a particle, could it?
In 1801m Thomas Young's double slit experiment cemented the notion in the scientific community that light was indeed a wave. This was followed by Maxwell's electromagnetic theory, which seemed to be the clincher. He believed light was not only a wave, but an electromagnetic wave or electromagnetic radiation with well-defined properties - which we will look at next.
Under most circumstances, the properties of light can be derived from the theory of classical electromagnetism, perfectly summarized in Maxwell's equation. All the sciences of electricity and magnetism come from Maxwell’s equation, including Coulombs law, Ohms law, our detailed understandings of magnetic fields, and much more. Let's take a brief look at these beautiful equations.

Maxwell's Equations - the Origin of Light
Scottish physicist James Clerk Maxwell made a monumental discovery that unified electricity, magnetism AND light with four equations (known as “Maxwell's equations”) in which contain the entirety of classical electrodynamics. These are among the most influential equations in science - Gauss's law for electric fields, Gauss's law for magnetic fields, Faraday's Law and the Ampere-Maxwell Law. If you need evidence of Maxwell's equations, by all means, just look around - radio, television, smart phones, radar, computers, wireless internet access, and bluetooth technology are just a few examples of contemporary technology rooted in Maxwell's electromagnetic field theory. So it’s little wonder that the readers of Physics World selected Maxwell's equations as "the most important equations of all time".
Scottish physicist James Clerk Maxwell made a monumental discovery that unified electricity, magnetism AND light with four equations (known as “Maxwell's equations”) in which contain the entirety of classical electrodynamics. These are among the most influential equations in science - Gauss's law for electric fields, Gauss's law for magnetic fields, Faraday's Law and the Ampere-Maxwell Law. If you need evidence of Maxwell's equations, by all means, just look around - radio, television, smart phones, radar, computers, wireless internet access, and bluetooth technology are just a few examples of contemporary technology rooted in Maxwell's electromagnetic field theory. So it’s little wonder that the readers of Physics World selected Maxwell's equations as "the most important equations of all time".
How Electromagnetic Waves (a.k.a. Light) is Created
From these four equations, we see a pattern in the production of both electric and magnetic fields and how the two are connected, something that was not known before Maxwell came on the scene. Maxwell’s equations naturally lead to electromagnetic waves, which includes visible light! This happens because Maxwell’s correction to Ampere’s law informs us that a changing electric field induces a changing magnetic field, whereas Faraday’s law says that a changing magnetic field induces a changing electric field. This cycle continues ad infinitum. These oscillations are electromagnetic waves. So in a classical sense, light is a coupled electric and magnetic field propagating through space as a traveling wave. If for whatever reason the light wave is not absorbed, it will continue going on forever. Just think about this. We can still see light traveling from over 13 billion years ago, close in time to the Big Bang)!!
From these four equations, we see a pattern in the production of both electric and magnetic fields and how the two are connected, something that was not known before Maxwell came on the scene. Maxwell’s equations naturally lead to electromagnetic waves, which includes visible light! This happens because Maxwell’s correction to Ampere’s law informs us that a changing electric field induces a changing magnetic field, whereas Faraday’s law says that a changing magnetic field induces a changing electric field. This cycle continues ad infinitum. These oscillations are electromagnetic waves. So in a classical sense, light is a coupled electric and magnetic field propagating through space as a traveling wave. If for whatever reason the light wave is not absorbed, it will continue going on forever. Just think about this. We can still see light traveling from over 13 billion years ago, close in time to the Big Bang)!!

Light Comes from Accelerating Charges [Optional]
Technically, accelerating or oscillating charges like electrons radiate electromagnetic waves. In a radio transmitter, for example, electricity flowing into the transmitter antenna makes electrons vibrate, which produces radio waves. When you reheat that extra cup of coffee or tea, in the morning, your microwave oven also sends electromagnetic waves, called microwaves, from a concealed antenna that has an oscillating current imposed on it. In LEDs, there is also acceleration of electrons that drop across a band gap of just the right energy to create the wavelengths of light you see in the LED. The sun is obviously a bit more complicated as the radiant energy comes from nuclear fusion. But in all these cases, it is the same LIGHT - changing electric and magnetic fields that are coupled and keep recreating each other! As we'll see in a later chapter, electromagnetic waves also carry ENERGY related to their wavelength. Before we can get into that, let’s work on a clear definition of a wavelength, which is ESSENTIAL to understanding the science of red light therapy!
Technically, accelerating or oscillating charges like electrons radiate electromagnetic waves. In a radio transmitter, for example, electricity flowing into the transmitter antenna makes electrons vibrate, which produces radio waves. When you reheat that extra cup of coffee or tea, in the morning, your microwave oven also sends electromagnetic waves, called microwaves, from a concealed antenna that has an oscillating current imposed on it. In LEDs, there is also acceleration of electrons that drop across a band gap of just the right energy to create the wavelengths of light you see in the LED. The sun is obviously a bit more complicated as the radiant energy comes from nuclear fusion. But in all these cases, it is the same LIGHT - changing electric and magnetic fields that are coupled and keep recreating each other! As we'll see in a later chapter, electromagnetic waves also carry ENERGY related to their wavelength. Before we can get into that, let’s work on a clear definition of a wavelength, which is ESSENTIAL to understanding the science of red light therapy!

What is Wavelength?
One of the main parameters of red light therapy!
In red and near infrared light therapy, wavelength is perhaps the most important property of light. The wavelength of light is the distance from peak to peak between successive crests of a wave. Surfers as well as scientists can agree on this! It is usually denoted by the Greek letter lambda (λ). Wavelength is inversely proportional to frequency.
Note: frequency (v) and wavelength (λ) are related by the equation c=λv, where c is the speed of light. From this equation, you can see that frequency and wavelength are inversely proportional. This means that a higher frequency has a shorter wavelength and a lower frequency has a longer wavelength, though essentially, they both measure the same thing. The subtle nuance is that frequency is measuring light in the time domain and wavelength is measuring it in the spatial domain.
One of the main parameters of red light therapy!
In red and near infrared light therapy, wavelength is perhaps the most important property of light. The wavelength of light is the distance from peak to peak between successive crests of a wave. Surfers as well as scientists can agree on this! It is usually denoted by the Greek letter lambda (λ). Wavelength is inversely proportional to frequency.
Note: frequency (v) and wavelength (λ) are related by the equation c=λv, where c is the speed of light. From this equation, you can see that frequency and wavelength are inversely proportional. This means that a higher frequency has a shorter wavelength and a lower frequency has a longer wavelength, though essentially, they both measure the same thing. The subtle nuance is that frequency is measuring light in the time domain and wavelength is measuring it in the spatial domain.
If you look at the image below, you can see the peaks of these waves are very close together on the left, indicating shorter wavelengths, and much farther apart on the right, indicating longer wavelengths. Related to red light therapy, shorter wavelengths have more energy and are less penetrating, while longer wavelengths have less energy and are more penetrating. And that is roughly true (with penetration) until we get up to around 905 nm.
Wavelengths are measured in nanometers (nm), which are units of measurement equal to one billionth of a meter. Try to wrap your head around the infinitesimal nature of that! The most widely used wavelengths in LASER and LED therapy are between 600-1100 nm. Why? Because wavelengths in this range are able to reach what are called chromophores, aka light absorbing molecules in cells and tissues where they can affect the most change. We’ll get into chromophores in more detail in Chapter 5. It's also because this range of wavelengths is where most of the clinical evidence exists at the present time.
Visible Spectrum - The "Familiar" Light
Visual perception is a key part of our conscious experience, integral to our day-to-day functioning. Human eyes are especially sensitive to light, able to detect a single photon and differentiate between up to 10 million individual colors! Or it it, “colours”? Yet they can ONLY detect light in the visible spectrum between the wavelengths of 400nm and 750nm.
Outside the Visible Spectrum
The longest wavelength our eyes can see appears to us as the color red, while the shortest appears as violet. The term Infrared comes from the Latin root "infra," meaning "under," so infra-red is literally "under red" in that it has a smaller frequency, but a longer wavelength. Once you get past 750 nm, it is a dark red we cannot see. This is why we cannot perceive the near infrared LED lights on a red light panel or bed that are typically above 800nm. It’s not that they’re turned off. It’s that our eyes do not have the machinery to "see" them. Though human beings cannot see infrared, some animals like vampire bats and wolves can see it! Lucky them, huh? And even though we are unable to detect infrared, we can feel infrared and longer wavelengths like microwaves in the form of HEAT. Think of microwave ovens and heat lamps at restaurants that keep your food warm.
So going from infrared, which is basically heat, to the other side of the spectrum, which is more damaging as the wavelengths get shorter, there is ultraviolet (of course a little is good for vitamin D), x-rays and gamma rays. Ultraviolet literally means "beyond" violet. Humans cannot see ultraviolet light but some animals can, such as butterflies, some birds, bees and reindeer. Think of this when you’re explaining the birds and the bees to your kids, or watching Rudolph on TV at Christmastime. Not only is his nose a red light, but he can see ultraviolet light.
Certainly we can feel the effects of UV (100-400nm) in the form of sunburns. As we go beyond UV, we get to X-rays and gamma rays (too much time on planes), which always have damaging effects on the cells.
While the eyes cannot see wavelengths outside 400-750nm, the human body can respond to wavelengths outside this spectrum in ways we just discussed. More importantly, there is a spectrum or window of frequencies (600-1100nm) that penetrate and interact with the mitochondria to produce energy! And THIS is felt by having more energy, better health, improved sleep, reduced pain AND more, as we'll see throughout this book!
Visual perception is a key part of our conscious experience, integral to our day-to-day functioning. Human eyes are especially sensitive to light, able to detect a single photon and differentiate between up to 10 million individual colors! Or it it, “colours”? Yet they can ONLY detect light in the visible spectrum between the wavelengths of 400nm and 750nm.
Outside the Visible Spectrum
The longest wavelength our eyes can see appears to us as the color red, while the shortest appears as violet. The term Infrared comes from the Latin root "infra," meaning "under," so infra-red is literally "under red" in that it has a smaller frequency, but a longer wavelength. Once you get past 750 nm, it is a dark red we cannot see. This is why we cannot perceive the near infrared LED lights on a red light panel or bed that are typically above 800nm. It’s not that they’re turned off. It’s that our eyes do not have the machinery to "see" them. Though human beings cannot see infrared, some animals like vampire bats and wolves can see it! Lucky them, huh? And even though we are unable to detect infrared, we can feel infrared and longer wavelengths like microwaves in the form of HEAT. Think of microwave ovens and heat lamps at restaurants that keep your food warm.
So going from infrared, which is basically heat, to the other side of the spectrum, which is more damaging as the wavelengths get shorter, there is ultraviolet (of course a little is good for vitamin D), x-rays and gamma rays. Ultraviolet literally means "beyond" violet. Humans cannot see ultraviolet light but some animals can, such as butterflies, some birds, bees and reindeer. Think of this when you’re explaining the birds and the bees to your kids, or watching Rudolph on TV at Christmastime. Not only is his nose a red light, but he can see ultraviolet light.
Certainly we can feel the effects of UV (100-400nm) in the form of sunburns. As we go beyond UV, we get to X-rays and gamma rays (too much time on planes), which always have damaging effects on the cells.
While the eyes cannot see wavelengths outside 400-750nm, the human body can respond to wavelengths outside this spectrum in ways we just discussed. More importantly, there is a spectrum or window of frequencies (600-1100nm) that penetrate and interact with the mitochondria to produce energy! And THIS is felt by having more energy, better health, improved sleep, reduced pain AND more, as we'll see throughout this book!

The Vast Electromagnetic Spectrum
Visible light is an electromagnetic wave, BUT it is only a tiny sliver of the vast electromagnetic spectrum. If this entire spectrum were laid out across the Brooklyn Bridge, the portion we can see with our eyes would be just a few feet wide! This electromagnetic spectrum starts from wavelengths of 10^-14 m at one extreme to 10^8 m at the other, spanning a range of 10^22. In terms of doublings, 10^22 ≈ 2^73, or 73 octaves. This is an ENORMOUS spectrum, ranging from sizes smaller than a proton to the size of the earth!
Visible light is an electromagnetic wave, BUT it is only a tiny sliver of the vast electromagnetic spectrum. If this entire spectrum were laid out across the Brooklyn Bridge, the portion we can see with our eyes would be just a few feet wide! This electromagnetic spectrum starts from wavelengths of 10^-14 m at one extreme to 10^8 m at the other, spanning a range of 10^22. In terms of doublings, 10^22 ≈ 2^73, or 73 octaves. This is an ENORMOUS spectrum, ranging from sizes smaller than a proton to the size of the earth!

Light as a Particle - The PHOTON!
It turns out that our view of light as an electromagnetic wave is only half the story! Light is also a particle called a photon and it’s got some strange properties and characteristics. Light sometimes behaves like a particle and sometimes more like a wave. We therefore have two very different ideas for how light works - as waves in the electric and magnetic fields, and as the motion of massless particles called photons. This pair of explanations, called "wave-particle duality," is a recurring theme of quantum mechanics. So at the risk of blaspheming, it turns out that neither Huygens nor Newton were entirely correct. Light is not a wave or a particle. It is BOTH, as can be understood in the complex math of quantum mechanics and the idea of "wave packets".
It turns out that our view of light as an electromagnetic wave is only half the story! Light is also a particle called a photon and it’s got some strange properties and characteristics. Light sometimes behaves like a particle and sometimes more like a wave. We therefore have two very different ideas for how light works - as waves in the electric and magnetic fields, and as the motion of massless particles called photons. This pair of explanations, called "wave-particle duality," is a recurring theme of quantum mechanics. So at the risk of blaspheming, it turns out that neither Huygens nor Newton were entirely correct. Light is not a wave or a particle. It is BOTH, as can be understood in the complex math of quantum mechanics and the idea of "wave packets".

Here is the easiest way to think of this paradox: Shorter wavelengths tend to act more like a particle and longer wavelengths tend to act more like a wave. Red and near infrared is only between 600-1100nm, and because a nanometer is billionth of a meter, this is an incredibly small wavelength. The width of a human hair by comparison is around 80,000 nm! With these short wavelengths used in red light therapy, it is easier and more natural to think of light as a photon or particle.

The Amount of Energy in a Photon
The amount of energy in a photon is solely defined by its wavelength (or frequency) as shown here. For our purposes, all you need to know is that as the wavelength gets smaller, the energy gets higher. Although photons are massless so we cannot use E=mc^2; still, the greater the energy, the more particle-like the photon becomes. This is because although photons have no mass but they DO have momentum!
For example, blue has a shorter wavelength than red and therefore has more energy (around 3 eV for blue compared to 2 eV for red). Thus, decreasing the wavelength makes the photon more particle-like and more energetic, while increasing the wavelength makes the photon more wave-like and less energetic. With this knowledge, we can describe the three fundamental ways how light interacts with the organic life on earth, which of course includes the human body aka us!
The amount of energy in a photon is solely defined by its wavelength (or frequency) as shown here. For our purposes, all you need to know is that as the wavelength gets smaller, the energy gets higher. Although photons are massless so we cannot use E=mc^2; still, the greater the energy, the more particle-like the photon becomes. This is because although photons have no mass but they DO have momentum!
For example, blue has a shorter wavelength than red and therefore has more energy (around 3 eV for blue compared to 2 eV for red). Thus, decreasing the wavelength makes the photon more particle-like and more energetic, while increasing the wavelength makes the photon more wave-like and less energetic. With this knowledge, we can describe the three fundamental ways how light interacts with the organic life on earth, which of course includes the human body aka us!
How light interacts with the human body.
The chart here shows the electromagnetic spectrum, which we have broken down for easier understanding into three main regions in terms of biological effects: photophysical (heating), photochemical (excitation) and ionizing radiation. In order to comprehend the core mechanism of how red light therapy energizes the body, and why it is so unique and exciting, it’s helpful to illuminate these three parts of the electromagnetic spectrum.
The chart here shows the electromagnetic spectrum, which we have broken down for easier understanding into three main regions in terms of biological effects: photophysical (heating), photochemical (excitation) and ionizing radiation. In order to comprehend the core mechanism of how red light therapy energizes the body, and why it is so unique and exciting, it’s helpful to illuminate these three parts of the electromagnetic spectrum.
1) Photophysical or Photothermal effects: Heat = Vibration
First, with longer wavelengths in the infrared and microwave ranges interacting with atoms or molecules (like in your body), we have photophysical or photothermal effects. Photophysical effects occur when atoms or molecules absorb light, then move, rotate, and vibrate due to the increase in energy. Here, light is still a bit wave-like and does not have a short enough wavelength (i.e., enough energy) to effectively move electrons around. But there is enough energy to jiggle and vibrate atoms and molecules, not to mention cells and tissues. This vibration and movement create heat or warming in the body. This explains why we feel warmth from the sun’s infrared radiation and saunas for example, and why microwave ovens reheat last night’s meat loaf or lasagna so well. These wavelengths vibrate the atoms and molecules in your body, which is made up of mostly water. Think of heat as vibration and vibration as heat. They are the same thing! So when you feel the warmth from your coffee or tea mug, you are feeling vibrating and jiggling molecules, which may be even more jittery than the caffeine makes you. It is important to note that photobiomodulation is defined as the nonthermal or non-heating effects of light which create many beneficial health effects through researched mechanisms.
First, with longer wavelengths in the infrared and microwave ranges interacting with atoms or molecules (like in your body), we have photophysical or photothermal effects. Photophysical effects occur when atoms or molecules absorb light, then move, rotate, and vibrate due to the increase in energy. Here, light is still a bit wave-like and does not have a short enough wavelength (i.e., enough energy) to effectively move electrons around. But there is enough energy to jiggle and vibrate atoms and molecules, not to mention cells and tissues. This vibration and movement create heat or warming in the body. This explains why we feel warmth from the sun’s infrared radiation and saunas for example, and why microwave ovens reheat last night’s meat loaf or lasagna so well. These wavelengths vibrate the atoms and molecules in your body, which is made up of mostly water. Think of heat as vibration and vibration as heat. They are the same thing! So when you feel the warmth from your coffee or tea mug, you are feeling vibrating and jiggling molecules, which may be even more jittery than the caffeine makes you. It is important to note that photobiomodulation is defined as the nonthermal or non-heating effects of light which create many beneficial health effects through researched mechanisms.

2) Photochemical effects = Excitation (Where the REAL Magic of Life on Earth Happens)
Electron excitation is the transfer of a bound electron in its ground state to a more energetic excited state while but still bound in the atom or molecule. This is achieved mainly by photoexcitation (PE), where the electron absorbs a photon with a precise amount of energy. That is, the electron must absorb an amount of energy equivalent to the energy difference between the electron's current energy level and an unoccupied higher (excited) level. Something to get excited about for sure!
Photochemical effects are where the real magic happens, but only from UV to near infrared (roughly 300-1100nm). This is because the orbital energy of most atoms and molecules are in this range! Photobiology works by this process of excitation in molecules like chlorophyll in the chloroplasts of plants and cytochrome c oxidase in the mitochondria of animals. This is also how red light therapy works as well! In nature, we have biological life absorbing photons of light with just the right amount of energy to nudge these electrons from one molecular orbit to another. This excitation enables photochemical effects like photosynthesis and even ATP production to occur. These excited states are like little batteries that store - however briefly - electrical energy. And you could say that from these energetic excited states emerges the electricity of life itself!!
Unlike far infrared and microwave wavelengths, visible light is energetic ENOUGH to cause excitation and not just vibration. Instead of using the energy to jiggle or move a molecule or atom for thermal effects, the energy is absorbed to move the electron to a higher energy orbit. This "electronic energy" is non-thermal, representing an amazing way for small molecules to store potential energy. Keep in mind, this only happens when wavelengths are between UV and near infrared (about 300-1100 nm). This small bandwidth is verily the light that stimulates the electricity that drives all life on earth which is also the peak emission of wavelengths from the sun! So it’s no accident that all the red light therapy wavelengths you see on panels and beds are also in this range. Additional fun fact: If all the electronic energy in your body were converted to thermal energy, your body would be almost 5000 degrees Fahrenheit. We are highly energetic beings of light! [1] So in religious terms, in Genesis, when God says, “Let there be light,” perhaps it’s not just about the sun but about the creation of human beings!
Electron excitation is the transfer of a bound electron in its ground state to a more energetic excited state while but still bound in the atom or molecule. This is achieved mainly by photoexcitation (PE), where the electron absorbs a photon with a precise amount of energy. That is, the electron must absorb an amount of energy equivalent to the energy difference between the electron's current energy level and an unoccupied higher (excited) level. Something to get excited about for sure!
Photochemical effects are where the real magic happens, but only from UV to near infrared (roughly 300-1100nm). This is because the orbital energy of most atoms and molecules are in this range! Photobiology works by this process of excitation in molecules like chlorophyll in the chloroplasts of plants and cytochrome c oxidase in the mitochondria of animals. This is also how red light therapy works as well! In nature, we have biological life absorbing photons of light with just the right amount of energy to nudge these electrons from one molecular orbit to another. This excitation enables photochemical effects like photosynthesis and even ATP production to occur. These excited states are like little batteries that store - however briefly - electrical energy. And you could say that from these energetic excited states emerges the electricity of life itself!!
Unlike far infrared and microwave wavelengths, visible light is energetic ENOUGH to cause excitation and not just vibration. Instead of using the energy to jiggle or move a molecule or atom for thermal effects, the energy is absorbed to move the electron to a higher energy orbit. This "electronic energy" is non-thermal, representing an amazing way for small molecules to store potential energy. Keep in mind, this only happens when wavelengths are between UV and near infrared (about 300-1100 nm). This small bandwidth is verily the light that stimulates the electricity that drives all life on earth which is also the peak emission of wavelengths from the sun! So it’s no accident that all the red light therapy wavelengths you see on panels and beds are also in this range. Additional fun fact: If all the electronic energy in your body were converted to thermal energy, your body would be almost 5000 degrees Fahrenheit. We are highly energetic beings of light! [1] So in religious terms, in Genesis, when God says, “Let there be light,” perhaps it’s not just about the sun but about the creation of human beings!
3) Ionizing radiation.
To more fully understand these processes, it is worth engaging in a brief discussion about ionizing radiation. Here, the photons (short wave UV to xrays and gamma rays) have TOO MUCH energy. Instead of nudging electrons from one molecular (or atomic) orbital to another, they rip them off, causing a lot of free radicals and ROS. Free radicals can chemically steal electrons (like the superoxide radical) or energetically steal electrons (like x-rays) – naturally and legally, of course - which creates all kinds of damaging effects!
Red light therapy is a local application of a non-invasive, low-intensity, non-thermal and non-ionizing electromagnetic waves. It is not a heat therapy like saunas; the effect is more like photosynthesis in plants or when your skin gets a tan. Red light therapy uses specific wavelengths of red and near-infrared light to penetrate the skin and stimulate the cells, tissues, and organs beneath. This stimulation triggers a series of metabolic and biochemical processes that increase ATP energy and promote healing and rejuvenation, as we'll explore in detail in chapters 6-9.
To more fully understand these processes, it is worth engaging in a brief discussion about ionizing radiation. Here, the photons (short wave UV to xrays and gamma rays) have TOO MUCH energy. Instead of nudging electrons from one molecular (or atomic) orbital to another, they rip them off, causing a lot of free radicals and ROS. Free radicals can chemically steal electrons (like the superoxide radical) or energetically steal electrons (like x-rays) – naturally and legally, of course - which creates all kinds of damaging effects!
Red light therapy is a local application of a non-invasive, low-intensity, non-thermal and non-ionizing electromagnetic waves. It is not a heat therapy like saunas; the effect is more like photosynthesis in plants or when your skin gets a tan. Red light therapy uses specific wavelengths of red and near-infrared light to penetrate the skin and stimulate the cells, tissues, and organs beneath. This stimulation triggers a series of metabolic and biochemical processes that increase ATP energy and promote healing and rejuvenation, as we'll explore in detail in chapters 6-9.

Photoelectric Effect [Optional]
A photon is a particle of electromagnetic radiation that has zero mass and carries a quantum of energy. The energy of photons of light is quantized according to the E=hν equation. This key particle-like behavior of photons was explained by Einstein using the photoelectric effect, which earned him his only Nobel Prize.
The photoelectric effect is a phenomenon that occurs when light shone onto a metal surface causes the ejection of electrons from that metal. It was observed that only certain frequencies of light were able to cause this ejection of electrons. If the frequency of the incident light was too low (red light, for example), then no electrons were ejected, even if the intensity of the light was very high or it shone onto the surface for a long time. If the frequency of the light was higher (green light, for example), electrons could be ejected from the metal surface even if the intensity was very low or it shone for only a short time. This minimum frequency needed to cause electron ejection is referred to as the “threshold frequency.”
This also occurs in atoms related to our three ranges of wavelengths. If the wavelength is too long (i.e., the frequency is too small), like in infrared, the photon is not particle-like or energetic enough to dislodge an electron from, say, the lowest energy state of cytochrome c oxidase (one of the target molecules in red light therapy). In the range between roughly 300nm - 1100nm, the energy is just enough to promote an electron to an excited or energetic state that can then be used to do work. But if the wavelength is too small like in x-rays, then the energy is beyond the threshold frequency and the electron is ejected from the molecule, doing damage that prevents any useful work from being accomplished.
A photon is a particle of electromagnetic radiation that has zero mass and carries a quantum of energy. The energy of photons of light is quantized according to the E=hν equation. This key particle-like behavior of photons was explained by Einstein using the photoelectric effect, which earned him his only Nobel Prize.
The photoelectric effect is a phenomenon that occurs when light shone onto a metal surface causes the ejection of electrons from that metal. It was observed that only certain frequencies of light were able to cause this ejection of electrons. If the frequency of the incident light was too low (red light, for example), then no electrons were ejected, even if the intensity of the light was very high or it shone onto the surface for a long time. If the frequency of the light was higher (green light, for example), electrons could be ejected from the metal surface even if the intensity was very low or it shone for only a short time. This minimum frequency needed to cause electron ejection is referred to as the “threshold frequency.”
This also occurs in atoms related to our three ranges of wavelengths. If the wavelength is too long (i.e., the frequency is too small), like in infrared, the photon is not particle-like or energetic enough to dislodge an electron from, say, the lowest energy state of cytochrome c oxidase (one of the target molecules in red light therapy). In the range between roughly 300nm - 1100nm, the energy is just enough to promote an electron to an excited or energetic state that can then be used to do work. But if the wavelength is too small like in x-rays, then the energy is beyond the threshold frequency and the electron is ejected from the molecule, doing damage that prevents any useful work from being accomplished.

Photochemical Effects Drive All Life on Earth!!!
We will conclude this chapter with a quote from Nobel prize winning scientist Albert Szent-Györgi. Keep this in mind throughout the book because it is the fundamental reason why red light therapy helps to heal the body of just about everything!!
“Life is driven by nothing else but electrons, by the energy given off by these electrons while cascading down from the high level to which they have been boosted up by photons. An electron going down around is a little current. What drives live is thus electric current.”
— Albert Szent-Gyorgi (1960), Introduction to Submolecular Biology [2]
In the next chapter, we will examine the human body from a more energetic and photonic perspective so you can more deeply understand that we really are “beings of light!”
References
[1] The Rainbow and the Worm. Mae-Wan Ho (Institute of Science in Society, UK). Non-Series Books. August 2008
[2] Szent-Gyorgi, Albert. (1960). Introduction to Submolecular Biology (pgs. 20-21). Academic Press.
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NO MORE EDITING OR ILLUSTRATIONS PAST THIS POINT
We will conclude this chapter with a quote from Nobel prize winning scientist Albert Szent-Györgi. Keep this in mind throughout the book because it is the fundamental reason why red light therapy helps to heal the body of just about everything!!
“Life is driven by nothing else but electrons, by the energy given off by these electrons while cascading down from the high level to which they have been boosted up by photons. An electron going down around is a little current. What drives live is thus electric current.”
— Albert Szent-Gyorgi (1960), Introduction to Submolecular Biology [2]
In the next chapter, we will examine the human body from a more energetic and photonic perspective so you can more deeply understand that we really are “beings of light!”
References
[1] The Rainbow and the Worm. Mae-Wan Ho (Institute of Science in Society, UK). Non-Series Books. August 2008
[2] Szent-Gyorgi, Albert. (1960). Introduction to Submolecular Biology (pgs. 20-21). Academic Press.
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NO MORE EDITING OR ILLUSTRATIONS PAST THIS POINT

Keep all this in mind when we look at Tissue optics and how light is absorbed in the body. We'll see that certain wavelengths are absorbed better than others and on top of that certain wavelengths are better at generating ATP energy in the body.
But first lets take a step back and use our understanding of light to see how deeply connected our bodies and minds (and all life on earth) with the sun.
But first lets take a step back and use our understanding of light to see how deeply connected our bodies and minds (and all life on earth) with the sun.
The New Physics and Red Light Therapy
There are many new whole-istic sciences of cooperative phenomenon, non-equilibrium thermodynamics, chaos theory, quantum electrodynamics, quantum optics and the most exciting quantum biology and quantum computing. These newer understanding are overturning the mechanistic Newtonian view of the world, universe and our biology. Atoms and matter, genes and biochemical molecules, and of course the physics of light, all have their rightful place in this new and integrative science, but like the biofield, even physics shows evidence of holism, macroscopic quantum phenomenon, cooperative behavior of large ensembles of molecules (like Benard Cells), and the deep quantum entanglement within our organism and between us and the surrounding earth, sun and stars. While reductionistic science helps us to flesh out all the details, it is ultimately an incomplete view of reality. So even moving forward in this book, we are going to focus more on how red light therapy works using mostly more standard physics, biophysics and biology; but try to always keep the biofield and this more integrative understanding we touched on in the last chapter.
In this chapter I want to go through the basics of the physics needed to understand red light therapy, which is mainly Maxwells Equations (Classical Electromagnetic theory) and quantum electrodynamics (QED - the quantum theory of how light interacts with matter). QED is more accurate and includes Maxwells equations via the correspondence principle, but it is much harder to understand. So classical electromagnetism is still an excellent and accurate model in the scales of our everyday world so we'll focus more on it, but always keep in mind the real fundamental interconnected and entangled quantum nature of light and matter.
Because this is a book about red and near infrared light therapy, our focus will be centered on light as an electromagnetic wave (classically), and also light as a photon particle/wave (quantum mechanically). It turns out the basics of both are very relevant to understand RLT.
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In a molecule, the energy is absorbed not only by the electrons, which are excited to higher energy levels, but also by the whole molecule, which is excited to discrete modes of vibration and rotation. Photochemistry transfer of this excitation energy to create a chemical reaction. Photobiology is this process occurring in living organisms or more broadly, it is the study of the effects of light on living things and biological processes.
There are many new whole-istic sciences of cooperative phenomenon, non-equilibrium thermodynamics, chaos theory, quantum electrodynamics, quantum optics and the most exciting quantum biology and quantum computing. These newer understanding are overturning the mechanistic Newtonian view of the world, universe and our biology. Atoms and matter, genes and biochemical molecules, and of course the physics of light, all have their rightful place in this new and integrative science, but like the biofield, even physics shows evidence of holism, macroscopic quantum phenomenon, cooperative behavior of large ensembles of molecules (like Benard Cells), and the deep quantum entanglement within our organism and between us and the surrounding earth, sun and stars. While reductionistic science helps us to flesh out all the details, it is ultimately an incomplete view of reality. So even moving forward in this book, we are going to focus more on how red light therapy works using mostly more standard physics, biophysics and biology; but try to always keep the biofield and this more integrative understanding we touched on in the last chapter.
In this chapter I want to go through the basics of the physics needed to understand red light therapy, which is mainly Maxwells Equations (Classical Electromagnetic theory) and quantum electrodynamics (QED - the quantum theory of how light interacts with matter). QED is more accurate and includes Maxwells equations via the correspondence principle, but it is much harder to understand. So classical electromagnetism is still an excellent and accurate model in the scales of our everyday world so we'll focus more on it, but always keep in mind the real fundamental interconnected and entangled quantum nature of light and matter.
Because this is a book about red and near infrared light therapy, our focus will be centered on light as an electromagnetic wave (classically), and also light as a photon particle/wave (quantum mechanically). It turns out the basics of both are very relevant to understand RLT.
--
In a molecule, the energy is absorbed not only by the electrons, which are excited to higher energy levels, but also by the whole molecule, which is excited to discrete modes of vibration and rotation. Photochemistry transfer of this excitation energy to create a chemical reaction. Photobiology is this process occurring in living organisms or more broadly, it is the study of the effects of light on living things and biological processes.
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