A light your body already knows.
The red of a sunrise. The embers of a fire settling for the night. Long before the light bulb, this was the light of our mornings and our evenings. We kept five of its wavelengths and put them in panels you switch on at home.
Follow it from the source to the cell: what it is, how far it goes, what the cell does with it, what people use it for. In plain words.
Light is not only for seeing. It is energy, travelling. When it touches skin, some of it bounces away and some of it goes in. You have seen this already: with your eyes closed in the sun, everything turns red. That is light passing through your eyelids.
All light is a wave, and every colour has its own length, counted in nanometres: the “nm” you will see all over this page. Blue is short. Red is long. Just past red the wave stretches further and the eye stops following: that is near-infrared, a light with no colour.
Why light? Because living things have always used it. A leaf turns it into sugar. An eye turns it into an image. Our days are set by it. And our own bodies have their way of receiving it too: that is where this page is taking you.
The wave
One light, five wavelengths.
A lit panel looks like a single red. In fact it carries five waves: 630, 660, 810, 830 and 850 nm. The first two are a true red, the one you see. The other three are near-infrared: the eye does not see them, the skin receives them all the same. So there is more light in the room than your eyes are telling you.
Depth
Near-infrared goes further than red.
How much light gets under the skin can be measured. Two published measurements, taken on the human body, give the shape of the journey. The first compares red with near-infrared. The second shows how light fades along the way.
Through a cheek: 12% versus 2%.
A source on one side of a living human cheek. A sensor on the other. 12% of the 830 nm light arrived, versus 2% of the 633 nm. One person, one device.
Jagdeo et al., PLoS One, 2012 · table 6 · PMID 23077622
A slope, never a wall.
At 808 nm, through a human skull, 37% of the light remains roughly every 4.5 mm. Then 37% of that, and so on. Light does not stop dead at a given depth: it fades little by little, like a sound moving away.
Tedford et al., Lasers Surg Med, 2015 · PMID 25772014
The cell
At the end of the path, a cell.
Cleveland Clinic describes what follows in a few words: certain cells absorb the light and are stimulated to work. It places the scene in the mitochondria, the small power plants that supply the cell’s energy. Three steps, one after the other.
- 1
It absorbs.
The mitochondria pick up red and near-infrared, the way an antenna picks up its frequency.
- 2
It has more energy.
By that description, the cell then has more energy available for what it does every day.
- 3
It does its work.
A skin cell tends to skin, a muscle cell to muscle. Light gives no orders: it can support that work.
The uses
Each depth has its use.
Now that you know which one goes further, the uses sort themselves. Visible red is used for what sits near the surface. Near-infrared, for what lies underneath. And in the evening, a use that has less to do with depth than with colour.
Near the surface · 630 · 660 nm
Skin
Red light is used for skin firmness, fine lines and facial texture. It is also studied for redness, marks left by the sun and age spots. The mechanism Cleveland Clinic describes: light stimulates fibroblasts, the cells that make collagen, the structure of skin.
Near the surface · the scalp
Hair
On the scalp, red light is used for hair density and thickness. Head under the light, a book in your hands: that is the whole method.
Deeper · 810 · 830 · 850 nm
Muscles and joints
A muscle or a joint sits under the skin, not in it. These are the areas near-infrared is used for, after exertion. The light is also studied for stiffness, soreness and recovery. A shoulder, a knee, the lower back, facing the light.
The evening · a light with no blue
Sleep and energy
Red light does not carry the blue that delays falling asleep. It is the light you can turn on in the evening. Many people sit in front of it instead of a screen: no notifications, nothing to scroll. The room glows red, and the day comes to a close.
The session
A session comes down to three things.
10 min
Ten minutes.
The length of a chapter. Short enough to slip into a real day, simple enough to come back to tomorrow.
1 distance
One distance, always the same.
Light weakens as it moves away from its source. Find your spot in front of the panel and take it again each time: that is what makes two sessions alike.
0:00
A timer that ends it.
You set the time, the panel switches itself off. Nothing to watch, nothing to remember. The session ends and your evening carries on.
All that is left is to switch it on.
After that, it comes down to room: each object says what it asks of the space, never what it is worth. Choose the one that fits your life.