You may have noticed that this blog seems to focus on flashlights (or “torches” in the UK). They’re simple things compared to most technology but their elemental nature makes them almost entrancing. Here’s why.

Darkness is the unknown, the unexplorable. Night rules us with its recurrent temporal restriction, constraining our productivity to what we call day. The dark renders our sense of sight worthless for half of our lives.

People have attempted to overcome dark’s reign by harnessing fire since people have existed. Trees absorb energy from the sun to grow. These biological batteries are harvested as wood, then turned into heat and light. This light is used to push back darkness. To make the invisible visible. To extend the day.


Harnessing the sun’s energy like this requires technology and is a core trait that separates us from animals. As people learned to make fire hotter, brighter and last longer, their technological advancement rewarded them with a greater chance of survival and more time away from darkness.

Wood was replaced with animal fat, beeswax or plant resin. These let people carry light as candles and torches, allowing them to explore more new places. These were replaced with processed coal and oil, bringing light to everyone’s home, as long as they were rich enough.

Lamps let people read books late into the evening. More hours of the “day” could be used for gaining knowledge. Lighting meant factories no longer relied on daylight. Winter months became as productive as summer. People now controlled the seasons.

Coal and oil gave way to the electric incandescent light: the light bulb. Switches turned light on and off in an instant. Each Watt of power produced 10 lumens of light. More electrical power meant more light and more light gave people more power.

Battery technology advanced, as people wanted more power in their hand as well as their home. The humble alkaline AA could produce 5 lumens from a bulb with half a Watt, lasting 10 hours. New Ni-Mh chemistry meant AA batteries could sustain twice the lumens for the same time.

This was enough light to make flashlights a reality. People could point at darkness anywhere and it would depart from them if they were close enough to it.

But 10 lumens for every Watt means 98% of the energy is wasted as heat. 700 lumens from a household bulb was just enough to light a room but that took a massive 60W of power: much more than could fit in one’s hand. More efficiency was needed and tungsten incandescent bulbs gave way to halogen, compact fluorescent lamps and finally LEDs.

White LEDs now produce over 10 times as many lumens per Watt of energy as incandescent bulbs. Within a few decades, this generation of people are now used to harnessing 10 times the brightness or staying out in the dark for 10 times as long as our incandescent-wielding ancestors.

Taking energy from a battery cell to make light is a simple system, with only a few components that technology has the opportunity to advance. Technology means battery cells can pump out more watts for more time, light sources become more efficient and optics such as reflectors and total-internal-reflection lenses point the light in the right direction.

We’ve reached the point where palm-sized flashlights now can accompany us on a year long expedition without needing new batteries or to be recharged, producing light not stop for a whole year. Something you take out of your pocket now makes more light when you turn it on than 20 mains powered incandescent bulbs. If we want to see something far away, we can now take something from a jacket pocket, press a button and light something up over a mile away.

Years ago none of this was possible. Now dark departs from us at the first click of a switch.

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