What happened in the 1 second that humans learned to use fire?

Recently I had the great challenge (and fun) of explaining energy to a high school science summer camp. I wanted to do it as objectively as possible - not as a Shell employee but as a fellow citizen on planet earth. I also wanted to make it RELATABLE, fully recognizing that energy can be a bit abstract and vague for most people, unlike food or sports or entertainment which people can see, touch and feel.

So I did it in 10 bites. Today I'll share the first bite.

1.

What happened in the 1 second that humans learned to use fire?

i.e., if we assumed the earth has lived 1 full day of 24 hours.

The first few recorded fire uses occurred about 200,000 years ago. Relative to the earth's 5 billion years of history, that is approximately 23:59:59 in a 24 hour span.

How significant is that moment?

Let's think about the before and after of that moment.

2.

(much of this section comes from Vaclav Smil's book "How the world really works")

Before that moment, plants, animals, and humans essentially have two ways of using energy:

1) The chemistry processes inside the body. Plants take the energy from the sun and convert them inside their body; animals and humans eat food and breathe in oxygen, and convert them to nutrition and energy inside their body.

2) The muscle energy: animals and humans use their muscles to create mechanical energy that may be useful for their lives and livelihood, e.g. throwing rocks, picking fruits, etc.

After that moment, all the above still exist, however humans now have two new ways of using energy:

1) "out of the body" energy: they start a fire for all kinds of uses, including cooking food. This is fundamentally different from using or converting energy using one's own body.

2) "out of the body" mechanical energy: they use the energy from "burning" something, be it biomass or coal/oil/gas, to create mechanical energy to do all kinds of things, including moving a car or a plane. This is fundamentally different from creating mechanical energy using animal or human muscles.

These "out of the body" energy, are called "extrasomatic" energy.

3.

Many philosophers and thinkers have thought about the fundamental differences between animals and humans.

Some think humans can make and use tools. This is mostly true - although it can be arguable whether it's a "tool" when a monkey uses a stick to get a banana on the tree.

Some think humans are the only animal species who can pre-meditate a murder, i.e. to plan something to be carried out later, rather than the more spontaneous killings observed in the animal world.

Immanual Kant thought humans are different because they are the only species who are curious about "the root cause". For example, if a moving tennis ball appears before a dog, its most natural reaction is to catch it; while a human may be more likely to look at the direction and think where the ball comes from.

Jean Paul Sartre thought humans are the only species who are fully aware of their "existence" - i.e., no animals appear to be anticipating their ultimate death one day when they are still alive, and hence active plan how they should live "meaningfully" so that they can feel fulfilled when they die. Humans on the other hand, just got free will without even working for it, and hence "condemned" to be aware of their existence and "condemned to be free".

Renowned Stanford Professor Robert Sapolsky, even has a full lecture, explaining what makes human unique, and what makes human "unique-er" than animals. His conclusion - humans are the only species who can hold competing and conflicting thoughts in their brain the same time.

To me though, if you examine the impact humans have had in changing planet earth, there is no other factor that distinguishes humans more from any animals, than the ability to use "extrasomatic" energy.

That single fact, in my view, makes Prometheus the single most important god-like figure that actually makes human human.

4.

How much extrasomatic energy have humans used in the 200,000 years?

Well it turns out that for most of these years, it was quite modest.

In the 1600s, England started using more coal; but even so, human and animal muscle still provided around 90% of mechanical energy in year 1800.

It started accelerating after that for the past 200 years or so. In year 2000, fossil fuels provided 90% of heat and light energy, and machines provided 95% of mechanical energy globally.

The per capita extrasomatic energy use, according to Vaclav Smil, jumped from 0.05 GigaJoules/person/year in 1800, to 34 GigaJoules/person/year in 2020.

34 GigaJoules/person/year is equivalent to, again according to Vaclav Smil's calculation, "as if 60 adults would be working non-stop, day and night, for each average person”.

5.

So, that was what happened in the 1 second since humans learned to use fire.

In fact, it's really only about 200 years out of 200,000 years, that humans used energy with such massive scale.

That is to say, 1/000 of 1 second.

With it, the human society has seen enormous development that totally transformed the surface of the earth; it brought more materials wealth; it brought packaging and cold chain for vaccines; it extended human life expectancy by multiple decades per person; it brought intercontinental mobility and endless possibilities; it brought comfort, convenience, prosperity; and - it also brought many negative consequences such as a lot more man-made CO2 emissions.

As a geoscientist myself, I know the earth has experienced a lot of changes over geologic time - volcanic eruptions, ice ages, change of composition of the air (the earth's atmosphere used to be mostly CO2 before the first emergence of plants), the fall and rise of sea levels, large change of global temperatures, etc.

What's unique of the changes in the last 200 years though, is the really compressed time scale: 1/1000 of 1 second, in the earth's 24 hour history.

In the next "bite", I will explain exactly how much energy an average household in modern day United States use in a month, and gain an appreciation of the scale.

To be continued ...

Note:

Energy literacy matters to every citizen on this planet.

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