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    I Asked 12 Scientists: What Is The One Fact Humanity Needs To Know?

    "If civilisation was destroyed, what scientific information would you pass on to the survivors?"

    Richard Feynman, the physicist, was once asked: "If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words?"

    He replied: "I believe it is the atomic hypothesis that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another."

    I asked some scientists the same question (although I said they were allowed a little more than one sentence).

    1. Dr Ceri Brenner, physicist working with high-powered lasers:

    "Energy is always conserved, never created or destroyed. Life and the processes that surround us in the world and the universe are governed by the constant flow of energy transforming from one state to another, never disappearing but emerging in a different form.

    "Our state of being, of breathing, of consuming, of reproducing is a cycle of energy transfer from chemical to heat to chemical to mass, etc. Our state of experiencing the world through sight, sound, touch, communication is the conversion of electrical energy to heat or light. Inside our sun is a conversion of mass energy into heat and movement energy, keeping all of us alive.

    "All scientific experiments start with the same question: What happens when I add a bit of energy or change the energy balance, where does the energy then go? What biological, chemical, or physical processes does that energy transfer trigger?

    "Philosophically, this is also a very nice sentiment when thinking of those who have died. Their energy, stored up in their mass, will never be destroyed; it will be conserved and transformed into something else or will simply remain constant."

    2. Dr Buddhini Samarasinghe, molecular biologist:

    "The elegant double-helix structure of the DNA molecule, found inside nearly every living cell, is the most important piece of scientific information that humanity would need to know. Made up of just four letters, A, T, C, and G, representing four different chemicals, this is the very Code of Life. These four letters, and the order in which they are arranged, can tell us about our past, present, and future.

    "The DNA code helps us learn where we came from and who our ancestors were. It can help us understand the diseases that ail us, and how to fight them. The structure of DNA allows us to comprehend life on our planet, to learn where we fit within the natural order, and how we can best participate in the world we share."

    3. Dr Lewis Dartnell, astrobiologist and author of The Knowledge: How to Rebuild our World from Scratch:

    "While Feynman's sentence is all good and true, it isn't particularly useful in an immediate pragmatic sense. I wrote a book recently which was intended as a guidebook for rebooting civilisation after an apocalypse, looking at the key technologies and central scientific principles that underpin our lives – the behind-the-scenes fundamentals that we all just take for granted today – and what enabled society to progress through the centuries of history. I argue how the greatest invention of history is the scientific method itself – the knowledge-generation machinery that we have been using for over 350 years now to come to understand how the world works. So if you could preserve only one single sentence, I would push for: 'The natural world is not governed by whimsical gods, but is essentially mechanical and can therefore be understood and then predicted by people, using careful observation, experimentation, and measurement, and importantly by testing your explanations to try to refute them.' It's this reiterative process of refinement that sets science apart from any other system for explaining how the world works.

    "There are other tips that could help with immediate survival. Diarrhoeal disease kills millions of people every year – all preventable by simple means. One method recommended by the World Health Organisation in developing nations for low-tech treatment of drinking water is called SODIS, or solar disinfection. All you need to do is pour your suspect water into a plastic bottle and leave it in the sun. Ultraviolet rays in sunlight pass straight through and kill any germs. So you can come back to your bottle a day or two later and know that the water you put to your lips isn't going to kill you."

    4. Dr Susannah Fleming, engineer:

    "I would think about knowledge that is immediately applicable by a civilisation with little or no science or technology, to produce a wide benefit. So I would go for infection prevention and control: 'Illness is often caused by tiny lifeforms, invisible to the naked eye, which can be transmitted by breath, touch, and body fluids; transmission can be minimised by keeping waste out of water supplies, and by cleaning people and surfaces who have been in contact with a sick person or creature.'

    "Not ideal, but it would at least help avoid the 'miasma' theory that probably contributed to human ill health for many centuries."

    5. Dr Duncan Casey, chemist/biophysicist/engineer:

    "I'd have to go with 'Spin a magnet inside a loop of copper and the form of energy you create can provide you with light, heat, food and clean water.' Discovering electricity was a huge step in our development – the ability to provide consistent power in a useful form meant that suddenly we could keep houses at a controlled temperature year-round, keep food fresh for longer, and communicate with each other over long distances, to name but a few of the more basic applications. It drives our farms, our factories, and our trains, it dominates the way we share information and has largely replaced our physical currencies.

    "However, electricity also gave us the impetus to start unpicking the fabric of nature at a fundamental level, but also gave us the tools to do it and to analyse the findings we generate. It's so integral to the way we live now that it still astonishes me that we only began to experiment with it in a useful form 200 years ago. Look at how far and how fast we've come since then: If I could provide a surviving society with one transformative, step-change discovery, it would be how to generate electricity."

    6. Ying Lia Li, PhD student in optomechanics:

    "The simple act of sitting on the beach and watching the ocean tide can be enough to come up with a mathematical description that describes nearly all motion around us: from the orbits of planets in space to the vibrations of the sand between your toes (and even the billions and billions of atoms inside a grain of that sand). This model is called the harmonic oscillator model, where the motion of an object goes back and forth or up and down in a pattern known as a sinusoidal wave.

    "Normally this is intuitive, and we see a lot of harmonic motion in real life: the pendulum inside a grandfather clock, the motion of a diving board, or the distinct sound of resonance when you turn up the bass in your car radio. However, many complex behaviours can also be described in a similar way, such as electronic circuits, the motion of individual atoms and molecules, and even quantum field theory. In fact, understanding the quantum harmonic oscillator model has been crucial for scientists to find ways to manipulate the motion of atoms, allowing research labs all over the world to regularly and easily create the coldest atoms in the universe."

    7. Dr Liam Gaffney, nuclear physicist:

    "Being a nuclear physicist, it may not be unexpected that my answer is similar to Feynman's. The atomic hypothesis is fundamental to our very existence, how we were born in the stars and how we are all made of the same stuff. Just three little particles – the proton, neutron, and electron – constitute everything that we see around us. This is profound knowledge that we only discovered in the 20th century.

    "If I had to put it somewhat less concisely than the original, I would say that 'We and everything that we see around us are made of the same three unimaginably tiny particles, born out of violently exploding stars hundreds of millions of years ago.'

    "With knowledge like this, and the understanding that we're all just extremely fortunate lumps of the same matter, one might hope for a relatively peaceful post-scientific world. More likely though, humankind's struggle to understand its own consciousness will still be played out in bloody battle. However, with no scientific knowledge, maybe we'll be back to sticks and stones and not guns and bombs. "

    8. Alom Shaha, physics teacher:

    "I'd really love to be able to answer this question by conveying some idea of the 'scientific method' in a few words. As a science teacher, I teach my students about a particular set of knowledge and ideas – Newtonian mechanics, the theory of evolution by natural selection, the atomic theory of matter and so on – which have tremendous explanatory and predictive power.

    "Science does not come naturally to humans; 'scientific' models are often counter-intuitive and can be far removed from 'common sense' explanations of how the world works. It's remarkable to me that humans have worked out ways of modelling nature which allow us to do everything from eradicating deadly diseases to knowing how to land a probe on a comet that's flying through space at thousands of metres per second. So, if there was some kind of cataclysm which destroyed all existing scientific knowledge, the important thing to preserve is not any particular facts or theories, but the requirements for what constitutes a 'scientific' theory, perhaps something like:

    "A scientific theory must put forward a comprehensive explanation for something we observe in nature, provide strong evidence for that explanation, and provide the means with which to make predictions about the aspect of the world it explains, which we can then test by observation."

    9. Dr Samuel Godfrey, biochemist:

    "We know so many wonderful things thanks to science that I just don't think a single piece of information could cut it. Instead I would try and pass on the idea of the scientific method. I would tell the future creatures that 'There is nothing more important than being a curious sceptic. Demand evidence for everything and expect others to demand it of you. Tell the world what you've learned, no matter how small, and if it stands up to scrutiny, then you're on the right track. Get this right and you will change the world.'

    "If this new society thrives and embraces this way of thinking (and doesn't get side-tracked by fairies and things), then in just a few hundred years they will know everything we could have told them anyway."

    10. Dr Dean Burnett, psychologist:

    "If you're going to rebuild society, you need people to help you. So, rather than the more fundamental sciences or processes of nature that would help rebuild things, I'd say the most important thing to know about is people themselves. Basically, the human brain isn't 100% rational, so if you want to achieve large groups of people working together, you need to know this and not assume everyone will pitch in because it's the logical thing to do. Cognitive biases, group mentality, social hierarchies, differing motivations and experiences, these and more all mean that people can have wildly differing conclusions about what the 'correct' course of action is.

    "You can't just present the course of action that has the most evidence to support it and expect everyone to fall in line. See the antivaccination movement, climate change denial, intelligent design proponents, and more, for modern examples of this. Bottom line: People aren't logical or rational by default, and it's vitally important to remember this when trying to impart knowledge and guidance. Having some useful knowledge like atomic theory or the nature of gravity isn't going to be much use if enough people don't want to believe it."

    11. Dr Sujata Kundu, materials chemist:

    "As a materials chemist, I see everything in the world as an arrangement of atoms. These atoms are like the Lego bricks of our universe, except that there is also a game-playing element to it. There are rules that cannot be broken. Knowing the rules of the game and how the Lego bricks interact with themselves and others helps us to make sense of everything – why glass is transparent, why ceramic cracks, why ice is less dense than liquid water.

    "But Einstein once said that 'imagination is more important than knowledge' and I agree. We know what we know, but our imagination takes us to places beyond that which we have already established, and on to new discoveries, theories, and explanations.

    "If all scientific knowledge were destroyed, the next generation of creatures would find a way. They always do. We always do. Evolution, survival of the fittest, adapting to live, it's still all science, but by trial and error. Experimentation. Imagination. Maybe the next generation of creatures don't need information. Maybe all they need is a little encouragement."

    12. Dr Greig Cowan, particle physicist:

    "It's difficult to beat Feynman! However, something that immediately comes to my mind is a small equation that every physics/mathematics student should know that encapsulates a lot of deep concepts (arithmetic, pi, complex numbers, logarithms, zero, one). It's called Euler's identity, and it goes like this: e+1=0."