Here’s the paradox: If life arises wherever conditions are right, where are all the aliens? How comes when we look up to the skies with our big telescopes, all we see is endless nothingness and no signs of advanced civilisations?
Thanks to recent advances in astronomy we are discovering more and more earth like planets in the cosmos. We haven’t found one exactly like the Earth yet, but so many are being discovered, and at such a rate, that it appears that the galaxy must be teeming with planets that can support life.
These discoveries are bringing an old paradox back to the fore. In 1950 a physicist called Enrico Fermi asked, if there are many suitable homes for life out there and alien life-forms are common, then where are they all? More than half a century of searching for extraterrestrial intelligence has so far come up with nothing. Zilch.
Of course, the universe is a very big place. As my favourite author (of all time) Douglas Adam’s once wrote in the Hitchhikers Guide to the Galaxy:
“Space is big. You just won’t believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space”
Then there is the famous ‘Drake Equation’ for life’s probability, which suggests that we will be lucky to stumble across intelligent aliens: they may be out there, but we’ll never know it.
There are deeper explanations. Perhaps alien civilisations appear and disappear in a galactic blink of an eye, destroying themselves long before they become capable of colonising new planets. This does make some biological sense since we know that 99.9% of all species that have ever existed on earth, have become extinct. Why should alien civilisations be any different?
Or maybe life very rarely gets started even when conditions are perfect?
If we cannot answer these kinds of questions by looking out at the stars, might it be possible to get some clues by looking in? Life arose only once on Earth, and if a sample of one were all we had to go on, no grand conclusions could be drawn. But there is more to it than that. We can look at life on earth. Look at how it works and how it emerged. Answers to such questions can reveal much about what it means to be alive. Such insights can also tell us about the probability of finding life in the universe. Ongoing research is building a convincing picture of our precarious existence in the nothingness of Space. Looking at a vital ingredient for life – energy – suggests that simple life is common throughout the universe, but it does not inevitably evolve into more complex forms such as animals.
It seems that the immense delay between life first appearing on Earth and the emergence of complex life points to another, very different explanation for why we have yet to discover aliens. It also points a beam into what it means to be alive in the first place. The fact that life ‘might’ be common in the universe, but complex life that can think and reason not common at all – has immense repercussions for us as humans. It means we could be unique. One off’s. Flukes. These questions will be discussed in the following series.
The following articles will be ‘sciency’ and demanding reads – which is why I’ve chopped the whole thing up into 4 easily digestible parts! But I will try my best, to make it as easy as possible. Knowing the stuff you are about to learn will (should) open your eyes. Your eyes and mind will span billions of years of space and time – and you will see yourself in relation to it all. A thrilling ride indeed!
The role of energy
Living things consume an extraordinary amount of energy, just to go on living and doing the things they do. The food we eat gets turned into the fuel that powers all living cells, called ATP. This fuel is continually recycled: over the course of a day, humans each churn through 70 to 100 kilograms of the stuff. This huge quantity of fuel is made by enzymes, biological catalysts fine-tuned over aeons to extract every last joule of usable energy from reactions. Enzymes are protein molecules that speed up reactions that would normally take much longer to occur. They do this by bringing substrates together and also by lowering the energies required to get the reaction started. The enzymes in our body are amazingly efficient. Over billions of years of evolution that have been perfected into perfect little machines and they can churn out products at astonishing speeds.
However, the enzymes that powered the first life cannot have been as efficient, and the first cells must have needed a lot more energy to grow and divide – probably thousands or millions of times as much energy as modern cells. The same must be true throughout the universe.
This phenomenal energy requirement is often left out of considerations of life’s origin.
What could the primordial energy source have been here on Earth? Old ideas of lightning or ultraviolet radiation just don’t pass muster. Aside from the fact that no living cells obtain their energy this way, there is nothing to focus the energy in one place. The first life could not go looking for energy, so it must have arisen where energy was plentiful.
Today, most life ultimately gets its energy from the sun, but photosynthesis is complex and probably didn’t power the first life. So what did? Reconstructing the history of life by comparing the genomes of simple cells is fraught with problems. Nevertheless, such studies all point in the same direction. The earliest cells seem to have gained their energy and carbon from the gases hydrogen and carbon dioxide. The reaction of H2 with CO2 produces organic molecules directly, and releases energy. That is important, because it is not enough to form simple molecules: it takes buckets of energy to join them up into the long chains that are the building blocks of life.
A second clue to how the first life got its energy comes from the energy-harvesting mechanism found in all known life forms. This mechanism was so unexpected that there were two decades of heated altercations after it was proposed by British biochemist Peter Mitchell in 1961.
[to be continued…]
Brief Summary of part 1
- When we look up at the skies with our telescopes we see no signs of aliens
- Why is this? Either we are alone. Or there is life in the universe but it is simple and non-complex and non-intelligent
- Since we cannot yet travel throughout the Cosmos can we study the only life we know about on earth to tell us more about life in the universe?
- Yes! We can study the details of the origin of life on earth to shed light on its cosmic footprint (if any)
- Life on earth requires energy. Lots of energy. Today most life gets its energy from the sun via photosynthesis or indirectly through food. But ultimately all energy is derived from the sun.
- BUT, the first life did not get its energy from the sun directly because photosynthesis and eating food are complex processes. The first life would have been simple and it must have used a simple mechanism to generate energy. We now know that it probably used the reaction of H2 and CO2 to build its molecules and get its energy that way.
- ATP is the universal currency of energy in all living things alive today. ATP is an energetic molecule that is produced from the respiration of the food you eat or from photosynthesis and it is ATP that directly powers all life’s processes inside of you.
- How is energy from food and the sun converted into ATP – the currency of energy? The UNDERLYING mechanism of how this is done today is the same mechanism that was used by the first life on earth!
- Peter Mitchell discovered this universal mechanism in 1961
- He was British (obviously!)
- It is one of the most amazing things known to science. The mechanism will be revealed in part 2.