LIFE ON OTHER PLANETS

This topic came spontaneously to me: I suddenly felt inspired by the thought of how tremendously important it is to popularise science - important for the whole human race and its development. If you search on YouTube, you will quickly see that pseudoscientific videos about the supernatural, psychics, or haunted houses gather many more views than videos about real science. And understandably so: many people consciously refuse to draw a line between the world of fantasy and objective reality.

The difference between science and the supernatural is simple: science shows what is really going on and draws useful conclusions. Fantasy will not help you start your car, and a psychic will not launch a satellite.

Nature is a genius sculptor, the greatest painter of all time, the most virtuosic of musicians. And most importantly, Nature is our first teacher. Think of all the ideas we had to borrow from nature to create what we call the gifts of civilization. Just imagine: all living things on Earth have come into being essentially by accident. First living organisms appeared as a result of microbes going through innumerable trials and tribulations billions of years ago and eventually evolving into us - all without understanding what was happening. We can understand, though, and now we can do ourselves what it took Nature 3 billion years to do.

For many of us, it is hard to admit how insignificant we are in comparison with the Universe. Looking at the night sky, we gaze not just into faraway space, but back into the past. The thing is, since the speed of light is finite, it takes time for light to move from point A to point B. Imagine that right now we could suddenly watch Alexander the Great and his conquests, or bet on the first Olympic Games of 776 BC. And now imagine that it is indeed possible, even though we cannot practically do that. Aliens on a distant cosmic body located two thousand light years away from us can watch what was happening on Earth two thousand years ago. But while they can do that, being where they are, we cannot, since we are here and now. If we were to travel to a distant planet in order to watch our past, it would take us much more time to get there than light needs to make the same journey. We would, however, be able to see what was happening on Earth 4 thousand years ago if those aliens were to install a gigantic mirror on their planet: light would take 2 thousand years to get there, get reflected and return to us, while we would watch it in a telescope. Among the drawbacks is the huge relative speed of movement of cosmic bodies and their rotation: the mirror would have to be constantly adjusted for us to gaze across 2 thousand light years. The idea with a mirror, though very interesting, is practically unrealisable. On the other hand, we ourselves can act as those aliens, giving civilizations on other planets a chance to observe their own history. For that, we would have to build a gigantic mirror and direct it at a chosen planet, then just wait.

And now let's think for a moment: what difference does it make that light arrives to us with a delay, if nothing can outstrip it anyway? Looking at the sky, all we see is a set of points of light, and we see essentially the same thing in a telescope. We cannot really see distant planets and galaxies. So here is a logical question: how do we know how far they are and the delay with which we see them? Here we can use a great tool called trigonometric parallax. In a nutshell, we can calculate exactly how far a certain cosmic body within our galaxy is located, as well as make a rough estimate of the distance to a specific galaxy. It is very useful, considering that even light takes four years to travel to the nearest star system, to say nothing about us…

Of course, we cannot say for sure that there are no aliens in the explored part of space, but now that we have touched upon the subject of aliens, let us investigate this matter in more detail. Why do scientists talk about them so often, even though the very fact of their existence has not been established? As the astrophysicist Neil deGrasse Tyson once said, considering all the probabilities and the fact that we are a carbon-based form of life, it would be egocentric to suggest that we are alone in the cosmos. What's more, we haven't even looked at faraway stars in our own galaxy properly, to say nothing of other galaxies. The probability of life existing on other planets is huge, and of course we would like to find it. The most widespread misconception about life on other planets is that they should be populated by people more or like us. I will try to refute this idea. Life on other planets simply cannot resemble the life forms that exist on Earth. It would be totally different, we cannot even imagine how different. Here are the four main reasons why living organisms on other planets must differ from the ones we know:

1. The inhabitants of other planets may very well represent non-carbon-based life forms (unlike us) and use another solvent instead of water. The discipline that studies the possibility of such life forms’ existence is called alternative biochemistry. Interestingly, the most probable candidate for the role of an alternative solvent seems to be... ammonia! It is poisonous to us, but it could be used in place of water by other life forms.

2. Environment must also depend on the geology and topography of a planet. Five main ecosystems are found on Earth: tundra, steppe, desert, forest, and water. Well-adapted living organisms differ greatly between these ecosystems, even though they all populate the same planet. The same would be true for other planets: there, life forms would differ not only from us, but also from each other, depending on their environment.

3. Alternative energy sources. Life has much better chances on those planets that orbit smallish stars: such stars have much longer lifespans than our Sun. Thus, life would have much more time to emerge and develop. The conditions for the appearance and evolution of life there would be completely different from those that exist in our solar system. Moreover, life could even emerge on a so-called wandering planet that is not tied to a specific star. There are at least 200 billion such planets in our galaxy. They could use the heat of their own cores as a source of energy. That would not be enough for complex life forms, but as the paleontologist David Stephenson suggests, a dense atmosphere (much denser than that of our Earth) could prevent the heat from dissipating into space, thus creating a strong greenhouse effect. That would be enough for life to emerge, and clearly, life that evolves independently of any star cannot possibly resemble the one we are used to.

4. The random factor. There is almost nothing to limit the range of mutations that cause the evolution of life. And only natural selection determines who survives and who destined for oblivion. Even the best-adapted of species on Earth would not pass the natural selection under different conditions.

The number of the facts in reality is much bigger, and I've mentioned only major ones.

In this article, I have tried to show how interesting even the simplest facts about our world can be. As you may have noticed, all things in our Universe are interconnected, and one can pass from one subject to another with ease. Science makes sense, it is well-grounded and useful, and it is science that moves human progress forward.