Are there Aliens?
People often report sightings of UFOs or Aliens, some even saying that they have communicated with them. These are often on the media for a few days before people figure out the truth behind the story or the photo. Nonetheless, aliens and extraterrestrial life does indeed sound plausible since space is vast; this raises the question: Where is everyone?
Scientists expect to encounter aliens in a matter of years. Yet, from the 1950s, people have not gotten a single signal that proves the existence of such lifeforms. The universe has been existing for around 13.8 billion years and with its vast area, people believe that aliens have already colonized the entire universe. Some people argue that the aliens created us or that the human civilization is trapped in a simulation created by aliens (like the Divergent series). Movies often portray aliens as intelligent, advanced species that try to destroy everything. However, the same question is asked: where is everyone?
Another theory is that we are alone. People tend to avoid this idea because it is so simple and boring. Everyone wants to see another lifeform that does not look like you or your friend, right? Well, no one truly knows the real answer. Aliens might come knocking our front doors but is this really what is going to happen? But how can we be alone?
There is a possible answer to this whole mystery. Try and think of the creation of complex lifeforms this way. There are four key barriers that life needs to pass in order to thrive and evolve.
Habitability is the first one. This requirement determines whether the planet has a suitable environment that is in the habitable zone, where water is a liquid. Earth is a planet in this habitable zone, around 149.6 million kilometers. However, a planet that is not in this habitable zone will either fry when it is too close to the sun or freeze when it is too far from the sun. Mercury is the closest planet in our solar system to the sun and has temperatures at around 801 Fahrenheit (427 Celsius). On the other hand, Neptune is the furthest planet in our solar system to the sun and has temperatures at around -353 Fahrenheit (-214 Celsius). We are not the only planet that is in this zone, however. A nearby star called Proxima Centauri has a planet in this zone. Thus, to house lifeforms, planets first have to be inside the habitable zone to evolve into intelligent species.
The second barrier is Abiogenesis. It is the creation of life from non-life. In other words, it is the creation of life from only items and phenomenons without interferences from other lifeforms. Life similar to ours is definitely unique. However, the building blocks of Earth is not too rare. Amino acids can be found in comets, complex organic molecules are in interstellar dust clouds, and water is found in exoplanetary systems. Hence, the ingredients are there but it is not combined to create life.